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+This eBook, including all associated images, markup, improvements,
+metadata, and any other content or labor, has been confirmed to be
+in the PUBLIC DOMAIN IN THE UNITED STATES.
+
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+Project Gutenberg (https://www.gutenberg.org) public repository for
+eBook #67569 (https://www.gutenberg.org/ebooks/67569)
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-The Project Gutenberg eBook of Tractor Principles, by Roger B.
-Whitman
-
-This eBook is for the use of anyone anywhere in the United States and
-most other parts of the world at no cost and with almost no restrictions
-whatsoever. You may copy it, give it away or re-use it under the terms
-of the Project Gutenberg License included with this eBook or online at
-www.gutenberg.org. If you are not located in the United States, you
-will have to check the laws of the country where you are located before
-using this eBook.
-
-Title: Tractor Principles
-
-Author: Roger B. Whitman
-
-Release Date: March 5, 2022 [eBook #67569]
-
-Language: English
-
-Produced by: deaurider and the Online Distributed Proofreading Team at
-             https://www.pgdp.net (This file was produced from images
-             generously made available by The Internet Archive)
-
-*** START OF THE PROJECT GUTENBERG EBOOK TRACTOR PRINCIPLES ***
-
-
-
-
-
-Transcriber’s Notes:
-
-  Underscores “_” before and after a word or phrase indicate _italics_
-    in the original text.
-  Equal signs “=” before and after a word or phrase indicate =bold=
-    in the original text.
-  Small capitals have been converted to SOLID capitals.
-  Illustrations have been moved so they do not break up paragraphs.
-  Typographical and punctuation errors have been silently corrected.
-
-
-
-
-              TRACTOR PRINCIPLES
-
-       THE ACTION, MECHANISM, HANDLING,
-         CARE, MAINTENANCE AND REPAIR
-           OF THE GAS ENGINE TRACTOR
-
-                      BY
-               ROGER B. WHITMAN
-
-                   AUTHOR OF
-            “MOTOR CAR PRINCIPLES,”
-           “GAS ENGINE PRINCIPLES,”
-           “MOTOR-CYCLE PRINCIPLES,”
-                     ETC.
-
-                [Illustration]
-
-               FULLY ILLUSTRATED
-
-            D. APPLETON AND COMPANY
-            NEW YORK        LONDON
-                      1920
-
-               COPYRIGHT, 1920,
-                      BY
-            D. APPLETON AND COMPANY
-
-    PRINTED IN THE UNITED STATES OF AMERICA
-
-
-
-
-FOREWORD
-
-
-The tractor of to-day is built in almost as many types and designs
-as there are tractor makers, and is far from being as standard as
-the automobile. There are tractors with one driving wheel, with two
-driving wheels, with three and with four, as well as three arrangements
-of the crawler principle; there are two-wheelers, three-wheelers and
-four-wheelers; tractors that are controlled by pedals and levers and
-tractors that are driven by reins.
-
-Thus if a man who is competent to handle and care for one make is given
-another make to run, he may be entirely at a loss as to how it works
-and how it should be handled.
-
-It is the purpose of this book to explain and describe all of the
-mechanisms that are in common use in tractor construction, to the end
-that the reader may be able to identify and understand the parts of
-whatever make he may see or handle.
-
-
-
-
-CONTENTS
-
-
-                                                                PAGE
-                         CHAPTER I
-                    TRACTOR PRINCIPLES
-    Comparison between tractors and automobiles—What is
-        required for each—Advantage of understanding the
-        mechanism—No standard tractor design—Principal
-        parts of a tractor—Necessity for each                     1
-
-                        CHAPTER II
-                     ENGINE PRINCIPLES
-    Power attained from heat—Combustible mixture—Principle
-        of engine operation—Combustion space—Gas engine
-        cycle—Dead strokes—Flywheel—Starting an
-        engine—Inlet stroke—Compression stroke—Importance
-        of compression—Ignition—Advance and retard of
-        ignition—Power stroke—Exhaust stroke—Production of
-        power—Vertical and horizontal engines—Firing order        9
-
-                         CHAPTER III
-                        ENGINE PARTS
-    Base—Bearings—Cylinders—Crankshaft—Piston—Connecting
-        rod—Wrist pin—Piston rings—Valves—Cam—Valve
-        mechanisms—Cooling system                                30
-
-                        CHAPTER IV
-                   FUELS AND CARBURETION
-    Oxygen necessary for combustion—Forming a mixture—Rich and
-        poor mixtures—Carbon—Preignition— Carbureter—Spray
-        nozzle—Evaporation of fuels—Carbureter principles—
-        Extra air inlet—Effect of heat on mixture—Loading—
-        Strangler                                                52
-
-                         CHAPTER V
-                        CARBURETERS
-    Carbureter parts—Manifold—Action of carbureter—Float
-        feed—Kerosene and gasoline—Descriptions of
-        carbureters—Pump feed—Use of water in the
-        mixture—Application of heat—Fuel pumps—Air
-        cleaners—Governors                                       70
-
-                        CHAPTER VI
-                         IGNITION
-    Principle of ignition—Point of
-        ignition—Preignition—Advance and retard—Parts of
-        ignition system—Magnetism—Induction—Magneto—Action
-        of armature—Armature windings—Circuit
-        breaker—Circuit—Shuttle and inductor
-        armatures—Sparking current—Grounded circuit—
-        Magneto parts—Impulse starter                           102
-
-                         CHAPTER VII
-                  BATTERY IGNITION SYSTEMS
-    Principle of spark coil—Windings—Timer—Atwater-Kent
-        system—Vibrator—Spark plugs                             131
-
-                         CHAPTER VIII
-                         TRANSMISSION
-    Transmission parts—Clutches—Necessity for change speed
-        gear—High and low gear—Types of change speed
-        gears—Necessity for differential—Principle of
-        differential—Drives—Worm                                143
-
-                        CHAPTER IX
-                    TRACTOR ARRANGEMENT
-    Tractor requirements—Tractor types—Engine position—
-        Front axles—Spring supports                             167
-
-                         CHAPTER X
-                        LUBRICATION
-    Importance of lubrication—Effect of oil—Kinds of
-        oil—Effect of temperature on oil—Using the right
-        kind of oil—Burning point—Viscosity—Lubrication
-        charts—Oiling systems—Oil pumps—Mechanical oiler—
-        Oil cup—Grease cup                                      175
-
-                        CHAPTER XI
-                     TRACTOR OPERATION
-    Using a new tractor—Breaking in—Daily
-        inspection—Driving—Shifting gears—Driving on
-        hills—Using the engine as a brake—Cold weather
-        conditions—Starting in cold weather—Protection
-        against freezing—Starting a tractor                     201
-
-                         CHAPTER XII
-                     ENGINE MAINTENANCE
-    Fuel system and carbureter—Carbureter adjustment—Dirt
-        in the fuel—Running on kerosene—Care—Magneto and
-        ignition system—Care of magneto—Smoothing platinum
-        points—Adjustment—Timing a magneto—Testing a
-        magneto—Ignition trouble—Compression—Testing
-        for compression leaks—Valve grinding—Valve
-        timing—Carbon—Removing carbon                           213
-
-                        CHAPTER XIII
-                      LOCATING TROUBLE
-    Engine will not start—Engine loses power—Engine
-        stops—Engine misses—Engine starts; but stops—Engine
-        overheats—Engine smokes                                 245
-
-                         CHAPTER XIV
-                      CAUSES OF TROUBLE
-    Troubles and their causes in tabular form                   259
-
-    INDEX                                                       261
-
-
-
-
-ILLUSTRATIONS
-
-
-    FIG.                                            PAGE
-      1 The Gas Engine Cycle                          15
-      2 1-cylinder power diagram                      21
-      3 2-cylinder power diagram                      22
-      4 2-cylinder power diagram, 180 shaft           24
-      5 H. D. O. power diagram                        26
-      6 4-cylinder power diagram                      27
-      7 2-cylinder crank shaft                        31
-      8 4-cylinder crank shaft                        32
-      9 Half of a plain bearing                       32
-     10 Connecting rod bearings                       33
-     11 Piston complete and in section                34
-     12 Wrist pin fastenings                          36
-     13 Valve                                         38
-     14 Action of cam                                 39
-     15 “Twin City” tractor engine                    41
-     16 “Hart-Parr” valve mechanism                   43
-     17 “Hart-Parr” engine                            45
-     18 “Oil-Pull” engine                             47
-     19 Horizontal double opposed engine              49
-     20 “Monarch” engine                              51
-     21 Principle of carburetor                       59
-     22 Principle of extra air inlet                  64
-     23 “Kingston” carburetor, model L                72
-     24 “Kingston” carburetor, model E                75
-     25 “Kingston” carburetor, dual model             77
-     26 “E-B” carburetor                              79
-     27 “E-B” carburetor, side view                   81
-     28 Pump-fed carburetor                           82
-     29 “Titan” carburetor                            84
-     30 Pump-fed carburetor with two fuel nozzles     85
-     31 “Hart-Parr” mixture heater                    87
-     32 “Twin City” manifold                          88
-     33 Fuel pump                                     90
-     34 “Avery” fuel connections                      92
-     35 “Oil-Pull” fuel system                        93
-     36 Air washer                                    95
-     37 Air strainer                                  96
-     38 “E-B” governor                                97
-     39 “Case” governor                               98
-     40 “Hart-Parr” governor                          99
-     41 Vertical governor                            101
-     42 Armature                                     107
-     43 Flow of magnetism through armature core      108
-     44 One complete revolution of the armature      111
-     45 Connections of Bosch magneto                 112
-     46 “K-W” inductor                               115
-     47 “K-W” inductor in three positions            117
-     48 “Dixie” inductor                             118
-     49 Three positions of “Dixie” inductor          120
-     50 “Bosch” circuit breaker                      121
-     51 “K-W” circuit breaker                        122
-     52 “Bosch” magneto in section                   126
-     53 “K-W” magneto in section                     129
-     54 Magnetism in a copper wire                   132
-     55 Magnetism from electricity                   133
-     56 Principle of spark coil                      134
-     57 “Atwater-Kent” ignition system               136
-     58 Vibrator coil ignition system                139
-     59 Spark plug                                   141
-     60 Internal clutch                              144
-     61 Plate clutch                                 147
-     62 Principle of sliding gear                    155
-     63 Principle of jaw clutch change speed gear    157
-     64 “I. H. C.” chain drive, showing differential 162
-     65 “Case” rear axle                             163
-     66 “Oil-Pull” rear axle                         164
-     67 Driving worm                                 165
-     68 Tractor arrangement                          168
-     69 Tractor arrangement                          169
-     70 “Gray” tractor                               171
-     71 Types of front axles                         172
-     72 Spring support                               173
-     73 “Mogul” oiling diagram                       180
-     74 “Illinois” oiling diagram                    183
-     75 End of “Twin City” connecting rod            185
-     76 Wrist pin lubrication                        186
-     77 Force feed oiling system of “Gray” engine    187
-     78 Oil pump                                     188
-     79 “E-B” oil pump                               189
-     80 Oil pump with hollow plunger                 190
-     81 Methods of preventing oil leaks              191
-     82 “Titan” lubricator                           192
-     83 “I. H. C.” method of oiling crank pins       193
-     84 “Hart-Parr” oiling system                    194
-     85 Oil cup                                      195
-     86 Proper use of a grease cup                   196
-     87 “Titan” 10-20 oiling diagram                 198
-     88 “International” oiling diagram               199
-     89 Grinding valve in engine with fixed head     231
-     90 Grinding valve in detachable head            233
-     91 Grinding valve in detachable seat            234
-     92 Valve seat cutter                            235
-     93 “Holt” valve arrangement                     236
-     94 Valve timing, using marks on flywheel        238
-     95 Valve timing                                 239
-
-
-
-
-TRACTOR PRINCIPLES
-
-
-
-
-CHAPTER I
-
-TRACTOR PRINCIPLES
-
-
-While tractors and automobiles are the same in general principles,
-there is a wide difference between them in design, construction, and
-handling, due to the differences in the work that they do and in the
-conditions under which they do it.
-
-An automobile is required to move only itself and the load that it
-carries. While it can run over rough roads, these must be hard enough
-to support it; on soft ground it will sink in and be unable to get
-itself out. It can make great speed over smooth, level roads; but only
-rarely do road and police conditions permit it to run its fastest for
-more than a few minutes at a time. For the greater part of its life it
-develops only a portion of the power of which it is capable.
-
-A tractor, on the other hand, is intended not to carry, but to haul.
-It must run and do its work on rough hillsides, soft bottoms, or any
-other land where it is required to go. Instead of developing speed it
-develops pulling power, and must be able to develop its full power
-continuously.
-
-Appearance and comfort count for a great deal in an automobile, and
-much attention is devoted to making it noiseless and simple to manage.
-These things do not apply in a tractor, which is a labor-saving and
-money-making machine, valuable only for the work that it can do. There
-is no question of upholstery or nickel-plating; all that is wanted is a
-machine that will do the required work with the least possible cost of
-operation.
-
-As is the case with any kind of machine that is purchased as a
-money-maker, its cost should be as low as is consistent with its
-ability to do its work. Any extra cost for accessories, or finish, or
-other detail, is wasted unless it permits the machine to do more work,
-or, by making the operator more comfortable, allows him to run the
-machine for a longer stretch of time or with greater efficiency.
-
-It may be taken for granted that any tractor will run and will do its
-work with satisfaction, provided it is sensibly handled and cared for.
-Far more troubles and breakdowns come from careless handling and from
-neglect than from faulty design and material. A tractor that is running
-and doing its work is earning a return on the money invested in it;
-when it is laid up for repairs there is not only a loss of interest on
-the investment, but a loss of the value of the work that it might be
-doing.
-
-To keep a tractor running is a matter only of understanding and of
-common sense; common sense to realize that any piece of machinery needs
-some degree of care and attention, and understanding of where the care
-and attention should be applied. The more thoroughly a tractor operator
-understands his machine, the more work he will be able to get out of
-it, and the more continuously it will run. This is only another way of
-saying that understanding and knowledge pay a direct return in work
-done and money earned.
-
-In the early days of the automobile there were as many types of cars
-as there were manufacturers. As time has gone on, the unsatisfactory
-ideas have been weeded out, and automobiles have approached what may be
-called a standard design.
-
-At the present time, tractor designs are varied, and it is hardly
-possible to speak of any type as standard. The reason for this lies in
-the fact that many manufacturers start with a design for one special
-part, and build the tractor around it.
-
-For example, a manufacturer may develop a method of driving the wheels
-that he feels is especially good for tractor work. In applying it he
-may find that the engine must be so placed on the frame that when the
-power pulley is in position the belt will interfere with the front
-wheels unless they are small; he therefore uses small front wheels, and
-advocates them for tractors.
-
-Another manufacturer with a patent steering gear may be able to place
-the power pulley so that there is ample clearance for the belt; he
-finds that by using high front wheels he can get a better support for
-the frame, and therefore claims that high front wheels are an advantage.
-
-Other designs may be based on having three wheels, or two; advantages
-are claimed for each type, and each type undoubtedly has them.
-
-The selection of a tractor is based on one’s own experience or on
-that of neighbors, or on the ability of the salesman to bring out the
-advantages of the make that he sells; but when the tractor is bought
-and delivered, its ability to do the work promised for it depends
-solely on the care with which it is handled and looked after.
-
-Whatever the design of a tractor may be, there are certain parts that
-it must have in order to do the work required of it. These parts, or
-groups of parts, are as follows:
-
-=Engine.=—This furnishes the power by which the tractor operates.
-
-=Clutch.=—By means of a clutch the engine may be connected with the
-mechanism, so that the tractor moves, or it may be disconnected, so
-that it may run without moving the tractor.
-
-=Change Speed Gear.=—As will be explained in later chapters, an engine,
-in order to work most efficiently, should run at a fixed speed; the
-tractor should be able to run fast or slow, according to conditions.
-A change speed gear is therefore provided, by which the speed of the
-tractor may be changed, although there is no change in the speed of the
-engine.
-
-=Drive.=—The drive is the mechanism that applies the power of the
-engine to the wheels, and makes them turn.
-
-=Differential.=—When a tractor makes a turn, the outside wheels cover
-a larger circle than the inside wheels, and therefore must run faster
-in order to get around in the same time. It is usually the case that
-the power of the engine is applied to both driving wheels; if both were
-solid on the axle, like the wheels of a railroad car, one would be
-forced to slip when making a turn, which would waste power. By applying
-a differential, the engine can drive both wheels, but the wheels may
-run at different speeds when conditions require it.
-
-The clutch, change speed gear, drive and differential form the
-_transmission_.
-
-=Steering gear.=—By means of the steering gear the direction in which
-the tractor moves may be changed.
-
-=Supports.=—A tractor moves on broad-tired wheels, or on crawlers,
-which are so formed that they grip the ground and do not slip. They
-give so broad a support that even on soft ground the weight of the
-tractor will not pack the soil sufficiently to injure it as a seed bed.
-
-=Frame.=—The frame is the foundation of the tractor, and holds the
-parts in the proper relation to each other. It is usually made of
-channel steel, the parts being bolted to it; in some tractors, however,
-the parts are so attached to each other that they form their own
-support, and no other frame is needed.
-
-Tractor manufacturers make these parts in different ways; all
-accomplish the same result, but do it by different methods. The main
-principles are much the same, and should be known and understood. They
-are described and explained in the succeeding chapters.
-
-
-
-
-CHAPTER II
-
-ENGINE PRINCIPLES
-
-
-The working part of a tractor is the engine; it is this that furnishes
-the power that makes the machine go.
-
-The engine gets its power from the burning of a mixture of fuel vapor
-and air. When this mixture burns, it becomes heated, and, as is usual
-with hot things, it tries to expand, or to occupy more room.
-
-The mixture is placed in a cylinder, between the closed end and the
-piston; it is then heated by being burned, and, in struggling to
-expand, it forces the piston to slide down the cylinder. This movement
-of the piston makes the crank shaft revolve, which in turn drives the
-tractor.
-
-The first step in making the engine run is to put a charge of mixture
-into the cylinder, and it is clear that if the burning of the charge is
-to move the piston, the piston must be in such a position that it is
-able to move. When the mixture is burned, the piston must therefore be
-at the closed end of the cylinder.
-
-After the charge of mixture has been burned, the cylinder must be
-cleared of the dead and useless gases that remain, in order to make
-room for a fresh charge.
-
-The charge of mixture is drawn into the cylinder just as a pump sucks
-in water. At a time when the piston is at the closed end of the
-cylinder, a valve is opened connecting the space above the piston with
-the device that forms the mixture; then by moving the piston outward,
-mixture is sucked into the space above it. When the piston reaches the
-end of its stroke the cylinder has been filled with mixture, and the
-valve then closes.
-
-It would be useless to set fire to the mixture at that time, for the
-piston is as far down the cylinder as it can be, and pressure could
-not move it any farther. To get the piston into such a position that
-the expanding mixture can move it, it is forced back to the closed end
-of the cylinder. This squeezes or _compresses_, the cylinderful of
-mixture into the small space, called the _combustion chamber_, between
-the piston and the cylinder head.
-
-If the mixture is now burned, the piston can move the length of the
-cylinder, and in so doing it develops power.
-
-The cylinder is cleared of the burned and useless gases by opening a
-valve and pushing them out by moving the piston back to the inner end
-of the cylinder. When this has been done, the valve is closed, and, by
-opening the inlet valve and moving the piston outward, a fresh charge
-is sucked in, and the several steps of the _gas engine cycle_ are
-repeated.
-
-The name _cycle_ is given to any series of steps or events that must be
-gone through in order that a thing may happen. Thus the empty shell
-must be taken out of a gun and a fresh cartridge put in before the gun
-can be fired again, and that series of steps might be called the gun
-cycle.
-
-The gas engine cycle requires the piston to make four strokes. An
-outward stroke sucks in a charge of mixture, and an inward stroke
-returns the piston to the firing position and compresses the charge.
-Then comes the outward stroke when the piston moves under power,
-followed by the inward stroke that clears the cylinder of the burned
-gases.
-
-For every stroke of the piston the crank shaft makes a half-revolution;
-the crank shaft therefore makes two revolutions to four strokes of the
-piston and to each repetition of the gas engine cycle.
-
-Of these four strokes of the piston only one produces power. The other
-three strokes, called the _dead strokes_, are required to prepare for
-another power stroke.
-
-A gas engine cylinder thus produces power for only one quarter of the
-time that it runs. This is one of the striking differences between the
-gas engine and the steam engine, for the piston of a steam engine moves
-under power all of the time that the engine runs.
-
-A one-cylinder gas engine must have something to make the piston go
-through the dead strokes, for otherwise the piston would stop at
-the end of the power stroke; the piston is kept in motion by heavy
-flywheels attached to the crank shaft. These, like any object, try to
-continue in motion when once they are started; a power stroke starts
-the crank shaft revolving and its flywheels keep it going.
-
-Thus, the piston drives the crank shaft during the power stroke, and
-the crank shaft drives the piston during the dead strokes.
-
-To start an engine, the crank shaft is revolved to make the piston suck
-in a charge of mixture and compress it; then the charge is burned, the
-power stroke takes place, and the engine runs.
-
-A clear idea of what goes on inside of the cylinder is quite necessary
-in order to take proper care of an engine and to get the best work
-out of it. The following description applies to any cylinder, for the
-action in all cylinders of an engine is the same.
-
-=Inlet Stroke.=—During the inlet stroke (No. 1, Fig. 1), the piston
-moves outward; the inlet valve is open, and the exhaust valve is
-closed. This movement of the piston creates suction, and if there
-are leaks in the cylinder, air will be sucked in and will spoil the
-proportions of the charge. This will prevent the proper burning of the
-mixture, and the engine will lose power.
-
-The piston moves at such high speed that the mixture cannot enter fast
-enough to keep up with it; mixture is still flowing in when the piston
-reaches the end of its stroke, and even when it begins to move inward
-on the next stroke. The more mixture there is in the cylinder, the more
-powerfully the engine will run; the inlet valve is therefore held open
-for as long a time as the mixture continues to enter.
-
-[Illustration]
-
-[Illustration: FIG. 1.—THE GAS ENGINE CYCLE]
-
-In slow-speed 1-cylinder and 2-cylinder engines the valve closes when
-the piston reaches the end of its stroke; on high-speed engines the
-valve does not close until the piston has moved ¼ inch or ½ inch on the
-compression stroke.
-
-=Compression Stroke.=—During the compression stroke (No. 2, Fig. 1)
-the piston moves inward, and both valves are closed. This movement
-places the piston in position to move outward on the power stroke.
-As the outlets to the cylinder are closed, the charge of mixture
-cannot escape, and is therefore compressed into the space between the
-piston and the cylinder head when the piston is at the inner end of
-its stroke. This space is usually about one quarter the volume of the
-cylinder; the charge is therefore compressed to about one quarter of
-its original volume.
-
-This compression of the charge is very important in the operation of
-the gas engine, and any interference with it will make the engine run
-poorly.
-
-In the first place, it improves the quality of the charge, and makes it
-burn very much better. When the charge enters the cylinder, the fuel
-vapor and air are not thoroughly mixed; much of the fuel is not turned
-into vapor. By compressing the charge it becomes heated; this vaporizes
-the fuel, and vapor and air become thoroughly mixed.
-
-Compression also increases the power. Suppose that the cylinder
-contains a quart of mixture which, when heated, will expand to a
-gallon. If this quart of mixture is compressed to a half pint, it
-will not lose its ability to expand to a gallon, and will exert more
-pressure in expanding from a half pint to a gallon than from a quart to
-a gallon.
-
-A leaky cylinder will cause a further loss of power because some of the
-charge will escape during the compression stroke, which will leave less
-to be burned and to develop power.
-
-=Ignition.=—Setting fire to the charge of mixture is called the
-_ignition_ of the charge, and it takes place close to the end of the
-compression stroke. To get the greatest power, all of the mixture
-should be on fire and heated most intensely as the piston begins the
-power stroke.
-
-When the mixture is set on fire, it does not explode like gunpowder,
-but burns comparatively slowly; the charge is ignited by an electric
-spark, and the flame spreads from that point until it is all on
-fire. In order to give the flame time to spread, the spark passes
-sufficiently before the end of the compression stroke to have the
-entire charge on fire as the power stroke begins. This is called the
-_advance_ of the ignition.
-
-The flame takes the same time to spread through the charge when the
-engine is running fast as when it is running slow. Therefore if the
-engine is speeded up, the spark must be advanced, for otherwise the
-piston would be on the power stroke before the flame would have time to
-spread all through the mixture.
-
-When the engine is slowed down, the spark must have less advance, or
-must be _retarded_, for, if it were not, the charge would all be in
-flame, and exerting its full pressure, before the piston reached the
-end of its compression stroke.
-
-The subject of ignition, which is of great importance, is covered more
-fully in Chapter VI.
-
-=Power Stroke.=—During the power stroke (No. 3, Fig. 1) the piston
-moves outward, and both valves are closed. As it begins, the mixture is
-all on fire, and great pressure is exerted against the piston.
-
-As the piston moves outward the combustion space becomes larger, and
-the gases obtain the room for expansion that they seek. As they expand,
-the pressure that they exert becomes less. By the time the piston
-is three quarters the way down the power stroke, the pressure is so
-reduced that it has little or no effect; the gases are still trying to
-expand, however, so the exhaust valve is opened at that point, and they
-begin to escape.
-
-=Exhaust Stroke.=—During the exhaust stroke (No. 4, Fig. 1) the piston
-moves inward and the exhaust valve is open. This movement of the piston
-pushes the burned gases out of the cylinder, and it is clear that the
-more thoroughly the cylinder is emptied of them, the more room there
-will be for a fresh charge.
-
-In high-speed engines the gases cannot escape as fast as the piston
-moves; they are still flowing out when the end of the stroke is
-reached. Therefore the valve is closed, not at the end of the stroke,
-but when the piston has moved about ⅛ inch outward on the inlet stroke.
-The inlet valve opens as the exhaust valve closes.
-
-It can be seen that through the inlet and compression strokes a leak
-will reduce the charge and so interfere with the production of full
-power. The piston must make a tight fit in the cylinder, the valves
-must seat tightly, and gaskets and other parts must be in proper
-condition.
-
-[Illustration: FIG. 2.—1-CYLINDER POWER DIAGRAM]
-
-Figure 2 shows a power diagram for a 1-cylinder engine, in which the
-crank shaft moves under power during one stroke out of every four. An
-engine with two cylinders can be built so that first one cylinder
-applies power and then the other, in which case the crank shaft moves
-under power during two strokes out of every four.
-
-[Illustration: FIG. 3.—2-CYLINDER POWER DIAGRAM]
-
-Figure 3 is a power diagram of an engine of this sort. If piston 1 is
-moving down under power, piston 2 is also moving down, but on the inlet
-stroke. The following stroke is exhaust in cylinder 1 and compression
-in cylinder 2, and cylinder 2 will then deliver a power stroke while
-cylinder 1 is on inlet. Thus the crank shaft will receive a power
-stroke, followed by a dead stroke; then another power stroke and
-another dead stroke, and so on.
-
-There will be the disadvantage, however, that the pistons, moving up
-and down together, will cause vibration, which in the course of time
-will be likely to give trouble. To overcome this, a 2-cylinder engine
-can be built as indicated in Figure 4.
-
-In this engine the cranks project on opposite sides of the crank shaft
-instead of on the same side, as in Figure 3; the pistons thus move in
-opposite directions, and produce no vibration. Power will be unevenly
-applied, however, for both power strokes occur in one revolution, with
-two dead strokes in the succeeding revolution.
-
-[Illustration]
-
-[Illustration: FIG. 4.—2-CYLINDER POWER DIAGRAM, 180 SHAFT]
-
-With piston 1 moving down on power, piston 2, moving upward, can only
-be performing compression or exhaust. If it is on compression, its
-power stroke will follow the power stroke of piston 1, while if it is
-on exhaust its power stroke will have occurred immediately before the
-power stroke of piston 1. In either case one power stroke follows the
-other, taking place in one revolution of the crank shaft, while in the
-following revolution both pistons will be performing dead strokes.
-
-While there is no vibration from the movement of the pistons in this
-engine, the uneven production of power will produce vibration of
-another kind.
-
-These two types may be built with the cylinders standing up or lying
-down; that is, they may be either _vertical engines_ or _horizontal
-engines_. The _double opposed_ engine, which is built only in horizontal
-form, is free from either kind of vibration, but has the disadvantage
-of occupying more room than the others. The cylinders, instead of being
-side by side, and on the same side of the crank shaft, are placed end
-to end, with the crank shaft between them, as shown in Figure 5.
-
-The pistons make their inward and outward strokes together, but in so
-doing they move in opposite directions. Thus every power stroke is
-followed by a dead stroke, as in the engine shown in Figure 3, while
-the movement of one piston balances that of the other, as is the case
-with the engine shown in Figure 4.
-
-[Illustration: FIG. 5.—H. D. O. POWER DIAGRAM]
-
-[Illustration]
-
-[Illustration: FIG. 6.—4-CYLINDER POWER DIAGRAM]
-
-In a 4-cylinder engine one power stroke follows another without any
-dead stroke intervals, which, of course, makes the crank shaft revolve
-more smoothly and with a steadier application of power. The power
-diagram is shown in Figure 6; in studying this it should be remembered
-that if two pistons move in opposite directions, as in Figure 4,
-one power stroke follows another, while if they move in the same
-direction, as in Figure 3, there is an interval of one stroke between
-their power strokes.
-
-The crank shaft of a 4-cylinder engine is so made that the middle
-pistons move in the same direction, and opposite to the end pistons.
-This construction has been found to make a smoother running engine than
-if pistons 1 and 3 moved one way while pistons 2 and 4 moved the other.
-
-If piston 1 is on the power stroke, either piston 2 or piston 3 can
-follow, for they are moving in the opposite direction. If we say that
-piston 2 is the next, then piston 4 must be the third to give a power
-stroke, for it is the only one left that is moving in the opposite
-direction to piston 2. Piston 3 is thus the fourth to move under power,
-and it is followed by another power stroke by piston 1; the _firing
-order_ is then said to be 1, 2, 4, 3.
-
-If it is piston 3 that follows piston 1, piston 4 will again be the
-third to produce power, and piston 2 will be the fourth. The firing
-order will then be 1, 3, 4, 2. There is no other order in which a
-4-cylinder engine can produce power, and there is no choice between
-them.
-
-The firing order of an engine is established by the manufacturer, and
-depends on the order in which the valves are operated.
-
-
-
-
-CHAPTER III
-
-ENGINE PARTS
-
-
-The foundation of an engine is the _base_, which supports the
-_bearings_ in which the crank shaft revolves, and to which the
-cylinders are attached. The cylinders of tractor engines are made
-of cast-iron, and the cylinder heads, which close the upper ends of
-the cylinders, are usually in a separate piece, bolted on. The joint
-between the cylinders and the cylinder head is made tight by placing
-between them a _gasket_ of asbestos and thin sheet metal.
-
-The crank shaft has as many cranks, or _throws_, as the engine has
-cylinders. Crank shafts for 2-cylinder engines are shown in Figure 7;
-the upper one is for an engine of the type shown in Figure 3, with
-pistons moving in the same direction. With both cranks projecting from
-one side the shaft is out of balance, so _balance weights_ are attached
-to the opposite side.
-
-[Illustration: FIG. 7.—2-CYLINDER CRANK SHAFT]
-
-The other shaft shown in Figure 7 does not need balance weights, for
-one crank balances the other. A four-cylinder crank shaft, Figure 8, is
-also in balance.
-
-[Illustration: FIG. 8.—4-CYLINDER CRANK SHAFT]
-
-[Illustration: FIG. 9.—HALF OF A PLAIN BEARING]
-
-Crank shafts revolve in _main bearings_, which are set in the engine
-base. In tractor engines these are usually _plain bearings_, a half of
-such a bearing being shown in Figure 9. This is a bronze shell lined
-with a softer metal, making an exact fit on the shaft; with the two
-halves in place, the shaft should turn freely, but without looseness or
-side play. The grooves shown are to admit lubricating oil.
-
-[Illustration: FIG. 10.—CONNECTING ROD BEARINGS]
-
-[Illustration: FIG. 11.—PISTON COMPLETE AND IN SECTION]
-
-The _piston_ is attached to the crank shaft by a _connecting rod_,
-which is illustrated in Figure 10. Pistons are shown in Figures 11 and
-12; they are made as light as is consistent with the pressure that they
-must bear, and are hollow, and open at the lower end.
-
-The piston is attached to the connecting rod by a _wrist pin_, or
-_piston pin_, which is a shaft passing through it from side to side,
-and also through the bearing in the upper end of the connecting rod.
-The connecting rod swings on the wrist pin in following the rotation of
-the crank shaft, and its attachment to the wrist pin must permit this
-without being loose.
-
-The bearings at the two ends of a connecting rod are usually
-adjustable, so that wear can be taken up; some of the methods of
-doing this are illustrated in Figure 10. In A, the wrist pin bearing
-is a plain tube, ground to an exact fit; when it is worn it must be
-replaced. In B, the bearing is split, and the ends are drawn together
-by a bolt to the correct fit. The bearing in C is in two parts, held
-together by a U-shaped bolt, while in D the two parts are held together
-by a cap bolted to the end of the connecting rod. In E, the end of the
-connecting rod is a square loop enclosing the two parts of the bearing;
-the parts are held in the proper position by a wedge adjusted by screws.
-
-The crank shaft bearing of the connecting rod shown in F is in two
-parts which are hinged together. G, H, and K show the forms usually
-used in tractor engines, which consist of two parts bolted together.
-
-[Illustration: FIG. 12.—WRIST PIN FASTENINGS]
-
-The wrist pin is usually firmly attached to the piston, so that the
-connecting rod swings on it; methods of securing the wrist pin are
-shown in Figure 12, the wrist pin being held in supports cast in the
-piston. In A, the wrist pin is held by two set screws, and in B, by
-pins passing through it. The wrist pin shown in D is hollow, as is very
-common, and a bolt passes through part of the piston and into the wrist
-pin.
-
-In the construction shown in C the wrist pin is secured to the
-connecting rod and moves in bearings in the piston. In E, a ring
-fitting in a groove around the piston prevents the wrist pin from
-moving endways.
-
-The engine must usually be taken to pieces in order to get at the wrist
-pin; lock nuts, lock washers or cotter pins are always used to prevent
-the trouble that would be caused if the wrist pin worked loose.
-
-A leak-proof joint between the piston and the cylinder is made by means
-of _piston rings_ that fit in grooves around the piston, as shown in
-E, Figure 12. Piston ring grooves are shown in Figure 11. Piston rings
-are not solid, but are split so that they are elastic; they fit snugly
-in their grooves, and tend to spring open to a greater size than
-the cylinder. This causes them to maintain a close fit against the
-cylinder, and the gases are prevented from leaking past.
-
-[Illustration: FIG. 13.—VALVE]
-
-Each cylinder is provided with two valves: the _inlet valve_ that
-admits fresh mixture and the _exhaust valve_ through which the burned
-gases escape. These valves are metal disks with funnel-shaped edges
-fitting into funnel holes. A valve and its stem are shown in Figure 13
-and also in Figure 15.
-
-[Illustration: FIG. 14.—ACTION OF A CAM]
-
-A valve is opened at the proper time by a _cam_, and closed by a
-spring. A cam is a wheel with a bulge on one side, so that its rim is
-eccentric to its shaft, as illustrated in Figure 14, which shows a cam
-in three positions of a revolution. A rod resting on the rim of the
-cam is moved endways as the bulge passes under it, and the valve is
-operated by connecting it with the rod.
-
-A valve is opened once during two revolutions of the crank shaft;
-therefore the cam cannot be placed on the crank shaft, for, if it
-were, the valve would be opened every revolution. The cam is placed on
-a separate shaft which is driven by the crank shaft at half its speed.
-This is usually done with gears, a gear on the crank shaft meshing with
-a gear on the cam shaft having twice as many teeth; the crank shaft
-gear must make two revolutions in turning the cam shaft gear once.
-
-The valve in Figure 13 is held on its seat by a spring. The cam bears
-against the end of the valve stem, and as it revolves its bulge forces
-the valve stem and valve to move endways and thus to uncover the valve
-opening.
-
-As the movement of the piston depends on the crank shaft, the valve can
-be made to open at the right time by a proper setting of the gears that
-drive the cam shaft.
-
-The length of time that the cam will hold the valve open depends on
-the shape of the bulge of the cam. It can be seen that the pointed cam
-of Figure 13 will not hold the valve open for as long a time as the
-flat-end cam of Figure 14.
-
-[Illustration: FIG. 15.—“TWIN CITY” TRACTOR ENGINE]
-
-In the design shown in Figure 13 the cam bears directly against the
-end of the valve stem, the cam shaft in this case lying along the
-cylinder head. In the construction shown in Figure 15 the valves are
-not placed in the cylinder head, but are in an extension or _valve
-pocket_ projecting from the combustion chamber; this cam shaft is near
-the crank shaft. It would not be practicable to make the valve stem
-long enough to reach down to the cam, so a length of rod, called a
-_push rod_, or _tappet_, is placed between them; the cam moves the push
-rod and the push rod in turn moves the valve. This is a construction
-frequently used for automobile engines.
-
-[Illustration: FIG. 16.—“HART-PARR” VALVE MECHANISM]
-
-In tractor engines the cam shaft is usually placed near the crank
-shaft, as in Figure 15, and the valves are in the head, so that a valve
-moves in the opposite direction to the movement of the push rod. This
-requires still another part to be used, called the _rocker arm_. It is
-shown in Figure 16. It is a short bar, pivoted at or near the center,
-with one end at the push rod and the other at the valve stem. When it
-is moved by the push rod it in turn moves the valve.
-
-Valves operated by push rods and rocker arms are also shown in Figures
-17, 18 and 19; Figure 18 is a single-cylinder horizontal engine, while
-Figure 19 is a horizontal double opposed engine, in which one cam
-operates a valve in each cylinder. Figure 20 shows the valve mechanism
-of a vertical engine in which all parts, including the rocker arm, are
-enclosed to protect them from dust, and so they can run in oil.
-
-A small space is always left somewhere between the cam and the valve
-stem, to give the valve stem room to lengthen, which it will do when it
-gets hot. If this space were not left, the valve stem, in lengthening
-as it became hot, would strike the part next to it, and the valve would
-be lifted from its seat. This would cause the engine to lose power.
-This space must be kept properly adjusted, and instructions for this
-will be found in Chapter XII.
-
-[Illustration: FIG. 17.—“HART-PARR” ENGINE]
-
-A valve is held against its seat by a spring, which must be compressed
-when the valve is opened. If this spring is too weak, it will not hold
-the valve tightly on its seat, while if it is too stiff, the cam shaft
-and other parts will be needlessly strained in compressing it.
-
-Friction between the cam and the end of the valve stem or push rod
-would cause rapid wear if these parts were not of hardened steel, and
-kept well oiled. Still further to reduce wear, there is usually a
-roller on the end of the push rod, as shown in Figure 16 and some of
-the other illustrations. Figure 15 shows a construction in which the
-end of the push rod is a flat disk, which rotates as the cam comes into
-contact with it.
-
-[Illustration: FIG. 18.—“OIL-PULL” ENGINE]
-
-When the mixture burns, the top of the piston, the cylinder head, and
-the walls of the combustion chamber become heated, and if it is not
-prevented they will get so hot that they will expand sufficiently to
-cause the piston to stick, or _seize_. The upper part of the cylinder
-is, therefore, provided with a cooling system that keeps these parts
-from getting overheated. Channels are provided through which water is
-circulated; the water takes the heat from the metal parts, becoming
-heated itself, and then passes to a _cooler_, or _radiator_, where it
-gives up the heat to currents of air.
-
-In addition to the channels, or _water jackets_, around the cylinder,
-a cooling system includes the radiator, the connections, and usually a
-pump that keeps the water in motion.
-
-[Illustration: FIG. 19.—HORIZONTAL DOUBLE OPPOSED ENGINE]
-
-In some tractors, notably the Fordson, no pump is used; the water
-circulates because it is heated. This is called a _thermo-syphon_
-system. When the engine runs, the water in the cylinder jackets becomes
-heated; as hot water is lighter than cold water, it rises and flows out
-of the jackets to the radiator, its place being taken by cool water
-from the bottom of the radiator. This circulation continues as long as
-the water in one part of the system is hotter than the water in some
-other part of the system.
-
-The lubrication of an engine is described and explained in Chapter X.
-
-[Illustration: FIG. 20.—“MONARCH” ENGINE]
-
-
-
-
-CHAPTER IV
-
-FUELS AND CARBURETION
-
-
-In order that a thing may burn, it must be provided with oxygen. Oxygen
-is found in air, so it is usual to say that air is necessary in order
-that anything may burn.
-
-To prove this, light a candle and place an empty bottle over it, upside
-down; in a very short time the oxygen in the bottle will be used up,
-and the flame will flicker and get smoky, and finally die out. If a
-card is laid on the chimney of a coal-oil lamp so that it covers the
-opening, that flame also will flicker, get smoky and go out.
-
-In order to deaden the fire in a stove, the dampers are closed to
-prevent air from entering; the fire is kept alight by the very small
-quantity of air that leaks in below the fire-box. When the drafts are
-opened the fire will burn up brightly because a plentiful volume of air
-can then enter.
-
-In a similar way, air must be used in a gas engine in order that the
-fuel may burn. It is not possible to mix air with a liquid; the first
-step in making a gas that will burn is, therefore, to turn the fuel,
-whether it is gasoline, kerosene, distillate, or other oil, into a
-vapor; this vapor is then mixed with air.
-
-For good results it is very necessary that the vapor and air be in
-proper proportions. In the experiment with the candle and the bottle it
-was seen that as the air was used up, the candle flame became yellow
-and smoky: this is the effect of insufficient air. If there is not
-enough air in the mixture, part of the vapor will not be able to burn,
-and will only smoke.
-
-If, on the other hand, there is too much air, the mixture, if it will
-burn at all, will burn slowly, and the extra volume of air will reduce
-the heat.
-
-In a mixture of the proper proportions of air and fuel vapor, the
-burning, or _combustion_, will be very rapid, resulting in the sudden
-production of the greatest possible amount of heat. This, of course, is
-what is necessary if the engine is to produce its fullest power. With
-such a mixture, combustion will be complete before the piston has done
-more than start outward on the power stroke, and the greatest possible,
-or _maximum_, pressure will then be produced.
-
-When a mixture burns slowly, the piston will have gone through much
-of the power stroke before combustion is complete, in which case a
-considerable part of the pressure that should have been applied at the
-beginning of the stroke will be wasted.
-
-A mixture that is not correct will burn unevenly; it may burn better
-during one power stroke than during another, which will make the engine
-run unsteadily.
-
-If the mixture has too much air in proportion to the amount of vapor,
-it is known as a _thin_ mixture, or a _lean_ or _poor_ mixture. It
-burns so slowly that it is quite possible for the mixture that started
-burning before the beginning of the power stroke to continue burning
-through the exhaust stroke, and for enough flame to remain in the
-cylinder to set fire to the fresh charge that enters during the next
-inlet stroke. This will produce what is known as a _backfire_; that is,
-the mixture entering the cylinder will catch fire, and in burning will
-blow back through the open inlet valve. This is a dangerous condition,
-for the flame might spread to fuel dripping from the carburetor, or to
-the fuel tank.
-
-A mixture that has not enough air is called a _rich_ mixture; the air
-that is present will burn part of the vapor, while the rest will go out
-of the exhaust unburned, or will work past the piston into the oil in
-the crank case. This is wasteful of fuel.
-
-The most serious result of a rich mixture, however, is in the
-production of _carbon_, and the _carbonization_ of the engine. The
-flame of a rich mixture is smoky; the smoke of this flame, as is the
-case with smoke from all other sources, is composed of fine particles
-of carbon, or soot. These particles of carbon will deposit on all parts
-of the combustion space: on the top of the piston, on the valves, on
-the spark plugs, and on the inner wall of the cylinder head. At first
-it is gummy, but it rapidly hardens and forms a crust that must be
-scraped off with a steel tool.
-
-Carbon in an engine will reduce the power through causing
-_preignition_, or, in other words, by setting fire to the fresh charge
-before the proper point in the stroke. The heat of the combustion will
-cause the carbon deposit to become so heated that it will glow, these
-glowing particles being sufficient to ignite the incoming fresh charge.
-The remedy for this condition is to remove the carbon, which is usually
-done by taking off the cylinder head and scraping away the deposit.
-
-It may be added that carbon is also formed by the use of too much
-lubricating oil, as will be explained in the chapter on lubrication.
-
-Thus it is seen that if the engine is to run properly, and is to be
-kept in good condition, the proportions of the mixture must be very
-carefully maintained.
-
-The mixture is formed in a _carburetor_, or _mixer_. This is, roughly,
-in the form of a tube through which air is sucked during the inlet
-stroke; projecting into it is a fine tube called a _spray nozzle_
-through which the fuel enters. In action it is somewhat similar to the
-atomizer that is used for spraying the nose and throat. By forcing the
-fuel to flow rapidly through this small tube it comes out in the form
-of spray, and the tiny drops are picked up by the current of air and
-are carried into the cylinder.
-
-It is much easier to form a mixture of gasoline than of kerosene or
-distillate, because gasoline vaporizes more readily at ordinary
-temperatures. If saucers of gasoline and kerosene are placed in the
-sun, the gasoline will evaporate rapidly and completely, leaving only
-a faint oily deposit. The kerosene, on the other hand, will evaporate
-slowly, and much of it will not evaporate at all.
-
-To make kerosene and distillate evaporate completely, they must be
-heated, just as water must be heated to make it evaporate.
-
-In the case of a carburetor for gasoline, the current of air needs
-only to be warmed; the spray of gasoline will evaporate on coming into
-contact with the warmed air, and much of it will enter the cylinder as
-vapor. In order to evaporate kerosene and distillate much more heat
-must be provided, and it is usually considered necessary to heat not
-only the current of air, but the liquid fuel as well. Methods of doing
-this will be explained in the next chapter.
-
-[Illustration]
-
-[Illustration: FIG. 21.—PRINCIPLE OF CARBURETOR]
-
-When kerosene or distillate is used, there are conditions that make
-it necessary to add water vapor to the mixture, which prevents the
-overheating of the cylinder and reduces the deposit of carbon. The
-difficulty of making a complete vapor of kerosene and distillate
-results in a tendency on the part of these fuels to carbonize the
-cylinders; the use of water aids in keeping the cylinders clean.
-
-The general principle of a carburetor is shown in Figure 21, one
-drawing illustrating conditions when the inlet valve is closed and the
-other when it is open. It shows an engine cylinder connected with an
-inlet pipe or _mixing chamber_, through which there is a swift flow of
-air during an inlet stroke.
-
-Projecting into the intake pipe is the _spray nozzle_, which is
-connected with a small chamber containing fuel; inside of this chamber
-is a _float_, usually made of cork, although it is sometimes a light
-metal box. The fuel is intended to fill the chamber to a certain
-height, at which the valve will be closed by the float rising on the
-fuel. This level is such that the fuel does not quite reach the tip of
-the spray nozzle.
-
-During the compression, power, and exhaust strokes, the fuel stands at
-this level, for it cannot run out of the spray nozzle, and the float
-holds the valve closed. As soon as the inlet valve opens, air rushes
-through the intake pipe and sucks fuel out of the spray nozzle. This,
-of course, takes fuel out of the float chamber; the float in sinking
-opens the valve, and enough fuel enters to restore the level.
-
-The fuel comes out of the nozzle in the form of fine spray; it is in
-such small drops that it evaporates quickly, and the resulting mixture
-of fuel vapor and air passes into the cylinder. By using a spray nozzle
-of the proper size, any desired proportion of fuel and air may be
-obtained.
-
-If an engine runs at a single speed, a carburetor as simple as this one
-would be satisfactory, for if the suction is always the same, there
-will be little or no change in the proportions of the mixture that is
-formed.
-
-To get the best results, the proportions of fuel vapor and air should
-be the same for all running speeds of the engine. The proportions of
-the mixture, however, depend on the violence of the suction, which
-changes as the engine speed changes, becoming greater as the speed
-increases. The simple carburetor illustrated in Figure 21 can be
-adjusted to give a correct mixture for any particular speed, but will
-be out of adjustment for any other speed.
-
-The speed of a 1-cylinder engine does not change very greatly; it is
-built to run at practically a constant speed, and a simple carburetor
-is satisfactory for it. The speed of engines with a greater number of
-cylinders may be greatly changed, and the carburetor must be so made
-that it will give the same proportions of vapor and air at low speed as
-at high.
-
-In the simple carburetor described, the speeding-up of the engine will
-result in a greater rush of air through the intake pipe, which in turn
-will suck out a much greater quantity of fuel. If the carburetor is
-adjusted to give the proper quantity of fuel for the air that passes
-at low speed, at high speed it will give far more fuel than will be
-required by the quantity of air that then passes. Thus at high speed
-the mixture will be too rich.
-
-If, on the other hand, this carburetor is adjusted to give a proper
-mixture at high speed, too little fuel will be sucked out when the
-engine runs slowly, and the mixture will be too lean.
-
-A carburetor must thus have an additional device that will keep the
-mixture correct, regardless of the speed at which the engine runs.
-This is sometimes done by changing the size of the spray nozzle so
-that a greater or less quantity of fuel flows out, but more usually
-by permitting an extra quantity of air to enter the carburetor as
-the engine speeds up. This is done with an _extra air intake_, the
-principle of which is illustrated in Figure 22.
-
-As will be seen, this carburetor has two openings for air, one being
-the main air inlet and the other the extra air inlet. The latter is an
-opening provided with a valve which is held on its seat by a spring.
-The suction created by an inlet stroke is exerted in the carburetor,
-but at low speed is not sufficient to suck the extra air valve from its
-seat. Air then enters only through the main air inlet, and the spray
-nozzle is adjusted to give the proper proportion of fuel.
-
-[Illustration: FIG. 22.—PRINCIPLE OF EXTRA AIR INLET]
-
-As the engine speed increases the mixture becomes richer; but there
-is also an increase in suction, which becomes strong enough to pull
-the extra air valve from its seat. This provides another opening into
-the carburetor, through which enough air enters to keep the mixture
-in proper proportion. The higher the speed of the engine the more the
-valve will open, and the greater will be the quantity of air admitted.
-
-In order to get the fullest power from an engine, the carburetor is
-built to give its most perfect mixture at the usual working speed.
-This will be the speed at which the engine will run under ordinary
-conditions. As the engine will run at this speed most of the time, the
-carburetor should then deliver its best mixture on the least possible
-quantity of fuel.
-
-As an engine is run at low speed so little of the time, it is not
-necessary that the mixture should then be so perfect or that the fuel
-should be used so economically.
-
-The design of a carburetor is a complicated matter, because the
-production of mixture is due to the flow of air, which is a very
-changeable thing. On a cold, damp day, the air will be heavier and
-denser than on a day that is hot and dry, and different quantities of
-fuel will be necessary for the formation of the mixture. The carburetor
-manufacturer cannot make a commercial carburetor that will take care
-of such a difference as this; he strikes an average that gives good
-general results, and expects the user to change the adjustments when
-weather and temperature make it necessary.
-
-The formation of the mixture is affected by the condition of the
-engine. When all of the parts of the engine are tight, the suction in
-the carburetor is more violent than when there is a leakage of air past
-the piston rings, or through a leaky valve or spark plug.
-
-On a dry, hot day the fuel evaporates much more readily than on a
-day that is cold and damp; more of the fuel that flows out of the
-spray nozzle will be vaporized and the formation of the mixture will
-be easier. On a cold, damp day the fuel will not vaporize in the
-carburetor to any extent, and much of it will pass to the cylinder in
-drops that even there will not vaporize in time to form a mixture.
-In order to assure the vaporization of enough fuel to form a mixture
-under such conditions, the fuel and the air must be heated to a greater
-degree.
-
-As the engine becomes heated up, more and more of the fuel will
-vaporize, and the amount flowing out of the spray nozzle may therefore
-be cut down.
-
-With fuels like kerosene and distillate, which do not vaporize as
-readily as gasoline, it is not unusual to have them condense on the
-walls of the inlet pipe, which produces a condition known as _loading_.
-This condensation is similar to the sweating of an ice-water pitcher
-on a hot day. If an engine is running at a constant speed, loading
-does not make much difference, because the carburetor is so adjusted
-that it gives a proper mixture. If the engine is suddenly speeded up,
-however, the greater rush of air will pick up the condensed fuel, and
-the mixture will instantly become too rich, continuing so until this
-extra supply of fuel is used up. The result will be to choke the engine
-and make it lose power just at the time when extra power is needed.
-
-Loading can be prevented by heating the inlet pipe to such an extent
-that the fuel will not condense on it.
-
-The speed of a tractor engine is practically always controlled by a
-_throttle_, which is a valve set in the passage of the carburetor.
-It operates exactly the same as a damper in a stovepipe; when it is
-closed, it shuts the passage and prevents the flow of mixture to the
-engine. As it is opened, it permits a greater quantity of mixture to
-flow, and it follows, of course, that as the charges of mixture become
-larger, the engine runs with more power. A tractor carburetor usually
-has two throttles, one being operated by hand and the other by the
-governor.
-
-It is usual for a carburetor to be fitted with a _strangler_, or
-_choke_, which makes it easier to form a mixture at slow starting
-speed. When an engine is cold, the fuel evaporates slowly; and,
-furthermore, when an engine is cranked by hand its speed is so low that
-the suction in the carburetor is not sufficient to draw out enough fuel
-to form a mixture. The strangler is a valve similar in every way to the
-throttle, but placed between the main air inlet and the spray nozzle.
-When it is closed and the engine is cranked, very little air can enter
-the carburetor; the suction is therefore very great. Far more fuel
-than usual is then sucked out of the spray nozzle, and of this greater
-amount enough reaches the cylinder to form a combustible mixture. The
-engine will start, but as soon as it does so, the strangler must be
-opened so that the normal amount of air enters. If this is not done,
-the excessive suction will draw so much fuel out of the spray nozzle
-that the mixture formed will be too rich to burn.
-
-
-
-
-CHAPTER V
-
-CARBURETORS
-
-
-The apparatus that forms the mixture is in two parts, one being the
-carburetor that proportions the fuel to the quantity of air drawn into
-the cylinder, and the other the _mixing chamber_, or _manifold_, that
-connects the carburetor with the valve chamber. The mixing chamber has
-no adjustments; it is a passage, often a pipe, that is shaped to fit
-the conditions, and according to the ideas of the manufacturer. When
-kerosene and distillate are used, the mixing chamber must be heated, so
-it is frequently built into the _exhaust manifold_, which is the pipe
-that conducts the burned gases away from the engine. In some cases it
-gets heat from the water jacket of the engine, a water jacket formed
-around it being connected with the cooling system.
-
-The carburetor, on the other hand, has adjustments that must be
-understood in order to run the engine economically. The understanding
-of these adjustments is simplified if it is remembered that the object
-of the carburetor is to maintain a correct proportion of fuel to the
-volume of air that passes through it.
-
-All tractor carburetors operate on the same principles, and the
-principles are applied in much the same way. If these principles are
-understood, and there is an understanding of what the parts of a
-carburetor are for and what they do, there should be no difficulty in
-adjusting and caring for any kind of a carburetor that may be offered.
-
-The main body of the carburetor is the tube through which the air
-passes. This is a casting, and cannot be adjusted or altered. Into this
-passage projects the spray nozzle, which is usually provided with an
-adjustment to control the amount of liquid that may flow out of it.
-When no adjustment is provided, the spray nozzle is made removable, so
-that a nozzle with an opening of any desired size may be inserted.
-
-[Illustration: FIG. 23.—“KINGSTON” CARBURETOR, MODEL L]
-
-On some carburetors the extra air valve is set by the manufacturers,
-while on others it is adjustable by controlling the strength of the
-spring that holds it against its seat.
-
-The carburetor shown in Figure 23 has a spray nozzle adjustment of a
-very usual type. A rod is so arranged that its pointed end projects
-into the opening of the spray nozzle; by screwing it up or down the
-opening may be made larger or smaller, so that more or less fuel may
-flow out. The extra air valve is a flap valve that closes the air
-passage until the suction is great enough to lift it from its seat.
-Around the spray nozzle is a tube that connects the passage below the
-extra air valve with the passage above it; when the suction is too low
-to lift the extra air valve from its seat, any air flowing through the
-carburetor passes through this tube. The tube is so small that even a
-little air passing through it is enough to suck fuel out of the spray
-nozzle, and the spray nozzle is so adjusted that enough fuel comes out
-to make a proper mixture with that volume of air.
-
-This is the _low-speed adjustment_, which gives a mixture on which the
-engine will start and will run at its lowest or _idling_ speed. At this
-speed the engine produces just enough power to keep itself going.
-
-When the engine speeds up, and suction increases, the extra air valve
-is lifted off its seat, and a greater volume of air flows through the
-carburetor. The increased suction also draws more fuel out of the spray
-nozzle. If the greater amount of fuel were in proportion to the greater
-volume of air, there would be no change in the mixture, but this is not
-the case. As suction increases, the proportion of fuel drawn out of the
-spray nozzle becomes too great for the air, and the mixture becomes too
-rich. To overcome this, the extra air valve permits a still greater
-volume of air to pass, so that the proportions of fuel and air do not
-change.
-
-The chamber below the air passage in Figure 22 is the fuel cup, into
-which fuel flows from the tank. Inside the fuel cup is a ring of cork
-attached to a pivoted lever, on the other end of which is a needle
-valve that can close the opening through which the fuel enters the cup.
-As the cup fills, the cork floats on it, and in rising it moves the
-lever on its pivot. When the fuel reaches such a level that it is near
-the tip of the spray nozzle, the valve closes the opening and prevents
-more fuel from entering.
-
-[Illustration: FIG. 24.—“KINGSTON” CARBURETOR, MODEL E]
-
-In the carburetor shown in Figure 24, the principal air passage is past
-the spray nozzle, and all air goes by this passage when the engine
-is running at low speed. The extra air inlet consists of a number of
-holes through which air can pass without going past the spray nozzle.
-On each of these holes is a ball; when the suction is low the balls
-completely close the holes. When speed increases, the suction becomes
-great enough to lift the balls off the holes, and the extra volume of
-air that is necessary is permitted to enter. By making the balls of
-different weights, it can be seen that the volume of air admitted for
-any speed is under good control.
-
-Like the carburetor shown in Figure 23, this carburetor is of the
-_float feed_ type; that is, the flow of fuel to it is controlled by a
-valve that is operated by a float.
-
-Either of these two carburetors may be adjusted for gasoline or for
-kerosene, but the adjustment that is right for one is wrong for the
-other. Thus, if an engine is started on gasoline, with the intention of
-running on kerosene, the carburetor must be readjusted when the change
-is made. This is unsatisfactory, so a double carburetor is sometimes
-used, as shown in Figure 25. This consists of two carburetors of the
-kind shown in Figure 24, having a single mixture outlet, one being
-adjusted for gasoline and the other for kerosene. Either of them can be
-connected with the mixture outlet by means of a switch valve.
-
-[Illustration: FIG. 25.—“KINGSTON” CARBURETOR, DUAL MODEL]
-
-In order to run on kerosene or distillate it is necessary to apply heat
-for the reason that these oils do not evaporate readily at ordinary
-temperatures. Gasoline, on the other hand, evaporates readily, and a
-cold engine can be started on it. Tractors that run on kerosene or
-distillate are therefore started on gasoline and run on it until they
-are hot enough to vaporize the heavier oil.
-
-A carburetor that will run on either gasoline or kerosene is shown in
-Figure 26. The main air inlet is at E, which leads the air around the
-spray nozzle and into the chamber G. The mixture flows to the cylinder
-by the passage B. The control of the fuel at working speeds is by the
-high-speed adjustment, which is a needle valve screwing into the spray
-nozzle. Above this is another needle valve that adjusts the flow of
-fuel for slow speed.
-
-Extra air enters through the opening A, which is closed at slow speed
-by a valve held against it by a spring. This valve bears against one
-end of a pivoted lever, the other end of which is attached to the
-slow-speed needle valve; when the extra air valve opens it moves the
-lever and the slow-speed needle valve is lifted to permit the flow of a
-greater volume of fuel from the spray nozzle.
-
-[Illustration: FIG. 26.—“E-B” CARBURETOR]
-
-This carburetor is started on gasoline. When the engine is hot, a
-switch valve is operated to permit the burned gases from the engine to
-flow through the carburetor; they pass through the pipe C, D, and as
-the chamber G is directly in their path it becomes intensely heated.
-The carburetor can then be switched to kerosene. A side view of this
-carburetor is shown in Figure 27.
-
-These carburetors are all of the float feed type, and are used on
-engines of which the speed is variable. A carburetor that is fed by a
-pump is shown in Figure 28. This is a simple tube with a fuel cup cast
-on one side of it. Fuel is pumped to the bowl, and the proper level is
-maintained by an overflow through which excess fuel passes back to the
-tank.
-
-This carburetor is intended for an engine of which the speed does not
-change greatly. Its only adjustment is the spray nozzle, and this is
-altered to correspond with changes in engine speed.
-
-[Illustration: FIG. 27.—“E-B” CARBURETOR, SIDE VIEW]
-
-[Illustration: FIG. 28.—PUMP-FED CARBURETOR]
-
-If an engine is clean and in good condition, it will run as well on
-kerosene as on gasoline, although the heating effect of kerosene is
-greater. When an engine is carbonized, as is usually the case, a
-condition known as _preignition_ will occur unless it is prevented.
-Carbon from unburned fuel or from lubricating oil will deposit on the
-piston head and the parts of the combustion chamber, and particles will
-become heated to the glowing point, when they will set fire to the
-fresh mixture during the compression stroke and before the proper time.
-The effect is to make the engine lose power, and it also gives rise to
-a sharp metallic knocking. By reducing the temperature in the cylinder
-during the compression stroke this condition can be prevented. This can
-be done by adding water vapor to the mixture, and kerosene carburetors
-are therefore built with a water attachment. As can be seen in Figure
-28, this is a water cup and spray nozzle like those for the fuel. When
-the engine knocks, and shows that preignition is occurring, water is
-turned on, and, being carried into the cylinder, keeps the mixture from
-being heated to the point of ignition before the proper time.
-
-Figure 29 shows the attachment of this carburetor to an engine which,
-in this case, is horizontal. To start the engine, gasoline is injected
-into the carburetor, as shown; this will give a sufficiently good
-mixture for the purpose, and enough heat for running on kerosene is
-thus obtained.
-
-[Illustration: FIG. 29.—“TITAN” CARBURETOR]
-
-[Illustration: FIG. 30.—PUMP-FED CARBURETOR WITH TWO FUEL NOZZLES]
-
-The carburetor shown in Figure 30 is similar, but has a bowl and spray
-nozzle for gasoline, to use in starting. It is also provided with a
-heating jacket through which hot water or hot gases may circulate.
-
-In many cases the fuel is heated before reaching the carburetor. This
-is done by coiling the feed pipe around the exhaust pipe or putting it
-in a jacket through which hot water circulates.
-
-Another device sends the mixture through a chamber heated by the
-exhaust, as shown in Figure 31. Figure 32 shows an arrangement in which
-the mixture passes through a jacket around one branch of the exhaust
-pipe. By means of a switch valve, A, more or less of the exhaust gases
-may be permitted to flow through this branch, so that the mixture may
-be heated to any desired degree.
-
-[Illustration]
-
-[Illustration: FIG. 31.—“HART-PARR” MIXTURE HEATER]
-
-All of these heating devices are so arranged that the heat is under the
-control of the driver, which permits him to heat the mixture as much as
-he judges to be necessary. Enough heat must be used to prevent the fuel
-from condensing; but too much heat will cut down the efficiency of the
-engine because it will cause so much expansion of the mixture that a
-cylinderful of it will not produce the maximum power.
-
-[Illustration: FIG. 32.—“TWIN CITY” MANIFOLD]
-
-Figure 33 shows the pump that is used in a force feed carburetor of the
-type shown in Figure 28. Its plunger is forced through an inward stroke
-by a cam, and makes an outward stroke as its spring returns it to
-position. The inlet and outlet openings of the cylinder are closed by
-ball check valves, the inlet check being open on the outward strokes,
-and the outlet check being open on the inward strokes. A pump of this
-sort requires no attention beyond seeing that the check valves work
-properly, and that there are no leaks.
-
-Figure 34 shows the connections between the fuel tank and the
-carburetor. Under the tank, 1, is a chamber containing a fine wire
-strainer, 4, through which the fuel must pass to reach the carburetor;
-any dirt that may be present is strained out, and collects in the cup,
-2. Water in the fuel also settles here, and the cup is cleaned out by
-unscrewing the plug, 3. 5 is the shut-off cock; it should always be
-closed when the tractor is not working.
-
-[Illustration: FIG. 33.—FUEL PUMP]
-
-A complete fuel system is illustrated in Figure 35, showing the
-connections of the tanks, pumps, and carburetor.
-
-As dirt is injurious to an engine, the air that forms the mixture
-must be clean, so when a tractor works in a dusty field, it should be
-equipped with an air cleaner, of which there are three kinds. In one
-of these the air is required to pass through water, which washes it.
-A cleaner of this type is shown in Figure 36. The dusty air enters
-the central passage, and is forced to pass through the water in order
-to reach the outlet. Passage through the water and through the baffle
-plates frees the air of all its dust.
-
-In the cleaner shown in Figure 37, the air is passed through loose
-wool, which filters out the dust. Another type of cleaner works on
-the same principle as a cream separator; the air is given a whirling
-motion, which throws the dirt out at the sides, and it is collected in
-a glass jar.
-
-[Illustration: FIG. 34.—“AVERY” FUEL CONNECTIONS]
-
-[Illustration: FIG. 35.—“OIL-PULL” FUEL SYSTEM]
-
-These air cleaners must be emptied frequently, for if they are not kept
-clean it cannot be expected that they will do their work.
-
-A tractor engine is built to develop its maximum power at a certain
-speed; if it runs at greater speed, it will not operate efficiently,
-and there will be unnecessary wear of its parts. These engines are
-therefore usually fitted with _governors_ which hold them at their most
-efficient speed. A governor operates by _centrifugal force_.
-
-Anything in motion tries to move in a straight line; if it is forced to
-move in a circle, it will exert force in trying to move away from its
-center. It is this that is called centrifugal force. It is centrifugal
-force that holds water in a pail that is being swung around the head,
-and that makes the pail fly off if it is released.
-
-[Illustration: FIG. 36.—AIR WASHER]
-
-In applying this principle to a governor, weights are attached to a
-plate and made to revolve; springs hold them together, but in spite
-of this, centrifugal force throws them outward. In moving, they act
-on a rod that operates the throttle; as the speed increases, the move
-outward more and more, and it is a simple matter of adjustment to cause
-them to close the throttle when the speed reaches a desired point.
-
-[Illustration: FIG. 37.—AIR STRAINER]
-
-[Illustration: FIG. 38.—“E-B” GOVERNOR]
-
-A governor and its connections are shown in Figure 38. The weights,
-R, are L-shaped, and pivoted at the angle to a plate driven by the
-engine. The shaft that drives the plate also supports a collar, P, that
-is loose on it and can slide endways; the collar rests against the
-short bar of the L-shaped weights. The other end of the collar touches
-the lever, E, which is moved when the collar moves. As the lever is
-connected with the throttle, a movement of the collar will control the
-position of the throttle.
-
-[Illustration: FIG. 39.—“CASE” GOVERNOR]
-
-When the shaft revolves, the long arms of the L-shaped weights tend
-to fly outward; this moves them on their pivots, and the short arms
-thereupon force the collar to slide on the shaft, which moves the lever
-and operates the throttle. The speed at which the throttle will begin
-to close is determined by the setting of the spring that holds the
-weights in.
-
-[Illustration: FIG. 40.—“HART-PARR” GOVERNOR]
-
-Governors and governor connections are shown in Figures 39 and 40.
-
-The governor shown in Figure 41 is enclosed in a housing that can
-be locked or sealed. This prevents the unauthorized changing of the
-adjustment.
-
-[Illustration: FIG. 41.—VERTICAL GOVERNOR]
-
-
-
-
-CHAPTER VI
-
-IGNITION
-
-
-In order that a gas engine may run properly, the mixture must be set on
-fire, or _ignited_, at exactly the right time; if ignition occurs too
-early or too late, there will be a loss of power.
-
-The greatest pressure will be obtained at the instant when all of the
-mixture is burning, and this should take place just as the piston
-begins to move outward on the power stroke. A little time is required
-for the mixture to burn; there is a brief interval between the instant
-when it is set on fire and the instant when it is all in flame. Thus it
-is clear that if the mixture is all to be burning as the piston starts
-the power stroke, it must be set on fire before that time, or, in
-other words, toward the end of the compression stroke.
-
-The point at which ignition should occur depends on the speed of the
-engine and should change when the speed changes. The time required
-for the flame to spread throughout the mixture does not change; let
-us say that, with the engine running at 1200 revolutions a minute,
-the mixture can be ignited when the piston is ¼ inch from the end
-of the compression stroke, and will all be in flame by the time the
-piston starts on the power stroke. If the engine is slowed down to
-600 revolutions a minute and no change is made in the ignition, the
-mixture will all be in flame before the piston reaches the end of the
-compression stroke; pressure will then be produced before the piston
-is in position to perform the power stroke. The pressure will try to
-make the engine run backwards; it will sometimes be sufficient to make
-the engine stop. If the momentum of the flywheel is sufficient to
-force the piston to the end of the stroke against the pressure, this
-condition will cause a loss of power. This is called _preignition_, or
-ignition that occurs too soon. One effect of it is to produce a hard,
-metallic knocking, due to the oil being squeezed out of the bearings by
-the great pressure, which permits the bearing and shaft to strike. The
-remedy is to make ignition occur later in the stroke.
-
-If the engine is speeded up above 1200 revolutions, the piston will
-have had time to move some distance on the power stroke before the
-mixture is all in flame; the combustion space will then be too large to
-permit the mixture to produce its greatest pressure, and again there
-will be a loss of power. The remedy in this case is to make ignition
-occur earlier in the compression stroke.
-
-When ignition is made to occur early in the compression stroke, it is
-said to be _advanced_; when it is made to occur late in the stroke, it
-is said to be _retarded_.
-
-To get the best results, the engine should be run with ignition
-advanced as far as is possible without causing knocking.
-
-The charge of mixture is always set on fire by an electric spark, and
-the parts that produce and control this spark are called the _ignition
-system_.
-
-An ignition system consists of: First, the apparatus that produces the
-electric current, which is usually a _magneto_; second, a _timer_,
-which controls the instant at which the spark occurs; third, the _spark
-plugs_, which project into the cylinders, and at which the sparks take
-place; fourth, a _switch_, by which the sparking current can be turned
-on or off, and fifth, the wires, or _cables_, by which the parts are
-connected.
-
-The electric current that gives the spark is always produced by
-magnetism. In a magneto, magnetism is obtained from the heavy steel
-magnets that are part of it; there is a constant flow of magnetism from
-one end of these to the other. To obtain an electric current, a coil
-of wire is placed in the magnetism, and the strength of the magnetism
-is made to change; it alternately becomes weak and strong. Whenever a
-change in strength takes place, an electric current flows in the wire,
-and it continues to flow as long as the magnetism continues to change
-in strength. When the change in strength is very great, that is, when
-the magnetism changes from very weak to very strong, or from very
-strong to very weak, the electric current is more powerful than when
-there is only a little change in strength. A more powerful current is
-also produced by a change that takes place suddenly than by a change
-that takes place slowly.
-
-The electrical principle that produces a current in this manner is
-called _induction_; the current produced is known as an _induced_
-current.
-
-A magneto has two or more magnets, and between their ends, or _poles_,
-there revolves a piece of iron called the _armature_. A piece of iron
-placed between the poles of a magnet becomes a magnet itself; the
-armature is so shaped that, as it revolves, its magnetism continually
-changes in strength, and it is the changes in the strength of the
-magnetism of the armature that produce the sparking current.
-
-[Illustration: FIG. 42.—ARMATURE]
-
-The iron armature of the Bosch magneto, which is the best known type,
-is shown in Figure 42. It has a central bar with two heads, the wire
-being wound around the central bar, or _core_. The shafts on which it
-revolves are attached to the ends of the heads.
-
-Figure 43 shows different positions of the armature between the poles
-of the magnet, and illustrates the changes in the magnetism of the
-central bar. There is a continual flow of magnetism from one pole of a
-magnet to the other; if a piece of iron lies between them the magnetism
-will use it as a bridge, but often its easiest path will be through the
-air. In A, Figure 43, the armature lies crossways, and its central bar
-or core forms a perfect bridge for the magnetism. Practically all of
-the magnetism flows through it, and it then becomes a powerful magnet
-itself. It sets up its own flow of magnetism, which flows through the
-core to one head, through the air to the other head, and so back to the
-core.
-
-[Illustration: FIG. 43.—FLOW OF MAGNETISM THROUGH ARMATURE CORE]
-
-In B, the armature has revolved a little. Most of the magnetism is
-still flowing through the core, but some of it is finding an easier
-path by flowing through the heads and across the air space to the other
-pole. The magnetism of the core is, therefore, a little weaker than it
-is in A.
-
-In C, the heads alone form bridges between the poles, and none of the
-magnetism flows by the core because that no longer forms a path. The
-core is no longer producing magnetism; in moving from A to C there has
-thus been a complete change in the strength of the magnetism of the
-core, for from full strength it has died away to nothing.
-
-By a further movement, as in D, the core again acts as a bridge, and
-another change in strength occurs, this time from nothing to full
-strength again. In moving from D to B, there are slight changes in
-strength, but not enough to produce a sparking current; it is only in
-passing from B to D that a sparking current can be produced.
-
-In this type of magneto the space between the heads is wound full of
-wire, which of course revolves with the armature; the more turns of
-wire there are, the more intense will be the current, so very fine wire
-is used to get the greatest possible number of turns.
-
-In the Bosch magneto the first few layers are of coarse wire, and are
-the _primary winding_. The remainder, called the _secondary winding_,
-is very fine wire, and the two are connected so that one forms an
-extension of the other.
-
-It has been explained that it is most important to have the spark occur
-at exactly the right instant in the stroke. On a magneto the instant of
-sparking is controlled by a _timer_, or _circuit breaker_, which is a
-switch that is automatically operated at the time when the magneto is
-producing a current sufficiently intense to form a spark.
-
-Figure 44 illustrates one complete revolution of the armature, and
-it will be seen that it passes twice from position B to position
-D. This shows that it gives a sparking current twice during each
-revolution. The circuit breaker must therefore operate twice during
-each revolution. It is placed at the end of the magneto; in some makes
-it revolves with the armature and is operated by stationary cams, while
-in others it is stationary, and is operated by a cam on the armature
-shaft. In either case the effect is the same.
-
-[Illustration: FIG. 44.—ONE COMPLETE REVOLUTION OF THE ARMATURE]
-
-[Illustration: FIG. 45.—CONNECTIONS OF BOSCH MAGNETO]
-
-Figure 45 shows the way in which the winding on the armature of a Bosch
-magneto is connected with the circuit breaker and with the armature.
-The circuit breaker shown is not the kind used on the Bosch, and serves
-only to illustrate the principle. It consists of a lever pivoted at one
-end, with the other end resting against the tip of a screw. A cam bears
-against the lever and can move it to break the contact with the screw.
-The cam is so set that it moves the lever at the time when the current
-is most intense.
-
-The coarse wire, or primary winding, on the armature is connected with
-the lever and with the screw of the circuit breaker; when the lever is
-touching the screw, any current produced in the primary winding has a
-complete path, or _circuit_, in which to flow.
-
-The fine wire, or secondary winding, is wound on top of the primary,
-and its inmost end is connected to the outmost end of the primary
-so that one forms a continuation of the other. The outmost end of
-the secondary leads to the spark plug; any current produced in the
-secondary winding flows to the spark plug, and, if intense enough,
-will jump across the small gap in the plug, and return to the
-secondary by way of the primary.
-
-Referring to Figure 43, a weak current is produced in the primary while
-the armature revolves from D to B; at that time the circuit breaker is
-closed, so the current can flow in the path thus provided for it. A
-current also tries to flow in the secondary, but is too weak to jump
-across the gap in the spark plug. As the armature comes closer to the
-point C, Figure 43, the primary current becomes more intense, and the
-electricity in the secondary increases its endeavor to jump the gap in
-the spark plug, but is still unable to do so.
-
-As the armature passes over the point C, the circuit breaker opens.
-The primary current, which is then most intense, finds its path taken
-away from it, and it seeks another, which it finds by flowing into the
-secondary winding. This flow of primary current, added to the pressure
-already existing in the secondary, forms a current sufficiently
-intense to jump across the gap in the spark plug, and in so jumping it
-produces the ignition spark.
-
-As the armature passes to position D, Figure 43, the circuit breaker
-closes, and the action is repeated.
-
-[Illustration: FIG. 46.—“K-W” INDUCTOR]
-
-A magneto of this type is thus seen to give two sparks to every
-revolution of the armature.
-
-K-W and Dixie magnetos operate on the same general principle as the
-Bosch, with the difference that the wire windings are separate from
-the armature, and do not revolve. The revolving part, which is called
-an _inductor_, consists of blocks of iron, so shaped that, as they
-revolve, they alternately lead the magnetism to the core of the winding
-and then away from it. The result is that the core gains magnetism and
-then loses it, and these continual changes in strength produce sparking
-currents in the winding.
-
-The inductor of a K-W magneto is shown in Figure 46. It consists of
-a shaft on which are mounted two blocks of iron at right angles. The
-section of shaft that joins them is the core of the winding; the wire
-is wound on it just as thread is wound on a spool, but with a space
-between, so that the shaft may revolve inside of the coil.
-
-Figure 47 shows the inductor in three positions of its revolution
-between the poles of the magnet. When it is in the first position,
-magnetism can flow from one pole of the magnet to the other by going
-into one end, A, of one block, through the core, and out of one end,
-C, of the other block. This makes a magnet of the core and it forms
-magnetism of its own. When the inductor turns to the second position
-magnetism can get across without flowing through the core, for the
-blocks now give it a path. As the flow through the core ceases, the
-core’s magnetism dies away, which gives the change in strength that is
-needed to produce a sparking current.
-
-[Illustration: FIG. 47.—“K-W” INDUCTOR IN THREE POSITIONS]
-
-When the inductor is in the third position, the core again becomes the
-path for the magnetism and is magnetized; these changes continue as
-long as the inductor turns.
-
-[Illustration: FIG. 48.—“DIXIE” INDUCTOR]
-
-While an armature type of magneto, like the Bosch, produces two sparks
-to every revolution, the K-W produces four, for there are four periods
-during every revolution when there is sufficient change in the strength
-of the magnetism of the core to produce a sparking current.
-
-In these magnetos the revolving shaft is parallel to the ends of the
-magnets, but in the Dixie magneto it is at a right angle, as shown
-in Figure 48. The shaft is of some metal, such as brass or bronze,
-through which magnetism will not flow; otherwise the shaft would form a
-continuous path. The inductor blocks are mounted on the shaft, and act
-as extensions of the poles of the magnet. The core on which the wire is
-wound is a separate piece, placed under the arch of the magnets, with
-ends that extend down and form a tunnel in which the inductor revolves.
-
-Figure 49 shows an end view of the inductor, the magnets being cut
-away so that the core may be seen. As inductor block A is an extension
-of one pole of the magnet, magnetism tries to flow from it to block
-B, which is an extension of the other pole of the magnet. When the
-inductor is in position 1, Figure 49, magnetism can flow from block
-A through the core to block B, the core then being magnetized. In
-position 2, magnetism can flow from one block to the other by going
-through the ends of the core instead of through the core itself; the
-core then loses its magnetism, but regains it when the inductor moves
-to position 3.
-
-[Illustration: FIG. 49.—THREE POSITIONS OF “DIXIE” INDUCTOR]
-
-In practically all makes of magnetos the circuit breaker is at the
-end of the armature or inductor shaft, and is operated by it. The
-Bosch circuit breaker is illustrated in Figure 50, the parts being
-mounted on a plate attached to the shaft and revolving with it. The
-lever is L-shaped, pivoted at the angle, with one end resting on the
-tip of a screw. When the shaft revolves, the other end of the lever is
-dragged over a block of metal that acts as a cam; this makes it move
-on its pivot and separates it from the screw. By turning the screw the
-distance of separation may be adjusted.
-
-[Illustration: FIG. 50.—“BOSCH” CIRCUIT BREAKER]
-
-In the circuit breaker of the K-W magneto it is the cam that revolves,
-while the lever is stationary, as shown in Figure 51. It will be
-noticed that the cam will move the lever only twice during each
-revolution; the magneto can produce four sparks during a revolution,
-but with this arrangement of the cam only two of them are used.
-
-[Illustration: FIG. 51.—“K-W” CIRCUIT BREAKER]
-
-It has been said that an intense sparking current is produced when
-there is a great change in the strength of the magnetism, and when the
-change in strength occurs suddenly. There cannot be any alteration in
-the change in strength, for the greatest magnetic strength of the core
-is what is given it by the magnet, and changing from this to nothing
-is the greatest change possible. The suddenness with which the change
-takes place, however, depends on the speed at which the magneto runs. A
-4-cylinder engine requires two sparks to each revolution of the crank
-shaft; the armature of a Bosch magneto for this engine will therefore
-run at the same speed as the crank shaft.
-
-The K-W magneto, giving four sparks to the revolution, could run at
-half of the speed of the crank shaft, but then the change in the
-strength of the magnetism would take place slowly, and the sparking
-current would not be sufficiently intense. By using only two of the
-sparks the magneto is run at the same speed as the crank shaft; the
-change in strength then takes place more suddenly, and a more intense
-sparking current is produced.
-
-The circuit breaker of a magneto for a 1-cylinder engine has only one
-cam, so that a single spark is produced during each revolution of the
-armature; the armature makes one revolution to every two revolutions of
-the crank shaft.
-
-However many cylinders an engine may have, the magneto must be revolved
-from one point of sparking to the next in the interval between ignition
-in one cylinder and ignition in the next cylinder to fire. A magneto
-is driven by the crank shaft through gears or by a chain, which are so
-proportioned and set that the magneto is at a point of sparking at the
-instant when a piston is in position for ignition.
-
-A magneto for an engine with more than one cylinder is provided with
-a _distributor_, which passes the sparking current to the particular
-cylinder that is ready for ignition. A distributor is a revolving
-switch built into the magneto, with as many _points_, or _contacts_, as
-the engine has cylinders. At the instant when the magneto produces a
-sparking current, the revolving distributor arm is in position to pass
-the current to one of the contacts, and the current flows to the spark
-plug with which it is connected.
-
-An electric current must have a complete path, or circuit, in order
-to be able to flow. In a magneto ignition system this path is partly
-of wire and partly of the metal of the engine. The diagram in Figure
-45 indicates that the current returns to the magneto from the circuit
-breaker lever and the spark plug by wire, but in actual construction it
-returns by the metal of the engine. This is called a _ground return_;
-the circuit is said to be _grounded_.
-
-[Illustration: FIG. 52.—“BOSCH” MAGNETO IN SECTION]
-
-Figure 52 is a side view of a Bosch magneto, partly broken away to
-show the interior. As can be seen, one end of the primary winding is
-screwed to the armature, and is thereby connected with the metal of the
-magneto; as the magneto is attached to the engine the primary winding
-is thus in contact with that also. The other end of the primary winding
-leads to the insulated block of the circuit breaker, Figure 50. This
-block is _insulated_ from the disk; that is, while it is attached to
-the disk, it is kept from touching it by means of pieces of hard rubber
-or mica. Through these an electric current cannot pass.
-
-The lever is grounded; that is, it is in contact with the metal of
-the magneto. When the lever touches the screw of the insulated block,
-current can flow; when they are separated, the circuit is broken.
-
-One end of the secondary winding, Figure 52, is attached to the outer
-end of the primary. The other end leads to the _slip ring_, which is a
-metal rim on a hard rubber wheel attached to the armature and revolving
-with it. Sparking current flowing to the slip ring is led off by a
-carbon brush and passed to the distributor.
-
-Should a spark plug wire fall off while the engine is running, the
-current would lose its path and would seek another; it is quite
-powerful enough to make a path for itself by breaking through the
-windings. As this would injure the magneto, such a thing is prevented
-by providing a _safety spark gap_, which acts like a safety valve in
-giving the current a path when the regular path is interrupted. It
-consists of two points of metal, one attached to the metal of the
-magneto and the other connected with the slip ring brush; it is a more
-difficult path than the one through the spark plug, but easier than
-breaking down the windings.
-
-Figure 53 is a section of the K-W magneto. As the coil does not
-revolve, no slip ring is necessary; the sparking current flows directly
-to the distributor.
-
-[Illustration: FIG. 53.—“K-W” MAGNETO IN SECTION]
-
-To start an engine, the crank shaft must be turned at sufficient
-speed to drive the magneto fast enough to produce a spark. With large
-engines this is often a difficult matter, so it is very usual to equip
-a magneto with an _impulse starter_. One part of this is attached to
-the magneto shaft and the other to the engine shaft that drives the
-magneto; the two are connected by a spring. When starting, a catch
-holds the armature and prevents it from turning. The drive shaft
-turns, however, and in so doing winds up the spring. At a certain
-point the catch is automatically released, and the spring then throws
-the armature over at a speed that gives a good spark. A spark is thus
-assured, even though the engine is being cranked very slowly.
-
-
-
-
-CHAPTER VII
-
-BATTERY IGNITION SYSTEMS
-
-
-While the greater number of tractor engines use magneto ignition, many
-use battery and coil systems, which are the same in general principle
-as magneto systems, but produce magnetism in a different manner.
-
-Copper is a _nonmagnetic_ metal; that is, magnetism will not flow
-through it, nor can it be magnetized. If a pile of iron filings is
-stirred with a copper wire there will be no effect, as might be
-expected; but if a current of electricity flows through the wire, the
-iron filings will cling to it, as shown in Figure 54, as if it were a
-real magnet.
-
-[Illustration: FIG. 54.—MAGNETISM IN A COPPER WIRE]
-
-It is one of the principles of electricity that when a current flows
-through a wire, the wire is surrounded by magnetism, which continues as
-long as the current flows; when the circuit is broken and the current
-stops flowing, the magnetism dies away. The magnetism produced is
-feeble and can be very greatly increased by winding the wire around an
-iron bar. The magnetism produced by the current then flows into the
-bar, and that, like the core of the winding of a magneto, throws out
-magnetism of its own. This is indicated in Figure 55. By changing the
-intensity of the electric current, or by cutting it off, the strength
-of the magnetism can be made to change, and this change of strength can
-produce a sparking current.
-
-[Illustration: FIG. 55.—MAGNETISM FROM ELECTRICITY]
-
-The principle employed is illustrated in Figure 56. A is a coil of
-wire wound around one end of an iron bar and connected with a battery;
-B is an entirely separate coil of wire wound around the other end of
-the bar, with its ends separated by a short distance. By closing the
-battery switch the current will be permitted to flow in coil A, and
-the bar will become magnetized; the magnetism that it throws out will
-be felt by coil B. When the switch is opened the current stops flowing
-and the magnetism dies out of the bar; these changes in strength will
-create an electric current in coil B, which will form a spark as it
-passes across the space between the ends.
-
-[Illustration: FIG. 56.—PRINCIPLE OF SPARK COIL]
-
-In ignition coils, coil B is wound on top of coil A. Coil A, called the
-_primary winding_, consists of a few layers of coarse wire. The more
-turns of wire there are in coil B, called the _secondary winding_, the
-more intense will be the current that it produces, and the intensity
-is also increased by keeping the windings close to the iron core. The
-secondary winding is, therefore, made of exceedingly fine wire, and has
-a very great number of turns.
-
-To obtain a spark, a current is permitted to flow through the primary
-winding to create magnetism, and the flow is then stopped to cause
-the magnetism to die away. The secondary winding is affected by each
-of these changes in magnetic strength. The bar loses magnetism more
-rapidly than it gains it, however; it is therefore the dying out of the
-magnetism that has the greater effect on the secondary winding, and
-that causes it to produce a sparking current.
-
-To use this principle for ignition, the engine is fitted with a
-revolving switch, which closes the circuit as a piston is on the
-compression stroke, and then breaks the circuit at the instant when
-a spark is desired. Combined with the revolving switch, or _timer_,
-is a distributor like the distributor of a magneto, which passes the
-sparking current to the cylinder that is ready to receive it.
-
-[Illustration: FIG. 57.—“ATWATER-KENT” IGNITION SYSTEM]
-
-To produce an intense sparking current, it is necessary to break the
-circuit as abruptly as possible, in order to cause the magnetism to die
-away suddenly. Figure 57 shows how this is done in the Atwater-Kent
-system.
-
-The parts of the circuit breaker are carried on a plate, in the center
-of which revolves a shaft with a notch in it. Against the side of this
-shaft rests the hooked end of the sliding catch; as the notch comes
-under this hooked end, the sliding catch is drawn forward, only to be
-snapped back by its spring as the notch moves from under it. The lifter
-is a bit of metal, pivoted at one end, with its free end lying between
-the sliding catch and the flat steel spring that carries one of the
-contact points.
-
-A, Figure 57, is a diagram of the system. B shows the position of the
-parts as the notch carries the sliding catch forward, and C shows their
-positions as the spring snaps the sliding catch back to its place. It
-will be seen that in thus moving back it strikes the lifter, which
-in turn moves the contact spring, and so closes the circuit; but the
-circuit is instantly broken as the parts spring back to position. The
-movement of the parts is so rapid that to the eye they seem to be
-standing still. The circuit is closed only for an instant, but that
-is sufficient to magnetize and demagnetize the coil, and to produce a
-sparking current.
-
-The operation of this system depends on the very great swiftness with
-which the circuit is made and broken; there is not sufficient time
-for the core to get thoroughly magnetized, but such magnetism as is
-produced changes strength so quickly that it gives a sufficiently
-intense current to create an ignition spark.
-
-In other battery systems of like principle, the circuit is closed for
-a long enough time to allow the core to become fully magnetized, the
-circuit then being suddenly broken. In some of these systems the timer
-breaks the circuit, while in others it is broken by the magnetism,
-through a _vibrator_.
-
-A _vibrator coil_ system is illustrated in Figure 58. The timer is a
-ring made of some kind of insulating material, with a plate of metal
-set in it and forming one of the timer contacts. The other contact is
-the revolving brush, driven by the engine; the circuit is closed when
-the brush touches the metal plate.
-
-[Illustration: FIG. 58.—VIBRATOR COIL IGNITION SYSTEM]
-
-Opposite the end of the core is a flat steel spring, or _vibrator
-blade_, resting against the tip of a screw; when the core is magnetized
-it draws the end of the blade to it, and separates it from the screw.
-The battery current flows from the timer contact to the screw, then to
-the vibrator blade and to the primary winding of the coil. The core
-then becomes magnetized, and draws the blade away from the screw,
-which breaks the circuit; this causes the magnetism to die away, and
-a sparking current is produced in the secondary winding of the coil.
-The vibrator blade, no longer held down by the magnetism, springs
-back against the screw; the circuit is again made, and the action is
-repeated. The movement of the vibrator blade is very rapid, being some
-hundreds of vibrations a second.
-
-[Illustration: FIG. 59.—SPARK PLUG]
-
-A spark plug is illustrated in Figure 59. It consists of a metal shell
-screwed into the cylinder, enclosing an _insulator_ of porcelain, mica,
-or some similar material. Through the insulator passes the center
-electrode, which is a rod of metal, with its lower end separated by a
-short distance from the shell or from a wire attached to the shell.
-This separation is the gap across which the sparking current passes,
-and at which the spark occurs.
-
-Spark plugs receive the pressure of the power stroke, and must be
-strongly made in order to withstand it. A leaky spark plug will cut
-down the power of the engine, just as a leaky valve will.
-
-
-
-
-CHAPTER VIII
-
-TRANSMISSION
-
-
-The parts of a tractor by which the power of the engine is applied
-to the driving wheels are called the _transmission_, and include the
-_clutch_, _the change speed gear_, the _differential_ and the _drive_.
-
-It has been shown that a gas engine delivers power only when it is
-running at speed; it cannot run until some outside power drives it
-through the inlet and compression strokes.
-
-The tractor cannot move until the engine is running and delivering
-power, and it follows, therefore, that it must be possible to
-disconnect the engine from the driving mechanism in order that it may
-run independently. This is done by means of a _clutch_, which is a
-device that connects two shafts, or disconnects them.
-
-[Illustration: FIG. 60.—INTERNAL CLUTCH]
-
-A clutch must be so made that when it is engaged it takes hold, not
-suddenly, but gradually. If it took hold suddenly, the tractor would be
-required to jump at once into full motion; this would cause a severe
-straining of the parts and probable breakage. The alternative would be
-the abrupt stopping of the engine, and this would also strain things.
-
-By making the clutch in such a way that it slips, and takes hold little
-by little, the tractor starts slowly, and gradually comes up to speed;
-the slipping of the clutch then ceases, and it takes hold firmly.
-
-All clutches operate by the friction of one surface against another; in
-some, the surfaces are curved and in others flat, while in still others
-the clutch is a band around a wheel, or _drum_. A clutch is operated by
-a hand lever or by a foot pedal.
-
-Figure 60 shows a type of clutch that operates inside a drum, which is
-often the overhanging rim of the flywheel. The shaft in the center is
-independent of the flywheel, and it is the purpose of the clutch, which
-is attached to the shaft, to lock the shaft and flywheel together when
-the tractor is to be started.
-
-The brake shoes, which bear against the drum, form the ends of pivoted
-levers, and are lined with an asbestos material that resists the heat
-caused by the friction against the drum.
-
-A cone-shaped block of steel slides lengthways on the shaft; when it
-is pushed into position, it forces out the yokes, and thus presses the
-brake shoes against the drum.
-
-A _plate clutch_, or _disk clutch_, is shown in Figure 61. The
-principle of a plate clutch may be illustrated by placing a half-dollar
-between two quarters and pinching them with the thumb and forefinger.
-If they are held loosely, the half-dollar may be turned between the
-quarters, but if they are pinched tightly, the friction between the
-coins will be so great that one cannot be turned without turning the
-others.
-
-[Illustration: FIG. 61.—PLATE CLUTCH]
-
-Attached to the flywheel are studs, which support a disk, or plate;
-this plate revolves with the flywheel, and is practically a part of it.
-On either side of this plate are other plates that are supported on the
-drive shaft; they revolve with it, but can slide along it. The end of
-the shaft is square and fits a square hole in a collar, so that while
-the collar may slide along the shaft, the two must turn together. Cams
-are mounted on the hub of one of the plates in such a position that
-they can press the outside plates together and pinch the flywheel plate
-between. The cams are operated by pressing the collar against them.
-
-The first drawing shows the clutch out, or released; the flywheel may
-then turn without turning the shaft, for the plates are not in contact.
-The second drawing shows the clutch in, or engaged. The collar is
-pressed against the cams, and the plates in turn are drawn together,
-pinching the flywheel plate between them. The flywheel and the drive
-shaft then revolve together.
-
-Plate clutches are often made with more than three plates; some makes
-run in a bath of oil, and some are intended to work dry.
-
-In a cone clutch, the overhanging rim of the flywheel is funnel-shaped,
-and into it fits a cone-shaped disk carried on the end of the drive
-shaft. To engage the clutch, the disk is slid along the shaft against
-the flywheel, the friction between the two being sufficient to drive
-the shaft.
-
-When a clutch is thrown in it should take hold gradually, slipping at
-first, but finally having a firm grip. When it is thrown out, it should
-release instantly and completely.
-
-The power delivered by an engine depends on the _bore_ and _stroke_
-of the cylinder, and on the speed. The greater the bore, or diameter
-of the cylinder, and the greater the stroke, or distance the piston
-moves in a half-revolution of the crank shaft, the larger will be the
-combustion space, and the larger will be the charge of mixture that
-it can take in; the larger the charge, the greater will be the power
-produced when the charge burns.
-
-Each cylinder produces power once during every two revolutions of the
-crank shaft; if the engine runs at 1,000 revolutions per minute there
-will be twice as many power strokes as there would be if it ran at 500
-revolutions per minute, and during that minute it will produce twice as
-much power.
-
-A traction engine is intended to run at a certain speed, at which it
-will produce its greatest power without overstraining its parts. This
-_normal speed_ for any particular engine depends on the number of
-cylinders, their size and design, and other details established by the
-manufacturer. To get the best from the engine, this is the speed at
-which it should always be run.
-
-The power required to move the tractor depends on various things;
-the hardness and smoothness of the ground, the grade, the load it is
-pulling, and so on. The tractor might be running on level ground,
-pulling so great a load that the engine is called on for all of the
-power that it can deliver.
-
-On coming to a hill, still more power will be required, for now the
-tractor and its load must be lifted as well as moved forward. The
-engine, already working at its limit, cannot deliver the extra power
-needed, and will slow down and stop unless something is done to aid
-it. In such a case, the change speed gear is used to give the engine
-a greater leverage on its work, just as a block and tackle gives a
-greater leverage or purchase to a man who must lift a heavy weight.
-
-Let us say that the normal speed of the engine is 1,000 revolutions per
-minute, and that it is so connected that it makes 40 revolutions while
-the driving wheels make 1, the speed of the tractor being 3 miles per
-hour. If it is a 4-cylinder engine there will thus be 80 power strokes
-to every revolution of the driving wheels. The engine is delivering its
-full power and cannot do more should the tractor be called on for an
-extra exertion, such as climbing a hill or crossing rough ground.
-
-By changing the connections between the engine and the driving wheels,
-the engine can be made to run twice as many revolutions to one turn of
-the driving wheels, which will give double the number of power strokes;
-the wheels will thus be turned with twice the force. As no change is
-made in the speed of the engine, the wheels will now turn at half their
-former speed, and the tractor will run at 1½ miles per hour. It will,
-however, have twice the ability to overcome obstacles.
-
-This change in the connections between the engine and the drive is
-performed by the _change speed gear_, which is driven by the engine and
-which in turn drives the wheels.
-
-There are many varieties of change speed gears, but the main principle
-in them all is the same, for they depend on the action of cog-wheels,
-or _gears_.
-
-When two gears running together, or _in mesh_, have the same number of
-teeth, they will revolve at the same speed. If one has half as many
-teeth as the other—10 teeth and 20, let us say—the 10-tooth gear will
-make two revolutions while the 20-tooth gear is making one.
-
-There are two shafts in a change speed gear, one driven by the engine
-and the other driving the wheels; each carries gears that mesh with
-gears on the other shaft. These pairs of gears are of different sizes,
-and any pair may be used; the shaft driven by the engine runs as the
-engine runs, while the speed of the other shaft depends on the pair of
-gears that is being used.
-
-By changing from one pair of gears to another, the driven shaft, and,
-consequently, the wheels, may be run at a greater or less number of
-revolutions, while the speed of the engine and the driving shaft do not
-change. The number of power strokes that occur during one revolution of
-the wheels is thus changed, and they turn with more force or with less.
-
-_High speed_, or _high gear_, means the combination of gears that
-gives the greatest speed to the wheels, but the fewest power strokes
-to each revolution. The combination that gives the slowest speed to
-the wheels, but the greatest number of power strokes, is called _low
-speed_, or _low gear_.
-
-Many tractors have but two speeds, a low and a high; but others have an
-intermediate combination for conditions too severe for running on high
-gear but too easy for low.
-
-The change speed gear mechanism also provides for reversing or backing
-the tractor. Two gears running together turn in opposite directions,
-while in a train of three gears the outside gears turn in the same
-direction. The usual combination in a change speed gear uses two gears
-for going ahead; to run the driven shaft the other way, which will make
-the tractor back, a third gear is meshed between the two.
-
-The differences between various makes of change speed gears are in the
-methods used to put into action the desired pair of gears.
-
-[Illustration: FIG. 62.—PRINCIPLE OF SLIDING GEAR]
-
-Two general plans are used. In one of them, a gear of each pair can
-slide endways on its shaft, but must revolve with it; thus it can be
-slid into mesh or out. In the other, the gears of a pair are always in
-mesh, but one of them is loose on its shaft, so that shaft and gear can
-revolve independently. To make the pair of gears operate, the loose
-gear is locked to its shaft.
-
-Figure 62 shows the principle of the _sliding gear_ type. One part of
-the shaft driven by the engine is square, and fits into square holes
-in its gears, which may thus slide along it, but must revolve with it.
-Each sliding gear is moved by a shifter block, which is operated by
-a shift lever. There is a shifter block for each gear, and the shift
-lever may be moved sideways to operate either one of them.
-
-Figure 63 shows the _jaw clutch_ type of change speed gear, in which
-the gears are in mesh all of the time, but run loose on their shaft
-when they are not working. The drawing shows _bevel gears_, which are
-used when the driving and driven shafts are at a right angle. The same
-principle is used for _spur gears_ on shafts that are parallel, as in
-Figure 62.
-
-[Illustration: FIG. 63.—PRINCIPLE OF JAW CLUTCH CHANGE SPEED GEAR]
-
-The center of the shaft is square, and fits a block that can slide
-endways, but that must revolve with it. The ends of the block have
-heavy teeth that can mesh with teeth on the hubs of the loose gears;
-meshing the block with one of the gears forces that gear to revolve
-with the shaft.
-
-The drawing shows only one speed forward; the reverse is obtained by a
-second gear on the same shaft, which is placed on the opposite side of
-the center of the driven gear, and turns it in the opposite direction.
-
-When a tractor turns, the outside wheel makes a larger circle than the
-inside wheel, and has a longer path to travel. Both wheels travel their
-paths in the same time, so it follows that the outside wheel must move
-faster than the inside wheel, although both are being driven by the
-engine. This is allowed for by the _differential_, which is driven by
-the change speed gear, and which in turn drives the wheels; it operates
-automatically by the difference in the resistance to the rolling of the
-wheels.
-
-The action of the differential is illustrated by an experiment that
-requires a pair of wheels on an axle, like buggy wheels, and a stick
-long enough to reach from one to the other. With the wheels on smooth
-ground, put the ends of the stick through the wheels at the top, each
-end pressing against a spoke. Hold the stick at its center and push it
-forward; the stick will transmit the pressure to the spokes, and the
-wheels will turn. The wheels being on smooth ground, there is equal
-resistance to their movement, and they will run straight forward.
-
-Now repeat the experiment with the wheels so placed that one is on
-a smooth roadway and the other on sand; as the wheel on the smooth
-surface meets with less resistance than the other does, it moves
-faster, and the pair of wheels circles, although the stick applies
-equal pressure to both.
-
-The power developed by the engine is transmitted by the differential
-to both rear wheels; when the wheels meet with equal resistance, they
-turn equally, but when one wheel meets with greater resistance than the
-other, it slows down, while the other speeds up to correspond.
-
-A tractor with two driving wheels must use a differential in order to
-make turns easily. Without a differential, the wheels would run always
-at equal speed, and in making a turn one would be obliged to slip.
-
-The use of a differential has a disadvantage, however. If one wheel
-is in a mudhole and the other is on hard ground, the wheel in the mud
-meets with little resistance, and all of the power of the engine goes
-to it; it spins without moving the tractor, while the other wheel
-remains stationary. In such a case all of the power should be applied
-to the wheel that has traction in order to move the tractor, but this
-the differential fails to allow.
-
-In some tractors the differential is so made that the parts may be
-locked together. This lock is used when one wheel is in a mud hole, and
-as by its use power is transmitted equally to both wheels, the tractor
-moves.
-
-Great care must be taken to unlock the differential as soon as the need
-for the lock has passed, for otherwise the wheels would slip on a turn,
-and the parts of the transmission might be strained or broken.
-
-A differential is usually made with two bevel gears placed face to
-face; between them is a frame holding three or more small bevel gears
-that are in mesh with them both. The engine revolves the frame with its
-small gears; each of the large bevel gears revolves a driving wheel.
-
-When the tractor moves straight ahead the differential turns as if it
-were one solid piece. When there is less resistance to one driving
-wheel than to the other, the small bevel gears, in addition to
-revolving with the frame that carries them, turn on their shafts. This
-transmits the power of the engine to one wheel more than the other,
-according to the resistance of the wheels.
-
-[Illustration: FIG. 64.—“I. H. C.” CHAIN DRIVE, SHOWING THE
-DIFFERENTIAL]
-
-Figure 64 shows one of the large bevel gears of a differential, with
-the three small gears, the other large bevel gear being removed. A
-differential in section is shown in Figure 65.
-
-A tractor with only one driving wheel has no differential. Such
-tractors usually have two wheels, but one of them runs loose on
-the axle, and serves only to support the tractor. The rear axle
-construction of a tractor with a 1-wheel drive is shown in Figure 66,
-which should be compared with the 2-wheel rear construction shown in
-Figure 65.
-
-[Illustration: FIG. 65.—“CASE” REAR AXLE]
-
-There are a number of methods used for transmitting power to the
-driving wheels. In Figure 64 a chain is used; there are tractors with
-but one chain, and others with a chain for each driving wheel.
-
-[Illustration: FIG. 66.—“OIL-PULL” REAR AXLE]
-
-The most usual method is by a _master gear_, or _bull gear_, which is a
-large and heavy gear attached to the driving wheel, as shown in Figures
-65 and 66. In some tractors this gear is nearly the size of the wheel,
-and is fully exposed; in others it is smaller, and enclosed in an
-oil-tight housing.
-
-[Illustration: FIG. 67.—DRIVING WORM]
-
-The small gears that drive the bull gears are on the ends of the cross
-shaft, called the _jack shaft_, that carries the differential.
-
-In the Fordson tractor the differential is built into the axle, as it
-is in an automobile, and power is applied by a _worm_. The worm is
-driven by the change speed gear, and is a screw meshing with a gear on
-the differential, whose teeth are cut at the proper angle to make them
-fit the threads of the worm. A worm, which is shown in Figure 67, is
-always enclosed, and runs in oil.
-
-
-
-
-CHAPTER IX
-
-TRACTOR ARRANGEMENT
-
-
-The uneven ground over which tractors must work requires the weight to
-be kept low, to prevent capsizing, and they are also built wide, for
-the narrower they are the more easily they tip over. They cannot be
-broad in front, however, for if they are the steering wheels cannot
-be swung enough to permit them to turn in the small circle that is
-desirable.
-
-To give a small turning circle some tractors are built with the front
-of the frame raised enough to permit the wheels to cut under. Others
-use small steering wheels, but this is not desirable because small
-wheels will not run over rough ground as readily as large ones, and
-steering is difficult.
-
-[Illustration]
-
-[Illustration: FIG. 68.—TRACTOR ARRANGEMENT]
-
-[Illustration]
-
-[Illustration: FIG. 69.—TRACTOR ARRANGEMENT]
-
-Types of tractors are indicated in Figures 68 and 69. A has a
-4-cylinder vertical engine in front, driving both wheels by bull gears,
-while B is a 2-cylinder horizontal engine in the center, driving both
-wheels by chains. C has a 4-cylinder vertical engine set across the
-frame. These three types have riveted steel frames, to which the parts
-are attached.
-
-In D, the drive is entirely enclosed within the rear axle housing,
-and the rear part of the frame is formed by the axle housing and the
-housing of the change speed gear.
-
-E has a 1-cylinder horizontal engine with a single chain drive, while F
-has a similar engine but drives to both wheels.
-
-G has no frame, its place being taken by the crank case of the engine
-and the housings of the parts of the transmission. G and H have
-4-cylinder vertical engines, G driving through an enclosed rear axle
-and H through bull gears.
-
-[Illustration: FIG. 70.—“GRAY” TRACTOR]
-
-Figure 70 has one broad wheel instead of two narrower ones, this being
-placed inside of the frame instead of outside. It has a 4-cylinder
-vertical engine placed across the frame, and drives through two chains.
-
-[Illustration]
-
-[Illustration: FIG. 71.—TYPES OF FRONT AXLES]
-
-The front axle of a tractor is almost always attached to the frame by
-a pivot, so that the wheels will follow uneven ground. Some of the
-forms of front axles are shown in Figure 71.
-
-[Illustration: FIG. 72.—SPRING SUPPORT]
-
-The first is a plain bar, while the second is arched to raise the front
-of the frame in order to permit the steering wheels to cut under. In
-the third the wheel axles are mounted on springs, which take up some of
-the vibration and act as shock absorbers.
-
-The fourth axle shown is built of steel bars riveted together to form
-a truss, and the fifth is similar, with the frame pivot carried on
-springs. The sketches at the bottom indicate the extent to which the
-pivoted front axle may swing.
-
-Figure 72 shows a spring support for the axles, front and rear.
-The axle bearing is in a block sliding in guides, the weight being
-supported by a heavy spring.
-
-
-
-
-CHAPTER X
-
-LUBRICATION
-
-
-The most important thing in the care of a tractor is to oil it; every
-moving part should be lubricated, and the greatest care should be taken
-to assure a never-failing supply of oil and grease.
-
-Carelessness in lubrication is the principal cause of tractor trouble.
-There is nothing complicated or difficult about keeping a tractor
-properly oiled; yet more tractors break down from careless lubrication
-than from any other cause. Every tractor-maker issues an oiling diagram
-and oiling instructions, and there is no excuse for an operator whose
-machine does not get the right kind of lubricant in the right quantity
-at each place where lubrication is necessary.
-
-The cause of wear is friction; oil reduces friction and so reduces
-wear. No matter how smooth and highly polished two pieces of steel may
-be, there will be friction between them if they are rubbed together,
-and they will wear each other. If they are oiled, the particles of oil
-will keep the pieces from touching each other, and there will be no
-wear.
-
-Other substances than oil can be used; there are some kinds of
-machinery that are lubricated with water, for instance. For general
-use, however, oil and grease are the best, and are practically always
-used.
-
-The object of a lubricant is to keep two pieces of metal from touching;
-it must therefore be able to get between them, and must stay there. If
-the pieces are large and heavy, there will be much greater pressure
-on the oil than if they are small and light, and the oil must be able
-to withstand this pressure and resist being squeezed out. The oil
-that would keep the small, light pieces apart might not be able to
-stand the pressure of a greater weight, and might be squeezed out from
-between two heavy pieces.
-
-Oil has a tendency to cling to whatever it touches, and thick oil
-or grease has more of this tendency than a thin, or “runny” oil. If
-a thick oil or grease is used on light machinery, such as a sewing
-machine, this clinging tendency would make the machine run hard, and
-might even prevent its operation.
-
-When oil is heated, it becomes thinner, or more “runny.” Through
-this, an oil used in a hot place might get so thin that it would not
-lubricate; and on the other hand, an oil that works all right in the
-heat of summer might get so thick on a cold winter day as to be useless.
-
-A slow-moving part of a machine uses a thick oil or a grease; a thin
-oil must be used for a part that moves at high speed.
-
-Some of the parts of a tractor move slowly and some at high speed; some
-are cool and some are hot. Different kinds of lubricants are therefore
-required, and it is a grave mistake to use a lubricant that is not
-suitable to the work that it is required to do.
-
-The engine is the most difficult part of a tractor to lubricate, and
-the part that suffers most if the supply fails or if the wrong kind
-of lubricant is used. In the first place, it is so hot that any oil
-will burn, being turned to carbon; the best that can be expected of
-an oil is that it will resist burning until it has done its work of
-lubricating the piston and cylinder.
-
-A tractor engine is more difficult to oil than an automobile or
-truck engine for the reason that it works harder and more steadily.
-An automobile engine is rarely driven to the limit of its power; it
-has frequent opportunities to cool when running down hill. A tractor
-engine, on the other hand, works at its full power all day long with
-no opportunities to cool off. An oil that gives good satisfaction on
-an automobile might ruin a tractor engine through its inability to
-withstand the greater heat.
-
-The makers of tractors understand the importance of using proper oils,
-and recommend certain brands and grades; these recommendations should
-be followed in order to get the best possible results. All makers
-specify at least two kinds of lubricants, and most of them three; one
-specifies six, which range from a light sewing machine oil to a grease
-so thick that it is nearly solid. Whatever the recommendations may be,
-they should be followed.
-
-In general, lubricants are classified according to their thickness, and
-they range from the light oil used for typewriters and sewing machines
-to grease so thick that it may be cut like butter. The thinnest oil
-is used for the circuit breaker pivot; this part is usually moved in
-one direction by a cam and in the other by a light spring. A thick oil
-would gum the bearing to such an extent that the spring might not be
-able to move the lever.
-
-[Illustration: FIG. 73.—“MOGUL” OILING DIAGRAM]
-
-    ----+----------------------+----------------------------+-----------
-    KEY |      DESCRIPTION     |         QUANTITY           |LUBRICATION
-    ----+----------------------+----------------------------+-----------
-                           ONCE EVERY HOUR
-    ----+----------------------+----------------------------+-----------
-     L  | Rear axle bearing    | Two complete turns         | Cup Grease
-    ----+----------------------+----------------------------+-----------
-                         ONCE EVERY TWO HOURS
-    ----+----------------------+----------------------------+-----------
-     A  | Differential hub     | One complete turn          | Cup Grease
-     B  | Rear wheel hub       | One complete turn          | Cup Grease
-     C  | Differential pinion  | One complete turn          | Cup Grease
-     H  | Front wheel hub      | Two complete turns         | Cup Grease
-     T  | Governor and cam     | Two complete turns         | Cup Grease
-        |   shaft bearing      |                            |
-    ----+----------------------+----------------------------+-----------
-                          TWICE EVERY DAY
-    ----+----------------------+----------------------------+-----------
-     E  | Governor             | Oil                        | Cylinder
-        |                      |                            |        oil
-     F  | Outboard bearing     | Two complete turns when    | Cup Grease
-        |   grease cups        |           plowing          |
-     G  | Transmission         | One pint                   | See note
-        |                      |                            |      below
-        |{ Magneto trip        | Grease every 5 hours       | Cup Grease
-     N  |{ Magneto roller and  | Oil every 5 hours          | Oil
-        |{   slide             |                            |
-     J  | Steering worm        | Keep covered               | Cup Grease
-     W  | Steering hub grease  | One complete turn          | Cup Grease
-        |   cups               |                            |
-     V  | Steering worm shaft  | Oil every 5 hours          |
-     R  | Lubricator eccentric | Oil every 5 hours (keep    |
-        |                      |        wool in pocket)     |
-     P  | Cam roller slide     | Oil every 5 hours          |
-     K  | Valve levers         | Fill with oil every 5 hours|
-        |                      |  (keep wool in pockets)    |
-    ----+----------------------+----------------------------+-----------
-                    ONCE EVERY DAY TRACTOR IS IN USE
-    ----+----------------------+----------------------------+-----------
-     U  | Steering sector shaft| One complete turn          | Cup Grease
-    ----+----------------------+----------------------------+-----------
-     D  | MECHANICAL LUBRICATOR
-        |   Fill with a good grade of heavy gas engine cylinder oil.
-        |   Turn the crank on the mechanical oiler 40 to 50 times when
-        |   starting the engine.
-        | IMPORTANT
-        |   In cool or cold weather the oil in lubricator tank must be
-        |   warmed as it will not flow readily unless of the right
-        |   temperature.
-    ----+---------------------------------------------------------------
-     G  | TRANSMISSION
-        |   In warm weather, use heavy oil such as “600” transmission
-        |   or Polarine transmission oil; in cold weather, use a good
-        |   light oil.
-     S  | GOVERNOR
-        |   Cylinder oil in governor should cover shoe.
-     M  | MAGNETO
-        |   Oil magneto bearings once a week with sewing machine or
-        |   cream separator oil.
-    ----+---------------------------------------------------------------
-
-The oil used in an engine is thicker, and has a high _burning point_
-and high _viscosity_; that is, it should be able to resist burning, and
-should not get so thin when it is heated that it will be squeezed out
-of the bearings. The same kind of oil that is used in the engine can be
-used in many other parts of the tractor.
-
-Grease is usually used for the gears of the transmission and drive.
-There is very great pressure between the teeth of two meshing gears,
-and only thick oil and grease have sufficient viscosity to resist being
-squeezed out.
-
-The thickest grease is used on the tracks of caterpillar-type tractors.
-
-Before operating a tractor, the lubrication chart supplied by the
-manufacturer should be studied with great care, and all of its
-requirements should be observed. This chart is usually in the form of
-a diagram accompanied by a table, as shown in Figure 73, which is the
-lubrication chart of one of the International Harvester tractors. This
-figure illustrates the constant attention that is demanded by this most
-important part of tractor operation.
-
-[Illustration: FIG. 74.—“ILLINOIS” OILING DIAGRAM]
-
-
-The table calls for four lubricants, these being sewing machine oil,
-which is very thin and liquid; gas engine cylinder oil; transmission
-oil, which is as thick as molasses; and cup grease, which is like
-butter.
-
-The engine is oiled automatically, the only requirements being to keep
-the oil tank filled, and to be sure that the oiler is working. The
-other parts of the tractor are oiled or greased by hand.
-
-Figure 74 is the oiling chart of the Illinois tractor.
-
-There are three systems used for engine lubrication: _splash_, _force
-feed_, and by a mechanical oiler. In the splash system, a pool of oil
-is maintained in the crank case, of such a depth that the ends of the
-connecting rods just dip into it. They strike it with sufficient force
-to splash it to all parts of the crank case, the oil that strikes the
-pistons being carried up into the cylinders and lubricating the walls.
-
-The end of the connecting rod is often fitted with a dipper, as shown
-in Figure 75, to strike into the oil, as well as an oil catcher,
-shown in the same drawing, which is a little trough that catches the
-splashing oil and guides it to the connecting rod bearing.
-
-[Illustration: FIG. 75.—END OF “TWIN CITY” CONNECTING ROD]
-
-To oil the wrist pin bearing there is an oil groove around the piston
-that collects oil from the cylinder walls; a hole connects this groove
-with the hollow wrist pin, from which other oil holes lead to the
-bearing. This is shown in Figure 76.
-
-[Illustration: FIG. 76.—WRIST PIN LUBRICATION]
-
-In the force feed system a pump driven by the engine forces oil through
-pipes and channels to all of the bearing surfaces. Oil collects in a
-pocket in the crank case, called the _sump_, and is drawn from it by
-the pump. The sump is usually provided with a wire mesh strainer that
-separates out any dirt.
-
-[Illustration: FIG. 77.—FORCE FEED OILING SYSTEM OF “GRAY” ENGINE]
-
-From the oil pump the oil is forced to the bearings by pipes and by
-holes drilled in the crank shaft and other parts, as shown in Figure 77.
-
-[Illustration: FIG. 78.—OIL PUMP]
-
-An oil pump is illustrated in Figure 78. It consists of a plunger
-driven by the engine, working in a cylinder provided with two ball
-check valves, one for inlet and the other for outlet. On an upward
-stroke of the plunger the cylinder fills with oil, which is forced to
-the engine bearings by the following inward stroke.
-
-[Illustration: FIG. 79.—“E.B.” OIL PUMP]
-
-Figure 79 shows a similar pump with a strainer over the intake, the
-outlet being through the holes L in the pipe H. In the pump illustrated
-in Figure 80 the plunger is hollow, and fills with oil during an
-inward stroke; the oil is forced out to a passage around the plunger,
-and passes to the bearings by the holes H.
-
-[Illustration: FIG. 80.—OIL PUMP WITH HOLLOW PLUNGER]
-
-Figure 81 shows two methods of preventing oil from leaking out around
-the plunger. In the first of these, a channel is formed in the upper
-part of the pump cylinder, leading to the crank case; any oil that
-leaks past the plunger flows to the crank case by this drain pipe and
-is not wasted. In the second method a packing of soft material, such
-as cotton or asbestos, is placed around the plunger, and is pressed
-against it by a _gland_, which is like a thick washer. A _packing nut_
-screws against the gland, and thus squeezes the packing against the
-plunger.
-
-[Illustration: FIG. 81.—METHODS OF PREVENTING OIL LEAKS]
-
-[Illustration: FIG. 82.—“TITAN” LUBRICATOR]
-
-A _mechanical lubricator_, or _oiler_, consists of several small oil
-pumps placed in an oil tank, each pump feeding one special bearing,
-and all driven by the engine. Figure 82 is a top view of a 2-cylinder
-horizontal engine oiled by a six-feed oiler. The bearings that it
-oils are the two ends of the crank shaft, the two ends of the cam
-shaft, and the two cylinders; the gears and other bearings are oiled
-by splash. An oiler is adjustable, so that it will feed any desired
-quantity of oil.
-
-[Illustration: FIG. 83.—“I.H.C.” METHOD OF OILING CRANK PINS]
-
-Figure 83 shows a side view and an end view of the crank shaft of a
-2-cylinder horizontal engine. To each end of the crank is attached a
-ring, B, formed into a channel; oil splashing into this ring is thrown
-into the channel by centrifugal force, and flows by holes, A, to the
-crank pin bearings.
-
-The oil forced to the cylinders from the oiler, Figure 82, reaches the
-wrist pin by grooves and holes, A, Figure 83.
-
-A 6-feed oiler is also shown in Figure 84.
-
-[Illustration: FIG. 84.—“HART-PARR” OILING SYSTEM]
-
-[Illustration: FIG. 85.—OIL CUP]
-
-[Illustration]
-
-[Illustration]
-
-[Illustration: FIG. 86.—PROPER USE OF A GREASE CUP]
-
-Figure 85 is an _oil cup_, which is used to feed an individual bearing.
-It is a glass cup holding oil with an opening at the bottom into which
-fits a needle valve. When the engine is at rest, the needle valve
-handle at the top is turned down, which allows a spring to close the
-needle valve; on starting the engine the needle valve is raised, and
-the oil flows out by gravity. The dripping oil may be seen through a
-sight glass at the bottom.
-
-In the force feed and oiler systems the oil feeds only when the engine
-is running, but with an oil cup the oil feeds all of the time that the
-needle valve is raised. Care must therefore be taken to turn on the oil
-cup when starting the engine, and to turn it off when the engine is
-stopped.
-
-Change speed gears and differentials are usually enclosed in oil-tight
-housings that contain a supply of oil or grease. The only attention
-that is required is to see that they have the necessary amount, and
-that the lubricant is of the right kind.
-
-[Illustration: FIG. 87.—“TITAN” 10-20 OILING DIAGRAM]
-
-[Illustration: FIG. 88.—“INTERNATIONAL” OILING DIAGRAM]
-
-The bearings of wheels and of many other parts of a tractor are
-lubricated with grease fed by _grease cups_; a grease cup has a cover
-that, when screwed down, forces the grease out of a hole in the bottom
-of the cup. In using a grease cup it is not sufficient simply to give
-the cover a turn or two; the cover should be screwed down enough to
-force an ample supply of grease to the bearing. This is illustrated in
-Figure 86.
-
-Figures 87 and 88 are oiling diagrams. They show the many points at
-which a tractor must be lubricated, and it should be remembered that
-the failure to maintain a plentiful supply of lubricant at any one of
-these points will mean the wear and breakdown of that particular part.
-
-
-
-
-CHAPTER XI
-
-TRACTOR OPERATION
-
-
-Before running a new tractor it should be given a careful examination
-to make sure that all nuts and bolts are tight, and not secured only
-by paint; that all grease cups are in position and filled; that all
-parts of the mechanism are properly lubricated; that oil holes are free
-from grit, and that nothing is cracked, broken or missing. It should be
-cleaned of cinders and mud that may have collected in shipment, and in
-general it should be seen to be in proper condition.
-
-A tractor, like any other piece of machinery, requires breaking in, and
-for the first few days it should be run slowly and with light loads.
-All parts should be plentifully oiled, for there will be rough and
-uneven places on the bearings that must be worn smooth, and without oil
-these would heat and be injured.
-
-A continual watch should be kept for loose nuts and bolts, which should
-be tightened without delay. Readjustments of the clutch and brake will
-be found necessary, for their linings when new may be lumpy; as these
-lumps wear down through use the clutch or brake will begin to slip and
-must be tightened. When the linings are worn in, this trouble will
-disappear, and readjustments will be necessary only at considerable
-intervals.
-
-Special care should be taken to keep the filler caps of the fuel and
-oil tanks clean and free from dirt. If these are dirty, the dirt will
-be carried into the tank when filling, and will sooner or later cause
-trouble.
-
-The vent holes in the filler caps should be kept clear. If they are
-plugged with dirt, air cannot enter the tank to take the place of the
-fuel that flows out, and the feed of fuel will stop.
-
-Beginning when the tractor is new, a system of daily inspection should
-be started, and should be continued for the working season. Big trouble
-starts with small trouble, and if small trouble is cured without delay,
-big trouble will be avoided. Trouble usually begins with looseness,
-which may be due to a slack nut or bolt, or may come with wear. If the
-loose part is not tightened, it will begin to shift its position; it
-will wear, and will rapidly lead to a breakdown.
-
-Every day, without fail, all parts of the tractor should be inspected
-for loose nuts, bolts, pipe and electrical connections, petcocks, drain
-plugs, steering connections, etc. This is also the time for wiping off
-the working parts, and cleaning mud and grit from rods, shafts, joints,
-and other places at which dirt could make its way into bearings.
-
-The change speed gears of a tractor should not be shifted while in
-motion, this being one of the differences between a tractor and an
-automobile. In the sliding gear type of change speed mechanism, the
-gears slide into mesh sideways, a tooth of one being opposite a space
-between two teeth of the other. If the gears are not in the right
-position for this, one tooth will strike another, and the gears cannot
-be meshed. In such a case the clutch is let in for a slight touch to
-move one gear, not for a dozen or twenty revolutions, but enough to
-bring a space between two teeth of one gear opposite a tooth of the
-other.
-
-If an attempt is made to shift the gears while they are in motion, the
-result will be that one will grind against the other, and there will be
-rapid wear and probable breakage. It is because gears cannot be shifted
-while they are moving that manufacturers instruct users not to attempt
-to shift on a hill without first blocking the wheels. The reason for
-this is that the brakes may not hold the tractor, and if the gears are
-pulled out of mesh, the machine may start to run down hill; as another
-speed cannot then be engaged because the gears are moving, there will
-be no control over the tractor.
-
-Never coast down hill; always run with one of the speeds engaged. By
-switching off the ignition the motion of the tractor will drive the
-engine, and this provides the best possible brake. On low gear, the
-engine will turn in the neighborhood of eighty revolutions to one turn
-of the driving wheels, and the work required to do this will check the
-tractor on the steepest of practicable grades.
-
-A tractor is not built for as accurate and delicate steering as an
-automobile and should always be slowed in making a turn; this is
-especially true when hauling plows or other loads in the field. It is
-difficult to control the tractor if a turn is made at high speed, and
-the machine is liable to tip over.
-
-In steering and in engaging the clutch, the action should not be jerky
-and abrupt, but gradual and smooth. Letting in the clutch suddenly will
-start the tractor with a jerk that will strain it from end to end, and
-an abrupt swing of the steering wheel will have the same effect. Making
-these motions smoothly and steadily will cause the tractor to change
-its direction or pace with the least possible strain and effort. This,
-of course, increases the tractor’s life.
-
-In much of the work done by the tractor, the varying conditions of
-field and soil make a continual change in the load, and the tractor
-must be handled accordingly. The change from an uphill to a downhill
-haul, and from sand or light loam to gumbo, will require the gears
-to be shifted in order that the engine may neither labor nor race in
-keeping the outfit at its work.
-
-There should be no hesitation in coming down to low speed when the
-engine shows by its laboring that the effort of working on high gear is
-becoming too great. The engine cannot deliver its full power unless its
-speed is maintained, and low gear is provided for those times when the
-load is too great to be handled on high. Use high speed whenever it is
-possible, but trying to force the tractor to run on high with too great
-a load will lead to a breakdown.
-
-High speed should be used for light work or for moving from place
-to place, but the engine should never be run at a greater number of
-revolutions than that specified by the manufacturers. It is very poor
-policy to run the tractor fast over rough roads, as the pounding will
-inevitably injure it.
-
-Cold weather changes conditions in the handling and operation of a
-tractor; there is difficulty in starting, lubrication is likely to be
-faulty, and there is danger of breakage in engine, radiator, and air
-washer through freezing.
-
-Difficulty in starting comes from the use of the usual medium grade
-of gasoline, which is satisfactory in mild weather, but will not
-vaporize at low temperatures. Cold gasoline will not vaporize in a cold
-engine; to form a mixture it is necessary to use high test gasoline,
-which will vaporize at low temperatures, or to warm the engine to a
-temperature at which medium grade gasoline will vaporize.
-
-It is advisable to keep on hand a few gallons of high test gasoline to
-use in starting, or even a mixture of high test gasoline and ether,
-half-and-half, for extreme cold weather.
-
-The engine may be warmed by pouring a bucket of hot water into the
-cooling system, cranking the engine to get it into the water jackets of
-the cylinders. Another plan is to wrap cloth around the intake manifold
-and carburetor, soaking it with hot water, being careful not to get
-water into the air intake.
-
-A drop of liquid gasoline on the points of the spark plug will
-short-circuit them and prevent the formation of a spark; the points
-should be dry, and it is an advantage to heat the plugs, screwing them
-hot into the engine at the last moment before trying to start.
-
-Kerosene is thicker when cold than when warm; it will not flow so
-freely, and the needle valve of the carburetor must be opened more in
-winter than in summer to obtain a proper mixture.
-
-Lubricating oil also thickens in cold weather, and flows much more
-sluggishly. The lubrication adjustments that are correct for summer
-will therefore be incorrect for winter. This may be provided for to
-a great extent by using a thinner oil in winter than the oil used in
-summer. A cold snap is likely to result in burned bearings if the
-change in lubrication that it brings is not allowed for.
-
-Grease thickens in cold weather more than oil does, and some kinds
-freeze solid. In winter a light, soft grease should be used, and the
-grease cups should be turned down several more turns than is usual when
-the weather is warm.
-
-While antifreezing compounds can be used in the cooling systems of
-automobiles, they are not suitable for tractors because the greater
-and more continuous heat quickly evaporates them. The danger of
-freezing is very great, and must be avoided; the water in the radiator
-and jackets is in thin sheets, and will freeze when a bucket of water
-standing in the open will not show any signs of ice.
-
-The only real protection against freezing is to drain out all the
-water whenever the tractor is to stand idle for a sufficient time for
-it to cool off. Petcocks are provided for this at the lowest points
-of the system, and also in the pump when forced circulation is used.
-The freezing of even a small pocket of water will be enough to crack a
-cast-iron water jacket wall, and the best assurance that the system is
-thoroughly drained is to open the drain cocks while the engine is still
-running, shutting down as the flow stops.
-
-When putting up a tractor for the winter it should be thoroughly
-protected from rust and corrosion. The last time that the tanks are
-filled a quart of light oil should be added for every five gallons of
-gasoline or kerosene; as the tank empties this will leave a coating of
-oil on the inside walls.
-
-Fuel tanks and water system should be drained, and particular care
-should be taken that all the water is out; the drain cocks should be
-left open. A mechanical oiler should be filled full, to protect the
-steel parts of the pumps from rust.
-
-A half pint of thick oil should be put into each cylinder, and spread
-to the cylinder and piston walls by cranking for a few turns. Oil
-should be run between the valves and their seats.
-
-All exterior parts should be protected by a coat of thick oil or
-by paint. The governor rod, push rods, and similar parts should be
-especially looked after. It is advisable to take off the magneto and
-store it in a safe, dry place; spark plugs should be left in position.
-
-The tractor should be covered with a tarpaulin and stored in a tight
-shed.
-
-When going over a tractor preparatory to laying it up, a list should
-be made of all parts that need renewal. These parts should be procured
-at once; they are more readily obtained during the winter than in the
-operating season, and will be on hand for the spring overhaul.
-
-
-
-
-CHAPTER XII
-
-ENGINE MAINTENANCE
-
-
-FUEL SYSTEM AND CARBURETOR
-
-The operation of a carburetor depends on so many things that no exact
-instructions for its adjustment can be given. The best that can be done
-is to give a general idea of the requirements, and to outline a plan by
-which the adjustment can be arrived at.
-
-The many makes and designs of carburetors and vaporizers that are
-used on tractors have different kinds of adjustments; on most of them
-the only adjustment is the needle valve that controls the fuel, but
-some also have adjustable air valves. In any case, the manufacturer’s
-instruction book should be studied for the understanding of the
-particular carburetor in question.
-
-The first step in adjusting a carburetor is to get the engine running.
-The needle valve should be closed, and then opened enough to give a
-mixture on which the engine will start; on many carburetors this will
-be about one and one half turns. The engine should then be _primed_;
-that is, a little gasoline should be put in the cylinder, which may be
-done with a squirt can.
-
-When the engine is running, and is well heated, the needle valve should
-be gradually closed until the engine begins to miss, and to send jets
-of flame out of the carburetor, or little explosions occur in the
-carburetor. These are signs of a thin mixture, and the needle valve
-should be gradually opened to make the mixture richer. The engine will
-run more steadily, and will pick up speed until the mixture becomes too
-rich, when it will choke and black smoke will come out of the exhaust.
-
-The positions of the needle valve for a mixture that is too thin and
-one that is too rich have thus been found, and it remains to set it at
-that point between at which the engine runs most steadily and at the
-best speed.
-
-With adjustable air valves it is usual to adjust for idling, that is,
-the slowest speed at which the engine will run steadily without load,
-and then to make any necessary additional adjustment for full speed and
-power.
-
-If a carburetor cannot be adjusted by following the usual methods,
-trouble may be looked for, and this may be in the carburetor itself,
-in the fuel supply, or in the intake manifold, taking for granted, of
-course, that the engine is in proper condition and that the ignition
-system is operating correctly.
-
-Dirt under the float valve will prevent the valve from seating, and the
-level in the float chamber will be too high, so that the mixture is
-too rich. Lifting the valve from its seat will let fuel rush through,
-and loose particles will thus be washed away. If dirt is ground into
-the valve and seat, or if these parts are worn, the valve must be
-reseated, which is done by turning the valve against its seat with
-light pressure, the end of the valve being gently tapped with a light
-hammer. Under no conditions use a grinding compound, for the particles
-would become imbedded in the soft metal and would ruin the valve.
-
-Other causes of flooding are a bent valve, the sticking of the float
-pivot, and the soaking of fuel into the cork float, which is thereby
-made too heavy to float properly. The remedy is to dry it, and then to
-give it three coats of shellac.
-
-A frequent cause of trouble is dirt in the pipe from the tank to the
-carburetor. While there may not be enough dirt to prevent the engine
-from running slowly, it is sufficient to prevent the flow of sufficient
-fuel for full power. A strainer is always provided, and this should be
-drained every day; if this is not done frequently, dirt will work its
-way through.
-
-A grain of sand in the spray nozzle will choke it, and every precaution
-should be taken to keep this from happening, as well as the other
-troubles that dirt brings. The best precaution is to strain the fuel
-through chamois leather, or, if this is not obtainable, through a very
-fine metal wire screen.
-
-In fuel systems that use a pump, the sticking of the check valves, and
-the leaking of the pump through poor packing, will cut down the supply
-of fuel.
-
-If air can leak into the carburetor or intake manifold, the proportions
-of the mixture will be altered. To test for leaks, run the engine, and
-with a squirt can squirt gasoline on the joints or other places that
-are suspected of leaking air. If there is a leak, the gasoline can be
-seen being sucked in.
-
-Air must enter the tank to take the place of the fuel that flows out,
-and this is provided for by a small hole drilled in the tank-filling
-cap. If this hole becomes stopped up, the fuel will not flow, and the
-engine will come to a stop. There is a similar hole in the top of the
-float bowl of most carburetors, and this also must be kept open.
-
-An engine is always started on gasoline, for that will form a mixture
-when it is cold. Before switching to kerosene the engine must be hot,
-and this will take several minutes of running on gasoline.
-
-With a double carburetor, which has a separate fuel bowl and spray
-nozzle for each fuel, nothing more is required than the switching
-of one or the other into action; when the two parts have once been
-adjusted, they require no further adjustment. Carburetors that use
-the same spray nozzle for both gasoline and kerosene will require a
-readjustment when the switch is made, for, as kerosene is thicker than
-gasoline, it will require a larger opening for a sufficient quantity
-to pass. This readjustment is a slight opening of the needle valve on
-switching to kerosene, and an equal closing when gasoline is again
-used.
-
-A few minutes before the engine is stopped the carburetor should be
-switched from kerosene to gasoline, so that when it is shut down the
-fuel bowl will contain gasoline and the cylinders gasoline mixture.
-This is done to make it possible to start the engine. If the engine is
-stopped on kerosene, it cannot be started if it has had time to cool.
-In such a case the fuel bowl must be drained of kerosene and filled
-with gasoline, and the engine must be cranked until the cylinders
-receive a clean gasoline mixture.
-
-When an engine is working at full power on kerosene, it gets much
-hotter than would be the case with a gasoline mixture. Carbon particles
-in the cylinder, and projecting bits of metal, such as thin spark plug
-points or the edge of a screw thread, become so hot that they glow,
-with the result that they ignite the incoming fresh charge and cause
-preignition. The effect of this is to cause a pounding or knocking
-that is very noticeable. It is then necessary to use water, which is
-provided for in the carburetor.
-
-Water has the effect of cooling the intensely heated parts, and only
-enough should be used to prevent preignition. When the knocking is
-heard, water should gradually be turned on, using no more than is
-necessary to stop the noise. Too much water will cause the engine to
-miss by collecting on the spark plug points, thereby preventing the
-passing of the ignition spark.
-
-Hard water should not be used, for it will form scale, which will
-interfere with the action of the carburetor. Only soft water should be
-used, and preferably rain water.
-
-Whenever the engine is stopped, the fuel valve at the tank should be
-closed to shut off the carburetor supply. If this is not done, the
-float valve will be the only thing that prevents the fuel from running
-out, and should the float valve leak, the fuel will be wasted.
-
-
-MAGNETO AND IGNITION SYSTEM
-
-A magneto that is kept clean and properly oiled rarely gives trouble,
-and it is a mistake to blame it whenever the engine runs irregularly or
-will not start. Its adjustments should be changed only when the other
-parts of the engine have been proved to be in good condition.
-
-The working parts of a magneto are enclosed, and practically proof
-against dust. It should be wiped off frequently, and dust and grit
-should not be allowed to collect around the oil holes, for otherwise it
-will work into the bearings and damage them.
-
-Dust and dirt are especially injurious to the circuit breaker, which
-should be frequently inspected and cleaned. Very little oil should be
-used on it, and this should be the light oil used for typewriters and
-sewing machines. A thicker oil will become gummy, and will prevent the
-free action of the lever.
-
-If there is much sparking at the platinum points, so that they become
-corroded and rough, it is an indication that the condenser of the
-magneto is not operating as it should, for the object of the condenser
-is to prevent such sparking. The only remedy is to renew the condenser.
-
-Rough points will spark more than smooth ones; should they get into
-this condition, they should be lightly filed with a file of the cut
-known as “dead smooth.” If this file cannot be obtained, pinch a strip
-of the finest sand paper—not emery paper—between the points, and draw
-it gently back and forth, smoothing down first one point and then the
-other. In smoothing platinum points the greatest care should be taken
-to make them flat and true to each other.
-
-After smoothing the points they should be readjusted so that when they
-are separated by the cam they are from ¹/₃₂ to ¹/₆₄ inch apart.
-
-A distributor made with a carbon brush that slides across the contacts
-will require wiping off at least once a month. Carbon dust will rub off
-the brush and collect on the face of the distributor; in the course of
-time this will cause a short-circuit. The distributor is always made so
-that it can easily be cleaned.
-
-A magneto is timed to an engine so that when the spark control is fully
-retarded, the circuit breaker points are just separating as a piston
-goes over top center. The engine is cranked until one of the pistons
-is at top center; the magneto should be in position, but its coupling
-should be loose, so that the armature can be revolved. The spark
-control is retarded; that is, it is moved as far as possible in the
-direction in which the armature turns. The armature is then revolved
-in the direction in which it will be driven by the engine until it is
-seen that the contact points are beginning to separate; holding the
-armature, the coupling is then made fast.
-
-It will now be found that the distributor brush is touching one of
-the contacts; that contact is to be connected with the spark plug of
-the cylinder that is at top center of the compression stroke. The
-following distributor contacts are connected to the remaining spark
-plugs in the order in which their cylinders fire.
-
-Should the magneto be suspected of being out of order, the first test
-is to disconnect a wire from its spark plug, and support the tip ⅛ inch
-from the metal of the engine while the engine is cranked briskly; if a
-spark appears, it is evidence that the magneto is operating and that
-the trouble is elsewhere.
-
-If there is no spark, repeat the test with the switch wire disconnected
-from the magneto. This wire and the switch form a circuit from the
-metal of the engine to the insulated part of the circuit breaker;
-when the switch is closed, or in the “off” position, this circuit is
-completed, and as the magneto current flows over it instead of over
-the regular sparking circuit, no spark is produced at the plug. It
-sometimes happens that the switch or wire is defective, and allows the
-current to take that circuit even when the switch is in the open or
-“run” position. If this is the case it will be shown by a spark on
-cranking the engine with the switch wire disconnected at the magneto,
-and no spark when it is connected.
-
-If the switch and wire are all right, examine the circuit breaker to
-see whether the contact points are clean, and that they touch when the
-cam allows them to; touch the circuit breaker lever to see that it is
-free to move and that its spring is not broken. In some tractors the
-magneto is in such a position that the circuit breaker cannot easily
-be seen; in such a case hold a small mirror in front of the circuit
-breaker and examine the reflection.
-
-If the circuit breaker is in good condition, examine the distributor to
-see whether it is dirty, or the brush broken; if these parts are all
-right, the trouble is of such a character as requires the magneto to be
-returned for repair.
-
-Ignition trouble is usually in the spark plugs. The insulator cracks
-easily in many makes, which will permit the current to leak across
-without forming a spark; it is frequently the case that the crack does
-not show, and the best test is to replace the suspected plug with a
-plug that is known to be good. If the cylinder fires with one plug and
-not with the other, there is no question as to the cause of the trouble.
-
-The insulator of the plug must be kept clean, for a deposit of carbon
-on it will form a path by which the current can pass without forming
-a spark. A dirty plug can best be cleaned by brushing it with a stiff
-toothbrush dipped in gasoline. A carbon deposit can be softened by
-soaking the plug in gasoline for a few hours, and can then be brushed
-off more easily.
-
-The spark gap of a plug should be from ¹/₃₂ to ¹/₆₄ inch. After
-considerable use the points will be burned off, and the gap will become
-too wide; the points should then be bent to form a proper gap.
-
-Oil and grease will rot rubber, and the ignition wires should
-therefore be wiped clean. Oil-soaked cables will give trouble, and
-should be replaced with new ones.
-
-It is frequently difficult to locate a leakage of current. If the
-engine is misfiring and losing power, and a leakage of current through
-poor insulation is suspected, the easiest way to detect it is to run
-the engine in the dark. Leaks will show themselves by sparks, which are
-then easily seen.
-
-
-COMPRESSION
-
-In order to deliver its full power a gas engine must have good
-compression, and compression should frequently be tested by cranking
-the engine slowly and steadily with the ignition switched off. If
-compression is good, there will be a springy, elastic resistance
-that becomes greater as a piston approaches the end of a compression
-stroke, and that throws the piston outward as dead center is passed.
-Compression should be the same for all cylinders.
-
-If there is a leakage of compression, the only resistance will be from
-the bearings, and it will be the same for all parts of the stroke.
-
-A compression leak often makes a hissing noise that can be distinctly
-heard, and by which it can be located, but more often it makes no
-sound, and its location must be found by testing. The leak may be at
-any of the openings into the combustion space; at the valves, around
-the spark plugs or piston rings, or at the cylinder head gasket.
-
-To discover whether the gasket leaks, run gasoline along the line of
-the gasket joint with a squirt can while the engine is being cranked
-briskly; at a leaky place it will be sucked in or blown out. The same
-test should be made around the spark plug.
-
-The remedy is to reset the cylinder head, using a new gasket, and being
-sure that the surfaces are clean and free from grit.
-
-Piston ring leaks are usually caused by the rings sticking in their
-grooves through the formation of carbon. To test for piston ring
-leaks, pour a half pint of cylinder oil into each cylinder, and crank
-the engine slowly. The oil will form a seal around the pistons, and if
-compression is then improved, the rings are shown to be at fault.
-
-To free the rings, pour a few tablespoonfuls of kerosene into each
-cylinder, and spread it by giving the engine a few turns; after
-standing for an hour or so the carbon should be sufficiently softened
-to free the rings.
-
-If the leakage of compression is due to the rings being worn and loose
-in their grooves, they must be replaced.
-
-The most usual cause of compression loss is leaking valves. With its
-continual pounding against its seat, and the heat to which it is
-exposed, a valve and its seat will become rough and pitted, and will
-leak; when in this condition the valve must be ground.
-
-A valve is ground by spreading grinding compound on the seat, and
-turning the valve against it. This requires the valve spring to be
-taken off; the exact method of doing this depends on how these parts
-are made.
-
-If the valves are in a removable cylinder head, valve grinding is most
-easily done by taking the cylinder head to a bench. In many designs the
-valve seats are part of the cylinder casting, and the job is done on
-the tractor.
-
-In grinding a valve the valve is not turned around in one direction
-only, for this would cut grooves in the valve and seat. To obtain
-smooth surfaces the valve should be given part of a turn in one
-direction, and then turned equally in the other direction; after every
-few turns the valve should be lifted and dropped to another position on
-the seat. In this way the grinding is made even all around.
-
-[Illustration: FIG. 89.—GRINDING VALVE IN ENGINE WITH FIXED HEAD]
-
-The best tool for valve grinding is a carpenter’s brace with a screw
-driver blade fitting the slot in the valve, as shown in Figure 89.
-This drawing illustrates a cylinder with a fixed head; the valve is
-reached by unscrewing the plug from the opening directly above it. When
-grinding valves in an engine of this design the opening between the
-valve pocket and the combustion space should be plugged with a rag or
-waste to prevent the grinding compound from getting into the cylinder.
-
-With the valve grinding tool in position, swing the handle back and
-forth ten or twelve times; then lift the valve, place it in a new
-position, and repeat. The valve is lifted most easily by a light spring
-placed under the valve disk, as shown in Figure 89.
-
-From time to time the valve disk and seat should be cleaned off and
-examined to see whether they are smooth and free from pits and scores.
-If they appear to be, make marks around the valve disk with a lead
-pencil, replace the valve, and give it a complete turn. If this wipes
-off the pencil marks all around the valve, the grinding is complete,
-and the valve may be replaced with its spring and spring retainer. It
-is not necessary to grind until the entire thickness of the valve disk
-and seat are smooth; a narrow band all around will make the valve tight.
-
-After grinding, and before replacing the valve, all traces of the
-grinding compound should be wiped off, and great care taken that none
-of it gets into the cylinder, valve stem guide, or other working part.
-
-[Illustration: FIG. 90.—GRINDING VALVE IN DETACHABLE HEAD]
-
-On an engine with a removable head containing the valves, the head
-may be taken to a work bench, which makes grinding easier. This is
-illustrated in Figure 90. On an engine in which the valve and its seat
-may be taken out, the seat may be clamped in a vise, as shown in Figure
-91. With valves of either of these types, the grinding may be tested by
-turning the head or the seat so that the disk is down, and pouring in
-gasoline. If the valve is not tight, the gasoline will leak through,
-and grinding must be continued.
-
-[Illustration: FIG. 91.—GRINDING VALVE IN DETACHABLE SEAT]
-
-When a valve seat is very badly worn it must be redressed, which is
-done with a cutting tool to be obtained from the maker of the tractor,
-and illustrated in Figure 92. This has a stem fitting the valve stem
-guide which centers the tool and assures a true cut. If a seat is so
-worn as to need redressing, the valve will be in such bad condition
-that it must be discarded and a new one used. This must be ground in
-before the engine is run.
-
-Grinding a valve lowers it in its seat, and usually makes it necessary
-to readjust the push rod. When an engine is cold there is a space of
-about ¹/₃₂ inch somewhere between the cam and the valve stem; in Figure
-93, this space is shown to be between the valve stem and the rocker
-arm. As the engine heats up the valve stem lengthens, and this space
-permits it to do so.
-
-[Illustration: FIG. 92.—VALVE SEAT CUTTER]
-
-If the space is too small, the stem will come against the rocker arm
-or the push rod, and the valve will be held off its seat, causing
-a compression leak. If the space is too great, the valve will open
-too late and close too early. The space must therefore be carefully
-adjusted, and this is arranged for on practically all makes of tractor
-engines.
-
-[Illustration: FIG. 93.—“HOLT” VALVE ARRANGEMENT]
-
-One-thirty-second of an inch is the thickness of a 10-cent piece; it
-should just be possible to slip a slightly worn dime into the space
-when the engine is cold.
-
-
-VALVE TIMING
-
-By _timing the valves_ is meant the setting of the cam shaft in such a
-position that the valves are opened at the correct point in the stroke.
-It is necessary to time the valves only when the cam shaft has been
-taken out and must be replaced. The principle of valve timing should be
-understood, however, in order to be able to tell whether an engine is
-timed correctly.
-
-It will usually be found that the face of the flywheel bears letters
-and figures that are indicators of the timing of the valves. This
-arrangement on the E-B engines is shown in Figure 94. Two lines are
-cut in the face of the flywheel, one marked ex. cl. 1-4, which means
-exhaust valve closes, cylinders 1 and 4, and the other marked CENTER
-1-4, to indicate that the pistons in those cylinders are on center. A
-straight-edge is held against the finished surface of the housing and
-the crank shaft is turned to bring one of the marks in line with it; at
-that point the valves or pistons are as indicated by the lettering.
-
-[Illustration: FIG. 94.—VALVE TIMING, USING MARKS ON FLYWHEEL]
-
-[Illustration: FIG. 95.—VALVE TIMING]
-
-The flywheel is also marked with a dot to indicate the firing point.
-When the dot is in line with the straight-edge, ignition should occur
-with the spark control fully advanced.
-
-Figure 95 shows the valve arrangement of the same engine, with the
-exhaust valve just closing; the point of the cam has passed under the
-lifter or push rod, and has permitted the valve to come to its seat,
-but is still holding the lifter against the valve stem.
-
-To check the valve setting, hold a slip of tissue paper, such as a
-cigarette paper, in the space between the lifter and the valve stem,
-while the engine is cranked slowly. While the cam is holding the valve
-off its seat the paper will be pinched between the lifter and the valve
-stem and held firmly. At the instant when the paper is freed and can
-be moved, the valve is seated and the point of the cam is just passing
-from under; the proper mark on the flywheel should then be in line with
-the straight-edge.
-
-As the cams for all valves are in one piece with the cam shaft, setting
-one valve sets them all and checking the setting of one checks the
-setting of all.
-
-Before taking out a cam shaft, two adjoining teeth of its gear should
-be marked with a prick punch or a small cold chisel, and a similar mark
-should be made on the tooth of the crank shaft gear that comes between
-them. In replacing the cam shaft it is then necessary only to return
-the teeth to the same position. Timing gears are usually marked in this
-way by the manufacturers.
-
-
-CARBON
-
-A kerosene lamp that is turned too high gives a dense black smoke that
-is composed of fine particles of carbon. A piece of paper held in the
-smoke is quickly covered with a deposit of carbon, commonly called
-soot, or lamp-black.
-
-All fuel oils and lubricating oils contain carbon. When these oils
-burn in the cylinder, they produce carbon, much of which passes out
-of the exhaust, while the rest deposits on the valves and on all parts
-of the combustion space. This deposit hardens, and eventually makes
-trouble through causing preignition.
-
-The deposit is rough, and the heat in the cylinder is sufficient to
-make the outstanding particles glow; they ignite the incoming charge,
-and cause preignition. The sign of carbon trouble is a sharp knocking
-in the cylinder, especially when the engine is under a heavy load. The
-sound is the same as that caused by too great an advance of the spark.
-
-Carbon deposit can be greatly reduced by pouring a few tablespoonfuls
-of kerosene into each cylinder and cranking for a few turns to spread
-it to all parts of the combustion space. This will soften the carbon
-and much of it will be blown out when the engine is next started. Best
-results will be obtained if the kerosene is poured in after a run, when
-the engine is hot.
-
-If the carbon deposit is too hard to be softened by kerosene, it can
-be removed by scraping. This requires the cylinder head to be taken
-off, when the deposit can be scraped and chipped with a screwdriver.
-Care should be taken to keep the carbon crumbs from getting into the
-cylinders, valve stem guides, or other places where it would cause wear.
-
-In taking off the cylinder head the gasket should be handled carefully,
-and protected from denting and bending. A battered or bent gasket is a
-sure cause of compression leaks. In replacing a metal gasket, give it a
-coat of cylinder oil on both sides to improve its seating.
-
-When replacing the cylinder head, set all of the bolts up a little at
-a time, instead of screwing some of them tight while others are loose.
-One bolt drawn tight may tilt the cylinder head slightly, and there
-will be a distortion when another bolt is tightened. This is avoided by
-setting up all of the bolts a little at a time.
-
-Running on too rich a mixture, giving the engine too much oil, and not
-using an air cleaner in dusty work will carbonize an engine rapidly.
-Blue smoke at the exhaust is a sign that too much lubricating oil is
-being used; black smoke indicates too rich a mixture. Carbonizing
-can be greatly reduced by careful adjustment of the lubricator and
-carburetor.
-
-
-
-
-CHAPTER XIII
-
-LOCATING TROUBLE
-
-
-There are many ways in which an engine can give trouble, but these are
-not serious to an operator who understands the action of an engine,
-and who works with his brain as well as with his hands. Each of these
-troubles has a distinct cause; proper care will avoid them, but if they
-come the reasons for them can be determined by simple tests.
-
-In order to develop full power, an engine must be in good mechanical
-condition; that is, the bearings must be free without being loose,
-the gears must run well, the pistons and their rings must not bind or
-be too free, and so on. It must be properly lubricated and cooled,
-compression must be correct, it must get a good mixture, and ignition
-must take place at the right time. If an engine gives trouble, it is
-because one of these systems is not working properly, and it is not at
-all difficult to locate the cause and to correct it.
-
-If an engine gets a good mixture, which is ignited properly, it will
-run; if it will not give any explosions it is because one or the other
-of these systems is not working properly. An inspection or a simple
-test will show which one is at fault.
-
-
-ENGINE WILL NOT START
-
-If an engine will not start after being cranked a dozen or twenty
-times, it is useless to continue to crank it. It is not getting either
-a proper mixture or an ignition spark, and it saves time and energy to
-find out where the trouble is, rather than to keep on cranking in the
-hope that something may happen.
-
-When a tractor engine refuses to start, the trouble is usually with the
-mixture, and, more often than not, this is due to carelessness or to
-forgetfulness. The tank may be empty, or the fuel valve may be closed,
-so that the carburetor is dry; see if there is fuel in the carburetor
-bowl. The engine may have been shut down while running on kerosene,
-instead of having been switched to gasoline for the last few minutes of
-its run, so that the carburetor, intake manifold and cylinders contain
-kerosene, which will not vaporize without heat, instead of gasoline,
-which will. In this case the engine must be primed with gasoline.
-
-If too much gasoline has been used for priming, the cylinders may
-contain a mixture that is too rich to ignite; the engine should then be
-cranked briskly with the fuel shut off and the compression relief cocks
-open, to clear out the rich mixture and fill the cylinders with air.
-
-Water in the fuel will make starting difficult or impossible. It is
-easy to forget to shut off the water valve of the carburetor when
-stopping the engine, and when starting, water from this valve will
-prevent the forming of a mixture and will also interfere with the
-ignition.
-
-If the mixture is apparently all right, the fault may be in the
-ignition. A drop of liquid fuel or of water, for instance, may be on
-the spark plug points; this will short-circuit them and no spark will
-be formed, although the sparking current is passing.
-
-If there is a suspicion that the ignition system is at fault, and that
-the magneto is not producing a sparking current, it should be tested,
-as explained in Chapter XII.
-
-Starting in cold weather is always more difficult than starting when it
-is warm. Helps in cold weather starting are given in Chapter XI.
-
-A leaky inlet manifold will admit an extra amount of air that will
-completely alter the proportions of a mixture. Thus the mixture will
-be wrong, although the carburetor adjustment seems to be correct.
-Manifold leaks are usually at the joints, but occasionally a manifold
-is found with a hole in it due to poor casting or material, or a crack
-may develop.
-
-Difficulty in starting due to poor compression caused by stuck valves
-or rings will show its cause by the ease with which the engine can be
-cranked.
-
-If an engine is free enough to turn over, poor lubrication or cooling
-will not interfere with starting it. Faults in these systems show
-themselves only when an engine is running.
-
-
-ENGINE LOSES POWER
-
-An engine will lose power through a defect of compression, carburetion,
-ignition, cooling or lubrication, or because of a mechanical fault.
-
-If the trouble comes from cooling or lubrication, the engine will
-overheat and thus make the cause known. A bearing that binds will
-become very hot, while if the cooling system fails, the engine will be
-hot all over. When the engine is excessively hot, the pistons will
-expand, and much of the power of the engine will be used up in forcing
-them to move.
-
-An engine that is not hotter than usual, and is having regular and even
-explosions, probably loses power through a loss of compression. This is
-the most usual cause of this trouble, and it is located and remedied as
-explained in Chapter XII.
-
-If compression is good, the loss of power may be due to a clogged
-muffler or exhaust pipe, which will not permit the free escape of the
-burned gases. This condition will prevent full charges of fresh mixture
-from entering the cylinders, and the engine then cannot be expected to
-deliver full power.
-
-Another possible cause of a loss of power with the engine apparently in
-proper condition is the sticking or poor adjustment of the governor.
-The factory adjustment of the governor should not be changed, however,
-until it is definitely proved that that is where the trouble lies.
-
-If the engine misses fire, or runs irregularly, the loss of power
-will be due to faulty carburetion or ignition. The mixture may be
-too rich or too lean; in either case the trouble will be remedied by
-readjusting the carburetor. A mixture that is very much too lean will
-make itself known by _backfiring_; there will be little explosions at
-the carburetor. This should be remedied at once, for the danger of
-fire from it is very great. Black smoke at the exhaust is a sign of a
-mixture that is too rich.
-
-An engine will not deliver full power if it is run on a retarded
-spark. A loss of power from this cause will be accompanied by general
-overheating of the engine.
-
-
-ENGINE STOPS
-
-The manner in which an engine stops will indicate the reason for it.
-
-A failure of the ignition system that stops the formation of current,
-like the sticking of the circuit breaker lever, will cut off all
-explosions instantly; the engine will stop abruptly. An engine will not
-stop abruptly from any fault with the mixture; with mixture trouble the
-explosions will become weaker and weaker until they cease.
-
-If an engine stops through a failure of the lubrication or cooling
-systems it will be intensely hot, which will not be the case if the
-fault is with carburetion or ignition.
-
-A running engine will not be brought to a stop by a loss of compression.
-
-
-ENGINE MISSES
-
-A steady or irregular miss in one cylinder is usually due to the spark
-plug’s being cracked or dirty. Carburetor trouble will affect all the
-cylinders; it cannot affect one cylinder only, and missing in one
-cylinder may be put down as ignition trouble. In this case ignition
-trouble does not mean magneto trouble, for if the magneto produces
-sparking current for one cylinder it will produce it for all. Therefore
-ignition trouble in only one cylinder is in those parts of the
-ignition system supplying that cylinder; that is, in the spark plug or
-in the spark plug cable.
-
-A less likely cause for missing in one cylinder only is poor
-compression. It is usually the case that if compression is poor in one
-cylinder it is poor in them all, but a broken valve or piston ring or a
-weak valve spring will weaken compression in one and not in the others.
-
-A cylinder that misses is cooler than the others, and can be located by
-feeling. It can also be located by short-circuiting the spark plugs one
-at a time; this will make no difference in the dead cylinder, but when
-the spark plug of an active cylinder is short-circuited the speed of
-the engine will drop.
-
-To short-circuit a spark plug, take a wooden-handled screwdriver or
-other tool and rest the blade on the engine near the spark plug; then
-tilt until its shank is close to the spark plug terminal. The spark
-current will then pass to the metal of the engine by way of the tool
-instead of by the spark plug points. This is also a test of ignition,
-for a spark will pass between the terminal and the tool.
-
-Irregular missing in all cylinders may be due to a fault at one of
-the parts of the ignition system that supplies them all; a dirty
-distributor, for instance, or a sticking circuit breaker lever, or
-rough platinum points. It may also be due to a clogged fuel line, which
-prevents the carburetor from getting a regular and sufficient flow.
-
-Irregular missing will also be caused by loose ignition connections,
-and by loose switch parts.
-
-
-ENGINE STARTS; BUT STOPS
-
-When an engine starts readily but quickly slows down and stops, the
-reason is almost always an insufficient supply of fuel. An obstruction
-in the pipe may prevent the fuel from flowing fast enough to keep the
-carburetor bowl filled when the engine is running; when the engine
-starts, the fuel is sucked out of the spray nozzle faster than it comes
-in through the float valve, so the carburetor is soon drained and the
-engine stops. The bowl then fills, only to be sucked dry again when the
-engine is next started.
-
-This difficulty is caused by dirt in the fuel, which collects in the
-strainer or the fuel pipe. The strainer is so arranged that it may be
-easily drained and cleaned; to clear out the pipe, shut off the fuel at
-the tank, disconnect the pipe at both ends, and blow through it.
-
-The strainer should be drained every day; it is sufficient to open the
-strainer drain cock for two or three seconds.
-
-Most of the troubles due to dirt in the fuel will be avoided if the
-fuel is strained when filling the tank.
-
-Another thing that will bring an engine to a stop is the clogging of
-the vent holes in the tank filler cap and in the top of the carburetor
-bowl. These holes should be clear, so that air can enter to replace
-the fuel that is used; if air cannot enter the fuel will not flow, and
-the tank is then said to be _air-bound_.
-
-
-ENGINE OVERHEATS
-
-An engine may overheat either because it produces more heat than the
-cooling system can take care of, or because the cooling system is not
-taking off all of the heat that it should.
-
-Running an engine with the spark retarded will cause it to overheat; so
-will a failure of the lubrication and an obstruction to the passage of
-the exhaust gases.
-
-If an engine has been taken down and overheats when it is reassembled,
-it may be that the magneto has been wrongly timed, and produces its
-spark too late. If an engine has been running properly but begins to
-overheat, the ignition cause will be the faulty setting of the spark
-control, or the slipping of the spark control rod.
-
-When an engine is run on kerosene, the oil in the crankcase must be
-frequently drained off and replaced with fresh oil. The reason for
-this is that part of the kerosene that goes to the cylinders does not
-vaporize and burn, but works its way past the pistons and into the
-crankcase, where it thins the lubricating oil. As the oil thins, it
-loses its ability to lubricate, and the engine begins to overheat.
-
-Anything that produces extra friction will cause overheating, as, for
-example, a wrist pin that works endways and rubs against the cylinder
-wall, or a tight bearing.
-
-For a cooling system to work properly it must contain a full supply of
-water, the passages must be clear, sufficient air must pass through the
-radiator, and the pump must be in proper condition.
-
-Hose connections will rot, and a strip of rubber may peel off the
-inside and be drawn across the passage; or if dirty water is used, the
-dirt may choke the fine radiator passages or other channels. If the
-radiator is covered with mud, air cannot get at the tubes to take the
-heat from the water that they contain.
-
-A very usual cause of overheating is a slipping fan belt; an adjustment
-is provided by which the belt can be tightened when it works loose.
-
-
-ENGINE SMOKES
-
-Black smoke indicates that the mixture is too rich; blue smoke is a
-sign of too plentiful lubrication. Oil that is too thin, or that is
-of a poor grade, will cause smoking; good quality oil of the grade
-recommended by the manufacturer should always be used.
-
-Broken piston rings, or rings stuck in their grooves, will be the cause
-of smoking because they will permit an excess of oil to pass by them.
-
-
-
-
-CHAPTER XIV
-
-CAUSES OF TROUBLE
-
-
-    Engine will not start.         No mixture.
-                                   No ignition.
-                                   No compression.
-
-    Engine starts,                 Clogged fuel pipe or strainer.
-      but will not                 Air-bound tank or carburetor.
-       continue running.           Clogged exhaust.
-                                   Wet spark plugs.
-                                   Governor out of adjustment.
-
-    Engine loses power.            Retarded spark.
-                                   Poor compression.
-                                   Overheating.
-                                   Clogged exhaust.
-                                   Incorrect mixture.
-                                   Governor out of adjustment.
-                                   Tight bearings.
-                                   Dragging brake.
-                                   Slipping clutch.
-                                   Overloaded.
-
-    Engine stops suddenly.         Ignition trouble.
-
-    Engine slows down              Clogged fuel supply.
-      and stops.                   Incorrect mixture.
-                                   Overheated.
-
-    Regular miss in one
-      cylinder.                    Defective spark plug or wire.
-
-    Irregular miss in all          Sticking contact breaker.
-      cylinders.                   Defective distributor.
-                                   Clogged fuel line.
-                                   Irregular fuel feed.
-                                   Water in fuel.
-                                   Faulty ignition connections.
-
-    Engine runs unevenly.          Incorrect spark plug gap.
-                                   Incorrect mixture.
-                                   Binding carburetor float.
-                                   Sticking valves.
-                                   Sticking governor.
-
-    Engine overheats.              Spark retarded.
-                                   Faulty cooling.
-                                   Faulty lubrication.
-
-    Engine smokes.                 Black smoke; mixture too rich.
-                                   Blue smoke; too much oil.
-                                   Broken or stuck piston rings.
-                                   Poor oil.
-
-    Engine backfires               Mixture too lean.
-      through carburetor.          Sticking inlet valve or weak
-                                         inlet valve spring.
-
-    Explosions in exhaust          Missing spark.
-      pipe.                        Mixture too rich.
-                                   Sticking exhaust valve.
-
-
-
-
-INDEX
-
-
-    Adjusting a carburetor, 213
-    Advance of ignition; theory of, 18
-    Air cleaner or washer, 71
-    Air inlet; extra, 63
-    Armature, 106
-    Atwater-Kent ignition system, 136
-    Automatic carburetor, 63
-    Automobiles and tractors compared, 1
-    Axles; types of front, 172
-
-    Backfire, 55
-    Balance weights, 31
-    Bearings, 31
-    Bosch magneto; theory of, 110
-    Bosch magneto circuit, 111
-    Bosch magneto windings, 110
-    Bull gear drive, 165
-    Burning point of oil, 182
-
-    Cam, 39
-    Carbon; formation of, 56
-    Carbonization, 56
-    Carbon; removing, 242
-    Carburetor, 57
-    Carburetor action, 60
-    Carburetor adjustment, 213
-    Carburetor adjustment for two fuels, 218
-    Carburetor; compensating, 63
-    Carburetor connections, 89
-    Carburetor; description of, 72
-    Carburetor; float feed, 76
-    Carburetor; heating the, 70
-    Carburetor; parts of, 70
-    Carburetor; pump feed, 80
-    Carburetor; stopping on gasoline, 218
-    Carburetor strainer, 89
-    Carburetor; trouble with, 215
-    Carburetor; using water in, 219
-    Causes of trouble, 259
-    Centrifugal force, 94
-    Change speed gear; action of, 152
-    Change speed gear; jaw clutch, 156
-    Change speed gear; purpose of, 6
-    Change speed gear; shifting, 203
-    Change speed gear; sliding, 154
-    Change speed gear; theory of, 149
-    Choke, 67
-    Circuit; Bosch magneto, 111
-    Circuit breaker; magneto, 110
-    Cleaner; air, 91
-    Clutch; action of, 144
-    Clutch; expanding, 145
-    Clutch; how to use, 205
-    Clutch; plate or disk, 146
-    Clutch; purpose of, 6
-    Cold weather care of tractor, 207
-    Cold weather starting, 207
-    Combustion space, 11
-    Combustion; theory of, 52
-    Compression; importance of, 16
-    Compression leaks; locating, 228
-    Compression stroke, 16
-    Compression; testing the, 227
-    Connecting rod, 35
-    Cooling system, 46
-    Crank shaft, 30
-    Cycle; gas engine, 11
-
-    Dead strokes, 12
-    Differential; action of, 161
-    Differential; purpose of, 7
-    Differential; theory of, 158
-    Dirt in the fuel, 215
-    Disk clutch, 146
-    Distributor; magneto, 124
-    Dixie magneto action, 119
-    Double bowl carburetor; adjustment of, 218
-    Double opposed engine, 25
-    Drive; master gear or bull gear, 165
-    Drive; purpose of, 6
-    Drive; worm, 166
-
-    Engine base, 30
-    Engine; double opposed, 25
-    Engine; horizontal, 25
-    Engine; how power is delivered by, 21
-    Engine loses power, 249
-    Engine misses, 252
-    Engine overheats, 256
-    Engine; priming, 214
-    Engine; principle of, 9
-    Engine; purpose of, 6
-    Engine smokes, 258
-    Engine starts; but stops, 254
-    Engine stops, 251
-    Engine trouble; locating, 246
-    Engine; vertical, 25
-    Engine will not start, 246
-    Exhaust stroke, 20
-    Exhaust valve, 38
-    Expanding clutch, 145
-    Extra air inlet, 63
-
-    Firing order, 28
-    Float feed carburetor, 76
-    Force feed oiling system, 186
-    Frame; purpose of, 8
-    Freezing; to prevent, 209
-    Front axles; types of, 172
-    Fuel; dirt in the, 215
-    Fuel; straining the, 89
-
-    Gas engine cycle, 11
-    Gasket, 30
-    Gasoline mixture, 57
-    Governor, 94
-    Grease cup, 197
-    Grease; when used, 182
-    Grinding valves, 229
-    Grounded circuit or ground return, 125
-
-    Heat; action of, 9
-    Heat; effect on oil of, 177
-    Heat necessary in forming mixture, 58
-    Heating the carburetor, 70
-    Heating the mixture, 86
-    Horizontal engine, 25
-
-    Ignition point; changing the, 103
-    Ignition system; Atwater-Kent, 136
-    Ignition system; parts of, 105
-    Ignition; theory of, 17, 102
-    Impulse starter, 128
-    Induction and induced current, 106
-    Inductor magneto, 115
-    Inlet stroke, 14
-    Inlet valve, 38
-
-    Jack shaft, 165
-    Jaw clutch change speed gear, 156
-
-    K-W magneto action, 115
-    Kerosene mixture, 57
-
-    Leaks of compression; locating, 228
-    Lean mixture, 54
-    Loading, 67
-    Lubricating systems, 184
-    Lubrication chart; use of, 182
-    Lubrication; importance of, 175
-
-    Magnetism, 105
-    Magnet; poles of, 106
-    Magneto action; Bosch, 110
-    Magneto action; Dixie, 119
-    Magneto action; K-W, 115
-    Magneto distributor, 124
-    Magneto distributor; cleaning, 222
-    Magneto inductor, 115
-    Magneto; oiling a, 221
-    Magneto platinum points; care of, 221
-    Magneto safety spark gap, 127
-    Magneto spark; theory of, 105
-    Magneto; theory of Bosch, 110
-    Magneto timer or circuit breaker, 110
-    Magneto timing, 223
-    Magneto trouble; testing for, 224
-    Manifold, 70
-    Master gear drive, 165
-    Mechanical oiler, 192
-    Mixer, 57
-    Mixing chamber, 70
-    Mixture changes with engine speed, 62
-    Mixture; formation of, 53
-    Mixture; gasoline and kerosene, 57
-    Mixture; heating the, 86
-    Mixture; heat necessary to form, 58
-    Mixture; rich, 55
-    Mixture; theory of, 9
-    Mixture; thin, or lean, 54
-
-    Oil affected by heat, 177
-    Oil; burning point and viscosity, 182
-    Oil cup, 193
-    Oiler; mechanical, 192
-    Oiling chart; use of, 182
-    Oiling; importance of, 175
-    Oiling systems, 184
-    Oil pump, 188
-    Oil; varieties used on tractors, 179
-
-    Piston, 34
-    Piston pin, 34
-    Piston rings, 37
-    Piston rings; care of, 228
-    Plate clutch, 146
-    Poles of magnet, 106
-    Power diagram, 21
-    Power production, 12
-    Power stroke, 19
-    Preignition, 56, 83, 104
-    Priming the engine, 214
-    Pump feed carburetor, 80
-    Push rod, 42
-    Push rod adjustment, 234
-
-    Radiator, 48
-    Retard of ignition; theory of, 19
-    Rich mixture, 55
-    Rocker arm, 42
-
-    Safety spark gap, 127
-    Shuttle armature, 107
-    Sliding change speed gear, 154
-    Spark coil; principle of, 133
-    Spark coil; vibrator, 138
-    Spark coil; windings of, 134
-    Spark plug, 140
-    Spark plug gap, 226
-    Spark plugs; trouble with, 225
-    Splash oiling system, 184
-    Spray nozzle, 57
-    Spring support, 173
-    Starter; impulse, 128
-    Starting in cold weather, 207
-    Starting the engine; theory of, 13
-    Steering gear; purpose of, 7
-    Steering; instruction in, 205
-    Storing a tractor, 210
-    Straining the fuel, 89
-    Strangler, 69
-
-    Tappet, 42
-    Tappet adjustment, 234
-    Temperature; effect of changes on mixture, 66
-    Testing for magneto trouble, 224
-    Testing the compression, 227
-    Theory of gas engine, 9
-    Thermo-syphon cooling system, 48
-    Thin mixture, 54
-    Throttle, 68
-    Throws of crank shaft, 30
-    Timer; magneto, 110, 121, 122
-    Timing a magneto, 223
-    Timing the valves, 237
-    Tractor; caring for in cold weather, 207
-    Tractor; difficulties in oiling, 178
-    Tractor driving, 205
-    Tractor; handling a new, 201
-    Tractor inspection, 203
-    Tractors and automobiles compared, 1
-    Tractor; storing, 210
-    Tractor types, 167
-    Transmission; parts of, 143
-    Trouble; causes of, 259
-    Trouble; locating, 246
-
-    Valve; exhaust, 38
-    Valve grinding, 229
-    Valve; inlet, 38
-    Valve mechanism, 42
-    Valve operation, 39
-    Valve seat; redressing, 234
-    Valve timing, 237
-    Vertical engine, 25
-    Vibrator coil, 138
-    Viscosity of oil, 182
-
-    Washer; air, 91
-    Water added to mixture, 58, 83, 219
-    Water jackets, 48
-    Windings; Bosch magneto, 110
-    Windings of spark coil, 134
-    Worm drive, 166
-    Wrist pin, 34
-
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-<p style='text-align:center; font-size:1.2em; font-weight:bold'>The Project Gutenberg eBook of Tractor Principles, by Roger B. Whitman</p>
-<div style='display:block; margin:1em 0'>
-This eBook is for the use of anyone anywhere in the United States and
-most other parts of the world at no cost and with almost no restrictions
-whatsoever. You may copy it, give it away or re-use it under the terms
-of the Project Gutenberg License included with this eBook or online
-at <a href="https://www.gutenberg.org">www.gutenberg.org</a>. If you
-are not located in the United States, you will have to check the laws of the
-country where you are located before using this eBook.
-</div>
-
-<p style='display:block; margin-top:1em; margin-bottom:1em; margin-left:2em; text-indent:-2em'>Title: Tractor Principles</p>
-<p style='display:block; margin-top:1em; margin-bottom:0; margin-left:2em; text-indent:-2em'>Author: Roger B. Whitman</p>
-<p style='display:block; text-indent:0; margin:1em 0'>Release Date: March 5, 2022 [eBook #67569]</p>
-<p style='display:block; text-indent:0; margin:1em 0'>Language: English</p>
-  <p style='display:block; margin-top:1em; margin-bottom:0; margin-left:2em; text-indent:-2em; text-align:left'>Produced by: deaurider and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)</p>
-<div style='margin-top:2em; margin-bottom:4em'>*** START OF THE PROJECT GUTENBERG EBOOK TRACTOR PRINCIPLES ***</div>
-<hr class="chap x-ebookmaker-drop" />
-
-<h1>TRACTOR PRINCIPLES</h1>
-
-<p class="f120"><b>THE ACTION, MECHANISM, HANDLING,<br />
-CARE, MAINTENANCE AND REPAIR<br />OF THE GAS ENGINE TRACTOR</b></p>
-
-<p class="center space-above2">BY</p>
-<p class="f150"><b>ROGER B. WHITMAN</b></p>
-
-<p class="center space-above2 space-below2">AUTHOR OF<br />
-“MOTOR CAR PRINCIPLES,”<br />“GAS ENGINE PRINCIPLES,”<br />
-“MOTOR-CYCLE PRINCIPLES,”<br />ETC.</p>
-
-<div class="figcenter">
-  <img  src="images/logo.jpg" alt="" width="150" height="135" />
-</div>
-
-<p class="center space-above2">FULLY ILLUSTRATED</p>
-
-<p class="center space-above2">D. APPLETON AND COMPANY<br />
-NEW YORK<span class="ws3">LONDON</span><br />1920</p>
-
-<p class="center space-above2">COPYRIGHT, 1920,<br />
-BY<br />D. APPLETON AND COMPANY</p>
-
-<p class="center space-above2">PRINTED IN THE UNITED STATES OF AMERICA</p>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_v">[Pg v]</span></p>
-<h2 class="nobreak">FOREWORD</h2>
-</div>
-
-<div class="blockquot">
-<p>The tractor of to-day is built in almost as many types and designs
-as there are tractor makers, and is far from being as standard as
-the automobile. There are tractors with one driving wheel, with two
-driving wheels, with three and with four, as well as three arrangements
-of the crawler principle; there are two-wheelers, three-wheelers and
-four-wheelers; tractors that are controlled by pedals and levers and
-tractors that are driven by reins.</p>
-
-<p>Thus if a man who is competent to handle and care for one make is given
-another make to run, he may be entirely at a loss as to how it works
-and how it should be handled.</p>
-
-<p>It is the purpose of this book to explain and describe all of the
-mechanisms that are in common use in tractor construction, to the end
-that the reader may be able to identify and understand the parts of
-whatever make he may see or handle.</p>
-</div>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_vii">[Pg vii]</span></p>
-<h2 class="nobreak">CONTENTS</h2>
-</div>
-
-<table border="0" cellspacing="0" summary="TOC" cellpadding="2" >
-  <tbody><tr>
-      <td class="tdr" colspan="2"><small>PAGE</small></td>
-   </tr><tr>
-      <td class="tdc fontsize_120" colspan="2"><b>CHAPTER I</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">TRACTOR PRINCIPLES</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Comparison between tractors and automobiles—What is
-                           required for each—Advantage of understanding the
-                           mechanism—No standard tractor design—Principal parts
-                           of a tractor—Necessity for each</p></td>
-      <td class="tdr_bott"><a href="#Page_1">&nbsp;1</a></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER II</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">ENGINE PRINCIPLES</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Power attained from heat—Combustible mixture—Principle
-           of engine operation—Combustion space—Gas engine
-           cycle—Dead strokes—Flywheel—Starting an
-           engine—Inlet stroke—Compression stroke—Importance
-           of compression—Ignition—Advance and retard of
-           ignition—Power stroke—Exhaust stroke—Production of
-           power—Vertical and horizontal engines—Firing order</p></td>
-      <td class="tdr_bott"><a href="#Page_9">&nbsp;9</a></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER III</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">ENGINE PARTS</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Base—Bearings—Cylinders—Crankshaft—Piston—Connecting
-             rod—Wrist pin—Piston rings—Valves—Cam—Valve
-             mechanisms—Cooling system</p></td>
-      <td class="tdr_bott"><a href="#Page_30">30</a></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER IV</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">FUELS AND CARBURETION</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Oxygen necessary for combustion—Forming a mixture—Rich and
-             poor mixtures—Carbon—Preignition— Carbureter—Spray
-             nozzle—Evaporation of fuels—Carbureter principles—
-             Extra air inlet—Effect of heat on mixture—Loading—Strangler</p></td>
-      <td class="tdr_bott"><a href="#Page_52">52</a>
-                <span class="pagenum" id="Page_viii">[Pg viii]</span></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER V</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">CARBURETERS</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Carbureter parts—Manifold—Action of carbureter—Float
-                feed—Kerosene and gasoline—Descriptions of
-                carbureters—Pump feed—Use of water in the
-                mixture—Application of heat—Fuel pumps—Air
-                cleaners—Governors</p></td>
-      <td class="tdr_bott"><a href="#Page_70">70</a></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER VI</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">IGNITION</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Principle of ignition—Point of
-              ignition—Preignition—Advance and retard—Parts of
-              ignition system—Magnetism—Induction—Magneto—Action
-              of armature—Armature windings—Circuit
-              breaker—Circuit—Shuttle and inductor
-              armatures—Sparking current—Grounded circuit—
-              Magneto parts—Impulse starter</p></td>
-      <td class="tdr_bott"><a href="#Page_102">102</a></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER VII</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">BATTERY IGNITION SYSTEMS</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Principle of spark coil—Windings—Timer—Atwater-Kent
-              system—Vibrator—Spark plugs</p></td>
-      <td class="tdr_bott"><a href="#Page_131">131</a></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER VIII</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">TRANSMISSION</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Transmission parts—Clutches—Necessity for change speed
-             gear—High and low gear—Types of change speed
-             gears—Necessity for differential—Principle of
-             differential—Drives—Worm</p></td>
-      <td class="tdr_bott"><a href="#Page_143">143</a>
-                         <span class="pagenum" id="Page_ix">[Pg ix]</span></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER IX</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">TRACTOR ARRANGEMENT</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Tractor requirements—Tractor types—Engine
-              position—Front axles—Spring supports</p></td>
-      <td class="tdr_bott"><a href="#Page_167">167</a></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER X</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">LUBRICATION</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Importance of lubrication—Effect of oil—Kinds
-             of oil—Effect of temperature on oil—Using the right
-             kind of oil—Burning point—Viscosity—Lubrication
-             charts—Oiling systems—Oil pumps—Mechanical oiler—
-             Oil cup—Grease cup</p></td>
-      <td class="tdr_bott"><a href="#Page_175">175</a></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER XI</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">TRACTOR OPERATION</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Using a new tractor—Breaking in—Daily
-               inspection—Driving—Shifting gears—Driving on
-               hills—Using the engine as a brake—Cold weather
-               conditions—Starting in cold weather—Protection
-               against freezing—Starting a tractor</p></td>
-      <td class="tdr_bott"><a href="#Page_201">201</a></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER XII</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">ENGINE MAINTENANCE</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Fuel system and carbureter—Carbureter adjustment—Dirt
-             in the fuel—Running on kerosene—Care—Magneto and
-             ignition system—Care of magneto—Smoothing platinum
-             points—Adjustment—Timing a magneto—Testing a
-             magneto—Ignition trouble—Compression—Testing
-             for compression leaks—Valve grinding—Valve
-             timing—Carbon—Removing carbon</p></td>
-      <td class="tdr_bott"><a href="#Page_213">213</a>
-                 <span class="pagenum" id="Page_x">[Pg x]</span></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER XIII</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">LOCATING TROUBLE</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Engine will not start—Engine loses power—Engine
-             stops—Engine misses—Engine starts; but stops—Engine
-             overheats—Engine smokes</p></td>
-      <td class="tdr_bott"><a href="#Page_245">245</a></td>
-   </tr><tr>
-      <td class="tdc_space-above1 fontsize_120" colspan="2"><b>CHAPTER XIV</b></td>
-   </tr><tr>
-      <td class="tdc fontsize_110" colspan="2">CAUSES OF TROUBLE</td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">Troubles and their causes in tabular form</p></td>
-      <td class="tdr_bott"><a href="#Page_259">259</a></td>
-   </tr><tr>
-      <td class="tdl"><p class="toc">INDEX</p></td>
-      <td class="tdr_bott"><a href="#Page_261">261</a></td>
-   </tr>
- </tbody>
-</table>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_xi">[Pg xi]</span></p>
-<h2 class="nobreak">ILLUSTRATIONS</h2>
-</div>
-
-<table border="0" cellspacing="0" summary="LOI" cellpadding="2" >
-  <tbody><tr>
-      <td class="tdr"><small>FIG.</small></td>
-      <td class="tdc">&nbsp;</td>
-      <td class="tdr"><small>PAGE</small></td>
-   </tr><tr>
-      <td class="tdr">1</td>
-      <td class="tdl_ws1">The Gas Engine Cycle</td>
-      <td class="tdr"><a href="#FIG_1">15</a></td>
-   </tr><tr>
-      <td class="tdr">2</td>
-      <td class="tdl_ws1">1-cylinder power diagram</td>
-      <td class="tdr"><a href="#FIG_2">21</a></td>
-   </tr><tr>
-      <td class="tdr">3</td>
-      <td class="tdl_ws1">2-cylinder power diagram</td>
-      <td class="tdr"><a href="#FIG_3">22</a></td>
-   </tr><tr>
-      <td class="tdr">4</td>
-      <td class="tdl_ws1">2-cylinder power diagram, 180 shaft</td>
-      <td class="tdr"><a href="#FIG_4">24</a></td>
-   </tr><tr>
-      <td class="tdr">5</td>
-      <td class="tdl_ws1">H. D. O. power diagram</td>
-      <td class="tdr"><a href="#FIG_5">26</a></td>
-   </tr><tr>
-      <td class="tdr">6</td>
-      <td class="tdl_ws1">4-cylinder power diagram</td>
-      <td class="tdr"><a href="#FIG_6">27</a></td>
-   </tr><tr>
-      <td class="tdr">7</td>
-      <td class="tdl_ws1">2-cylinder crank shaft</td>
-      <td class="tdr"><a href="#FIG_7">31</a></td>
-   </tr><tr>
-      <td class="tdr">8</td>
-      <td class="tdl_ws1">4-cylinder crank shaft</td>
-      <td class="tdr"><a href="#FIG_8">32</a></td>
-   </tr><tr>
-      <td class="tdr">9</td>
-      <td class="tdl_ws1">Half of a plain bearing</td>
-      <td class="tdr"><a href="#FIG_9">32</a></td>
-   </tr><tr>
-      <td class="tdr">10</td>
-      <td class="tdl_ws1">Connecting rod bearings</td>
-      <td class="tdr"><a href="#FIG_10">33</a></td>
-   </tr><tr>
-      <td class="tdr">11</td>
-      <td class="tdl_ws1">Piston complete and in section</td>
-      <td class="tdr"><a href="#FIG_11">34</a></td>
-   </tr><tr>
-      <td class="tdr">12</td>
-      <td class="tdl_ws1">Wrist pin fastenings</td>
-      <td class="tdr"><a href="#FIG_12">36</a></td>
-   </tr><tr>
-      <td class="tdr">13</td>
-      <td class="tdl_ws1">Valve</td>
-      <td class="tdr"><a href="#FIG_13">38</a></td>
-   </tr><tr>
-      <td class="tdr">14</td>
-      <td class="tdl_ws1">Action of cam</td>
-      <td class="tdr"><a href="#FIG_14">39</a></td>
-   </tr><tr>
-      <td class="tdr">15</td>
-      <td class="tdl_ws1">“Twin City” tractor engine</td>
-      <td class="tdr"><a href="#FIG_15">41</a></td>
-   </tr><tr>
-      <td class="tdr">16</td>
-      <td class="tdl_ws1">“Hart-Parr” valve mechanism</td>
-      <td class="tdr"><a href="#FIG_16">43</a></td>
-   </tr><tr>
-      <td class="tdr">17</td>
-      <td class="tdl_ws1">“Hart-Parr” engine</td>
-      <td class="tdr"><a href="#FIG_17">45</a></td>
-   </tr><tr>
-      <td class="tdr">18</td>
-      <td class="tdl_ws1">“Oil-Pull” engine</td>
-      <td class="tdr"><a href="#FIG_18">47</a></td>
-   </tr><tr>
-      <td class="tdr">19</td>
-      <td class="tdl_ws1">Horizontal double opposed engine</td>
-      <td class="tdr"><a href="#FIG_19">49</a></td>
-   </tr><tr>
-      <td class="tdr">20</td>
-      <td class="tdl_ws1">“Monarch” engine</td>
-      <td class="tdr"><a href="#FIG_20">51</a></td>
-   </tr><tr>
-      <td class="tdr">21</td>
-      <td class="tdl_ws1">Principle of carburetor</td>
-      <td class="tdr"><a href="#FIG_21">59</a></td>
-   </tr><tr>
-      <td class="tdr">22</td>
-      <td class="tdl_ws1">Principle of extra air inlet</td>
-      <td class="tdr"><a href="#FIG_22">64</a></td>
-   </tr><tr>
-      <td class="tdr">23</td>
-      <td class="tdl_ws1">“Kingston” carburetor, model L</td>
-      <td class="tdr"><a href="#FIG_23">72</a>
-               <span class="pagenum" id="Page_xii">[Pg xii]</span></td>
-   </tr><tr>
-      <td class="tdr">24</td>
-      <td class="tdl_ws1">“Kingston” carburetor, model E</td>
-      <td class="tdr"><a href="#FIG_24">75</a></td>
-   </tr><tr>
-      <td class="tdr">25</td>
-      <td class="tdl_ws1">“Kingston” carburetor, dual model</td>
-      <td class="tdr"><a href="#FIG_25">77</a></td>
-   </tr><tr>
-      <td class="tdr">26</td>
-      <td class="tdl_ws1">“E-B” carburetor</td>
-      <td class="tdr"><a href="#FIG_26">79</a></td>
-   </tr><tr>
-      <td class="tdr">27</td>
-      <td class="tdl_ws1">“E-B” carburetor, side view</td>
-      <td class="tdr"><a href="#FIG_27">81</a></td>
-   </tr><tr>
-      <td class="tdr">28</td>
-      <td class="tdl_ws1">Pump-fed carburetor</td>
-      <td class="tdr"><a href="#FIG_28">82</a></td>
-   </tr><tr>
-      <td class="tdr">29</td>
-      <td class="tdl_ws1">“Titan” carburetor</td>
-      <td class="tdr"><a href="#FIG_29">84</a></td>
-   </tr><tr>
-      <td class="tdr">30</td>
-      <td class="tdl_ws1">Pump-fed carburetor with two fuel nozzles</td>
-      <td class="tdr"><a href="#FIG_30">85</a></td>
-   </tr><tr>
-      <td class="tdr">31</td>
-      <td class="tdl_ws1">“Hart-Parr” mixture heater</td>
-      <td class="tdr"><a href="#FIG_31">87</a></td>
-   </tr><tr>
-      <td class="tdr">32</td>
-      <td class="tdl_ws1">“Twin City” manifold</td>
-      <td class="tdr"><a href="#FIG_32">88</a></td>
-   </tr><tr>
-      <td class="tdr">33</td>
-      <td class="tdl_ws1"> Fuel pump</td>
-      <td class="tdr"><a href="#FIG_33">90</a></td>
-   </tr><tr>
-      <td class="tdr">34</td>
-      <td class="tdl_ws1">“Avery” fuel connections</td>
-      <td class="tdr"><a href="#FIG_34">92</a></td>
-   </tr><tr>
-      <td class="tdr">35</td>
-      <td class="tdl_ws1">“Oil-Pull” fuel system</td>
-      <td class="tdr"><a href="#FIG_35">93</a></td>
-   </tr><tr>
-      <td class="tdr">36</td>
-      <td class="tdl_ws1">Air washer</td>
-      <td class="tdr"><a href="#FIG_36">95</a></td>
-   </tr><tr>
-      <td class="tdr">37</td>
-      <td class="tdl_ws1">Air strainer</td>
-      <td class="tdr"><a href="#FIG_37">96</a></td>
-   </tr><tr>
-      <td class="tdr">38</td>
-      <td class="tdl_ws1">“E-B” governor</td>
-      <td class="tdr"><a href="#FIG_38">97</a></td>
-   </tr><tr>
-      <td class="tdr">39</td>
-      <td class="tdl_ws1">“Case” governor</td>
-      <td class="tdr"><a href="#FIG_39">98</a></td>
-   </tr><tr>
-      <td class="tdr">40</td>
-      <td class="tdl_ws1">“Hart-Parr” governor</td>
-      <td class="tdr"><a href="#FIG_40">99</a></td>
-   </tr><tr>
-      <td class="tdr">41</td>
-      <td class="tdl_ws1">Vertical governor</td>
-      <td class="tdr"><a href="#FIG_41">101</a></td>
-   </tr><tr>
-      <td class="tdr">42</td>
-      <td class="tdl_ws1">Armature</td>
-      <td class="tdr"><a href="#FIG_42">107</a></td>
-   </tr><tr>
-      <td class="tdr">43</td>
-      <td class="tdl_ws1">Flow of magnetism through armature core</td>
-      <td class="tdr"><a href="#FIG_43">108</a></td>
-   </tr><tr>
-      <td class="tdr">44</td>
-      <td class="tdl_ws1">One complete revolution of the armature</td>
-      <td class="tdr"><a href="#FIG_44">111</a></td>
-   </tr><tr>
-      <td class="tdr">45</td>
-      <td class="tdl_ws1">Connections of Bosch magneto</td>
-      <td class="tdr"><a href="#FIG_45">112</a></td>
-   </tr><tr>
-      <td class="tdr">46</td>
-      <td class="tdl_ws1">“K-W” inductor</td>
-      <td class="tdr"><a href="#FIG_46">115</a></td>
-   </tr><tr>
-      <td class="tdr">47</td>
-      <td class="tdl_ws1">“K-W” inductor in three positions</td>
-      <td class="tdr"><a href="#FIG_47">117</a></td>
-   </tr><tr>
-      <td class="tdr">48</td>
-      <td class="tdl_ws1">“Dixie” inductor</td>
-      <td class="tdr"><a href="#FIG_48">118</a></td>
-   </tr><tr>
-      <td class="tdr">49</td>
-      <td class="tdl_ws1">Three positions of “Dixie” inductor</td>
-      <td class="tdr"><a href="#FIG_49">120</a></td>
-   </tr><tr>
-      <td class="tdr">50</td>
-      <td class="tdl_ws1">“Bosch” circuit breaker</td>
-      <td class="tdr"><a href="#FIG_50">121</a></td>
-   </tr><tr>
-      <td class="tdr">51</td>
-      <td class="tdl_ws1">“K-W” circuit breaker</td>
-      <td class="tdr"><a href="#FIG_51">122</a></td>
-   </tr><tr>
-      <td class="tdr">52</td>
-      <td class="tdl_ws1">“Bosch” magneto in section</td>
-      <td class="tdr"><a href="#FIG_52">126</a></td>
-   </tr><tr>
-      <td class="tdr">53</td>
-      <td class="tdl_ws1">“K-W” magneto in section</td>
-      <td class="tdr"><a href="#FIG_53">129</a></td>
-   </tr><tr>
-      <td class="tdr">54</td>
-      <td class="tdl_ws1">Magnetism in a copper wire</td>
-      <td class="tdr"><a href="#FIG_54">132</a>
-              <span class="pagenum" id="Page_xiii">[Pg xiii]</span></td>
-   </tr><tr>
-      <td class="tdr">55</td>
-      <td class="tdl_ws1">Magnetism from electricity</td>
-      <td class="tdr"><a href="#FIG_56">133</a></td>
-   </tr><tr>
-      <td class="tdr">56</td>
-      <td class="tdl_ws1">Principle of spark coil</td>
-      <td class="tdr"><a href="#FIG_56">134</a></td>
-   </tr><tr>
-      <td class="tdr">57</td>
-      <td class="tdl_ws1">“Atwater-Kent” ignition system</td>
-      <td class="tdr"><a href="#FIG_57">136</a></td>
-   </tr><tr>
-      <td class="tdr">58</td>
-      <td class="tdl_ws1">Vibrator coil ignition system</td>
-      <td class="tdr"><a href="#FIG_58">139</a></td>
-   </tr><tr>
-      <td class="tdr">59</td>
-      <td class="tdl_ws1">Spark plug</td>
-      <td class="tdr"><a href="#FIG_59">141</a></td>
-   </tr><tr>
-      <td class="tdr">60</td>
-      <td class="tdl_ws1">Internal clutch</td>
-      <td class="tdr"><a href="#FIG_60">144</a></td>
-   </tr><tr>
-      <td class="tdr">61</td>
-      <td class="tdl_ws1">Plate clutch</td>
-      <td class="tdr"><a href="#FIG_61">147</a></td>
-   </tr><tr>
-      <td class="tdr">62</td>
-      <td class="tdl_ws1">Principle of sliding gear</td>
-      <td class="tdr"><a href="#FIG_62">155</a></td>
-   </tr><tr>
-      <td class="tdr">63</td>
-      <td class="tdl_ws1">Principle of jaw clutch change speed gear</td>
-      <td class="tdr"><a href="#FIG_63">157</a></td>
-   </tr><tr>
-      <td class="tdr">64</td>
-      <td class="tdl_ws1">“I. H. C.” chain drive, showing differential
-                    <span class="ws2">&nbsp;</span></td>
-      <td class="tdr"><a href="#FIG_64">162</a></td>
-   </tr><tr>
-      <td class="tdr">65</td>
-      <td class="tdl_ws1">“Case” rear axle</td>
-      <td class="tdr"><a href="#FIG_65">163</a></td>
-   </tr><tr>
-      <td class="tdr">66</td>
-      <td class="tdl_ws1">“Oil-Pull” rear axle</td>
-      <td class="tdr"><a href="#FIG_66">164</a></td>
-   </tr><tr>
-      <td class="tdr">67</td>
-      <td class="tdl_ws1">Driving worm</td>
-      <td class="tdr"><a href="#FIG_67">165</a></td>
-   </tr><tr>
-      <td class="tdr">68</td>
-      <td class="tdl_ws1">Tractor arrangement</td>
-      <td class="tdr"><a href="#FIG_68">168</a></td>
-   </tr><tr>
-      <td class="tdr">69</td>
-      <td class="tdl_ws1">Tractor arrangement</td>
-      <td class="tdr"><a href="#FIG_69">169</a></td>
-   </tr><tr>
-      <td class="tdr">70</td>
-      <td class="tdl_ws1">“Gray” tractor</td>
-      <td class="tdr"><a href="#FIG_70">171</a></td>
-   </tr><tr>
-      <td class="tdr">71</td>
-      <td class="tdl_ws1">Types of front axles</td>
-      <td class="tdr"><a href="#FIG_71">172</a></td>
-   </tr><tr>
-      <td class="tdr">72</td>
-      <td class="tdl_ws1">Spring support</td>
-      <td class="tdr"><a href="#FIG_72">173</a></td>
-   </tr><tr>
-      <td class="tdr">73</td>
-      <td class="tdl_ws1">“Mogul” oiling diagram</td>
-      <td class="tdr"><a href="#FIG_73">180</a></td>
-   </tr><tr>
-      <td class="tdr">74</td>
-      <td class="tdl_ws1">“Illinois” oiling diagram</td>
-      <td class="tdr"><a href="#FIG_74">183</a></td>
-   </tr><tr>
-      <td class="tdr">75</td>
-      <td class="tdl_ws1">End of “Twin City” connecting rod</td>
-      <td class="tdr"><a href="#FIG_75">185</a></td>
-   </tr><tr>
-      <td class="tdr">76</td>
-      <td class="tdl_ws1">Wrist pin lubrication</td>
-      <td class="tdr"><a href="#FIG_76">186</a></td>
-   </tr><tr>
-      <td class="tdr">77</td>
-      <td class="tdl_ws1">Force feed oiling system of “Gray” engine</td>
-      <td class="tdr"><a href="#FIG_77">187</a></td>
-   </tr><tr>
-      <td class="tdr">78</td>
-      <td class="tdl_ws1">Oil pump</td>
-      <td class="tdr"><a href="#FIG_78">188</a></td>
-   </tr><tr>
-      <td class="tdr">79</td>
-      <td class="tdl_ws1">“E-B” oil pump</td>
-      <td class="tdr"><a href="#FIG_79">189</a></td>
-   </tr><tr>
-      <td class="tdr">80</td>
-      <td class="tdl_ws1">Oil pump with hollow plunger</td>
-      <td class="tdr"><a href="#FIG_80">190</a></td>
-   </tr><tr>
-      <td class="tdr">81</td>
-      <td class="tdl_ws1">Methods of preventing oil leaks</td>
-      <td class="tdr"><a href="#FIG_81">191</a></td>
-   </tr><tr>
-      <td class="tdr">82</td>
-      <td class="tdl_ws1">“Titan” lubricator</td>
-      <td class="tdr"><a href="#FIG_82">192</a></td>
-   </tr><tr>
-      <td class="tdr">83</td>
-      <td class="tdl_ws1">“I. H. C.” method of oiling crank pins</td>
-      <td class="tdr"><a href="#FIG_83">193</a></td>
-   </tr><tr>
-      <td class="tdr">84</td>
-      <td class="tdl_ws1">“Hart-Parr” oiling system</td>
-      <td class="tdr"><a href="#FIG_84">194</a></td>
-   </tr><tr>
-      <td class="tdr">85</td>
-      <td class="tdl_ws1">Oil cup</td>
-      <td class="tdr"><a href="#FIG_85">195</a>
-                 <span class="pagenum" id="Page_xiv">[Pg xiv]</span></td>
-   </tr><tr>
-      <td class="tdr">86</td>
-      <td class="tdl_ws1">Proper use of a grease cup</td>
-      <td class="tdr"><a href="#FIG_86">196</a></td>
-   </tr><tr>
-      <td class="tdr">87</td>
-      <td class="tdl_ws1">“Titan” 10-20 oiling diagram</td>
-      <td class="tdr"><a href="#FIG_87">198</a></td>
-   </tr><tr>
-      <td class="tdr">88</td>
-      <td class="tdl_ws1">“International” oiling diagram</td>
-      <td class="tdr"><a href="#FIG_88">199</a></td>
-   </tr><tr>
-      <td class="tdr">89</td>
-      <td class="tdl_ws1">Grinding valve in engine with fixed head</td>
-      <td class="tdr"><a href="#FIG_89">231</a></td>
-   </tr><tr>
-      <td class="tdr">90</td>
-      <td class="tdl_ws1">Grinding valve in detachable head</td>
-      <td class="tdr"><a href="#FIG_90">233</a></td>
-   </tr><tr>
-      <td class="tdr">91</td>
-      <td class="tdl_ws1">Grinding valve in detachable seat</td>
-      <td class="tdr"><a href="#FIG_91">234</a></td>
-   </tr><tr>
-      <td class="tdr">92</td>
-      <td class="tdl_ws1">Valve seat cutter</td>
-      <td class="tdr"><a href="#FIG_92">235</a></td>
-   </tr><tr>
-      <td class="tdr">93</td>
-      <td class="tdl_ws1">“Holt” valve arrangement</td>
-      <td class="tdr"><a href="#FIG_93">236</a></td>
-   </tr><tr>
-      <td class="tdr">94</td>
-      <td class="tdl_ws1">Valve timing, using marks on flywheel</td>
-      <td class="tdr"><a href="#FIG_94">238</a></td>
-   </tr><tr>
-      <td class="tdr">95</td>
-      <td class="tdl_ws1">Valve timing</td>
-      <td class="tdr"><a href="#FIG_95">239</a></td>
-   </tr>
- </tbody>
-</table>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p class="f200"><b>TRACTOR PRINCIPLES</b></p>
-</div>
-
-<hr class="chap x-ebookmaker-drop" />
-<div class="chapter">
-<p><span class="pagenum" id="Page_1">[Pg 1]</span></p>
-<h2 class="nobreak" id="CHAPTER_I">CHAPTER I<br />
-<span class="h_subtitle">TRACTOR PRINCIPLES</span></h2>
-</div>
-
-<p>While tractors and automobiles are the same in general principles,
-there is a wide difference between them in design, construction, and
-handling, due to the differences in the work that they do and in the
-conditions under which they do it.</p>
-
-<p>An automobile is required to move only itself and the load that it
-carries. While it can run over rough roads, these must be hard enough
-to support it; on soft ground it will sink in and be unable to get
-itself out. It can make great speed over smooth, level roads; but only
-rarely do road and police conditions permit it to run its fastest for
-<span class="pagenum" id="Page_2">[Pg 2]</span>
-more than a few minutes at a time. For the greater part of its life it
-develops only a portion of the power of which it is capable.</p>
-
-<p>A tractor, on the other hand, is intended not to carry, but to haul.
-It must run and do its work on rough hillsides, soft bottoms, or any
-other land where it is required to go. Instead of developing speed it
-develops pulling power, and must be able to develop its full power
-continuously.</p>
-
-<p>Appearance and comfort count for a great deal in an automobile, and
-much attention is devoted to making it noiseless and simple to manage.
-These things do not apply in a tractor, which is a labor-saving and
-money-making machine, valuable only for the work that it can do. There
-is no question of upholstery or nickel-plating; all that is wanted is a
-machine that will do the required work with the least possible cost of
-operation.</p>
-
-<p>As is the case with any kind of machine that is purchased as a
-money-maker, its cost should be as low as is consistent with its
-<span class="pagenum" id="Page_3">[Pg 3]</span>
-ability to do its work. Any extra cost for accessories, or finish, or
-other detail, is wasted unless it permits the machine to do more work,
-or, by making the operator more comfortable, allows him to run the
-machine for a longer stretch of time or with greater efficiency.</p>
-
-<p>It may be taken for granted that any tractor will run and will do its
-work with satisfaction, provided it is sensibly handled and cared for.
-Far more troubles and breakdowns come from careless handling and from
-neglect than from faulty design and material. A tractor that is running
-and doing its work is earning a return on the money invested in it;
-when it is laid up for repairs there is not only a loss of interest on
-the investment, but a loss of the value of the work that it might be doing.</p>
-
-<p>To keep a tractor running is a matter only of understanding and of
-common sense; common sense to realize that any piece of machinery needs
-some degree of care and attention, and understanding of where the care
-<span class="pagenum" id="Page_4">[Pg 4]</span>
-and attention should be applied. The more thoroughly a tractor operator
-understands his machine, the more work he will be able to get out of
-it, and the more continuously it will run. This is only another way of
-saying that understanding and knowledge pay a direct return in work
-done and money earned.</p>
-
-<p>In the early days of the automobile there were as many types of cars
-as there were manufacturers. As time has gone on, the unsatisfactory
-ideas have been weeded out, and automobiles have approached what may be
-called a standard design.</p>
-
-<p>At the present time, tractor designs are varied, and it is hardly
-possible to speak of any type as standard. The reason for this lies in
-the fact that many manufacturers start with a design for one special
-part, and build the tractor around it.</p>
-
-<p>For example, a manufacturer may develop a method of driving the wheels
-that he feels is especially good for tractor work. In applying it he
-<span class="pagenum" id="Page_5">[Pg 5]</span>
-may find that the engine must be so placed on the frame that when the
-power pulley is in position the belt will interfere with the front
-wheels unless they are small; he therefore uses small front wheels, and
-advocates them for tractors.</p>
-
-<p>Another manufacturer with a patent steering gear may be able to place
-the power pulley so that there is ample clearance for the belt; he
-finds that by using high front wheels he can get a better support for
-the frame, and therefore claims that high front wheels are an advantage.</p>
-
-<p>Other designs may be based on having three wheels, or two; advantages
-are claimed for each type, and each type undoubtedly has them.</p>
-
-<p>The selection of a tractor is based on one’s own experience or on
-that of neighbors, or on the ability of the salesman to bring out the
-advantages of the make that he sells; but when the tractor is bought
-and delivered, its ability to do the work promised for it depends solely
-<span class="pagenum" id="Page_6">[Pg 6]</span>
-on the care with which it is handled and looked after.</p>
-
-<p>Whatever the design of a tractor may be, there are certain parts that
-it must have in order to do the work required of it. These parts, or
-groups of parts, are as follows:</p>
-
-<p><span class="fontsize_120"><b>Engine.</b></span>—This furnishes the
-power by which the tractor operates.</p>
-
-<p><span class="fontsize_120"><b>Clutch.</b></span>—By means of a
-clutch the engine may be connected with the mechanism, so that the
-tractor moves, or it may be disconnected, so that it may run without
-moving the tractor.</p>
-
-<p><span class="fontsize_120"><b>Change Speed Gear.</b></span>—As
-will be explained in later chapters, an engine, in order to work
-most efficiently, should run at a fixed speed; the tractor should be
-able to run fast or slow, according to conditions. A change speed
-gear is therefore provided, by which the speed of the tractor may be
-changed, although there is no change in the speed of the engine.
-<span class="pagenum" id="Page_7">[Pg 7]</span></p>
-
-<p><span class="fontsize_120"><b>Drive.</b></span>—The drive is the
-mechanism that applies the power of the engine to the wheels, and makes
-them turn.</p>
-
-<p><span class="fontsize_120"><b>Differential.</b></span>—When a
-tractor makes a turn, the outside wheels cover a larger circle than the
-inside wheels, and therefore must run faster in order to get around in
-the same time. It is usually the case that the power of the engine is
-applied to both driving wheels; if both were solid on the axle, like
-the wheels of a railroad car, one would be forced to slip when making a
-turn, which would waste power. By applying a differential, the engine
-can drive both wheels, but the wheels may run at different speeds when
-conditions require it.</p>
-
-<p>The clutch, change speed gear, drive and differential form the
-<i>transmission</i>.</p>
-
-<p><span class="fontsize_120"><b>Steering gear.</b></span>—By means
-of the steering gear the direction in which the tractor moves may be
-changed.</p>
-
-<p><span class="fontsize_120"><b>Supports.</b></span>—A tractor moves
-on broad-tired wheels, or on crawlers, which are so formed that they
-grip the ground and do not slip.
-<span class="pagenum" id="Page_8">[Pg 8]</span>
-They give so broad a support that even on soft ground the
-weight of the tractor will not pack the soil sufficiently to injure it
-as a seed bed.</p>
-
-<p><span class="fontsize_120"><b>Frame.</b></span>—The frame is the
-foundation of the tractor, and holds the parts in the proper relation
-to each other. It is usually made of channel steel, the parts being
-bolted to it; in some tractors, however, the parts are so attached to
-each other that they form their own support, and no other frame is needed.</p>
-
-<p>Tractor manufacturers make these parts in different ways; all
-accomplish the same result, but do it by different methods. The main
-principles are much the same, and should be known and understood. They
-are described and explained in the succeeding chapters.</p>
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_9">[Pg 9]</span></p>
-<h2 class="nobreak" id="CHAPTER_II">CHAPTER II<br />
-<span class="h_subtitle">ENGINE PRINCIPLES</span></h2>
-</div>
-
-<p>The working part of a tractor is the engine; it is this that furnishes
-the power that makes the machine go.</p>
-
-<p>The engine gets its power from the burning of a mixture of fuel vapor
-and air. When this mixture burns, it becomes heated, and, as is usual
-with hot things, it tries to expand, or to occupy more room.</p>
-
-<p>The mixture is placed in a cylinder, between the closed end and the
-piston; it is then heated by being burned, and, in struggling to
-expand, it forces the piston to slide down the cylinder. This movement
-of the piston makes the crank shaft revolve, which in turn drives the tractor.</p>
-
-<p>The first step in making the engine run is to put a charge of mixture
-<span class="pagenum" id="Page_10">[Pg 10]</span>
-into the cylinder, and it is clear that if the burning of the charge is
-to move the piston, the piston must be in such a position that it is
-able to move. When the mixture is burned, the piston must therefore be
-at the closed end of the cylinder.</p>
-
-<p>After the charge of mixture has been burned, the cylinder must be
-cleared of the dead and useless gases that remain, in order to make
-room for a fresh charge.</p>
-
-<p>The charge of mixture is drawn into the cylinder just as a pump sucks
-in water. At a time when the piston is at the closed end of the
-cylinder, a valve is opened connecting the space above the piston with
-the device that forms the mixture; then by moving the piston outward,
-mixture is sucked into the space above it. When the piston reaches the
-end of its stroke the cylinder has been filled with mixture, and the
-valve then closes.</p>
-
-<p>It would be useless to set fire to the mixture at that time, for the
-piston is as far down the cylinder as it can be, and pressure could not
-<span class="pagenum" id="Page_11">[Pg 11]</span>
-move it any farther. To get the piston into such a position that the
-expanding mixture can move it, it is forced back to the closed end of
-the cylinder. This squeezes or <i>compresses</i>, the cylinderful of
-mixture into the small space, called the <i>combustion chamber</i>,
-between the piston and the cylinder head.</p>
-
-<p>If the mixture is now burned, the piston can move the length of the
-cylinder, and in so doing it develops power.</p>
-
-<p>The cylinder is cleared of the burned and useless gases by opening a
-valve and pushing them out by moving the piston back to the inner end
-of the cylinder. When this has been done, the valve is closed, and, by
-opening the inlet valve and moving the piston outward, a fresh charge
-is sucked in, and the several steps of the <i>gas engine cycle</i> are
-repeated.</p>
-
-<p>The name <i>cycle</i> is given to any series of steps or events that
-must be gone through in order that a thing may happen. Thus the empty
-<span class="pagenum" id="Page_12">[Pg 12]</span>
-shell must be taken out of a gun and a fresh cartridge put in before
-the gun can be fired again, and that series of steps might be called
-the gun cycle.</p>
-
-<p>The gas engine cycle requires the piston to make four strokes. An
-outward stroke sucks in a charge of mixture, and an inward stroke
-returns the piston to the firing position and compresses the charge.
-Then comes the outward stroke when the piston moves under power, followed
-by the inward stroke that clears the cylinder of the burned gases.</p>
-
-<p>For every stroke of the piston the crank shaft makes a half-revolution;
-the crank shaft therefore makes two revolutions to four strokes of the
-piston and to each repetition of the gas engine cycle.</p>
-
-<p>Of these four strokes of the piston only one produces power. The other
-three strokes, called the <i>dead strokes</i>, are required to prepare
-for another power stroke.</p>
-
-<p>A gas engine cylinder thus produces power for only one quarter of the
-time that it runs. This is one of the striking differences between the
-<span class="pagenum" id="Page_13">[Pg 13]</span>
-gas engine and the steam engine, for the piston of a steam engine moves
-under power all of the time that the engine runs.</p>
-
-<p>A one-cylinder gas engine must have something to make the piston go
-through the dead strokes, for otherwise the piston would stop at
-the end of the power stroke; the piston is kept in motion by heavy
-flywheels attached to the crank shaft. These, like any object, try to
-continue in motion when once they are started; a power stroke starts
-the crank shaft revolving and its flywheels keep it going.</p>
-
-<p>Thus, the piston drives the crank shaft during the power stroke, and
-the crank shaft drives the piston during the dead strokes.</p>
-
-<p>To start an engine, the crank shaft is revolved to make the piston suck
-in a charge of mixture and compress it; then the charge is burned, the
-power stroke takes place, and the engine runs.</p>
-
-<p>A clear idea of what goes on inside of the cylinder is quite necessary
-<span class="pagenum" id="Page_14">[Pg 14]</span>
-in order to take proper care of an engine and to get the best work
-out of it. The following description applies to any cylinder, for the
-action in all cylinders of an engine is the same.</p>
-
-<p><span class="fontsize_120"><b>Inlet Stroke.</b></span>—During the
-inlet stroke (<a href="#FIG_1">No. 1, Fig. 1</a>), the piston moves outward; the
-inlet valve is open, and the exhaust valve is closed. This movement of the piston
-creates suction, and if there are leaks in the cylinder, air will be
-sucked in and will spoil the proportions of the charge. This will prevent
-the proper burning of the mixture, and the engine will lose power.</p>
-
-<p>The piston moves at such high speed that the mixture cannot enter fast
-enough to keep up with it; mixture is still flowing in when the piston
-reaches the end of its stroke, and even when it begins to move inward
-on the next stroke. The more mixture there is in the cylinder, the more
-powerfully the engine will run; the inlet valve is therefore held open
-for as long a time as the mixture continues to enter.
-<span class="pagenum" id="Page_15">[Pg 15]</span></p>
-
-<div id="FIG_1" class="figcenter">
-  <img src="images/i_p015a.jpg" alt="" width="400" height="405" />
-  <img src="images/i_p015b.jpg" alt="" width="400" height="410" />
-  <p class="center"><span class="smcap">Fig. 1.—The Gas Engine Cycle</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_16">[Pg 16]</span>
-In slow-speed 1-cylinder and 2-cylinder engines the valve closes when
-the piston reaches the end of its stroke; on high-speed engines the
-valve does not close until the piston has moved ¼ inch or ½ inch on the
-compression stroke.</p>
-
-<p><span class="fontsize_120"><b>Compression Stroke.</b></span>—During
-the compression stroke (<a href="#FIG_1">No. 2, Fig. 1</a>) the piston moves inward,
-and both valves are closed. This movement places the piston in position
-to move outward on the power stroke. As the outlets to the cylinder
-are closed, the charge of mixture cannot escape, and is therefore
-compressed into the space between the piston and the cylinder head when
-the piston is at the inner end of its stroke. This space is usually
-about one quarter the volume of the cylinder; the charge is therefore
-compressed to about one quarter of its original volume.</p>
-
-<p>This compression of the charge is very important in the operation of
-the gas engine, and any interference with it will make the engine run poorly.
-<span class="pagenum" id="Page_17">[Pg 17]</span></p>
-
-<p>In the first place, it improves the quality of the charge, and makes it
-burn very much better. When the charge enters the cylinder, the fuel
-vapor and air are not thoroughly mixed; much of the fuel is not turned
-into vapor. By compressing the charge it becomes heated; this vaporizes
-the fuel, and vapor and air become thoroughly mixed.</p>
-
-<p>Compression also increases the power. Suppose that the cylinder
-contains a quart of mixture which, when heated, will expand to a
-gallon. If this quart of mixture is compressed to a half pint, it
-will not lose its ability to expand to a gallon, and will exert more
-pressure in expanding from a half pint to a gallon than from a quart to
-a gallon.</p>
-
-<p>A leaky cylinder will cause a further loss of power because some of the
-charge will escape during the compression stroke, which will leave less
-to be burned and to develop power.</p>
-
-<p><span class="fontsize_120"><b>Ignition.</b></span>—Setting fire to the
-charge of mixture is called the <i>ignition</i> of the charge, and it
-<span class="pagenum" id="Page_18">[Pg 18]</span>
-takes place close to the end of the compression stroke. To get the
-greatest power, all of the mixture should be on fire and heated most
-intensely as the piston begins the power stroke.</p>
-
-<p>When the mixture is set on fire, it does not explode like gunpowder,
-but burns comparatively slowly; the charge is ignited by an electric
-spark, and the flame spreads from that point until it is all on
-fire. In order to give the flame time to spread, the spark passes
-sufficiently before the end of the compression stroke to have the
-entire charge on fire as the power stroke begins. This is called the
-<i>advance</i> of the ignition.</p>
-
-<p>The flame takes the same time to spread through the charge when the
-engine is running fast as when it is running slow. Therefore if the
-engine is speeded up, the spark must be advanced, for otherwise the
-piston would be on the power stroke before the flame would have time to
-spread all through the mixture.
-<span class="pagenum" id="Page_19">[Pg 19]</span></p>
-
-<p>When the engine is slowed down, the spark must have less advance, or
-must be <i>retarded</i>, for, if it were not, the charge would all be
-in flame, and exerting its full pressure, before the piston reached the
-end of its compression stroke.</p>
-
-<p>The subject of ignition, which is of great importance, is covered more
-fully in <a href="#CHAPTER_VI">Chapter VI</a>.</p>
-
-<p><span class="fontsize_120"><b>Power Stroke.</b></span>—During
-the power stroke (<a href="#FIG_1">No. 3, Fig. 1</a>) the piston moves outward,
-and both valves are closed. As it begins, the mixture is all on fire, and great
-pressure is exerted against the piston.</p>
-
-<p>As the piston moves outward the combustion space becomes larger, and
-the gases obtain the room for expansion that they seek. As they expand,
-the pressure that they exert becomes less. By the time the piston
-is three quarters the way down the power stroke, the pressure is so
-reduced that it has little or no effect; the gases are still trying to
-<span class="pagenum" id="Page_20">[Pg 20]</span>
-expand, however, so the exhaust valve is opened at that point, and they
-begin to escape.</p>
-
-<p><span class="fontsize_120"><b>Exhaust Stroke.</b></span>—During the
-exhaust stroke (<a href="#FIG_1">No. 4, Fig. 1</a>) the piston moves inward and the
-exhaust valve is open. This movement of the piston pushes the burned gases out
-of the cylinder, and it is clear that the more thoroughly the cylinder
-is emptied of them, the more room there will be for a fresh charge.</p>
-
-<p>In high-speed engines the gases cannot escape as fast as the piston
-moves; they are still flowing out when the end of the stroke is
-reached. Therefore the valve is closed, not at the end of the stroke,
-but when the piston has moved about ⅛ inch outward on the inlet stroke.
-The inlet valve opens as the exhaust valve closes.</p>
-
-<p>It can be seen that through the inlet and compression strokes a leak
-will reduce the charge and so interfere with the production of full
-power. The piston must make a tight fit in the cylinder, the valves
-<span class="pagenum" id="Page_21">[Pg 21]</span>
-must seat tightly, and gaskets and other parts must be in proper condition.</p>
-
-<div id="FIG_2" class="figcenter">
-  <img src="images/i_p021.jpg" alt="" width="400" height="559" />
-  <p class="center"><span class="smcap">Fig. 2.—1-Cylinder Power Diagram</span></p>
-</div>
-
-<p><a href="#FIG_2">Figure 2</a> shows a power diagram for a 1-cylinder engine,
-in which the crank shaft moves under power during one stroke out of every four.
-An engine with two cylinders can be built so that first one cylinder
-<span class="pagenum" id="Page_22">[Pg 22]</span>
-applies power and then the other, in which case the crank shaft moves
-under power during two strokes out of every four.</p>
-
-<div id="FIG_3" class="figcenter">
-  <img src="images/i_p022.jpg" alt="" width="400" height="563" />
-  <p class="center"><span class="smcap">Fig. 3.—2-Cylinder Power Diagram</span></p>
-</div>
-
-<p><a href="#FIG_3">Figure 3</a> is a power diagram of an engine of this sort. If
-piston 1 is moving down under power, piston 2 is also moving down, but on the inlet
-stroke. The following stroke is exhaust in cylinder 1 and compression
-<span class="pagenum" id="Page_23">[Pg 23]</span>
-in cylinder 2, and cylinder 2 will then deliver a power stroke while
-cylinder 1 is on inlet. Thus the crank shaft will receive a power
-stroke, followed by a dead stroke; then another power stroke and
-another dead stroke, and so on.</p>
-
-<p>There will be the disadvantage, however, that the pistons, moving up
-and down together, will cause vibration, which in the course of time
-will be likely to give trouble. To overcome this, a 2-cylinder engine
-can be built as indicated in <a href="#FIG_4">Figure 4</a>.</p>
-
-<p>In this engine the cranks project on opposite sides of the crank shaft
-instead of on the same side, as in <a href="#FIG_3">Figure 3</a>; the pistons thus
-move in opposite directions, and produce no vibration. Power will be unevenly
-applied, however, for both power strokes occur in one revolution, with
-two dead strokes in the succeeding revolution.
-<span class="pagenum" id="Page_24">[Pg 24]</span></p>
-
-<div id="FIG_4" class="figcenter">
-  <img src="images/i_p024a.jpg" alt="" width="400" height="302" />
-  <img src="images/i_p024b.jpg" alt="" width="400" height="280" />
-  <p class="center"><span class="smcap">Fig. 4.—2-Cylinder Power Diagram, 180 Shaft</span></p>
-</div>
-
-<p>With piston 1 moving down on power, piston 2, moving upward, can only
-be performing compression or exhaust. If it is on compression, its power
-stroke will follow the power stroke of piston 1, while if it is on
-exhaust its power stroke will have occurred immediately before the
-<span class="pagenum" id="Page_25">[Pg 25]</span>
-power stroke of piston 1. In either case one power stroke follows the
-other, taking place in one revolution of the crank shaft, while in the
-following revolution both pistons will be performing dead strokes.</p>
-
-<p>While there is no vibration from the movement of the pistons in this
-engine, the uneven production of power will produce vibration of
-another kind.</p>
-
-<p>These two types may be built with the cylinders standing up or
-lying down; that is, they may be either <i>vertical engines</i> or
-<i>horizontal engines</i>. The <i>double opposed</i> engine, which is
-built only in horizontal form, is free from either kind of vibration,
-but has the disadvantage of occupying more room than the others. The
-cylinders, instead of being side by side, and on the same side of the
-crank shaft, are placed end to end, with the crank shaft between them,
-as shown in <a href="#FIG_5">Figure 5</a>.
-<span class="pagenum" id="Page_26">[Pg 26]</span></p>
-
-<p>The pistons make their inward and outward strokes together, but in so
-doing they move in opposite directions. Thus every power stroke is
-followed by a dead stroke, as in the engine shown in <a href="#FIG_3">Figure 3</a>,
-while the movement of one piston balances that of the other, as is the case
-with the engine shown in <a href="#FIG_4">Figure 4</a>.</p>
-
-<div id="FIG_5" class="figcenter">
-  <img src="images/i_p026.jpg" alt="" width="600" height="346" />
-  <p class="center space-below2"><span class="smcap">Fig. 5.—H. D. O. Power Diagram</span></p>
-</div>
-<p><span class="pagenum" id="Page_27">[Pg 27]</span></p>
-<div id="FIG_6" class="figcenter">
-  <img src="images/i_p027a.jpg" alt="" width="600" height="372" />
-  <img src="images/i_p027b.jpg" alt="" width="600" height="269" />
-  <p class="center"><span class="smcap">Fig. 6.—4-Cylinder Power Diagram</span></p>
-</div>
-
-<p>In a 4-cylinder engine one power stroke follows another without any
-dead stroke intervals, which, of course, makes the crank shaft revolve
-more smoothly and with a steadier application of power. The power
-diagram is shown in <a href="#FIG_6">Figure 6</a>; in studying this it should be
-remembered that if two pistons move in opposite directions, as in <a href="#FIG_4">Figure 4</a>,
-one power stroke follows another, while if they move in the same direction,
-<span class="pagenum" id="Page_28">[Pg 28]</span>
-as in <a href="#FIG_3">Figure 3</a>, there is an interval of one stroke between
-their power strokes.</p>
-
-<p>The crank shaft of a 4-cylinder engine is so made that the middle
-pistons move in the same direction, and opposite to the end pistons.
-This construction has been found to make a smoother running engine than
-if pistons 1 and 3 moved one way while pistons 2 and 4 moved the other.</p>
-
-<p>If piston 1 is on the power stroke, either piston 2 or piston 3 can
-follow, for they are moving in the opposite direction. If we say that
-piston 2 is the next, then piston 4 must be the third to give a power
-stroke, for it is the only one left that is moving in the opposite
-direction to piston 2. Piston 3 is thus the fourth to move under power,
-and it is followed by another power stroke by piston 1; the <i>firing
-order</i> is then said to be 1, 2, 4, 3.</p>
-
-<p>If it is piston 3 that follows piston 1, piston 4 will again be the
-third to produce power, and piston 2 will be the fourth. The firing
-<span class="pagenum" id="Page_29">[Pg 29]</span>
-order will then be 1, 3, 4, 2. There is no other order in which a
-4-cylinder engine can produce power, and there is no choice between them.</p>
-
-<p>The firing order of an engine is established by the manufacturer, and
-depends on the order in which the valves are operated.</p>
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_30">[Pg 30]</span></p>
-<h2 class="nobreak" id="CHAPTER_III">CHAPTER III<br />
-<span class="h_subtitle">ENGINE PARTS</span></h2>
-</div>
-
-<p>The foundation of an engine is the <i>base</i>, which supports the
-<i>bearings</i> in which the crank shaft revolves, and to which the
-cylinders are attached. The cylinders of tractor engines are made
-of cast-iron, and the cylinder heads, which close the upper ends of
-the cylinders, are usually in a separate piece, bolted on. The joint
-between the cylinders and the cylinder head is made tight by placing
-between them a <i>gasket</i> of asbestos and thin sheet metal.</p>
-
-<p>The crank shaft has as many cranks, or <i>throws</i>, as the engine
-has cylinders. Crank shafts for 2-cylinder engines are shown in <a href="#FIG_7">Figure 7</a>;
-the upper one is for an engine of the type shown in <a href="#FIG_3">Figure 3</a>, with
-<span class="pagenum" id="Page_31">[Pg 31]</span>
-pistons moving in the same direction. With both cranks projecting from
-one side the shaft is out of balance, so <i>balance weights</i> are
-attached to the opposite side.</p>
-
-<div id="FIG_7" class="figcenter">
-  <img src="images/i_p031.jpg" alt="" width="600" height="543" />
-  <p class="center space-below2"><span class="smcap">Fig. 7.—2-Cylinder Crank Shaft</span></p>
-</div>
-
-<p>The other shaft shown in <a href="#FIG_7">Figure 7</a> does not need balance weights,
-for one crank balances the other. A four-cylinder crank shaft, <a href="#FIG_8">Figure 8</a>,
-is also in balance.
-<span class="pagenum" id="Page_32">[Pg 32]</span></p>
-
-<div id="FIG_8" class="figcenter">
-  <img src="images/i_p032a.jpg" alt="" width="600" height="198" />
-  <p class="center space-below2"><span class="smcap">Fig. 8.—4-Cylinder Crank Shaft</span></p>
-</div>
-<div id="FIG_9" class="figcenter">
-  <img src="images/i_p032b.jpg" alt="" width="400" height="223" />
-  <p class="center space-below2"><span class="smcap">Fig. 9.—Half of a Plain Bearing</span></p>
-</div>
-
-<p>Crank shafts revolve in <i>main bearings</i>, which are set in
-the engine base. In tractor engines these are usually <i>plain
-bearings</i>, a half of such a bearing being shown in <a href="#FIG_9">Figure 9</a>.
-This is a bronze shell lined with a softer metal, making an exact fit on
-the shaft; with the two halves in place, the shaft should turn freely,
-but without looseness or side play. The grooves shown are to admit
-lubricating oil.
-<span class="pagenum" id="Page_33">[Pg 33]</span></p>
-
-<div id="FIG_10" class="figcenter">
-  <img src="images/i_p033.jpg" alt="" width="600" height="450" />
-  <p class="center space-below2"><span class="smcap">Fig. 10.—Connecting Rod Bearings</span></p>
-</div>
-<p><span class="pagenum" id="Page_34">[Pg 34]</span></p>
-<div id="FIG_11" class="figcenter">
-  <img src="images/i_p034.jpg" alt="" width="600" height="356" />
-  <p class="center space-below2"><span class="smcap">Fig. 11.—Piston Complete and in Section</span></p>
-</div>
-
-<p>The <i>piston</i> is attached to the crank shaft by a <i>connecting
-rod</i>, which is illustrated in <a href="#FIG_10">Figure 10</a>. Pistons are
-shown in <a href="#FIG_11">Figures 11</a> and <a href="#FIG_12">12</a>;
-they are made as light as is consistent with the pressure that they must bear,
-and are hollow, and open at the lower end.</p>
-
-<p>The piston is attached to the connecting rod by a <i>wrist pin</i>, or
-<i>piston pin</i>, which is a shaft passing through it from side to
-<span class="pagenum" id="Page_35">[Pg 35]</span>
-side, and also through the bearing in the upper end of the connecting
-rod. The connecting rod swings on the wrist pin in following the
-rotation of the crank shaft, and its attachment to the wrist pin must
-permit this without being loose.</p>
-
-<p>The bearings at the two ends of a connecting rod are usually
-adjustable, so that wear can be taken up; some of the methods of
-doing this are illustrated in <a href="#FIG_10">Figure 10</a>. In A, the wrist pin
-bearing is a plain tube, ground to an exact fit; when it is worn it must be
-replaced. In B, the bearing is split, and the ends are drawn together
-by a bolt to the correct fit. The bearing in C is in two parts, held
-together by a U-shaped bolt, while in D the two parts are held together
-by a cap bolted to the end of the connecting rod. In E, the end of the
-connecting rod is a square loop enclosing the two parts of the bearing;
-the parts are held in the proper position by a wedge adjusted by screws.</p>
-
-<p>The crank shaft bearing of the connecting rod <a href="#FIG_10">shown in F</a> is in two parts
-<span class="pagenum" id="Page_36">[Pg 36]</span>
-which are hinged together. G, H, and K show the forms usually used in
-tractor engines, which consist of two parts bolted together.</p>
-
-<div id="FIG_12" class="figcenter">
-  <img src="images/i_p036.jpg" alt="" width="600" height="483" />
-  <p class="center space-below2"><span class="smcap">Fig. 12.—Wrist Pin Fastenings</span></p>
-</div>
-
-<p>The wrist pin is usually firmly attached to the piston, so that the
-connecting rod swings on it; methods of securing the wrist pin are
-shown in <a href="#FIG_12">Figure 12</a>, the wrist pin being held in supports cast in the
-<span class="pagenum" id="Page_37">[Pg 37]</span>
-piston. In A, the wrist pin is held by two set screws, and in B, by
-pins passing through it. The wrist pin shown in D is hollow, as is very
-common, and a bolt passes through part of the piston and into the wrist pin.</p>
-
-<p>In the construction shown in C the wrist pin is secured to the
-connecting rod and moves in bearings in the piston. In E, a ring
-fitting in a groove around the piston prevents the wrist pin from
-moving endways.</p>
-
-<p>The engine must usually be taken to pieces in order to get at the wrist
-pin; lock nuts, lock washers or cotter pins are always used to prevent
-the trouble that would be caused if the wrist pin worked loose.</p>
-
-<p>A leak-proof joint between the piston and the cylinder is made by means
-of <i>piston rings</i> that fit in grooves around the piston, as shown
-in <a href="#FIG_12">E, Figure 12</a>. Piston ring grooves are shown in
-<a href="#FIG_11">Figure 11</a>. Piston
-rings are not solid, but are split so that they are elastic; they fit
-snugly in their grooves, and tend to spring open to a greater size than
-<span class="pagenum" id="Page_38">[Pg 38]</span>
-the cylinder. This causes them to maintain a close fit against the
-cylinder, and the gases are prevented from leaking past.</p>
-
-<div id="FIG_13" class="figcenter">
-  <img src="images/i_p038.jpg" alt="" width="400" height="593" />
-  <p class="center space-below2"><span class="smcap">Fig. 13.—Valve</span></p>
-</div>
-
-<p>Each cylinder is provided with two valves: the <i>inlet valve</i> that
-admits fresh mixture and the <i>exhaust valve</i> through which the
-<span class="pagenum" id="Page_39">[Pg 39]</span>
-burned gases escape. These valves are metal disks with funnel-shaped
-edges fitting into funnel holes. A valve and its stem are shown in
-<a href="#FIG_13">Figure 13</a> and also in <a href="#FIG_15">Figure 15</a>.</p>
-
-<div id="FIG_14" class="figcenter">
-  <img src="images/i_p039.jpg" alt="" width="600" height="188" />
-  <p class="center space-below2"><span class="smcap">Fig. 14.—Action of a Cam</span></p>
-</div>
-
-<p>A valve is opened at the proper time by a <i>cam</i>, and closed by a
-spring. A cam is a wheel with a bulge on one side, so that its rim is
-eccentric to its shaft, as illustrated in <a href="#FIG_14">Figure 14</a>, which
-shows a cam in three positions of a revolution. A rod resting on the rim of the
-cam is moved endways as the bulge passes under it, and the valve is
-operated by connecting it with the rod.</p>
-
-<p>A valve is opened once during two revolutions of the crank shaft;
-therefore the cam cannot be placed on the crank shaft, for, if it were,
-<span class="pagenum" id="Page_40">[Pg 40]</span>
-the valve would be opened every revolution. The cam is placed on a
-separate shaft which is driven by the crank shaft at half its speed.
-This is usually done with gears, a gear on the crank shaft meshing with
-a gear on the cam shaft having twice as many teeth; the crank shaft
-gear must make two revolutions in turning the cam shaft gear once.</p>
-
-<p>The valve in <a href="#FIG_13">Figure 13</a> is held on its seat by a spring. The
-cam bears against the end of the valve stem, and as it revolves its bulge forces the
-valve stem and valve to move endways and thus to uncover the valve opening.</p>
-
-<p>As the movement of the piston depends on the crank shaft, the valve can
-be made to open at the right time by a proper setting of the gears that
-drive the cam shaft.</p>
-
-<p>The length of time that the cam will hold the valve open depends on
-the shape of the bulge of the cam. It can be seen that the pointed cam
-of <a href="#FIG_13">Figure 13</a> will not hold the valve open for as
-long a time as the flat-end cam of <a href="#FIG_14">Figure 14</a>.
-<span class="pagenum" id="Page_41">[Pg 41]</span></p>
-
-<div id="FIG_15" class="figcenter">
-  <img src="images/i_p041.jpg" alt="" width="400" height="540" />
-  <p class="center space-below2"><span class="smcap">Fig. 15.—“Twin City” Tractor Engine</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_42">[Pg 42]</span>
-In the design shown in <a href="#FIG_13">Figure 13</a> the cam bears directly
-against the end of the valve stem, the cam shaft in this case lying along the
-cylinder head. In the construction shown in <a href="#FIG_15">Figure 15</a> the
-valves are not placed in the cylinder head, but are in an extension or <i>valve
-pocket</i> projecting from the combustion chamber; this cam shaft is
-near the crank shaft. It would not be practicable to make the valve
-stem long enough to reach down to the cam, so a length of rod, called
-a <i>push rod</i>, or <i>tappet</i>, is placed between them; the cam
-moves the push rod and the push rod in turn moves the valve. This is a
-construction frequently used for automobile engines.
-<span class="pagenum" id="Page_43">[Pg 43]</span></p>
-
-<div id="FIG_16" class="figcenter">
-  <img src="images/i_p043.jpg" alt="" width="600" height="305" />
-  <p class="center space-below2"><span class="smcap">Fig. 16.—“Hart-Parr” Valve Mechanism</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_44">[Pg 44]</span>
-In tractor engines the cam shaft is usually placed near the crank
-shaft, as in <a href="#FIG_15">Figure 15</a>, and the valves are in the head, so
-that a valve moves in the opposite direction to the movement of the push rod. This
-requires still another part to be used, called the <i>rocker arm</i>.
-It is shown in <a href="#FIG_16">Figure 16</a>. It is a short bar, pivoted at or
-near the center, with one end at the push rod and the other at the valve stem.
-When it is moved by the push rod it in turn moves the valve.</p>
-
-<p>Valves operated by push rods and rocker arms are also shown in
-<a href="#FIG_17">Figures 17</a>, <a href="#FIG_18">18</a> and
-<a href="#FIG_19">19</a>; Figure 18 is a single-cylinder horizontal engine, while
-<a href="#FIG_19">Figure 19</a> is a horizontal double opposed engine, in which one cam
-operates a valve in each cylinder. <a href="#FIG_20">Figure 20</a> shows the valve mechanism
-of a vertical engine in which all parts, including the rocker arm, are
-enclosed to protect them from dust, and so they can run in oil.</p>
-
-<p>A small space is always left somewhere between the cam and the valve
-stem, to give the valve stem room to lengthen, which it will do when it
-gets hot. If this space were not left, the valve stem, in lengthening
-as it became hot, would strike the part next to it, and the valve would
-be lifted from its seat. This would cause the engine to lose power.
-This space must be kept properly adjusted, and instructions for this
-will be found in <a href="#CHAPTER_XII">Chapter XII</a>.
-<span class="pagenum" id="Page_45">[Pg 45]</span></p>
-
-<div id="FIG_17" class="figcenter">
-  <img src="images/i_p045.jpg" alt="" width="600" height="419" />
-  <p class="center space-below2"><span class="smcap">Fig. 17.—“Hart-Parr” Engine</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_46">[Pg 46]</span>
-A valve is held against its seat by a spring, which must be compressed
-when the valve is opened. If this spring is too weak, it will not hold
-the valve tightly on its seat, while if it is too stiff, the cam shaft
-and other parts will be needlessly strained in compressing it.</p>
-
-<p>Friction between the cam and the end of the valve stem or push rod
-would cause rapid wear if these parts were not of hardened steel, and
-kept well oiled. Still further to reduce wear, there is usually a
-roller on the end of the push rod, as shown in <a href="#FIG_16">Figure 16</a>
-and some of the other illustrations. <a href="#FIG_15">Figure 15</a> shows a
-construction in which the end of the push rod is a flat disk, which rotates
-as the cam comes into contact with it.
-<span class="pagenum" id="Page_47">[Pg 47]</span></p>
-
-<div id="FIG_18" class="figcenter">
-  <img src="images/i_p047.jpg" alt="" width="600" height="401" />
-  <p class="center space-below2"><span class="smcap">Fig. 18.—“Oil-Pull” Engine</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_48">[Pg 48]</span>
-When the mixture burns, the top of the piston, the cylinder head, and
-the walls of the combustion chamber become heated, and if it is not
-prevented they will get so hot that they will expand sufficiently to
-cause the piston to stick, or <i>seize</i>. The upper part of the
-cylinder is, therefore, provided with a cooling system that keeps
-these parts from getting overheated. Channels are provided through
-which water is circulated; the water takes the heat from the metal
-parts, becoming heated itself, and then passes to a <i>cooler</i>, or
-<i>radiator</i>, where it gives up the heat to currents of air.</p>
-
-<p>In addition to the channels, or <i>water jackets</i>, around the
-cylinder, a cooling system includes the radiator, the connections, and
-usually a pump that keeps the water in motion.
-<span class="pagenum" id="Page_49">[Pg 49]</span></p>
-
-<div id="FIG_19" class="figcenter">
-  <img src="images/i_p049.jpg" alt="" width="600" height="331" />
-  <p class="center space-below2"><span class="smcap">Fig. 19.—Horizontal Double Opposed Engine</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_50">[Pg 50]</span>
-In some tractors, notably the Fordson, no pump is used; the water
-circulates because it is heated. This is called a <i>thermo-syphon</i>
-system. When the engine runs, the water in the cylinder jackets becomes
-heated; as hot water is lighter than cold water, it rises and flows out
-of the jackets to the radiator, its place being taken by cool water
-from the bottom of the radiator. This circulation continues as long as
-the water in one part of the system is hotter than the water in some
-other part of the system.</p>
-
-<p>The lubrication of an engine is described and explained in <a href="#CHAPTER_X">Chapter X</a>.
-<span class="pagenum" id="Page_51">[Pg 51]</span></p>
-
-<div id="FIG_20" class="figcenter">
-  <img src="images/i_p051.jpg" alt="" width="400" height="606" />
-  <p class="center space-below2"><span class="smcap">Fig. 20.—“Monarch” Engine</span></p>
-</div>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_52">[Pg 52]</span></p>
-<h2 class="nobreak" id="CHAPTER_IV">CHAPTER IV<br />
-<span class="h_subtitle">FUELS AND CARBURETION</span></h2>
-</div>
-
-<p>In order that a thing may burn, it must be provided with oxygen. Oxygen
-is found in air, so it is usual to say that air is necessary in order
-that anything may burn.</p>
-
-<p>To prove this, light a candle and place an empty bottle over it, upside
-down; in a very short time the oxygen in the bottle will be used up,
-and the flame will flicker and get smoky, and finally die out. If a
-card is laid on the chimney of a coal-oil lamp so that it covers the
-opening, that flame also will flicker, get smoky and go out.</p>
-
-<p>In order to deaden the fire in a stove, the dampers are closed to
-prevent air from entering; the fire is kept alight by the very small
-quantity of air that leaks in below the fire-box. When the drafts are
-<span class="pagenum" id="Page_53">[Pg 53]</span>
-opened the fire will burn up brightly because a plentiful volume of air
-can then enter.</p>
-
-<p>In a similar way, air must be used in a gas engine in order that the
-fuel may burn. It is not possible to mix air with a liquid; the first
-step in making a gas that will burn is, therefore, to turn the fuel,
-whether it is gasoline, kerosene, distillate, or other oil, into a
-vapor; this vapor is then mixed with air.</p>
-
-<p>For good results it is very necessary that the vapor and air be in
-proper proportions. In the experiment with the candle and the bottle it
-was seen that as the air was used up, the candle flame became yellow
-and smoky: this is the effect of insufficient air. If there is not
-enough air in the mixture, part of the vapor will not be able to burn,
-and will only smoke.</p>
-
-<p>If, on the other hand, there is too much air, the mixture, if it will burn
-at all, will burn slowly, and the extra volume of air will reduce the heat.
-<span class="pagenum" id="Page_54">[Pg 54]</span></p>
-
-<p>In a mixture of the proper proportions of air and fuel vapor, the
-burning, or <i>combustion</i>, will be very rapid, resulting in the
-sudden production of the greatest possible amount of heat. This, of
-course, is what is necessary if the engine is to produce its fullest
-power. With such a mixture, combustion will be complete before the
-piston has done more than start outward on the power stroke, and the
-greatest possible, or <i>maximum</i>, pressure will then be produced.</p>
-
-<p>When a mixture burns slowly, the piston will have gone through much
-of the power stroke before combustion is complete, in which case a
-considerable part of the pressure that should have been applied at the
-beginning of the stroke will be wasted.</p>
-
-<p>A mixture that is not correct will burn unevenly; it may burn better
-during one power stroke than during another, which will make the engine
-run unsteadily.</p>
-
-<p>If the mixture has too much air in proportion to the amount of vapor,
-<span class="pagenum" id="Page_55">[Pg 55]</span>
-it is known as a <i>thin</i> mixture, or a <i>lean</i> or <i>poor</i>
-mixture. It burns so slowly that it is quite possible for the mixture
-that started burning before the beginning of the power stroke to
-continue burning through the exhaust stroke, and for enough flame to
-remain in the cylinder to set fire to the fresh charge that enters
-during the next inlet stroke. This will produce what is known as a
-<i>backfire</i>; that is, the mixture entering the cylinder will catch
-fire, and in burning will blow back through the open inlet valve. This
-is a dangerous condition, for the flame might spread to fuel dripping
-from the carburetor, or to the fuel tank.</p>
-
-<p>A mixture that has not enough air is called a <i>rich</i> mixture; the
-air that is present will burn part of the vapor, while the rest will go
-out of the exhaust unburned, or will work past the piston into the oil
-in the crank case. This is wasteful of fuel.</p>
-
-<p>The most serious result of a rich mixture, however, is in the
-production of <i>carbon</i>, and the <i>carbonization</i> of the
-<span class="pagenum" id="Page_56">[Pg 56]</span>
-engine. The flame of a rich mixture is smoky; the smoke of this flame,
-as is the case with smoke from all other sources, is composed of fine
-particles of carbon, or soot. These particles of carbon will deposit
-on all parts of the combustion space: on the top of the piston, on the
-valves, on the spark plugs, and on the inner wall of the cylinder head.
-At first it is gummy, but it rapidly hardens and forms a crust that
-must be scraped off with a steel tool.</p>
-
-<p>Carbon in an engine will reduce the power through causing
-<i>preignition</i>, or, in other words, by setting fire to the
-fresh charge before the proper point in the stroke. The heat of the
-combustion will cause the carbon deposit to become so heated that it
-will glow, these glowing particles being sufficient to ignite the
-incoming fresh charge. The remedy for this condition is to remove the
-carbon, which is usually done by taking off the cylinder head and
-scraping away the deposit.
-<span class="pagenum" id="Page_57">[Pg 57]</span></p>
-
-<p>It may be added that carbon is also formed by the use of too much
-lubricating oil, as will be explained in the chapter on lubrication.</p>
-
-<p>Thus it is seen that if the engine is to run properly, and is to be
-kept in good condition, the proportions of the mixture must be very
-carefully maintained.</p>
-
-<p>The mixture is formed in a <i>carburetor</i>, or <i>mixer</i>. This
-is, roughly, in the form of a tube through which air is sucked during
-the inlet stroke; projecting into it is a fine tube called a <i>spray
-nozzle</i> through which the fuel enters. In action it is somewhat
-similar to the atomizer that is used for spraying the nose and throat.
-By forcing the fuel to flow rapidly through this small tube it comes
-out in the form of spray, and the tiny drops are picked up by the
-current of air and are carried into the cylinder.</p>
-
-<p>It is much easier to form a mixture of gasoline than of kerosene
-or distillate, because gasoline vaporizes more readily at ordinary
-<span class="pagenum" id="Page_58">[Pg 58]</span>
-temperatures. If saucers of gasoline and kerosene are placed in the
-sun, the gasoline will evaporate rapidly and completely, leaving only
-a faint oily deposit. The kerosene, on the other hand, will evaporate
-slowly, and much of it will not evaporate at all.</p>
-
-<p>To make kerosene and distillate evaporate completely, they must be
-heated, just as water must be heated to make it evaporate.</p>
-
-<p>In the case of a carburetor for gasoline, the current of air needs
-only to be warmed; the spray of gasoline will evaporate on coming into
-contact with the warmed air, and much of it will enter the cylinder as
-vapor. In order to evaporate kerosene and distillate much more heat
-must be provided, and it is usually considered necessary to heat not
-only the current of air, but the liquid fuel as well. Methods of doing
-this will be explained in the next chapter.
-<span class="pagenum" id="Page_59">[Pg 59]</span></p>
-
-<div id="FIG_21" class="figcenter">
-  <img src="images/i_p059a.jpg" alt="" width="500" height="364" />
-</div>
-<div class="figcenter">
-  <img src="images/i_p059b.jpg" alt="" width="500" height="319" />
-  <p class="center space-below2"><span class="smcap">Fig. 21.—Principle of Carburetor</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_60">[Pg 60]</span>
-When kerosene or distillate is used, there are conditions that make
-it necessary to add water vapor to the mixture, which prevents the
-overheating of the cylinder and reduces the deposit of carbon. The
-difficulty of making a complete vapor of kerosene and distillate
-results in a tendency on the part of these fuels to carbonize the
-cylinders; the use of water aids in keeping the cylinders clean.</p>
-
-<p>The general principle of a carburetor is shown in <a href="#FIG_21">Figure 21</a>,
-one drawing illustrating conditions when the inlet valve is closed and the
-other when it is open. It shows an engine cylinder connected with an
-inlet pipe or <i>mixing chamber</i>, through which there is a swift
-flow of air during an inlet stroke.</p>
-
-<p>Projecting into the intake pipe is the <i>spray nozzle</i>, which is
-connected with a small chamber containing fuel; inside of this chamber
-is a <i>float</i>, usually made of cork, although it is sometimes a
-light metal box. The fuel is intended to fill the chamber to a certain
-height, at which the valve will be closed by the float rising on the
-fuel. This level is such that the fuel does not quite reach the tip of
-the spray nozzle.
-<span class="pagenum" id="Page_61">[Pg 61]</span></p>
-
-<p>During the compression, power, and exhaust strokes, the fuel stands at
-this level, for it cannot run out of the spray nozzle, and the float
-holds the valve closed. As soon as the inlet valve opens, air rushes
-through the intake pipe and sucks fuel out of the spray nozzle. This,
-of course, takes fuel out of the float chamber; the float in sinking
-opens the valve, and enough fuel enters to restore the level.</p>
-
-<p>The fuel comes out of the nozzle in the form of fine spray; it is in
-such small drops that it evaporates quickly, and the resulting mixture
-of fuel vapor and air passes into the cylinder. By using a spray nozzle
-of the proper size, any desired proportion of fuel and air may be obtained.</p>
-
-<p>If an engine runs at a single speed, a carburetor as simple as this one
-would be satisfactory, for if the suction is always the same, there will be
-little or no change in the proportions of the mixture that is formed.
-<span class="pagenum" id="Page_62">[Pg 62]</span></p>
-
-<p>To get the best results, the proportions of fuel vapor and air should
-be the same for all running speeds of the engine. The proportions of
-the mixture, however, depend on the violence of the suction, which
-changes as the engine speed changes, becoming greater as the speed
-increases. The simple carburetor illustrated in <a href="#FIG_21">Figure 21</a>
-can be adjusted to give a correct mixture for any particular speed, but will
-be out of adjustment for any other speed.</p>
-
-<p>The speed of a 1-cylinder engine does not change very greatly; it is
-built to run at practically a constant speed, and a simple carburetor
-is satisfactory for it. The speed of engines with a greater number of
-cylinders may be greatly changed, and the carburetor must be so made
-that it will give the same proportions of vapor and air at low speed as
-at high.</p>
-
-<p>In the simple carburetor described, the speeding-up of the engine will
-result in a greater rush of air through the intake pipe, which in turn
-<span class="pagenum" id="Page_63">[Pg 63]</span>
-will suck out a much greater quantity of fuel. If the carburetor is
-adjusted to give the proper quantity of fuel for the air that passes
-at low speed, at high speed it will give far more fuel than will be
-required by the quantity of air that then passes. Thus at high speed
-the mixture will be too rich.</p>
-
-<p>If, on the other hand, this carburetor is adjusted to give a proper
-mixture at high speed, too little fuel will be sucked out when the
-engine runs slowly, and the mixture will be too lean.</p>
-
-<p>A carburetor must thus have an additional device that will keep the
-mixture correct, regardless of the speed at which the engine runs.
-This is sometimes done by changing the size of the spray nozzle so
-that a greater or less quantity of fuel flows out, but more usually
-by permitting an extra quantity of air to enter the carburetor as the
-engine speeds up. This is done with an <i>extra air intake</i>, the
-principle of which is illustrated in <a href="#FIG_22">Figure 22</a>.
-<span class="pagenum" id="Page_64">[Pg 64]</span></p>
-
-<p>As will be seen, this carburetor has two openings for air, one being
-the main air inlet and the other the extra air inlet. The latter is an
-opening provided with a valve which is held on its seat by a spring.
-The suction created by an inlet stroke is exerted in the carburetor,
-but at low speed is not sufficient to suck the extra air valve from its
-seat. Air then enters only through the main air inlet, and the spray
-nozzle is adjusted to give the proper proportion of fuel.</p>
-
-<div id="FIG_22" class="figcenter">
-  <img src="images/i_p064.jpg" alt="" width="600" height="363" />
-  <p class="center space-below2"><span class="smcap">Fig. 22.—Principle
-       of Extra Air Inlet</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_65">[Pg 65]</span>
-As the engine speed increases the mixture becomes richer; but there
-is also an increase in suction, which becomes strong enough to pull
-the extra air valve from its seat. This provides another opening into
-the carburetor, through which enough air enters to keep the mixture
-in proper proportion. The higher the speed of the engine the more the
-valve will open, and the greater will be the quantity of air admitted.</p>
-
-<p>In order to get the fullest power from an engine, the carburetor is
-built to give its most perfect mixture at the usual working speed.
-This will be the speed at which the engine will run under ordinary
-conditions. As the engine will run at this speed most of the time, the
-carburetor should then deliver its best mixture on the least possible
-quantity of fuel.</p>
-
-<p>As an engine is run at low speed so little of the time, it is not
-necessary that the mixture should then be so perfect or that the fuel
-should be used so economically.</p>
-
-<p>The design of a carburetor is a complicated matter, because the
-<span class="pagenum" id="Page_66">[Pg 66]</span>
-production of mixture is due to the flow of air, which is a very
-changeable thing. On a cold, damp day, the air will be heavier and
-denser than on a day that is hot and dry, and different quantities of
-fuel will be necessary for the formation of the mixture. The carburetor
-manufacturer cannot make a commercial carburetor that will take care
-of such a difference as this; he strikes an average that gives good
-general results, and expects the user to change the adjustments when
-weather and temperature make it necessary.</p>
-
-<p>The formation of the mixture is affected by the condition of the
-engine. When all of the parts of the engine are tight, the suction in
-the carburetor is more violent than when there is a leakage of air past
-the piston rings, or through a leaky valve or spark plug.</p>
-
-<p>On a dry, hot day the fuel evaporates much more readily than on a day
-that is cold and damp; more of the fuel that flows out of the spray
-nozzle will be vaporized and the formation of the mixture will be
-<span class="pagenum" id="Page_67">[Pg 67]</span>
-easier. On a cold, damp day the fuel will not vaporize in the
-carburetor to any extent, and much of it will pass to the cylinder in
-drops that even there will not vaporize in time to form a mixture.
-In order to assure the vaporization of enough fuel to form a mixture under
-such conditions, the fuel and the air must be heated to a greater degree.</p>
-
-<p>As the engine becomes heated up, more and more of the fuel will
-vaporize, and the amount flowing out of the spray nozzle may therefore
-be cut down.</p>
-
-<p>With fuels like kerosene and distillate, which do not vaporize as
-readily as gasoline, it is not unusual to have them condense on
-the walls of the inlet pipe, which produces a condition known as
-<i>loading</i>. This condensation is similar to the sweating of an
-ice-water pitcher on a hot day. If an engine is running at a constant
-speed, loading does not make much difference, because the carburetor is
-so adjusted that it gives a proper mixture. If the engine is suddenly
-<span class="pagenum" id="Page_68">[Pg 68]</span>
-speeded up, however, the greater rush of air will pick up the condensed
-fuel, and the mixture will instantly become too rich, continuing so
-until this extra supply of fuel is used up. The result will be to choke
-the engine and make it lose power just at the time when extra power is
-needed.</p>
-
-<p>Loading can be prevented by heating the inlet pipe to such an extent
-that the fuel will not condense on it.</p>
-
-<p>The speed of a tractor engine is practically always controlled by a
-<i>throttle</i>, which is a valve set in the passage of the carburetor.
-It operates exactly the same as a damper in a stovepipe; when it is
-closed, it shuts the passage and prevents the flow of mixture to the
-engine. As it is opened, it permits a greater quantity of mixture to
-flow, and it follows, of course, that as the charges of mixture become
-larger, the engine runs with more power. A tractor carburetor usually
-has two throttles, one being operated by hand and the other by the governor.
-<span class="pagenum" id="Page_69">[Pg 69]</span></p>
-
-<p>It is usual for a carburetor to be fitted with a <i>strangler</i>, or
-<i>choke</i>, which makes it easier to form a mixture at slow starting
-speed. When an engine is cold, the fuel evaporates slowly; and,
-furthermore, when an engine is cranked by hand its speed is so low that
-the suction in the carburetor is not sufficient to draw out enough fuel
-to form a mixture. The strangler is a valve similar in every way to the
-throttle, but placed between the main air inlet and the spray nozzle.
-When it is closed and the engine is cranked, very little air can enter
-the carburetor; the suction is therefore very great. Far more fuel
-than usual is then sucked out of the spray nozzle, and of this greater
-amount enough reaches the cylinder to form a combustible mixture. The
-engine will start, but as soon as it does so, the strangler must be
-opened so that the normal amount of air enters. If this is not done,
-the excessive suction will draw so much fuel out of the spray nozzle
-that the mixture formed will be too rich to burn.</p>
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_70">[Pg 70]</span></p>
-<h2 class="nobreak" id="CHAPTER_V">CHAPTER V<br />
-<span class="h_subtitle">CARBURETORS</span></h2>
-</div>
-
-<p>The apparatus that forms the mixture is in two parts, one being the
-carburetor that proportions the fuel to the quantity of air drawn
-into the cylinder, and the other the <i>mixing chamber</i>, or
-<i>manifold</i>, that connects the carburetor with the valve chamber.
-The mixing chamber has no adjustments; it is a passage, often a pipe,
-that is shaped to fit the conditions, and according to the ideas of
-the manufacturer. When kerosene and distillate are used, the mixing
-chamber must be heated, so it is frequently built into the <i>exhaust
-manifold</i>, which is the pipe that conducts the burned gases away
-from the engine. In some cases it gets heat from the water jacket of
-the engine, a water jacket formed around it being connected with the
-cooling system.
-<span class="pagenum" id="Page_71">[Pg 71]</span></p>
-
-<p>The carburetor, on the other hand, has adjustments that must be
-understood in order to run the engine economically. The understanding
-of these adjustments is simplified if it is remembered that the object
-of the carburetor is to maintain a correct proportion of fuel to the
-volume of air that passes through it.</p>
-
-<p>All tractor carburetors operate on the same principles, and the
-principles are applied in much the same way. If these principles are
-understood, and there is an understanding of what the parts of a
-carburetor are for and what they do, there should be no difficulty in
-adjusting and caring for any kind of a carburetor that may be offered.</p>
-
-<p>The main body of the carburetor is the tube through which the air
-passes. This is a casting, and cannot be adjusted or altered. Into this
-passage projects the spray nozzle, which is usually provided with an
-adjustment to control the amount of liquid that may flow out of it.
-<span class="pagenum" id="Page_72">[Pg 72]</span>
-When no adjustment is provided, the spray nozzle is made removable, so
-that a nozzle with an opening of any desired size may be inserted.</p>
-
-<div id="FIG_23" class="figcenter">
-  <img src="images/i_p072.jpg" alt="" width="500" height="398" />
-  <p class="center space-below2"><span class="smcap">Fig. 23.—“Kingston”
-               Carburetor, Model L</span></p>
-</div>
-
-<p>On some carburetors the extra air valve is set by the manufacturers,
-while on others it is adjustable by controlling the strength of the
-spring that holds it against its seat.</p>
-
-<p>The carburetor shown in <a href="#FIG_23">Figure 23</a> has a spray nozzle adjustment of
-<span class="pagenum" id="Page_73">[Pg 73]</span>
-a very usual type. A rod is so arranged that its pointed end projects
-into the opening of the spray nozzle; by screwing it up or down the
-opening may be made larger or smaller, so that more or less fuel may
-flow out. The extra air valve is a flap valve that closes the air
-passage until the suction is great enough to lift it from its seat.
-Around the spray nozzle is a tube that connects the passage below the
-extra air valve with the passage above it; when the suction is too low
-to lift the extra air valve from its seat, any air flowing through the
-carburetor passes through this tube. The tube is so small that even a
-little air passing through it is enough to suck fuel out of the spray
-nozzle, and the spray nozzle is so adjusted that enough fuel comes out
-to make a proper mixture with that volume of air.</p>
-
-<p>This is the <i>low-speed adjustment</i>, which gives a mixture on which
-the engine will start and will run at its lowest or <i>idling</i>
-speed. At this speed the engine produces just enough power to keep
-itself going.
-<span class="pagenum" id="Page_74">[Pg 74]</span></p>
-
-<p>When the engine speeds up, and suction increases, the extra air valve
-is lifted off its seat, and a greater volume of air flows through the
-carburetor. The increased suction also draws more fuel out of the spray
-nozzle. If the greater amount of fuel were in proportion to the greater
-volume of air, there would be no change in the mixture, but this is not
-the case. As suction increases, the proportion of fuel drawn out of the
-spray nozzle becomes too great for the air, and the mixture becomes too
-rich. To overcome this, the extra air valve permits a still greater volume
-of air to pass, so that the proportions of fuel and air do not change.</p>
-
-<p>The chamber below the air passage in <a href="#FIG_22">Figure 22</a> is the fuel
-cup, into which fuel flows from the tank. Inside the fuel cup is a ring of cork
-attached to a pivoted lever, on the other end of which is a needle
-valve that can close the opening through which the fuel enters the cup.
-As the cup fills, the cork floats on it, and in rising it moves the
-<span class="pagenum" id="Page_75">[Pg 75]</span>
-lever on its pivot. When the fuel reaches such a level that it is near
-the tip of the spray nozzle, the valve closes the opening and prevents
-more fuel from entering.</p>
-
-<div id="FIG_24" class="figcenter">
-  <img src="images/i_p075.jpg" alt="" width="500" height="414" />
-  <p class="center space-below2"><span class="smcap">Fig. 24.—“Kingston”
-                 Carburetor, Model E</span></p>
-</div>
-
-<p>In the carburetor shown in <a href="#FIG_24">Figure 24</a>, the principal air
-passage is past the spray nozzle, and all air goes by this passage when the engine is
-running at low speed. The extra air inlet consists of a number of holes
-<span class="pagenum" id="Page_76">[Pg 76]</span>
-through which air can pass without going past the spray nozzle. On each
-of these holes is a ball; when the suction is low the balls completely
-close the holes. When speed increases, the suction becomes great enough
-to lift the balls off the holes, and the extra volume of air that is
-necessary is permitted to enter. By making the balls of different
-weights, it can be seen that the volume of air admitted for any speed
-is under good control.</p>
-
-<p>Like the carburetor shown in <a href="#FIG_23">Figure 23</a>, this carburetor
-is of the <i>float feed</i> type; that is, the flow of fuel to it is controlled
-by a valve that is operated by a float.</p>
-
-<p>Either of these two carburetors may be adjusted for gasoline or for
-kerosene, but the adjustment that is right for one is wrong for the
-other. Thus, if an engine is started on gasoline, with the intention of
-running on kerosene, the carburetor must be readjusted when the change
-is made. This is unsatisfactory, so a double carburetor is sometimes
-used, as shown in <a href="#FIG_25">Figure 25</a>. This consists of two carburetors of the
-<span class="pagenum" id="Page_77">[Pg 77]</span>
-kind shown in <a href="#FIG_24">Figure 24</a>, having a single mixture outlet, one being
-adjusted for gasoline and the other for kerosene. Either of them can be
-connected with the mixture outlet by means of a switch valve.</p>
-
-<div id="FIG_25" class="figcenter">
-  <img src="images/i_p077.jpg" alt="" width="600" height="462" />
-  <p class="center space-below2"><span class="smcap">Fig. 25.—“Kingston”
-               Carburetor, Dual Model</span></p>
-</div>
-
-<p>In order to run on kerosene or distillate it is necessary to apply heat
-for the reason that these oils do not evaporate readily at ordinary
-<span class="pagenum" id="Page_78">[Pg 78]</span>
-temperatures. Gasoline, on the other hand, evaporates readily, and a
-cold engine can be started on it. Tractors that run on kerosene or
-distillate are therefore started on gasoline and run on it until they
-are hot enough to vaporize the heavier oil.</p>
-
-<p>A carburetor that will run on either gasoline or kerosene is shown in
-<a href="#FIG_26">Figure 26</a>. The main air inlet is at E, which leads the air
-around the spray nozzle and into the chamber G. The mixture flows to the cylinder
-by the passage B. The control of the fuel at working speeds is by the
-high-speed adjustment, which is a needle valve screwing into the spray
-nozzle. Above this is another needle valve that adjusts the flow of
-fuel for slow speed.</p>
-
-<p>Extra air enters through the opening A, which is closed at slow speed
-by a valve held against it by a spring. This valve bears against one
-end of a pivoted lever, the other end of which is attached to the
-slow-speed needle valve; when the extra air valve opens it moves the
-lever and the slow-speed needle valve is lifted to permit the flow of a
-greater volume of fuel from the spray nozzle.
-<span class="pagenum" id="Page_79">[Pg 79]</span></p>
-
-<div id="FIG_26" class="figcenter">
-  <img src="images/i_p079.jpg" alt="" width="400" height="478" />
-  <p class="center space-below2"><span class="smcap">Fig. 26.—“E-B” Carburetor</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_80">[Pg 80]</span>
-This carburetor is started on gasoline. When the engine is hot, a
-switch valve is operated to permit the burned gases from the engine to
-flow through the carburetor; they pass through the pipe C, D, and as
-the chamber G is directly in their path it becomes intensely heated.
-The carburetor can then be switched to kerosene. A side view of this
-carburetor is shown in <a href="#FIG_27">Figure 27</a>.</p>
-
-<p>These carburetors are all of the float feed type, and are used on
-engines of which the speed is variable. A carburetor that is fed by a
-pump is shown in <a href="#FIG_28">Figure 28</a>. This is a simple tube with a fuel
-cup cast on one side of it. Fuel is pumped to the bowl, and the proper level is
-maintained by an overflow through which excess fuel passes back to the tank.</p>
-
-<p>This carburetor is intended for an engine of which the speed does not
-change greatly. Its only adjustment is the spray nozzle, and this is
-altered to correspond with changes in engine speed.
-<span class="pagenum" id="Page_81">[Pg 81]</span></p>
-
-<div id="FIG_27" class="figcenter">
-  <img src="images/i_p081.jpg" alt="" width="300" height="497" />
-  <p class="center space-below2"><span class="smcap">Fig. 27.—“E-B” Carburetor,<br />Side View</span></p>
-</div>
-<p><span class="pagenum" id="Page_82">[Pg 82]</span></p>
-
-<div id="FIG_28" class="figcenter">
-  <img src="images/i_p082.jpg" alt="" width="400" height="478" />
-  <p class="center space-below2"><span class="smcap">Fig. 28.—Pump-fed Carburetor</span></p>
-</div>
-
-<p>If an engine is clean and in good condition, it will run as well on
-kerosene as on gasoline, although the heating effect of kerosene is
-greater. When an engine is carbonized, as is usually the case, a
-<span class="pagenum" id="Page_83">[Pg 83]</span>
-condition known as <i>preignition</i> will occur unless it is
-prevented. Carbon from unburned fuel or from lubricating oil will
-deposit on the piston head and the parts of the combustion chamber, and
-particles will become heated to the glowing point, when they will set
-fire to the fresh mixture during the compression stroke and before the
-proper time. The effect is to make the engine lose power, and it also
-gives rise to a sharp metallic knocking. By reducing the temperature
-in the cylinder during the compression stroke this condition can be
-prevented. This can be done by adding water vapor to the mixture, and
-kerosene carburetors are therefore built with a water attachment. As
-can be seen in <a href="#FIG_28">Figure 28</a>, this is a water cup and spray nozzle
-like those for the fuel. When the engine knocks, and shows that preignition
-is occurring, water is turned on, and, being carried into the cylinder,
-keeps the mixture from being heated to the point of ignition before the
-proper time.
-<span class="pagenum" id="Page_84">[Pg 84]</span></p>
-
-<p><a href="#FIG_29">Figure 29</a> shows the attachment of this carburetor to an
-engine which, in this case, is horizontal. To start the engine, gasoline is injected
-into the carburetor, as shown; this will give a sufficiently good
-mixture for the purpose, and enough heat for running on kerosene is
-thus obtained.</p>
-
-<div id="FIG_29" class="figcenter">
-  <img src="images/i_p084.jpg" alt="" width="500" height="543" />
-  <p class="center space-below2"><span class="smcap">Fig. 29.—“Titan” Carburetor</span></p>
-</div>
-<p><span class="pagenum" id="Page_85">[Pg 85]</span></p>
-<div id="FIG_30" class="figcenter">
-  <img src="images/i_p085.jpg" alt="" width="400" height="702" />
-  <p class="center space-below2"><span class="smcap">Fig. 30.—Pump-fed Carburetor<br />
-             With Two Fuel Nozzles</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_86">[Pg 86]</span>
-The carburetor shown in <a href="#FIG_30">Figure 30</a> is similar, but has a bowl
-and spray nozzle for gasoline, to use in starting. It is also provided with a
-heating jacket through which hot water or hot gases may circulate.</p>
-
-<p>In many cases the fuel is heated before reaching the carburetor. This
-is done by coiling the feed pipe around the exhaust pipe or putting it
-in a jacket through which hot water circulates.</p>
-
-<p>Another device sends the mixture through a chamber heated by the
-exhaust, as shown in <a href="#FIG_31">Figure 31</a>. <a href="#FIG_32">Figure 32</a>
-shows an arrangement in which the mixture passes through a jacket
-around one branch of the exhaust pipe. By means of a switch valve, A,
-more or less of the exhaust gases may be permitted to flow through this
-branch, so that the mixture may be heated to any desired degree.
-<span class="pagenum" id="Page_87">[Pg 87]</span></p>
-
-<div id="FIG_31" class="figcenter">
-  <img src="images/i_p087a.jpg" alt="" width="600" height="193" />
-  <img src="images/i_p087b.jpg" alt="" width="600" height="575" />
-  <p class="center space-below2"><span class="smcap">Fig. 31.—“Hart-Parr” Mixture Heater</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_88">[Pg 88]</span>
-All of these heating devices are so arranged that the heat is under the
-control of the driver, which permits him to heat the mixture as much as
-he judges to be necessary. Enough heat must be used to prevent the fuel
-from condensing; but too much heat will cut down the efficiency of the
-engine because it will cause so much expansion of the mixture that a
-cylinderful of it will not produce the maximum power.</p>
-
-<div id="FIG_32" class="figcenter">
-  <img src="images/i_p088.jpg" alt="" width="500" height="514" />
-  <p class="center space-below2"><span class="smcap">Fig. 32.—“Twin City” Manifold</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_89">[Pg 89]</span>
-<a href="#FIG_33">Figure 33</a> shows the pump that is used in a force feed carburetor of the
-type shown in <a href="#FIG_28">Figure 28</a>. Its plunger is forced through an inward stroke
-by a cam, and makes an outward stroke as its spring returns it to
-position. The inlet and outlet openings of the cylinder are closed by
-ball check valves, the inlet check being open on the outward strokes,
-and the outlet check being open on the inward strokes. A pump of this
-sort requires no attention beyond seeing that the check valves work
-properly, and that there are no leaks.</p>
-
-<p><a href="#FIG_34">Figure 34</a> shows the connections between the fuel tank
-and the carburetor. Under the tank, 1, is a chamber containing a fine wire
-strainer, 4, through which the fuel must pass to reach the carburetor;
-any dirt that may be present is strained out, and collects in the cup,
-2. Water in the fuel also settles here, and the cup is cleaned out by
-unscrewing the plug, 3. 5 is the shut-off cock; it should always be
-closed when the tractor is not working.
-<span class="pagenum" id="Page_90">[Pg 90]</span></p>
-
-<div id="FIG_33" class="figcenter">
-  <img src="images/i_p090.jpg" alt="" width="500" height="697" />
-  <p class="center space-below2"><span class="smcap">Fig. 33.—Fuel Pump</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_91">[Pg 91]</span>
-A complete fuel system is illustrated in <a href="#FIG_35">Figure 35</a>,
-showing the connections of the tanks, pumps, and carburetor.</p>
-
-<p>As dirt is injurious to an engine, the air that forms the mixture
-must be clean, so when a tractor works in a dusty field, it should be
-equipped with an air cleaner, of which there are three kinds. In one
-of these the air is required to pass through water, which washes it.
-A cleaner of this type is shown in <a href="#FIG_36">Figure 36</a>. The dusty air
-enters the central passage, and is forced to pass through the water in order
-to reach the outlet. Passage through the water and through the baffle
-plates frees the air of all its dust.</p>
-
-<p>In the cleaner shown in <a href="#FIG_37">Figure 37</a>, the air is passed
-through loose wool, which filters out the dust. Another type of cleaner works on
-the same principle as a cream separator; the air is given a whirling
-motion, which throws the dirt out at the sides, and it is collected in
-a glass jar.
-<span class="pagenum" id="Page_92">[Pg 92]</span></p>
-
-<div id="FIG_34" class="figcenter">
-  <img src="images/i_p092.jpg" alt="" width="600" height="258" />
-  <p class="center space-below2"><span class="smcap">Fig. 34.—“Avery” Fuel Connections</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_93">[Pg 93]</span></p>
-
-<div id="FIG_35" class="figcenter">
-  <img src="images/i_p093.jpg" alt="" width="600" height="432" />
-  <p class="center space-below2"><span class="smcap">Fig. 35.—“Oil-Pull” Fuel System</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_94">[Pg 94]</span>
-These air cleaners must be emptied frequently, for if they are not kept
-clean it cannot be expected that they will do their work.</p>
-
-<p>A tractor engine is built to develop its maximum power at a certain
-speed; if it runs at greater speed, it will not operate efficiently,
-and there will be unnecessary wear of its parts. These engines are
-therefore usually fitted with <i>governors</i> which hold them at their
-most efficient speed. A governor operates by <i>centrifugal force</i>.</p>
-
-<p>Anything in motion tries to move in a straight line; if it is forced to
-move in a circle, it will exert force in trying to move away from its
-center. It is this that is called centrifugal force. It is centrifugal
-force that holds water in a pail that is being swung around the head,
-and that makes the pail fly off if it is released.
-<span class="pagenum" id="Page_95">[Pg 95]</span></p>
-
-<div id="FIG_36" class="figcenter">
-  <img src="images/i_p095.jpg" alt="" width="300" height="586" />
-  <p class="center space-below2"><span class="smcap">Fig. 36.—Air Washer</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_96">[Pg 96]</span>
-In applying this principle to a governor, weights are attached to a
-plate and made to revolve; springs hold them together, but in spite
-of this, centrifugal force throws them outward. In moving, they act
-on a rod that operates the throttle; as the speed increases, the move
-outward more and more, and it is a simple matter of adjustment to cause
-them to close the throttle when the speed reaches a desired point.</p>
-
-<div id="FIG_37" class="figcenter">
-  <img src="images/i_p096.jpg" alt="" width="400" height="417" />
-  <p class="center space-below2"><span class="smcap">Fig. 37.—Air Strainer</span></p>
-</div>
-<p><span class="pagenum" id="Page_97">[Pg 97]</span></p>
-
-<div id="FIG_38" class="figcenter">
-  <img src="images/i_p097.jpg" alt="" width="600" height="464" />
-  <p class="center space-below2"><span class="smcap">Fig. 38.—“E-B” Governor</span></p>
-</div>
-
-<p>A governor and its connections are shown in <a href="#FIG_38">Figure 38</a>. The
-weights, R, are L-shaped, and pivoted at the angle to a plate driven by the engine.
-The shaft that drives the plate also supports a collar, P, that is
-loose on it and can slide endways; the collar rests against the short
-bar of the L-shaped weights. The other end of the collar touches the
-<span class="pagenum" id="Page_98">[Pg 98]</span>
-lever, E, which is moved when the collar moves. As the lever is
-connected with the throttle, a movement of the collar will control the
-position of the throttle.</p>
-
-<div id="FIG_39" class="figcenter">
-  <img src="images/i_p098.jpg" alt="" width="600" height="450" />
-  <p class="center space-below2"><span class="smcap">Fig. 39.—“Case” Governor</span></p>
-</div>
-
-<p>When the shaft revolves, the long arms of the L-shaped weights tend
-to fly outward; this moves them on their pivots, and the short arms
-thereupon force the collar to slide on the shaft, which moves the lever
-and operates the throttle. The speed at which the throttle will begin
-to close is determined by the setting of the spring that holds the
-weights in.
-<span class="pagenum" id="Page_99">[Pg 99]</span></p>
-
-<div id="FIG_40" class="figcenter">
-  <img src="images/i_p099.jpg" alt="" width="600" height="345" />
-  <p class="center space-below2"><span class="smcap">Fig. 40.—“Hart-Parr” Governor</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_100">[Pg 100]</span>
-Governors and governor connections are shown in <a href="#FIG_39">Figures 39</a>
-and <a href="#FIG_40">40</a>.</p>
-
-<p>The governor shown in <a href="#FIG_41">Figure 41</a> is enclosed in a housing that can
-be locked or sealed. This prevents the unauthorized changing of the adjustment.
-<span class="pagenum" id="Page_101">[Pg 101]</span></p>
-
-<div id="FIG_41" class="figcenter">
-  <img src="images/i_p101.jpg" alt="" width="300" height="478" />
-  <p class="center space-below2"><span class="smcap">Fig. 41.—Vertical Governor</span></p>
-</div>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_102">[Pg 102]</span></p>
-<h2 class="nobreak" id="CHAPTER_VI">CHAPTER VI<br />
-<span class="h_subtitle">IGNITION</span></h2>
-</div>
-
-<p>In order that a gas engine may run properly, the mixture must be set on
-fire, or <i>ignited</i>, at exactly the right time; if ignition occurs
-too early or too late, there will be a loss of power.</p>
-
-<p>The greatest pressure will be obtained at the instant when all of the
-mixture is burning, and this should take place just as the piston
-begins to move outward on the power stroke. A little time is required
-for the mixture to burn; there is a brief interval between the instant
-when it is set on fire and the instant when it is all in flame. Thus it
-is clear that if the mixture is all to be burning as the piston starts
-the power stroke, it must be set on fire before that time, or, in other
-<span class="pagenum" id="Page_103">[Pg 103]</span>
-words, toward the end of the compression stroke.</p>
-
-<p>The point at which ignition should occur depends on the speed of the
-engine and should change when the speed changes. The time required
-for the flame to spread throughout the mixture does not change; let
-us say that, with the engine running at 1200 revolutions a minute,
-the mixture can be ignited when the piston is ¼ inch from the end
-of the compression stroke, and will all be in flame by the time the
-piston starts on the power stroke. If the engine is slowed down to
-600 revolutions a minute and no change is made in the ignition, the
-mixture will all be in flame before the piston reaches the end of the
-compression stroke; pressure will then be produced before the piston is
-in position to perform the power stroke. The pressure will try to make
-the engine run backwards; it will sometimes be sufficient to make the
-engine stop. If the momentum of the flywheel is sufficient to force the
-<span class="pagenum" id="Page_104">[Pg 104]</span>
-piston to the end of the stroke against the pressure, this condition
-will cause a loss of power. This is called <i>preignition</i>, or
-ignition that occurs too soon. One effect of it is to produce a hard,
-metallic knocking, due to the oil being squeezed out of the bearings by
-the great pressure, which permits the bearing and shaft to strike. The
-remedy is to make ignition occur later in the stroke.</p>
-
-<p>If the engine is speeded up above 1200 revolutions, the piston will
-have had time to move some distance on the power stroke before the
-mixture is all in flame; the combustion space will then be too large to
-permit the mixture to produce its greatest pressure, and again there
-will be a loss of power. The remedy in this case is to make ignition
-occur earlier in the compression stroke.</p>
-
-<p>When ignition is made to occur early in the compression stroke, it
-is said to be <i>advanced</i>; when it is made to occur late in the
-stroke, it is said to be <i>retarded</i>.
-<span class="pagenum" id="Page_105">[Pg 105]</span></p>
-
-<p>To get the best results, the engine should be run with ignition
-advanced as far as is possible without causing knocking.</p>
-
-<p>The charge of mixture is always set on fire by an electric spark,
-and the parts that produce and control this spark are called the
-<i>ignition system</i>.</p>
-
-<p>An ignition system consists of: First, the apparatus that produces
-the electric current, which is usually a <i>magneto</i>; second, a
-<i>timer</i>, which controls the instant at which the spark occurs;
-third, the <i>spark plugs</i>, which project into the cylinders, and
-at which the sparks take place; fourth, a <i>switch</i>, by which the
-sparking current can be turned on or off, and fifth, the wires, or
-<i>cables</i>, by which the parts are connected.</p>
-
-<p>The electric current that gives the spark is always produced by
-magnetism. In a magneto, magnetism is obtained from the heavy steel
-magnets that are part of it; there is a constant flow of magnetism from
-one end of these to the other. To obtain an electric current, a coil of
-<span class="pagenum" id="Page_106">[Pg 106]</span>
-wire is placed in the magnetism, and the strength of the magnetism is
-made to change; it alternately becomes weak and strong. Whenever a
-change in strength takes place, an electric current flows in the wire,
-and it continues to flow as long as the magnetism continues to change
-in strength. When the change in strength is very great, that is, when
-the magnetism changes from very weak to very strong, or from very
-strong to very weak, the electric current is more powerful than when
-there is only a little change in strength. A more powerful current is
-also produced by a change that takes place suddenly than by a change
-that takes place slowly.</p>
-
-<p>The electrical principle that produces a current in this manner
-is called <i>induction</i>; the current produced is known as an
-<i>induced</i> current.</p>
-
-<p>A magneto has two or more magnets, and between their ends,
-or <i>poles</i>, there revolves a piece of iron called the
-<i>armature</i>. A piece of iron placed between the poles of a magnet
-<span class="pagenum" id="Page_107">[Pg 107]</span>
-becomes a magnet itself; the armature is so shaped that, as it
-revolves, its magnetism continually changes in strength, and it is the
-changes in the strength of the magnetism of the armature that produce
-the sparking current.</p>
-
-<div id="FIG_42" class="figcenter">
-  <img src="images/i_p107.jpg" alt="" width="600" height="258" />
-  <p class="center space-below2"><span class="smcap">Fig. 42.—Armature</span></p>
-</div>
-
-<p>The iron armature of the Bosch magneto, which is the best known type,
-is shown in <a href="#FIG_42">Figure 42</a>. It has a central bar with two heads,
-the wire being wound around the central bar, or <i>core</i>. The shafts on which
-it revolves are attached to the ends of the heads.</p>
-
-<p><a href="#FIG_43">Figure 43</a> shows different positions of the armature
-between the poles of the magnet, and illustrates the changes in the magnetism of the
-<span class="pagenum" id="Page_108">[Pg 108]</span>
-central bar. There is a continual flow of magnetism from one pole of a
-magnet to the other; if a piece of iron lies between them the magnetism
-will use it as a bridge, but often its easiest path will be through the
-air. In <a href="#FIG_43">A, Figure 43</a>, the armature lies crossways, and its
-central bar or core forms a perfect bridge for the magnetism. Practically all of
-the magnetism flows through it, and it then becomes a powerful magnet
-itself. It sets up its own flow of magnetism, which flows through the core
-to one head, through the air to the other head, and so back to the core.</p>
-
-<div id="FIG_43" class="figcenter">
-  <img src="images/i_p108.jpg" alt="" width="600" height="260" />
-  <p class="center space-below2"><span class="smcap">Fig. 43.—Flow of
-       Magnetism Through Armature Core</span></p>
-</div>
-
-<p>In B, the armature has revolved a little. Most of the magnetism is
-<span class="pagenum" id="Page_109">[Pg 109]</span>
-still flowing through the core, but some of it is finding an easier
-path by flowing through the heads and across the air space to the other
-pole. The magnetism of the core is, therefore, a little weaker than it
-is in A.</p>
-
-<p>In C, the heads alone form bridges between the poles, and none of the
-magnetism flows by the core because that no longer forms a path. The
-core is no longer producing magnetism; in moving from A to C there has
-thus been a complete change in the strength of the magnetism of the
-core, for from full strength it has died away to nothing.</p>
-
-<p>By a further movement, as in D, the core again acts as a bridge, and
-another change in strength occurs, this time from nothing to full
-strength again. In moving from D to B, there are slight changes in
-strength, but not enough to produce a sparking current; it is only in
-passing from B to D that a sparking current can be produced.</p>
-
-<p>In this type of magneto the space between the heads is wound full of
-<span class="pagenum" id="Page_110">[Pg 110]</span>
-wire, which of course revolves with the armature; the more turns of
-wire there are, the more intense will be the current, so very fine wire
-is used to get the greatest possible number of turns.</p>
-
-<p>In the Bosch magneto the first few layers are of coarse wire, and are
-the <i>primary winding</i>. The remainder, called the <i>secondary
-winding</i>, is very fine wire, and the two are connected so that one
-forms an extension of the other.</p>
-
-<p>It has been explained that it is most important to have the spark occur
-at exactly the right instant in the stroke. On a magneto the instant of
-sparking is controlled by a <i>timer</i>, or <i>circuit breaker</i>,
-which is a switch that is automatically operated at the time when the
-magneto is producing a current sufficiently intense to form a spark.</p>
-
-<p><a href="#FIG_44">Figure 44</a> illustrates one complete revolution of the armature,
-and it will be seen that it passes twice from position B to position D. This
-shows that it gives a sparking current twice during each revolution.
-<span class="pagenum" id="Page_111">[Pg 111]</span>
-The circuit breaker must therefore operate twice during each revolution.
-It is placed at the end of the magneto; in some makes it revolves with
-the armature and is operated by stationary cams, while in others it is
-stationary, and is operated by a cam on the armature shaft. In either
-case the effect is the same.</p>
-
-<div id="FIG_44" class="figcenter">
-  <img src="images/i_p111.jpg" alt="" width="600" height="404" />
-  <p class="center space-below2"><span class="smcap">Fig. 44.—One
-             Complete Revolution of the Armature</span></p>
-</div>
-<p><span class="pagenum" id="Page_112">[Pg 112]</span></p>
-<div id="FIG_45" class="figcenter">
-  <img src="images/i_p112.jpg" alt="" width="600" height="430" />
-  <p class="center space-below2"><span class="smcap">Fig. 45.—Connections
-              of Bosch Magneto</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_113">[Pg 113]</span>
-<a href="#FIG_45">Figure 45</a> shows the way in which the winding on the armature
-of a Bosch magneto is connected with the circuit breaker and with the armature.
-The circuit breaker shown is not the kind used on the Bosch, and serves
-only to illustrate the principle. It consists of a lever pivoted at one
-end, with the other end resting against the tip of a screw. A cam bears
-against the lever and can move it to break the contact with the screw.
-The cam is so set that it moves the lever at the time when the current
-is most intense.</p>
-
-<p>The coarse wire, or primary winding, on the armature is connected with
-the lever and with the screw of the circuit breaker; when the lever is
-touching the screw, any current produced in the primary winding has a
-complete path, or <i>circuit</i>, in which to flow.</p>
-
-<p>The fine wire, or secondary winding, is wound on top of the primary,
-and its inmost end is connected to the outmost end of the primary
-so that one forms a continuation of the other. The outmost end of
-the secondary leads to the spark plug; any current produced in the
-secondary winding flows to the spark plug, and, if intense enough, will
-<span class="pagenum" id="Page_114">[Pg 114]</span>
-jump across the small gap in the plug, and return to the secondary by
-way of the primary.</p>
-
-<p>Referring to <a href="#FIG_43">Figure 43</a>, a weak current is produced in the
-primary while the armature revolves from D to B; at that time the circuit breaker is
-closed, so the current can flow in the path thus provided for it. A
-current also tries to flow in the secondary, but is too weak to jump
-across the gap in the spark plug. As the armature comes closer to the
-point <a href="#FIG_43">C, Figure 43</a>, the primary current becomes more intense,
-and the electricity in the secondary increases its endeavor to jump the gap in
-the spark plug, but is still unable to do so.</p>
-
-<p>As the armature passes over the point C, the circuit breaker opens.
-The primary current, which is then most intense, finds its path taken
-away from it, and it seeks another, which it finds by flowing into the
-secondary winding. This flow of primary current, added to the pressure
-already existing in the secondary, forms a current sufficiently intense
-<span class="pagenum" id="Page_115">[Pg 115]</span>
-to jump across the gap in the spark plug, and in so jumping it produces
-the ignition spark.</p>
-
-<p>As the armature passes to position <a href="#FIG_43">D, Figure 43</a>,
-the circuit breaker closes, and the action is repeated.</p>
-
-<div id="FIG_46" class="figcenter">
-  <img src="images/i_p115.jpg" alt="" width="600" height="313" />
-  <p class="center space-below2"><span class="smcap">Fig. 46.—“K-W” Inductor</span></p>
-</div>
-
-<p>A magneto of this type is thus seen to give two sparks to every
-revolution of the armature.</p>
-
-<p>K-W and Dixie magnetos operate on the same general principle as the
-Bosch, with the difference that the wire windings are separate from the
-<span class="pagenum" id="Page_116">[Pg 116]</span>
-armature, and do not revolve. The revolving part, which is called an
-<i>inductor</i>, consists of blocks of iron, so shaped that, as they
-revolve, they alternately lead the magnetism to the core of the winding
-and then away from it. The result is that the core gains magnetism and
-then loses it, and these continual changes in strength produce sparking
-currents in the winding.</p>
-
-<p>The inductor of a K-W magneto is shown in <a href="#FIG_46">Figure 46</a>.
-It consists of a shaft on which are mounted two blocks of iron at right angles.
-The section of shaft that joins them is the core of the winding; the wire
-is wound on it just as thread is wound on a spool, but with a space
-between, so that the shaft may revolve inside of the coil.</p>
-
-<p><a href="#FIG_47">Figure 47</a> shows the inductor in three positions of its
-revolution between the poles of the magnet. When it is in the first position,
-magnetism can flow from one pole of the magnet to the other by going
-into one end, A, of one block, through the core, and out of one end, C,
-<span class="pagenum" id="Page_117">[Pg 117]</span>
-of the other block. This makes a magnet of the core and it forms
-magnetism of its own. When the inductor turns to the second position
-magnetism can get across without flowing through the core, for the
-blocks now give it a path. As the flow through the core ceases, the
-core’s magnetism dies away, which gives the change in strength that is
-needed to produce a sparking current.</p>
-
-<div id="FIG_47" class="figcenter">
-  <img src="images/i_p117.jpg" alt="" width="600" height="391" />
-  <p class="center space-below2"><span class="smcap">Fig. 47.—“K-W”
-             Inductor in Three Positions</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_118">[Pg 118]</span>
-When the inductor is in the third position, the core again becomes the
-path for the magnetism and is magnetized; these changes continue as
-long as the inductor turns.</p>
-
-<div id="FIG_48" class="figcenter">
-  <img src="images/i_p118.jpg" alt="" width="400" height="459" />
-  <p class="center space-below2"><span class="smcap">Fig. 48.—“Dixie” Inductor</span></p>
-</div>
-
-<p>While an armature type of magneto, like the Bosch, produces two sparks
-to every revolution, the K-W produces four, for there are four periods
-<span class="pagenum" id="Page_119">[Pg 119]</span>
-during every revolution when there is sufficient change in the strength
-of the magnetism of the core to produce a sparking current.</p>
-
-<p>In these magnetos the revolving shaft is parallel to the ends of the
-magnets, but in the Dixie magneto it is at a right angle, as shown
-in <a href="#FIG_48">Figure 48</a>. The shaft is of some metal, such as brass or
-bronze, through which magnetism will not flow; otherwise the shaft would form a
-continuous path. The inductor blocks are mounted on the shaft, and act
-as extensions of the poles of the magnet. The core on which the wire is
-wound is a separate piece, placed under the arch of the magnets, with
-ends that extend down and form a tunnel in which the inductor revolves.</p>
-
-<p><a href="#FIG_49">Figure 49</a> shows an end view of the inductor, the magnets
-being cut away so that the core may be seen. As inductor block A is an extension
-of one pole of the magnet, magnetism tries to flow from it to block
-B, which is an extension of the other pole of the magnet. When the
-<span class="pagenum" id="Page_120">[Pg 120]</span>
-inductor is in position <a href="#FIG_49">1, Figure 49</a>, magnetism can flow
-from block A through the core to block B, the core then being magnetized. In
-position 2, magnetism can flow from one block to the other by going
-through the ends of the core instead of through the core itself; the
-core then loses its magnetism, but regains it when the inductor moves
-to position 3.</p>
-
-<div id="FIG_49" class="figcenter">
-  <img src="images/i_p120.jpg" alt="" width="600" height="361" />
-  <p class="center space-below2"><span class="smcap">Fig. 49.—Three
-              Positions of “Dixie” Inductor</span></p>
-</div>
-
-<p>In practically all makes of magnetos the circuit breaker is at the end
-of the armature or inductor shaft, and is operated by it. The Bosch
-<span class="pagenum" id="Page_121">[Pg 121]</span>
-circuit breaker is illustrated in <a href="#FIG_50">Figure 50</a>, the parts being
-mounted on a plate attached to the shaft and revolving with it. The lever
-is L-shaped, pivoted at the angle, with one end resting on the tip
-of a screw. When the shaft revolves, the other end of the lever is
-dragged over a block of metal that acts as a cam; this makes it move
-on its pivot and separates it from the screw. By turning the screw the
-distance of separation may be adjusted.</p>
-
-<div id="FIG_50" class="figcenter">
-  <img src="images/i_p121.jpg" alt="" width="600" height="406" />
-  <p class="center space-below2"><span class="smcap">Fig. 50.—“Bosch”
-           Circuit Breaker</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_122">[Pg 122]</span>
-In the circuit breaker of the K-W magneto it is the cam that revolves,
-while the lever is stationary, as shown in <a href="#FIG_51">Figure 51</a>.
-It will be noticed that the cam will move the lever only twice during each
-revolution; the magneto can produce four sparks during a revolution,
-but with this arrangement of the cam only two of them are used.</p>
-
-<div id="FIG_51" class="figcenter">
-  <img src="images/i_p122.jpg" alt="" width="600" height="310" />
-  <p class="center space-below2"><span class="smcap">Fig. 51.—“K-W”
-                  Circuit Breaker</span></p>
-</div>
-
-<p>It has been said that an intense sparking current is produced when
-there is a great change in the strength of the magnetism, and when the
-<span class="pagenum" id="Page_123">[Pg 123]</span>
-change in strength occurs suddenly. There cannot be any alteration in
-the change in strength, for the greatest magnetic strength of the core
-is what is given it by the magnet, and changing from this to nothing
-is the greatest change possible. The suddenness with which the change
-takes place, however, depends on the speed at which the magneto runs.
-A 4-cylinder engine requires two sparks to each revolution of the crank
-shaft; the armature of a Bosch magneto for this engine will therefore
-run at the same speed as the crank shaft.</p>
-
-<p>The K-W magneto, giving four sparks to the revolution, could run
-at half of the speed of the crank shaft, but then the change in the
-strength of the magnetism would take place slowly, and the sparking
-current would not be sufficiently intense. By using only two of the
-sparks the magneto is run at the same speed as the crank shaft; the
-change in strength then takes place more suddenly, and a more intense
-sparking current is produced.
-<span class="pagenum" id="Page_124">[Pg 124]</span></p>
-
-<p>The circuit breaker of a magneto for a 1-cylinder engine has only one
-cam, so that a single spark is produced during each revolution of the
-armature; the armature makes one revolution to every two revolutions of
-the crank shaft.</p>
-
-<p>However many cylinders an engine may have, the magneto must be revolved
-from one point of sparking to the next in the interval between ignition
-in one cylinder and ignition in the next cylinder to fire. A magneto
-is driven by the crank shaft through gears or by a chain, which are so
-proportioned and set that the magneto is at a point of sparking at the
-instant when a piston is in position for ignition.</p>
-
-<p>A magneto for an engine with more than one cylinder is provided
-with a <i>distributor</i>, which passes the sparking current to the
-particular cylinder that is ready for ignition. A distributor is a
-revolving switch built into the magneto, with as many <i>points</i>, or
-<i>contacts</i>, as the engine has cylinders. At the instant when the
-<span class="pagenum" id="Page_125">[Pg 125]</span>
-magneto produces a sparking current, the revolving distributor arm is
-in position to pass the current to one of the contacts, and the current
-flows to the spark plug with which it is connected.</p>
-
-<p>An electric current must have a complete path, or circuit, in order
-to be able to flow. In a magneto ignition system this path is partly
-of wire and partly of the metal of the engine. The diagram in <a href="#FIG_45">Figure 45</a>
-indicates that the current returns to the magneto from the circuit
-breaker lever and the spark plug by wire, but in actual construction
-it returns by the metal of the engine. This is called a <i>ground
-return</i>; the circuit is said to be <i>grounded</i>.
-<span class="pagenum" id="Page_126">[Pg 126]</span></p>
-
-<div id="FIG_52" class="figcenter">
-  <img src="images/i_p126.jpg" alt="" width="600" height="431" />
-  <p class="center space-below2"><span class="smcap">Fig. 52.—“Bosch”
-                   Magneto in Section</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_127">[Pg 127]</span>
-<a href="#FIG_52">Figure 52</a> is a side view of a Bosch magneto, partly broken
-away to show the interior. As can be seen, one end of the primary winding is
-screwed to the armature, and is thereby connected with the metal of the
-magneto; as the magneto is attached to the engine the primary winding
-is thus in contact with that also. The other end of the primary winding
-leads to the insulated block of the circuit breaker, <a href="#FIG_50">Figure 50</a>.
-This block is <i>insulated</i> from the disk; that is, while it is attached
-to the disk, it is kept from touching it by means of pieces of hard
-rubber or mica. Through these an electric current cannot pass.</p>
-
-<p>The lever is grounded; that is, it is in contact with the metal of
-the magneto. When the lever touches the screw of the insulated block,
-current can flow; when they are separated, the circuit is broken.</p>
-
-<p>One end of the secondary winding, <a href="#FIG_52">Figure 52</a>, is attached
-to the outer end of the primary. The other end leads to the <i>slip ring</i>, which
-is a metal rim on a hard rubber wheel attached to the armature and
-revolving with it. Sparking current flowing to the slip ring is led off
-by a carbon brush and passed to the distributor.</p>
-
-<p>Should a spark plug wire fall off while the engine is running, the
-current would lose its path and would seek another; it is quite powerful
-<span class="pagenum" id="Page_128">[Pg 128]</span>
-enough to make a path for itself by breaking through the windings. As
-this would injure the magneto, such a thing is prevented by providing a
-<i>safety spark gap</i>, which acts like a safety valve in giving the
-current a path when the regular path is interrupted. It consists of
-two points of metal, one attached to the metal of the magneto and the
-other connected with the slip ring brush; it is a more difficult path
-than the one through the spark plug, but easier than breaking down the
-windings.</p>
-
-<p><a href="#FIG_53">Figure 53</a> is a section of the K-W magneto. As the coil
-does not revolve, no slip ring is necessary; the sparking current flows directly
-to the distributor.
-<span class="pagenum" id="Page_129">[Pg 129]</span></p>
-
-<div id="FIG_53" class="figcenter">
-  <img src="images/i_p129.jpg" alt="" width="600" height="453" />
-  <p class="center space-below2"><span class="smcap">Fig. 53.—“K-W”
-               Magneto in Section</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_130">[Pg 130]</span>
-To start an engine, the crank shaft must be turned at sufficient
-speed to drive the magneto fast enough to produce a spark. With large
-engines this is often a difficult matter, so it is very usual to
-equip a magneto with an <i>impulse starter</i>. One part of this is
-attached to the magneto shaft and the other to the engine shaft that
-drives the magneto; the two are connected by a spring. When starting,
-a catch holds the armature and prevents it from turning. The drive
-shaft turns, however, and in so doing winds up the spring. At a certain
-point the catch is automatically released, and the spring then throws
-the armature over at a speed that gives a good spark. A spark is thus
-assured, even though the engine is being cranked very slowly.</p>
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_131">[Pg 131]</span></p>
-<h2 class="nobreak" id="CHAPTER_VII">CHAPTER VII<br />
-<span class="h_subtitle">BATTERY IGNITION SYSTEMS</span></h2>
-</div>
-
-<p>While the greater number of tractor engines use magneto ignition, many
-use battery and coil systems, which are the same in general principle
-as magneto systems, but produce magnetism in a different manner.</p>
-
-<p>Copper is a <i>nonmagnetic</i> metal; that is, magnetism will not
-flow through it, nor can it be magnetized. If a pile of iron filings
-is stirred with a copper wire there will be no effect, as might be
-expected; but if a current of electricity flows through the wire, the
-iron filings will cling to it, as shown in <a href="#FIG_54">Figure 54</a>,
-as if it were a real magnet.
-<span class="pagenum" id="Page_132">[Pg 132]</span></p>
-
-<div id="FIG_54" class="figcenter">
-  <img src="images/i_p132.jpg" alt="" width="500" height="374" />
-  <p class="center space-below2"><span class="smcap">Fig. 54.—Magnetism
-             in a Copper Wire</span></p>
-</div>
-
-<p>It is one of the principles of electricity that when a current flows
-through a wire, the wire is surrounded by magnetism, which continues
-as long as the current flows; when the circuit is broken and the
-current stops flowing, the magnetism dies away. The magnetism produced
-is feeble and can be very greatly increased by winding the wire around
-an iron bar. The magnetism produced by the current then flows into the
-bar, and that, like the core of the winding of a magneto, throws out
-magnetism of its own. This is indicated in <a href="#FIG_55">Figure 55</a>.
-By changing the intensity of the electric current, or by cutting it off, the strength
-<span class="pagenum" id="Page_133">[Pg 133]</span>
-of the magnetism can be made to change, and this change of strength can
-produce a sparking current.</p>
-
-<div id="FIG_55" class="figcenter">
-  <img src="images/i_p133.jpg" alt="" width="600" height="443" />
-  <p class="center space-below2"><span class="smcap">Fig. 55.—Magnetism
-               from Electricity</span></p>
-</div>
-
-<p>The principle employed is illustrated in <a href="#FIG_56">Figure 56</a>. A is
-a coil of wire wound around one end of an iron bar and connected with a battery;
-B is an entirely separate coil of wire wound around the other end of
-the bar, with its ends separated by a short distance. By closing the
-battery switch the current will be permitted to flow in coil A, and the
-<span class="pagenum" id="Page_134">[Pg 134]</span>
-bar will become magnetized; the magnetism that it throws out will be
-felt by coil B. When the switch is opened the current stops flowing
-and the magnetism dies out of the bar; these changes in strength will
-create an electric current in coil B, which will form a spark as it
-passes across the space between the ends.</p>
-
-<div id="FIG_56" class="figcenter">
-  <img src="images/i_p134.jpg" alt="" width="600" height="326" />
-  <p class="center space-below2"><span class="smcap">Fig. 56.—Principle
-              of Spark Coil</span></p>
-</div>
-
-<p>In ignition coils, coil B is wound on top of coil A. Coil A, called
-the <i>primary winding</i>, consists of a few layers of coarse wire.
-The more turns of wire there are in coil B, called the <i>secondary
-winding</i>, the more intense will be the current that it produces, and
-<span class="pagenum" id="Page_135">[Pg 135]</span>
-the intensity is also increased by keeping the windings close to the
-iron core. The secondary winding is, therefore, made of exceedingly
-fine wire, and has a very great number of turns.</p>
-
-<p>To obtain a spark, a current is permitted to flow through the primary
-winding to create magnetism, and the flow is then stopped to cause
-the magnetism to die away. The secondary winding is affected by each
-of these changes in magnetic strength. The bar loses magnetism more
-rapidly than it gains it, however; it is therefore the dying out of the
-magnetism that has the greater effect on the secondary winding, and
-that causes it to produce a sparking current.</p>
-
-<p>To use this principle for ignition, the engine is fitted with a
-revolving switch, which closes the circuit as a piston is on the
-compression stroke, and then breaks the circuit at the instant when a
-spark is desired. Combined with the revolving switch, or <i>timer</i>,
-<span class="pagenum" id="Page_136">[Pg 136]</span>
-is a distributor like the distributor of a magneto, which passes the
-sparking current to the cylinder that is ready to receive it.</p>
-
-<div id="FIG_57" class="figcenter">
-  <img src="images/i_p136a.jpg" alt="" width="600" height="366" />
-  <img src="images/i_p136b.jpg" alt="" width="600" height="190" />
-  <p class="center space-below2"><span class="smcap">Fig. 57.—“Atwater-Kent”
-           Ignition System</span></p>
-</div>
-
-<p>To produce an intense sparking current, it is necessary to break the
-circuit as abruptly as possible, in order to cause the magnetism to die
-away suddenly. <a href="#FIG_57">Figure 57</a> shows how this is done in the Atwater-Kent system.
-<span class="pagenum" id="Page_137">[Pg 137]</span></p>
-
-<p>The parts of the circuit breaker are carried on a plate, in the center
-of which revolves a shaft with a notch in it. Against the side of this
-shaft rests the hooked end of the sliding catch; as the notch comes
-under this hooked end, the sliding catch is drawn forward, only to be
-snapped back by its spring as the notch moves from under it. The lifter
-is a bit of metal, pivoted at one end, with its free end lying between
-the sliding catch and the flat steel spring that carries one of the
-contact points.</p>
-
-<p><a href="#FIG_57">A, Figure 57</a>, is a diagram of the system. B shows the
-position of the parts as the notch carries the sliding catch forward, and C shows
-their positions as the spring snaps the sliding catch back to its
-place. It will be seen that in thus moving back it strikes the lifter,
-which in turn moves the contact spring, and so closes the circuit; but
-the circuit is instantly broken as the parts spring back to position.
-The movement of the parts is so rapid that to the eye they seem to be
-<span class="pagenum" id="Page_138">[Pg 138]</span>
-standing still. The circuit is closed only for an instant, but that
-is sufficient to magnetize and demagnetize the coil, and to produce a
-sparking current.</p>
-
-<p>The operation of this system depends on the very great swiftness with
-which the circuit is made and broken; there is not sufficient time
-for the core to get thoroughly magnetized, but such magnetism as is
-produced changes strength so quickly that it gives a sufficiently
-intense current to create an ignition spark.</p>
-
-<p>In other battery systems of like principle, the circuit is closed for
-a long enough time to allow the core to become fully magnetized, the
-circuit then being suddenly broken. In some of these systems the timer
-breaks the circuit, while in others it is broken by the magnetism,
-through a <i>vibrator</i>.</p>
-
-<p>A <i>vibrator coil</i> system is illustrated in <a href="#FIG_58">Figure 58</a>.
-The timer is a ring made of some kind of insulating material, with a plate of
-metal set in it and forming one of the timer contacts. The other
-contact is the revolving brush, driven by the engine; the circuit is
-closed when the brush touches the metal plate.
-<span class="pagenum" id="Page_139">[Pg 139]</span></p>
-
-<div id="FIG_58" class="figcenter">
-  <img src="images/i_p139.jpg" alt="" width="600" height="408" />
-  <p class="center space-below2"><span class="smcap">Fig. 58.—Vibrator
-           Coil Ignition System</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_140">[Pg 140]</span>
-Opposite the end of the core is a flat steel spring, or <i>vibrator
-blade</i>, resting against the tip of a screw; when the core is
-magnetized it draws the end of the blade to it, and separates it from
-the screw. The battery current flows from the timer contact to the
-screw, then to the vibrator blade and to the primary winding of the
-coil. The core then becomes magnetized, and draws the blade away from
-the screw, which breaks the circuit; this causes the magnetism to die
-away, and a sparking current is produced in the secondary winding of
-the coil. The vibrator blade, no longer held down by the magnetism,
-springs back against the screw; the circuit is again made, and the
-action is repeated. The movement of the vibrator blade is very rapid,
-being some hundreds of vibrations a second.
-<span class="pagenum" id="Page_141">[Pg 141]</span></p>
-
-<div id="FIG_59" class="figcenter">
-  <img src="images/i_p141.jpg" alt="" width="400" height="466" />
-  <p class="center space-below2"><span class="smcap">Fig. 59.—Spark Plug</span></p>
-</div>
-
-<p>A spark plug is illustrated in <a href="#FIG_59">Figure 59</a>. It consists of
-a metal shell screwed into the cylinder, enclosing an <i>insulator</i> of porcelain,
-mica, or some similar material. Through the insulator passes the center
-<span class="pagenum" id="Page_142">[Pg 142]</span>
-electrode, which is a rod of metal, with its lower end separated by a
-short distance from the shell or from a wire attached to the shell.
-This separation is the gap across which the sparking current passes,
-and at which the spark occurs.</p>
-
-<p>Spark plugs receive the pressure of the power stroke, and must be
-strongly made in order to withstand it. A leaky spark plug will cut
-down the power of the engine, just as a leaky valve will.</p>
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_143">[Pg 143]</span></p>
-<h2 class="nobreak" id="CHAPTER_VIII">CHAPTER VIII<br />
-<span class="h_subtitle">TRANSMISSION</span></h2>
-</div>
-
-<p>The parts of a tractor by which the power of the engine is applied to
-the driving wheels are called the <i>transmission</i>, and include the
-<i>clutch</i>, <i>the change speed gear</i>, the <i>differential</i>
-and the <i>drive</i>.</p>
-
-<p>It has been shown that a gas engine delivers power only when it is
-running at speed; it cannot run until some outside power drives it
-through the inlet and compression strokes.</p>
-
-<p>The tractor cannot move until the engine is running and delivering
-power, and it follows, therefore, that it must be possible to
-disconnect the engine from the driving mechanism in order that it may
-run independently. This is done by means of a <i>clutch</i>, which is a
-device that connects two shafts, or disconnects them.
-<span class="pagenum" id="Page_144">[Pg 144]</span></p>
-
-<div id="FIG_60" class="figcenter">
-  <img src="images/i_p144.jpg" alt="" width="500" height="473" />
-  <p class="center space-below2"><span class="smcap">Fig. 60.—Internal
-                Clutch</span></p>
-</div>
-
-<p>A clutch must be so made that when it is engaged it takes hold, not
-suddenly, but gradually. If it took hold suddenly, the tractor would be
-required to jump at once into full motion; this would cause a severe
-<span class="pagenum" id="Page_145">[Pg 145]</span>
-straining of the parts and probable breakage. The alternative would be
-the abrupt stopping of the engine, and this would also strain things.</p>
-
-<p>By making the clutch in such a way that it slips, and takes hold little
-by little, the tractor starts slowly, and gradually comes up to speed;
-the slipping of the clutch then ceases, and it takes hold firmly.</p>
-
-<p>All clutches operate by the friction of one surface against another;
-in some, the surfaces are curved and in others flat, while in still
-others the clutch is a band around a wheel, or <i>drum</i>. A clutch is
-operated by a hand lever or by a foot pedal.</p>
-
-<p><a href="#FIG_60">Figure 60</a> shows a type of clutch that operates inside a
-drum, which is often the overhanging rim of the flywheel. The shaft in the center is
-independent of the flywheel, and it is the purpose of the clutch, which
-is attached to the shaft, to lock the shaft and flywheel together when
-the tractor is to be started.
-<span class="pagenum" id="Page_146">[Pg 146]</span></p>
-
-<p>The brake shoes, which bear against the drum, form the ends of pivoted
-levers, and are lined with an asbestos material that resists the heat
-caused by the friction against the drum.</p>
-
-<p>A cone-shaped block of steel slides lengthways on the shaft; when it is
-pushed into position, it forces out the yokes, and thus presses the
-brake shoes against the drum.</p>
-
-<p>A <i>plate clutch</i>, or <i>disk clutch</i>, is shown in <a href="#FIG_61">Figure 61</a>.
-The principle of a plate clutch may be illustrated by placing a
-half-dollar between two quarters and pinching them with the thumb and
-forefinger. If they are held loosely, the half-dollar may be turned
-between the quarters, but if they are pinched tightly, the friction
-between the coins will be so great that one cannot be turned without
-turning the others.
-<span class="pagenum" id="Page_147">[Pg 147]</span></p>
-
-<div id="FIG_61" class="figcenter">
-  <img src="images/i_p147.jpg" alt="" width="600" height="439" />
-  <p class="center space-below2"><span class="smcap">Fig. 61.—Plate Clutch</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_148">[Pg 148]</span>
-Attached to the flywheel are studs, which support a disk, or plate;
-this plate revolves with the flywheel, and is practically a part of it.
-On either side of this plate are other plates that are supported on the
-drive shaft; they revolve with it, but can slide along it. The end of
-the shaft is square and fits a square hole in a collar, so that while
-the collar may slide along the shaft, the two must turn together. Cams
-are mounted on the hub of one of the plates in such a position that
-they can press the outside plates together and pinch the flywheel plate
-between. The cams are operated by pressing the collar against them.</p>
-
-<p>The first drawing shows the clutch out, or released; the flywheel may
-then turn without turning the shaft, for the plates are not in contact.
-The second drawing shows the clutch in, or engaged. The collar is
-pressed against the cams, and the plates in turn are drawn together,
-pinching the flywheel plate between them. The flywheel and the drive
-shaft then revolve together.</p>
-
-<p>Plate clutches are often made with more than three plates; some makes
-run in a bath of oil, and some are intended to work dry.
-<span class="pagenum" id="Page_149">[Pg 149]</span></p>
-
-<p>In a cone clutch, the overhanging rim of the flywheel is funnel-shaped,
-and into it fits a cone-shaped disk carried on the end of the drive
-shaft. To engage the clutch, the disk is slid along the shaft against
-the flywheel, the friction between the two being sufficient to drive
-the shaft.</p>
-
-<p>When a clutch is thrown in it should take hold gradually, slipping at
-first, but finally having a firm grip. When it is thrown out, it should
-release instantly and completely.</p>
-
-<p>The power delivered by an engine depends on the <i>bore</i> and
-<i>stroke</i> of the cylinder, and on the speed. The greater the bore,
-or diameter of the cylinder, and the greater the stroke, or distance
-the piston moves in a half-revolution of the crank shaft, the larger
-will be the combustion space, and the larger will be the charge of
-mixture that it can take in; the larger the charge, the greater will be
-the power produced when the charge burns.</p>
-
-<p>Each cylinder produces power once during every two revolutions of the
-<span class="pagenum" id="Page_150">[Pg 150]</span>
-crank shaft; if the engine runs at 1,000 revolutions per minute there
-will be twice as many power strokes as there would be if it ran at 500
-revolutions per minute, and during that minute it will produce twice as
-much power.</p>
-
-<p>A traction engine is intended to run at a certain speed, at which it
-will produce its greatest power without overstraining its parts. This
-<i>normal speed</i> for any particular engine depends on the number of
-cylinders, their size and design, and other details established by the
-manufacturer. To get the best from the engine, this is the speed at
-which it should always be run.</p>
-
-<p>The power required to move the tractor depends on various things;
-the hardness and smoothness of the ground, the grade, the load it is
-pulling, and so on. The tractor might be running on level ground,
-pulling so great a load that the engine is called on for all of the
-power that it can deliver.</p>
-
-<p>On coming to a hill, still more power will be required, for now the
-tractor and its load must be lifted as well as moved forward. The
-<span class="pagenum" id="Page_151">[Pg 151]</span>
-engine, already working at its limit, cannot deliver the extra power
-needed, and will slow down and stop unless something is done to aid
-it. In such a case, the change speed gear is used to give the engine
-a greater leverage on its work, just as a block and tackle gives a
-greater leverage or purchase to a man who must lift a heavy weight.</p>
-
-<p>Let us say that the normal speed of the engine is 1,000 revolutions per
-minute, and that it is so connected that it makes 40 revolutions while
-the driving wheels make 1, the speed of the tractor being 3 miles per
-hour. If it is a 4-cylinder engine there will thus be 80 power strokes
-to every revolution of the driving wheels. The engine is delivering its
-full power and cannot do more should the tractor be called on for an
-extra exertion, such as climbing a hill or crossing rough ground.</p>
-
-<p>By changing the connections between the engine and the driving wheels,
-<span class="pagenum" id="Page_152">[Pg 152]</span>
-the engine can be made to run twice as many revolutions to one turn of
-the driving wheels, which will give double the number of power strokes;
-the wheels will thus be turned with twice the force. As no change is
-made in the speed of the engine, the wheels will now turn at half their
-former speed, and the tractor will run at 1½ miles per hour. It will,
-however, have twice the ability to overcome obstacles.</p>
-
-<p>This change in the connections between the engine and the drive is
-performed by the <i>change speed gear</i>, which is driven by the
-engine and which in turn drives the wheels.</p>
-
-<p>There are many varieties of change speed gears, but the main principle
-in them all is the same, for they depend on the action of cog-wheels,
-or <i>gears</i>.</p>
-
-<p>When two gears running together, or <i>in mesh</i>, have the same
-number of teeth, they will revolve at the same speed. If one has half
-as many teeth as the other—10 teeth and 20, let us say—the 10-tooth
-gear will make two revolutions while the 20-tooth gear is making one.
-<span class="pagenum" id="Page_153">[Pg 153]</span></p>
-
-<p>There are two shafts in a change speed gear, one driven by the engine
-and the other driving the wheels; each carries gears that mesh with
-gears on the other shaft. These pairs of gears are of different sizes,
-and any pair may be used; the shaft driven by the engine runs as the
-engine runs, while the speed of the other shaft depends on the pair of
-gears that is being used.</p>
-
-<p>By changing from one pair of gears to another, the driven shaft, and,
-consequently, the wheels, may be run at a greater or less number of
-revolutions, while the speed of the engine and the driving shaft do not
-change. The number of power strokes that occur during one revolution of
-the wheels is thus changed, and they turn with more force or with less.</p>
-
-<p><i>High speed</i>, or <i>high gear</i>, means the combination of gears
-that gives the greatest speed to the wheels, but the fewest power
-strokes to each revolution. The combination that gives the slowest
-<span class="pagenum" id="Page_154">[Pg 154]</span>
-speed to the wheels, but the greatest number of power strokes, is
-called <i>low speed</i>, or <i>low gear</i>.</p>
-
-<p>Many tractors have but two speeds, a low and a high; but others have an
-intermediate combination for conditions too severe for running on high
-gear but too easy for low.</p>
-
-<p>The change speed gear mechanism also provides for reversing or backing
-the tractor. Two gears running together turn in opposite directions,
-while in a train of three gears the outside gears turn in the same
-direction. The usual combination in a change speed gear uses two gears
-for going ahead; to run the driven shaft the other way, which will make
-the tractor back, a third gear is meshed between the two.</p>
-
-<p>The differences between various makes of change speed gears are in the
-methods used to put into action the desired pair of gears.
-<span class="pagenum" id="Page_155">[Pg 155]</span></p>
-
-<div id="FIG_62" class="figcenter">
-  <img src="images/i_p155.jpg" alt="" width="350" height="627" />
-  <p class="center space-below2"><span class="smcap">Fig. 62.—Principle
-              of Sliding Gear</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_156">[Pg 156]</span>
-Two general plans are used. In one of them, a gear of each pair can
-slide endways on its shaft, but must revolve with it; thus it can be
-slid into mesh or out. In the other, the gears of a pair are always in
-mesh, but one of them is loose on its shaft, so that shaft and gear can
-revolve independently. To make the pair of gears operate, the loose
-gear is locked to its shaft.</p>
-
-<p><a href="#FIG_62">Figure 62</a> shows the principle of the <i>sliding gear</i>
-type. One part of the shaft driven by the engine is square, and fits into square
-holes in its gears, which may thus slide along it, but must revolve with it.
-Each sliding gear is moved by a shifter block, which is operated by
-a shift lever. There is a shifter block for each gear, and the shift
-lever may be moved sideways to operate either one of them.</p>
-
-<p><a href="#FIG_63">Figure 63</a> shows the <i>jaw clutch</i> type of change speed
-gear, in which the gears are in mesh all of the time, but run loose on their
-shaft when they are not working. The drawing shows <i>bevel gears</i>,
-which are used when the driving and driven shafts are at a right angle.
-The same principle is used for <i>spur gears</i> on shafts that are
-parallel, as in <a href="#FIG_62">Figure 62</a>.
-<span class="pagenum" id="Page_157">[Pg 157]</span></p>
-
-<div id="FIG_63" class="figcenter">
-  <img src="images/i_p157.jpg" alt="" width="350" height="486" />
-  <p class="center space-below2"><span class="smcap">Fig. 63.—Principle
-            of Jaw Clutch Change Speed Gear</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_158">[Pg 158]</span>
-The center of the shaft is square, and fits a block that can slide
-endways, but that must revolve with it. The ends of the block have
-heavy teeth that can mesh with teeth on the hubs of the loose gears;
-meshing the block with one of the gears forces that gear to revolve
-with the shaft.</p>
-
-<p>The drawing shows only one speed forward; the reverse is obtained by a
-second gear on the same shaft, which is placed on the opposite side of
-the center of the driven gear, and turns it in the opposite direction.</p>
-
-<p>When a tractor turns, the outside wheel makes a larger circle than the
-inside wheel, and has a longer path to travel. Both wheels travel their
-paths in the same time, so it follows that the outside wheel must move
-faster than the inside wheel, although both are being driven by the
-engine. This is allowed for by the <i>differential</i>, which is driven
-<span class="pagenum" id="Page_159">[Pg 159]</span>
-by the change speed gear, and which in turn drives the wheels; it
-operates automatically by the difference in the resistance to the
-rolling of the wheels.</p>
-
-<p>The action of the differential is illustrated by an experiment that
-requires a pair of wheels on an axle, like buggy wheels, and a stick
-long enough to reach from one to the other. With the wheels on smooth
-ground, put the ends of the stick through the wheels at the top, each
-end pressing against a spoke. Hold the stick at its center and push it
-forward; the stick will transmit the pressure to the spokes, and the
-wheels will turn. The wheels being on smooth ground, there is equal
-resistance to their movement, and they will run straight forward.</p>
-
-<p>Now repeat the experiment with the wheels so placed that one is on
-a smooth roadway and the other on sand; as the wheel on the smooth
-surface meets with less resistance than the other does, it moves
-faster, and the pair of wheels circles, although the stick applies
-equal pressure to both.
-<span class="pagenum" id="Page_160">[Pg 160]</span></p>
-
-<p>The power developed by the engine is transmitted by the differential
-to both rear wheels; when the wheels meet with equal resistance, they
-turn equally, but when one wheel meets with greater resistance than the
-other, it slows down, while the other speeds up to correspond.</p>
-
-<p>A tractor with two driving wheels must use a differential in order to
-make turns easily. Without a differential, the wheels would run always
-at equal speed, and in making a turn one would be obliged to slip.</p>
-
-<p>The use of a differential has a disadvantage, however. If one wheel
-is in a mudhole and the other is on hard ground, the wheel in the mud
-meets with little resistance, and all of the power of the engine goes
-to it; it spins without moving the tractor, while the other wheel
-remains stationary. In such a case all of the power should be applied
-to the wheel that has traction in order to move the tractor, but this
-the differential fails to allow.
-<span class="pagenum" id="Page_161">[Pg 161]</span></p>
-
-<p>In some tractors the differential is so made that the parts may be
-locked together. This lock is used when one wheel is in a mud hole, and
-as by its use power is transmitted equally to both wheels, the tractor moves.</p>
-
-<p>Great care must be taken to unlock the differential as soon as the need
-for the lock has passed, for otherwise the wheels would slip on a turn,
-and the parts of the transmission might be strained or broken.</p>
-
-<p>A differential is usually made with two bevel gears placed face to
-face; between them is a frame holding three or more small bevel gears
-that are in mesh with them both. The engine revolves the frame with its
-small gears; each of the large bevel gears revolves a driving wheel.</p>
-
-<p>When the tractor moves straight ahead the differential turns as
-if it were one solid piece. When there is less resistance to one
-driving wheel than to the other, the small bevel gears, in addition to
-<span class="pagenum" id="Page_162">[Pg 162]</span>
-revolving with the frame that carries them, turn on their shafts. This
-transmits the power of the engine to one wheel more than the other,
-according to the resistance of the wheels.</p>
-
-<div id="FIG_64" class="figcenter">
-  <img src="images/i_p162.jpg" alt="" width="600" height="318" />
-  <p class="center space-below2"><span class="smcap">Fig. 64.—“I. H. C.” Chain
-            Drive, Showing the Differential</span></p>
-</div>
-
-<p><a href="#FIG_64">Figure 64</a> shows one of the large bevel gears of a differential,
-with the three small gears, the other large bevel gear being removed. A
-differential in section is shown in <a href="#FIG_65">Figure 65</a>.</p>
-
-<p>A tractor with only one driving wheel has no differential. Such
-tractors usually have two wheels, but one of them runs loose on the
-<span class="pagenum" id="Page_163">[Pg 163]</span>
-axle, and serves only to support the tractor. The rear axle construction
-of a tractor with a 1-wheel drive is shown in <a href="#FIG_66">Figure 66</a>,
-which should be compared with the 2-wheel rear construction shown in
-<a href="#FIG_65">Figure 65</a>.</p>
-
-<div id="FIG_65" class="figcenter">
-  <img src="images/i_p163.jpg" alt="" width="600" height="473" />
-  <p class="center space-below2"><span class="smcap">Fig. 65.—“Case” Rear Axle</span></p>
-</div>
-
-<p>There are a number of methods used for transmitting power to the
-driving wheels. In <a href="#FIG_64">Figure 64</a> a chain is used; there are
-tractors with but one chain, and others with a chain for each driving wheel.
-<span class="pagenum" id="Page_164">[Pg 164]</span></p>
-
-<div id="FIG_66" class="figcenter">
-  <img src="images/i_p164.jpg" alt="" width="600" height="374" />
-  <p class="center space-below2"><span class="smcap">Fig. 66.—“Oil-Pull”
-                 Rear Axle</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_165">[Pg 165]</span>
-The most usual method is by a <i>master gear</i>, or <i>bull gear</i>,
-which is a large and heavy gear attached to the driving wheel, as shown
-in <a href="#FIG_65">Figures 65</a> and <a href="#FIG_66">66</a>.
-In some tractors this gear is nearly the size of the wheel, and is
-fully exposed; in others it is smaller, and enclosed in an oil-tight
-housing.</p>
-
-<div id="FIG_67" class="figcenter">
-  <img src="images/i_p165.jpg" alt="" width="600" height="329" />
-  <p class="center space-below2"><span class="smcap">Fig. 67.—Driving Worm</span></p>
-</div>
-
-<p>The small gears that drive the bull gears are on the ends of the cross
-shaft, called the <i>jack shaft</i>, that carries the differential.
-<span class="pagenum" id="Page_166">[Pg 166]</span></p>
-
-<p>In the Fordson tractor the differential is built into the axle, as it
-is in an automobile, and power is applied by a <i>worm</i>. The worm is
-driven by the change speed gear, and is a screw meshing with a gear on
-the differential, whose teeth are cut at the proper angle to make them
-fit the threads of the worm. A worm, which is shown in <a href="#FIG_67">Figure 67</a>,
-is always enclosed, and runs in oil.</p>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_167">[Pg 167]</span></p>
-<h2 class="nobreak" id="CHAPTER_IX">CHAPTER IX<br />
-<span class="h_subtitle">TRACTOR ARRANGEMENT</span></h2>
-</div>
-
-<p>The uneven ground over which tractors must work requires the weight to
-be kept low, to prevent capsizing, and they are also built wide, for
-the narrower they are the more easily they tip over. They cannot be
-broad in front, however, for if they are the steering wheels cannot
-be swung enough to permit them to turn in the small circle that is
-desirable.</p>
-
-<p>To give a small turning circle some tractors are built with the front
-of the frame raised enough to permit the wheels to cut under. Others
-use small steering wheels, but this is not desirable because small
-wheels will not run over rough ground as readily as large ones, and
-steering is difficult.
-<span class="pagenum" id="Page_168">[Pg 168]</span></p>
-
-<div id="FIG_68" class="figcenter">
-  <img src="images/i_p168a.jpg" alt="" width="500" height="452" />
-  <img src="images/i_p168b.jpg" alt="" width="500" height="468" />
-  <p class="center space-below2"><span class="smcap">Fig. 68.—Tractor
-                Arrangement</span></p>
-</div>
-<p><span class="pagenum" id="Page_169">[Pg 169]</span></p>
-<div id="FIG_69" class="figcenter">
-  <img src="images/i_p169a.jpg" alt="" width="500" height="417" />
-  <img src="images/i_p169b.jpg" alt="" width="500" height="405" />
-  <p class="center space-below2"><span class="smcap">Fig. 69.—Tractor
-                Arrangement</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_170">[Pg 170]</span>
-Types of tractors are indicated in <a href="#FIG_68">Figures 68</a>
-and <a href="#FIG_69">69</a>. A has a 4-cylinder vertical engine in
-front, driving both wheels by bull gears, while B is a 2-cylinder
-horizontal engine in the center, driving both wheels by chains. C has a
-4-cylinder vertical engine set across the frame. These three types have
-riveted steel frames, to which the parts are attached.</p>
-
-<p>In D, the drive is entirely enclosed within the rear axle housing,
-and the rear part of the frame is formed by the axle housing and the
-housing of the change speed gear.</p>
-
-<p>E has a 1-cylinder horizontal engine with a single chain drive, while F
-has a similar engine but drives to both wheels.</p>
-
-<p>G has no frame, its place being taken by the crank case of the engine
-and the housings of the parts of the transmission. G and H have
-4-cylinder vertical engines, G driving through an enclosed rear axle
-and H through bull gears.
-<span class="pagenum" id="Page_171">[Pg 171]</span></p>
-
-<div id="FIG_70" class="figcenter">
-  <img src="images/i_p171.jpg" alt="" width="600" height="281" />
-  <p class="center space-below2"><span class="smcap">Fig. 70.—“Gray” Tractor</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_172">[Pg 172]</span>
-<a href="#FIG_70">Figure 70</a> has one broad wheel instead of two narrower
-ones, this being placed inside of the frame instead of outside. It has a
-4-cylinder vertical engine placed across the frame, and drives through two chains.</p>
-
-<div id="FIG_71" class="figcenter">
-  <img src="images/i_p172a.jpg" alt="" width="600" height="305" />
-  <img src="images/i_p172b.jpg" alt="" width="600" height="339" />
-  <p class="center space-below2"><span class="smcap">Fig. 71.—Types
-             of Front Axles</span></p>
-</div>
-
-<p>The front axle of a tractor is almost always attached to the frame by
-<span class="pagenum" id="Page_173">[Pg 173]</span>
-a pivot, so that the wheels will follow uneven ground. Some of the
-forms of front axles are shown in <a href="#FIG_71">Figure 71</a>.</p>
-
-<div id="FIG_72" class="figcenter">
-  <img src="images/i_p173.jpg" alt="" width="500" height="499" />
-  <p class="center space-below2"><span class="smcap">Fig. 72.—Spring Support</span></p>
-</div>
-
-<p>The first is a plain bar, while the second is arched to raise the front
-of the frame in order to permit the steering wheels to cut under. In
-the third the wheel axles are mounted on springs, which take up some of
-the vibration and act as shock absorbers.</p>
-
-<p>The fourth axle shown is built of steel bars riveted together to form
-<span class="pagenum" id="Page_174">[Pg 174]</span>
-a truss, and the fifth is similar, with the frame pivot carried on
-springs. The sketches at the bottom indicate the extent to which the
-pivoted front axle may swing.</p>
-
-<p><a href="#FIG_72">Figure 72</a> shows a spring support for the
-axles, front and rear. The axle bearing is in a block sliding in
-guides, the weight being supported by a heavy spring.</p>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_175">[Pg 175]</span></p>
-<h2 class="nobreak" id="CHAPTER_X">CHAPTER X<br />
-<span class="h_subtitle">LUBRICATION</span></h2>
-</div>
-
-<p>The most important thing in the care of a tractor is to oil it; every
-moving part should be lubricated, and the greatest care should be taken
-to assure a never-failing supply of oil and grease.</p>
-
-<p>Carelessness in lubrication is the principal cause of tractor trouble.
-There is nothing complicated or difficult about keeping a tractor
-properly oiled; yet more tractors break down from careless lubrication
-than from any other cause. Every tractor-maker issues an oiling diagram
-and oiling instructions, and there is no excuse for an operator whose
-machine does not get the right kind of lubricant in the right quantity
-at each place where lubrication is necessary.
-<span class="pagenum" id="Page_176">[Pg 176]</span></p>
-
-<p>The cause of wear is friction; oil reduces friction and so reduces
-wear. No matter how smooth and highly polished two pieces of steel may
-be, there will be friction between them if they are rubbed together,
-and they will wear each other. If they are oiled, the particles of oil
-will keep the pieces from touching each other, and there will be no wear.</p>
-
-<p>Other substances than oil can be used; there are some kinds of
-machinery that are lubricated with water, for instance. For general
-use, however, oil and grease are the best, and are practically always used.</p>
-
-<p>The object of a lubricant is to keep two pieces of metal from
-touching; it must therefore be able to get between them, and must stay
-there. If the pieces are large and heavy, there will be much greater
-pressure on the oil than if they are small and light, and the oil must
-be able to withstand this pressure and resist being squeezed out. The
-oil that would keep the small, light pieces apart might not be able to
-<span class="pagenum" id="Page_177">[Pg 177]</span>
-stand the pressure of a greater weight, and might be squeezed out from
-between two heavy pieces.</p>
-
-<p>Oil has a tendency to cling to whatever it touches, and thick oil
-or grease has more of this tendency than a thin, or “runny” oil. If
-a thick oil or grease is used on light machinery, such as a sewing
-machine, this clinging tendency would make the machine run hard, and
-might even prevent its operation.</p>
-
-<p>When oil is heated, it becomes thinner, or more “runny.” Through
-this, an oil used in a hot place might get so thin that it would not
-lubricate; and on the other hand, an oil that works all right in the
-heat of summer might get so thick on a cold winter day as to be useless.</p>
-
-<p>A slow-moving part of a machine uses a thick oil or a grease; a thin
-oil must be used for a part that moves at high speed.</p>
-
-<p>Some of the parts of a tractor move slowly and some at high speed;
-some are cool and some are hot. Different kinds of lubricants are
-<span class="pagenum" id="Page_178">[Pg 178]</span>
-therefore required, and it is a grave mistake to use a lubricant that
-is not suitable to the work that it is required to do.</p>
-
-<p>The engine is the most difficult part of a tractor to lubricate, and
-the part that suffers most if the supply fails or if the wrong kind
-of lubricant is used. In the first place, it is so hot that any oil
-will burn, being turned to carbon; the best that can be expected of
-an oil is that it will resist burning until it has done its work of
-lubricating the piston and cylinder.</p>
-
-<p>A tractor engine is more difficult to oil than an automobile or
-truck engine for the reason that it works harder and more steadily.
-An automobile engine is rarely driven to the limit of its power; it
-has frequent opportunities to cool when running down hill. A tractor
-engine, on the other hand, works at its full power all day long with
-no opportunities to cool off. An oil that gives good satisfaction on
-an automobile might ruin a tractor engine through its inability to
-withstand the greater heat.
-<span class="pagenum" id="Page_179">[Pg 179]</span></p>
-
-<p>The makers of tractors understand the importance of using proper oils,
-and recommend certain brands and grades; these recommendations should
-be followed in order to get the best possible results. All makers
-specify at least two kinds of lubricants, and most of them three; one
-specifies six, which range from a light sewing machine oil to a grease
-so thick that it is nearly solid. Whatever the recommendations may be,
-they should be followed.</p>
-
-<p>In general, lubricants are classified according to their thickness, and
-they range from the light oil used for typewriters and sewing machines
-to grease so thick that it may be cut like butter. The thinnest oil
-is used for the circuit breaker pivot; this part is usually moved in
-one direction by a cam and in the other by a light spring. A thick oil
-would gum the bearing to such an extent that the spring might not be
-able to move the lever.
-<span class="pagenum" id="Page_180">[Pg 180]</span></p>
-
-<div id="FIG_73" class="figcenter">
-  <img src="images/i_p180.jpg" alt="" width="600" height="347" />
-  <p class="center space-below2"><span class="smcap">Fig. 73.—“Mogul”
-             Oiling Diagram</span></p>
-</div>
-<p><span class="pagenum" id="Page_181">[Pg 181]</span></p>
-
-<table border="0" cellspacing="0" summary="Lubrication Schedule" cellpadding="2" rules="cols">
-  <thead><tr>
-      <th class="tdc bb2" colspan="4">&nbsp;</th>
-   </tr><tr>
-      <th class="tdc bb2">KEY</th>
-      <th class="tdc bb2">DESCRIPTION</th>
-      <th class="tdc bb2">QUANTITY</th>
-      <th class="tdc bb2">LUBRICATION</th>
-   </tr>
-  </thead>
-  <tbody><tr>
-      <td class="tdc bb" colspan="4"><b>ONCE EVERY HOUR</b></td>
-   </tr><tr>
-      <td class="tdc">L</td>
-      <td class="tdl_ws1">Rear axle bearing</td>
-      <td class="tdl_ws1">Two complete turns</td>
-      <td class="tdl_ws1">Cup Grease</td>
-   </tr><tr>
-      <td class="tdc bb bt" colspan="4"><b>ONCE EVERY TWO HOURS</b></td>
-   </tr><tr>
-      <td class="tdc">A</td>
-      <td class="tdl_ws1">Differential hub</td>
-      <td class="tdl_ws1">One complete turn</td>
-      <td class="tdl_ws1">Cup Grease</td>
-   </tr><tr>
-      <td class="tdc">B</td>
-      <td class="tdl_ws1">Rear wheel hub</td>
-      <td class="tdl_ws1">One complete turn</td>
-      <td class="tdl_ws1">Cup Grease</td>
-   </tr><tr>
-      <td class="tdc">C</td>
-      <td class="tdl_ws1">Differential pinion</td>
-      <td class="tdl_ws1">One complete turn</td>
-      <td class="tdl_ws1">Cup Grease</td>
-   </tr><tr>
-      <td class="tdc">H</td>
-      <td class="tdl_ws1">Front wheel hub</td>
-      <td class="tdl_ws1">Two complete turns</td>
-      <td class="tdl_ws1">Cup Grease</td>
-   </tr><tr>
-      <td class="tdc">T</td>
-      <td class="tdl_ws1">Governor and cam shaft bearing</td>
-      <td class="tdl_ws1">Two complete turns</td>
-      <td class="tdl_ws1">Cup Grease</td>
-   </tr><tr>
-      <td class="tdc bb bt" colspan="4"><b>TWICE EVERY DAY</b></td>
-   </tr><tr>
-      <td class="tdc">E</td>
-      <td class="tdl_ws1">Governor</td>
-      <td class="tdl_ws1">Oil</td>
-      <td class="tdl_ws1">Cylinder oil</td>
-   </tr><tr>
-      <td class="tdc">F</td>
-      <td class="tdl_ws1">Outboard bearing grease cups</td>
-      <td class="tdl_ws1">Two complete turns when plowing</td>
-      <td class="tdl_ws1"> Cup Grease</td>
-   </tr><tr>
-      <td class="tdc bb">G</td>
-      <td class="tdl_ws1 bb">Transmission</td>
-      <td class="tdl_ws1 bb">One pint</td>
-      <td class="tdl_ws1 bb">See note below</td>
-   </tr><tr>
-      <td class="tdc bb" rowspan="2">N</td>
-      <td class="tdl_ws1">Magneto trip</td>
-      <td class="tdl_ws1">Grease every 5 hours</td>
-      <td class="tdl_ws1">Cup Grease</td>
-   </tr><tr>
-      <td class="tdl_ws1 bb">Magneto roller and slide</td>
-      <td class="tdl_ws1 bb">Oil every 5 hours</td>
-      <td class="tdl_ws1 bb">Oil</td>
-   </tr><tr>
-      <td class="tdc">J</td>
-      <td class="tdl_ws1">Steering worm</td>
-      <td class="tdl_ws1">Keep covered</td>
-      <td class="tdl_ws1">Cup Grease</td>
-   </tr><tr>
-      <td class="tdc">W</td>
-      <td class="tdl_ws1">Steering hub grease cup</td>
-      <td class="tdl_ws1">One complete turn</td>
-      <td class="tdl_ws1">Cup Grease</td>
-   </tr><tr>
-      <td class="tdc">V</td>
-      <td class="tdl_ws1">Steering worm shaft</td>
-      <td class="tdl_ws1">Oil every 5 hours</td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc">R</td>
-      <td class="tdl_ws1">Lubricator eccentric</td>
-      <td class="tdl_ws1">Oil every 5 hours</td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc">&nbsp;</td>
-      <td class="tdl_ws1">&nbsp;</td>
-      <td class="tdl_ws1">&emsp;(keep wool in pocket)</td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc">P</td>
-      <td class="tdl_ws1">Cam roller slide</td>
-      <td class="tdl_ws1">Oil every 5 hours</td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc">K</td>
-      <td class="tdl_ws1">Valve levers</td>
-      <td class="tdl_ws1">Fill with oil every 5 hours</td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc">&nbsp;</td>
-      <td class="tdl_ws1">&nbsp;</td>
-      <td class="tdl_ws1">&emsp;(keep wool in pocket)</td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc bb bt" colspan="4"><b>ONCE EVERY DAY TRACTOR IS IN USE</b></td>
-   </tr><tr>
-      <td class="tdc bb">U</td>
-      <td class="tdl_ws1 bb">Steering sector shaft</td>
-      <td class="tdl_ws1 bb">One complete turn</td>
-      <td class="tdl_ws1 bb">Cup Grease</td>
-   </tr><tr>
-      <td class="tdc">D</td>
-      <td class="tdl_ws1" colspan="2"><b>MECHANICAL LUBRICATOR</b></td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc">&nbsp;</td>
-      <td class="tdl_ws1" colspan="2"><p class="no-indent blockquot">Fill with a good grade of heavy gas engine cylinder oil.
-                    Turn the crank on the mechanical oiler 40 to 50 times when
-                    starting the engine.</p></td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc">D</td>
-      <td class="tdl_ws1" colspan="2"><b>IMPORTANT</b></td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc bb">&nbsp;</td>
-      <td class="tdl_ws1 bb" colspan="2"><p class="no-indent blockquot">In cool or cold weather the oil in lubricator tank must be
-                         warmed as it will not flow readily unless of the right temperature.</p></td>
-      <td class="tdl_ws1 bb">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc">G</td>
-      <td class="tdl_ws1" colspan="2"><b>TRANSMISSION</b></td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc bb">&nbsp;</td>
-      <td class="tdl_ws1 bb" colspan="2"><p class="no-indent blockquot">In warm weather, use heavy oil such as “600” transmission or
-                         Polarine transmission oil; in cold weather, use a good light oil.</p></td>
-      <td class="tdl_ws1 bb">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc">S</td>
-      <td class="tdl_ws1" colspan="2"><b>GOVERNOR</b></td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc bb">&nbsp;</td>
-      <td class="tdl_ws1 bb" colspan="2"><p class="no-indent blockquot">Cylinder oil in governor should cover shoe.</p></td>
-      <td class="tdl_ws1 bb">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc">M</td>
-      <td class="tdl_ws1" colspan="2"><b>MAGNETO</b></td>
-      <td class="tdl_ws1">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc bb">&nbsp;</td>
-      <td class="tdl_ws1 bb" colspan="2"><p class="no-indent blockquot">Oil magneto bearings once a week with sewing machine or
-                   cream separator oil.</p></td>
-      <td class="tdl_ws1 bb">&nbsp;</td>
-   </tr><tr>
-      <td class="tdc bt" colspan="4">&nbsp;</td>
-   </tr>
- </tbody>
-</table>
-
-<p><span class="pagenum" id="Page_182">[Pg 182]</span>
-The oil used in an engine is thicker, and has a high <i>burning
-point</i> and high <i>viscosity</i>; that is, it should be able to
-resist burning, and should not get so thin when it is heated that it
-will be squeezed out of the bearings. The same kind of oil that is used
-in the engine can be used in many other parts of the tractor.</p>
-
-<p>Grease is usually used for the gears of the transmission and drive.
-There is very great pressure between the teeth of two meshing gears,
-and only thick oil and grease have sufficient viscosity to resist being
-squeezed out.</p>
-
-<p>The thickest grease is used on the tracks of caterpillar-type tractors.</p>
-
-<p>Before operating a tractor, the lubrication chart supplied by the
-manufacturer should be studied with great care, and all of its
-requirements should be observed. This chart is usually in the form of
-a diagram accompanied by a table, as shown in <a href="#FIG_73">Figure 73</a>,
-which is the lubrication chart of one of the International Harvester tractors.
-This figure illustrates the constant attention that is demanded by this most
-important part of tractor operation.
-<span class="pagenum" id="Page_183">[Pg 183]</span></p>
-
-<div id="FIG_74" class="figcenter">
-  <img src="images/i_p183.jpg" alt="" width="600" height="330" />
-  <p class="center space-below2"><span class="smcap">Fig. 74.—“Illinois”
-                 Oiling Diagram</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_184">[Pg 184]</span>
-The table calls for four lubricants, these being sewing machine oil,
-which is very thin and liquid; gas engine cylinder oil; transmission
-oil, which is as thick as molasses; and cup grease, which is like butter.</p>
-
-<p>The engine is oiled automatically, the only requirements being to keep
-the oil tank filled, and to be sure that the oiler is working. The
-other parts of the tractor are oiled or greased by hand.</p>
-
-<p><a href="#FIG_74">Figure 74</a> is the oiling chart of the Illinois tractor.</p>
-
-<p>There are three systems used for engine lubrication: <i>splash</i>,
-<i>force feed</i>, and by a mechanical oiler. In the splash system,
-a pool of oil is maintained in the crank case, of such a depth that
-the ends of the connecting rods just dip into it. They strike it with
-sufficient force to splash it to all parts of the crank case, the oil
-<span class="pagenum" id="Page_185">[Pg 185]</span>
-that strikes the pistons being carried up into the cylinders and
-lubricating the walls.</p>
-
-<p>The end of the connecting rod is often fitted with a dipper, as shown
-in <a href="#FIG_75">Figure 75</a>, to strike into the oil, as well as an oil
-catcher, shown in the same drawing, which is a little trough that catches the
-splashing oil and guides it to the connecting rod bearing.</p>
-
-<div id="FIG_75" class="figcenter">
-  <img src="images/i_p185.jpg" alt="" width="500" height="337" />
-  <p class="center space-below2"><span class="smcap">Fig. 75.—End of
-                  “Twin City” Connecting Rod</span></p>
-</div>
-
-<p>To oil the wrist pin bearing there is an oil groove around the piston
-that collects oil from the cylinder walls; a hole connects this groove
-with the hollow wrist pin, from which other oil holes lead to the
-bearing. This is shown in <a href="#FIG_76">Figure 76</a>.
-<span class="pagenum" id="Page_186">[Pg 186]</span></p>
-
-<div id="FIG_76" class="figcenter">
-  <img src="images/i_p186.jpg" alt="" width="400" height="472" />
-  <p class="center space-below2"><span class="smcap">Fig. 76.—Wrist
-               Pin Lubrication</span></p>
-</div>
-
-<p>In the force feed system a pump driven by the engine forces oil through
-pipes and channels to all of the bearing surfaces. Oil collects in a
-pocket in the crank case, called the <i>sump</i>, and is drawn from it
-by the pump. The sump is usually provided with a wire mesh strainer
-that separates out any dirt.
-<span class="pagenum" id="Page_187">[Pg 187]</span></p>
-
-<div id="FIG_77" class="figcenter">
-  <img src="images/i_p187.jpg" alt="" width="600" height="373" />
-  <p class="center space-below2"><span class="smcap">Fig. 77.—Force Feed
-              Oiling System of “Gray” Engine</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_188">[Pg 188]</span>
-From the oil pump the oil is forced to the bearings by pipes and by
-holes drilled in the crank shaft and other parts, as shown in
-<a href="#FIG_77">Figure 77</a>.</p>
-
-<div id="FIG_78" class="figcenter">
-  <img src="images/i_p188.jpg" alt="" width="500" height="429" />
-  <p class="center space-below2"><span class="smcap">Fig. 78.—Oil Pump</span></p>
-</div>
-
-<p>An oil pump is illustrated in <a href="#FIG_78">Figure 78</a>. It consists
-of a plunger driven by the engine, working in a cylinder provided with two ball
-check valves, one for inlet and the other for outlet. On an upward
-stroke of the plunger the cylinder fills with oil, which is forced to
-<span class="pagenum" id="Page_189">[Pg 189]</span>
-the engine bearings by the following inward stroke.</p>
-
-<div id="FIG_79" class="figcenter">
-  <img src="images/i_p189.jpg" alt="" width="500" height="462" />
-  <p class="center space-below2"><span class="smcap">Fig. 79.—“E.B.”
-                    Oil Pump</span></p>
-</div>
-
-<p><a href="#FIG_79">Figure 79</a> shows a similar pump with a strainer over the
-intake, the outlet being through the holes L in the pipe H. In the pump illustrated
-in <a href="#FIG_80">Figure 80</a> the plunger is hollow, and fills with oil during an inward
-<span class="pagenum" id="Page_190">[Pg 190]</span>
-stroke; the oil is forced out to a passage around the plunger, and
-passes to the bearings by the holes H.</p>
-
-<div id="FIG_80" class="figcenter">
-  <img src="images/i_p190.jpg" alt="" width="350" height="451" />
-  <p class="center space-below2"><span class="smcap">Fig. 80.—Oil Pump
-                 with Hollow Plunger</span></p>
-</div>
-
-<p><a href="#FIG_81">Figure 81</a> shows two methods of preventing oil from leaking
-out around the plunger. In the first of these, a channel is formed in the upper
-<span class="pagenum" id="Page_191">[Pg 191]</span>
-part of the pump cylinder, leading to the crank case; any oil that
-leaks past the plunger flows to the crank case by this drain pipe
-and is not wasted. In the second method a packing of soft material,
-such as cotton or asbestos, is placed around the plunger, and is
-pressed against it by a <i>gland</i>, which is like a thick washer.
-A <i>packing nut</i> screws against the gland, and thus squeezes the
-packing against the plunger.</p>
-
-<div id="FIG_81" class="figcenter">
-  <img src="images/i_p191.jpg" alt="" width="500" height="401" />
-  <p class="center space-below2"><span class="smcap">Fig. 81.—Methods
-               of Preventing Oil Leaks</span></p>
-</div>
-<p><span class="pagenum" id="Page_192">[Pg 192]</span></p>
-<div id="FIG_82" class="figcenter">
-  <img src="images/i_p192.jpg" alt="" width="500" height="405" />
-  <p class="center space-below2"><span class="smcap">Fig. 82.—“Titan” Lubricator</span></p>
-</div>
-
-<p>A <i>mechanical lubricator</i>, or <i>oiler</i>, consists of several
-small oil pumps placed in an oil tank, each pump feeding one special
-bearing, and all driven by the engine. <a href="#FIG_82">Figure 82</a> is a top
-view of a 2-cylinder horizontal engine oiled by a six-feed oiler. The bearings
-that it oils are the two ends of the crank shaft, the two ends of the
-<span class="pagenum" id="Page_193">[Pg 193]</span>
-cam shaft, and the two cylinders; the gears and other bearings are
-oiled by splash. An oiler is adjustable, so that it will feed any
-desired quantity of oil.</p>
-
-<div id="FIG_83" class="figcenter">
-  <img src="images/i_p193.jpg" alt="" width="600" height="152" />
-  <p class="center space-below2"><span class="smcap">Fig. 83.—“I.H.C.”
-            Method of Oiling Crank Pins</span></p>
-</div>
-
-<p><a href="#FIG_83">Figure 83</a> shows a side view and an end view of the crank
-shaft of a 2-cylinder horizontal engine. To each end of the crank is attached a
-ring, B, formed into a channel; oil splashing into this ring is thrown
-into the channel by centrifugal force, and flows by holes, A, to the
-crank pin bearings.</p>
-
-<p>The oil forced to the cylinders from the oiler, <a href="#FIG_82">Figure 82</a>,
-reaches the wrist pin by grooves and holes, <a href="#FIG_83">A, Figure 83</a>.</p>
-
-<p>A 6-feed oiler is also shown in <a href="#FIG_84">Figure 84</a>.
-<span class="pagenum" id="Page_194">[Pg 194]</span></p>
-
-<div id="FIG_84" class="figcenter">
-  <img src="images/i_p194.jpg" alt="" width="600" height="404" />
-  <p class="center space-below2"><span class="smcap">Fig. 84.—“Hart-Parr”
-             Oiling System</span></p>
-</div>
-<p><span class="pagenum" id="Page_195">[Pg 195]</span></p>
-<div id="FIG_85" class="figcenter">
-  <img src="images/i_p195.jpg" alt="" width="400" height="669" />
-  <p class="center space-below2"><span class="smcap">Fig. 85.—Oil Cup</span></p>
-</div>
-<p><span class="pagenum" id="Page_196">[Pg 196]</span></p>
-<div id="FIG_86" class="figcenter">
-  <img src="images/i_p196a.jpg" alt="" width="600" height="326" />
-  <img src="images/i_p196b.jpg" alt="" width="600" height="361" />
-  <img src="images/i_p196c.jpg" alt="" width="600" height="362" />
-  <p class="center space-below2"><span class="smcap">Fig. 86.—Proper
-               Use of a Grease Cup</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_197">[Pg 197]</span>
-<a href="#FIG_85">Figure 85</a> is an <i>oil cup</i>, which is used to feed an
-individual bearing. It is a glass cup holding oil with an opening at the bottom
-into which fits a needle valve. When the engine is at rest, the needle
-valve handle at the top is turned down, which allows a spring to close
-the needle valve; on starting the engine the needle valve is raised,
-and the oil flows out by gravity. The dripping oil may be seen through
-a sight glass at the bottom.</p>
-
-<p>In the force feed and oiler systems the oil feeds only when the engine
-is running, but with an oil cup the oil feeds all of the time that the
-needle valve is raised. Care must therefore be taken to turn on the oil
-cup when starting the engine, and to turn it off when the engine is stopped.</p>
-
-<p>Change speed gears and differentials are usually enclosed in oil-tight
-housings that contain a supply of oil or grease. The only attention
-that is required is to see that they have the necessary amount, and
-that the lubricant is of the right kind.
-<span class="pagenum" id="Page_198">[Pg 198]</span></p>
-
-<div id="FIG_87" class="figcenter">
-  <img src="images/i_p198.jpg" alt="" width="600" height="305" />
-  <p class="center space-below2"><span class="smcap">Fig. 87.—“Titan”
-           10-20 Oiling Diagram</span></p>
-</div>
-<p><span class="pagenum" id="Page_199">[Pg 199]</span></p>
-<div id="FIG_88" class="figcenter">
-  <img src="images/i_p199.jpg" alt="" width="600" height="367" />
-  <p class="center space-below2"><span class="smcap">Fig. 88.—“International”
-             Oiling Diagram</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_200">[Pg 200]</span>
-The bearings of wheels and of many other parts of a tractor are
-lubricated with grease fed by <i>grease cups</i>; a grease cup has a
-cover that, when screwed down, forces the grease out of a hole in the
-bottom of the cup. In using a grease cup it is not sufficient simply to
-give the cover a turn or two; the cover should be screwed down enough
-to force an ample supply of grease to the bearing. This is illustrated
-in <a href="#FIG_86">Figure 86</a>.</p>
-
-<p><a href="#FIG_87">Figures 87</a> and <a href="#FIG_88">88</a> are oiling
-diagrams. They show the many points at which a tractor must be
-lubricated, and it should be remembered that the failure to maintain a
-plentiful supply of lubricant at any one of these points will mean the
-wear and breakdown of that particular part.</p>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_201">[Pg 201]</span></p>
-<h2 class="nobreak" id="CHAPTER_XI">CHAPTER XI<br />
-<span class="h_subtitle">TRACTOR OPERATION</span></h2>
-</div>
-
-<p>Before running a new tractor it should be given a careful examination
-to make sure that all nuts and bolts are tight, and not secured only
-by paint; that all grease cups are in position and filled; that all
-parts of the mechanism are properly lubricated; that oil holes are free
-from grit, and that nothing is cracked, broken or missing. It should be
-cleaned of cinders and mud that may have collected in shipment, and in
-general it should be seen to be in proper condition.</p>
-
-<p>A tractor, like any other piece of machinery, requires breaking in, and
-for the first few days it should be run slowly and with light loads.
-All parts should be plentifully oiled, for there will be rough and
-<span class="pagenum" id="Page_202">[Pg 202]</span>
-uneven places on the bearings that must be worn smooth, and without oil
-these would heat and be injured.</p>
-
-<p>A continual watch should be kept for loose nuts and bolts, which should
-be tightened without delay. Readjustments of the clutch and brake will
-be found necessary, for their linings when new may be lumpy; as these
-lumps wear down through use the clutch or brake will begin to slip and
-must be tightened. When the linings are worn in, this trouble will
-disappear, and readjustments will be necessary only at considerable
-intervals.</p>
-
-<p>Special care should be taken to keep the filler caps of the fuel and
-oil tanks clean and free from dirt. If these are dirty, the dirt will
-be carried into the tank when filling, and will sooner or later cause
-trouble.</p>
-
-<p>The vent holes in the filler caps should be kept clear. If they are
-plugged with dirt, air cannot enter the tank to take the place of the
-fuel that flows out, and the feed of fuel will stop.
-<span class="pagenum" id="Page_203">[Pg 203]</span></p>
-
-<p>Beginning when the tractor is new, a system of daily inspection should
-be started, and should be continued for the working season. Big trouble
-starts with small trouble, and if small trouble is cured without delay,
-big trouble will be avoided. Trouble usually begins with looseness,
-which may be due to a slack nut or bolt, or may come with wear. If the
-loose part is not tightened, it will begin to shift its position; it
-will wear, and will rapidly lead to a breakdown.</p>
-
-<p>Every day, without fail, all parts of the tractor should be inspected
-for loose nuts, bolts, pipe and electrical connections, petcocks, drain
-plugs, steering connections, etc. This is also the time for wiping off
-the working parts, and cleaning mud and grit from rods, shafts, joints,
-and other places at which dirt could make its way into bearings.</p>
-
-<p>The change speed gears of a tractor should not be shifted while in
-motion, this being one of the differences between a tractor and an
-<span class="pagenum" id="Page_204">[Pg 204]</span>
-automobile. In the sliding gear type of change speed mechanism, the
-gears slide into mesh sideways, a tooth of one being opposite a space
-between two teeth of the other. If the gears are not in the right
-position for this, one tooth will strike another, and the gears cannot
-be meshed. In such a case the clutch is let in for a slight touch to
-move one gear, not for a dozen or twenty revolutions, but enough to
-bring a space between two teeth of one gear opposite a tooth of the other.</p>
-
-<p>If an attempt is made to shift the gears while they are in motion, the
-result will be that one will grind against the other, and there will be
-rapid wear and probable breakage. It is because gears cannot be shifted
-while they are moving that manufacturers instruct users not to attempt
-to shift on a hill without first blocking the wheels. The reason for
-this is that the brakes may not hold the tractor, and if the gears are
-pulled out of mesh, the machine may start to run down hill; as another
-<span class="pagenum" id="Page_205">[Pg 205]</span>
-speed cannot then be engaged because the gears are moving, there will
-be no control over the tractor.</p>
-
-<p>Never coast down hill; always run with one of the speeds engaged. By
-switching off the ignition the motion of the tractor will drive the
-engine, and this provides the best possible brake. On low gear, the
-engine will turn in the neighborhood of eighty revolutions to one turn
-of the driving wheels, and the work required to do this will check the
-tractor on the steepest of practicable grades.</p>
-
-<p>A tractor is not built for as accurate and delicate steering as an
-automobile and should always be slowed in making a turn; this is
-especially true when hauling plows or other loads in the field. It is
-difficult to control the tractor if a turn is made at high speed, and
-the machine is liable to tip over.</p>
-
-<p>In steering and in engaging the clutch, the action should not be jerky
-and abrupt, but gradual and smooth. Letting in the clutch suddenly will
-start the tractor with a jerk that will strain it from end to end, and
-<span class="pagenum" id="Page_206">[Pg 206]</span>
-an abrupt swing of the steering wheel will have the same effect. Making
-these motions smoothly and steadily will cause the tractor to change
-its direction or pace with the least possible strain and effort. This,
-of course, increases the tractor’s life.</p>
-
-<p>In much of the work done by the tractor, the varying conditions of
-field and soil make a continual change in the load, and the tractor
-must be handled accordingly. The change from an uphill to a downhill
-haul, and from sand or light loam to gumbo, will require the gears
-to be shifted in order that the engine may neither labor nor race in
-keeping the outfit at its work.</p>
-
-<p>There should be no hesitation in coming down to low speed when the
-engine shows by its laboring that the effort of working on high gear is
-becoming too great. The engine cannot deliver its full power unless its
-speed is maintained, and low gear is provided for those times when the
-<span class="pagenum" id="Page_207">[Pg 207]</span>
-load is too great to be handled on high. Use high speed whenever it is
-possible, but trying to force the tractor to run on high with too great
-a load will lead to a breakdown.</p>
-
-<p>High speed should be used for light work or for moving from place
-to place, but the engine should never be run at a greater number of
-revolutions than that specified by the manufacturers. It is very poor
-policy to run the tractor fast over rough roads, as the pounding will
-inevitably injure it.</p>
-
-<p>Cold weather changes conditions in the handling and operation of a
-tractor; there is difficulty in starting, lubrication is likely to be
-faulty, and there is danger of breakage in engine, radiator, and air
-washer through freezing.</p>
-
-<p>Difficulty in starting comes from the use of the usual medium grade of
-gasoline, which is satisfactory in mild weather, but will not vaporize
-at low temperatures. Cold gasoline will not vaporize in a cold engine;
-to form a mixture it is necessary to use high test gasoline, which will
-<span class="pagenum" id="Page_208">[Pg 208]</span>
-vaporize at low temperatures, or to warm the engine to a temperature at
-which medium grade gasoline will vaporize.</p>
-
-<p>It is advisable to keep on hand a few gallons of high test gasoline to
-use in starting, or even a mixture of high test gasoline and ether,
-half-and-half, for extreme cold weather.</p>
-
-<p>The engine may be warmed by pouring a bucket of hot water into the
-cooling system, cranking the engine to get it into the water jackets of
-the cylinders. Another plan is to wrap cloth around the intake manifold
-and carburetor, soaking it with hot water, being careful not to get
-water into the air intake.</p>
-
-<p>A drop of liquid gasoline on the points of the spark plug will
-short-circuit them and prevent the formation of a spark; the points
-should be dry, and it is an advantage to heat the plugs, screwing them
-hot into the engine at the last moment before trying to start.</p>
-
-<p>Kerosene is thicker when cold than when warm; it will not flow so
-<span class="pagenum" id="Page_209">[Pg 209]</span>
-freely, and the needle valve of the carburetor must be opened more in
-winter than in summer to obtain a proper mixture.</p>
-
-<p>Lubricating oil also thickens in cold weather, and flows much more
-sluggishly. The lubrication adjustments that are correct for summer
-will therefore be incorrect for winter. This may be provided for to
-a great extent by using a thinner oil in winter than the oil used in
-summer. A cold snap is likely to result in burned bearings if the
-change in lubrication that it brings is not allowed for.</p>
-
-<p>Grease thickens in cold weather more than oil does, and some kinds
-freeze solid. In winter a light, soft grease should be used, and the
-grease cups should be turned down several more turns than is usual when
-the weather is warm.</p>
-
-<p>While antifreezing compounds can be used in the cooling systems of
-automobiles, they are not suitable for tractors because the greater and
-<span class="pagenum" id="Page_210">[Pg 210]</span>
-more continuous heat quickly evaporates them. The danger of freezing is
-very great, and must be avoided; the water in the radiator and jackets
-is in thin sheets, and will freeze when a bucket of water standing in
-the open will not show any signs of ice.</p>
-
-<p>The only real protection against freezing is to drain out all the
-water whenever the tractor is to stand idle for a sufficient time for
-it to cool off. Petcocks are provided for this at the lowest points
-of the system, and also in the pump when forced circulation is used.
-The freezing of even a small pocket of water will be enough to crack a
-cast-iron water jacket wall, and the best assurance that the system is
-thoroughly drained is to open the drain cocks while the engine is still
-running, shutting down as the flow stops.</p>
-
-<p>When putting up a tractor for the winter it should be thoroughly
-protected from rust and corrosion. The last time that the tanks are
-filled a quart of light oil should be added for every five gallons of
-<span class="pagenum" id="Page_211">[Pg 211]</span>
-gasoline or kerosene; as the tank empties this will leave a coating of
-oil on the inside walls.</p>
-
-<p>Fuel tanks and water system should be drained, and particular care
-should be taken that all the water is out; the drain cocks should be
-left open. A mechanical oiler should be filled full, to protect the
-steel parts of the pumps from rust.</p>
-
-<p>A half pint of thick oil should be put into each cylinder, and spread
-to the cylinder and piston walls by cranking for a few turns. Oil
-should be run between the valves and their seats.</p>
-
-<p>All exterior parts should be protected by a coat of thick oil or
-by paint. The governor rod, push rods, and similar parts should be
-especially looked after. It is advisable to take off the magneto and
-store it in a safe, dry place; spark plugs should be left in position.</p>
-
-<p>The tractor should be covered with a tarpaulin and stored in a tight shed.
-<span class="pagenum" id="Page_212">[Pg 212]</span></p>
-
-<p>When going over a tractor preparatory to laying it up, a list should
-be made of all parts that need renewal. These parts should be procured
-at once; they are more readily obtained during the winter than in the
-operating season, and will be on hand for the spring overhaul.</p>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_213">[Pg 213]</span></p>
-<h2 class="nobreak" id="CHAPTER_XII">CHAPTER XII<br />
-<span class="h_subtitle">ENGINE MAINTENANCE</span></h2>
-</div>
-
-<h3>FUEL SYSTEM AND CARBURETOR</h3>
-
-<p>The operation of a carburetor depends on so many things that no exact
-instructions for its adjustment can be given. The best that can be done
-is to give a general idea of the requirements, and to outline a plan by
-which the adjustment can be arrived at.</p>
-
-<p>The many makes and designs of carburetors and vaporizers that are
-used on tractors have different kinds of adjustments; on most of them
-the only adjustment is the needle valve that controls the fuel, but
-some also have adjustable air valves. In any case, the manufacturer’s
-instruction book should be studied for the understanding of the
-particular carburetor in question.
-<span class="pagenum" id="Page_214">[Pg 214]</span></p>
-
-<p>The first step in adjusting a carburetor is to get the engine
-running. The needle valve should be closed, and then opened enough to
-give a mixture on which the engine will start; on many carburetors
-this will be about one and one half turns. The engine should then
-be <i>primed</i>; that is, a little gasoline should be put in the
-cylinder, which may be done with a squirt can.</p>
-
-<p>When the engine is running, and is well heated, the needle valve should
-be gradually closed until the engine begins to miss, and to send jets
-of flame out of the carburetor, or little explosions occur in the
-carburetor. These are signs of a thin mixture, and the needle valve
-should be gradually opened to make the mixture richer. The engine will
-run more steadily, and will pick up speed until the mixture becomes too
-rich, when it will choke and black smoke will come out of the exhaust.</p>
-
-<p>The positions of the needle valve for a mixture that is too thin and
-<span class="pagenum" id="Page_215">[Pg 215]</span>
-one that is too rich have thus been found, and it remains to set it at
-that point between at which the engine runs most steadily and at the
-best speed.</p>
-
-<p>With adjustable air valves it is usual to adjust for idling, that is,
-the slowest speed at which the engine will run steadily without load,
-and then to make any necessary additional adjustment for full speed and
-power.</p>
-
-<p>If a carburetor cannot be adjusted by following the usual methods,
-trouble may be looked for, and this may be in the carburetor itself,
-in the fuel supply, or in the intake manifold, taking for granted, of
-course, that the engine is in proper condition and that the ignition
-system is operating correctly.</p>
-
-<p>Dirt under the float valve will prevent the valve from seating, and the
-level in the float chamber will be too high, so that the mixture is too
-rich. Lifting the valve from its seat will let fuel rush through, and
-loose particles will thus be washed away. If dirt is ground into the
-valve and seat, or if these parts are worn, the valve must be reseated,
-<span class="pagenum" id="Page_216">[Pg 216]</span>
-which is done by turning the valve against its seat with light
-pressure, the end of the valve being gently tapped with a light hammer.
-Under no conditions use a grinding compound, for the particles would
-become imbedded in the soft metal and would ruin the valve.</p>
-
-<p>Other causes of flooding are a bent valve, the sticking of the float
-pivot, and the soaking of fuel into the cork float, which is thereby
-made too heavy to float properly. The remedy is to dry it, and then to
-give it three coats of shellac.</p>
-
-<p>A frequent cause of trouble is dirt in the pipe from the tank to the
-carburetor. While there may not be enough dirt to prevent the engine
-from running slowly, it is sufficient to prevent the flow of sufficient
-fuel for full power. A strainer is always provided, and this should be drained
-every day; if this is not done frequently, dirt will work its way through.
-<span class="pagenum" id="Page_217">[Pg 217]</span></p>
-
-<p>A grain of sand in the spray nozzle will choke it, and every precaution
-should be taken to keep this from happening, as well as the other
-troubles that dirt brings. The best precaution is to strain the fuel
-through chamois leather, or, if this is not obtainable, through a very
-fine metal wire screen.</p>
-
-<p>In fuel systems that use a pump, the sticking of the check valves, and
-the leaking of the pump through poor packing, will cut down the supply of fuel.</p>
-
-<p>If air can leak into the carburetor or intake manifold, the proportions
-of the mixture will be altered. To test for leaks, run the engine, and
-with a squirt can squirt gasoline on the joints or other places that
-are suspected of leaking air. If there is a leak, the gasoline can be
-seen being sucked in.</p>
-
-<p>Air must enter the tank to take the place of the fuel that flows out,
-and this is provided for by a small hole drilled in the tank-filling
-cap. If this hole becomes stopped up, the fuel will not flow, and the
-<span class="pagenum" id="Page_218">[Pg 218]</span>
-engine will come to a stop. There is a similar hole in the top of the
-float bowl of most carburetors, and this also must be kept open.</p>
-
-<p>An engine is always started on gasoline, for that will form a mixture
-when it is cold. Before switching to kerosene the engine must be hot,
-and this will take several minutes of running on gasoline.</p>
-
-<p>With a double carburetor, which has a separate fuel bowl and spray
-nozzle for each fuel, nothing more is required than the switching
-of one or the other into action; when the two parts have once been
-adjusted, they require no further adjustment. Carburetors that use
-the same spray nozzle for both gasoline and kerosene will require a
-readjustment when the switch is made, for, as kerosene is thicker than
-gasoline, it will require a larger opening for a sufficient quantity
-to pass. This readjustment is a slight opening of the needle valve on
-switching to kerosene, and an equal closing when gasoline is again used.
-<span class="pagenum" id="Page_219">[Pg 219]</span></p>
-
-<p>A few minutes before the engine is stopped the carburetor should be
-switched from kerosene to gasoline, so that when it is shut down the
-fuel bowl will contain gasoline and the cylinders gasoline mixture.
-This is done to make it possible to start the engine. If the engine is
-stopped on kerosene, it cannot be started if it has had time to cool.
-In such a case the fuel bowl must be drained of kerosene and filled
-with gasoline, and the engine must be cranked until the cylinders
-receive a clean gasoline mixture.</p>
-
-<p>When an engine is working at full power on kerosene, it gets much
-hotter than would be the case with a gasoline mixture. Carbon particles
-in the cylinder, and projecting bits of metal, such as thin spark plug
-points or the edge of a screw thread, become so hot that they glow,
-with the result that they ignite the incoming fresh charge and cause
-preignition. The effect of this is to cause a pounding or knocking
-that is very noticeable. It is then necessary to use water, which is
-provided for in the carburetor.
-<span class="pagenum" id="Page_220">[Pg 220]</span></p>
-
-<p>Water has the effect of cooling the intensely heated parts, and only
-enough should be used to prevent preignition. When the knocking is
-heard, water should gradually be turned on, using no more than is
-necessary to stop the noise. Too much water will cause the engine to
-miss by collecting on the spark plug points, thereby preventing the
-passing of the ignition spark.</p>
-
-<p>Hard water should not be used, for it will form scale, which will
-interfere with the action of the carburetor. Only soft water should be
-used, and preferably rain water.</p>
-
-<p>Whenever the engine is stopped, the fuel valve at the tank should be
-closed to shut off the carburetor supply. If this is not done, the
-float valve will be the only thing that prevents the fuel from running
-out, and should the float valve leak, the fuel will be wasted.</p>
-
-<h3>MAGNETO AND IGNITION SYSTEM</h3>
-
-<p>A magneto that is kept clean and properly oiled rarely gives trouble,
-<span class="pagenum" id="Page_221">[Pg 221]</span>
-and it is a mistake to blame it whenever the engine runs irregularly or
-will not start. Its adjustments should be changed only when the other
-parts of the engine have been proved to be in good condition.</p>
-
-<p>The working parts of a magneto are enclosed, and practically proof
-against dust. It should be wiped off frequently, and dust and grit
-should not be allowed to collect around the oil holes, for otherwise it
-will work into the bearings and damage them.</p>
-
-<p>Dust and dirt are especially injurious to the circuit breaker, which
-should be frequently inspected and cleaned. Very little oil should be
-used on it, and this should be the light oil used for typewriters and
-sewing machines. A thicker oil will become gummy, and will prevent the
-free action of the lever.</p>
-
-<p>If there is much sparking at the platinum points, so that they become
-corroded and rough, it is an indication that the condenser of the
-magneto is not operating as it should, for the object of the condenser
-<span class="pagenum" id="Page_222">[Pg 222]</span>
-is to prevent such sparking. The only remedy is to renew the condenser.</p>
-
-<p>Rough points will spark more than smooth ones; should they get into
-this condition, they should be lightly filed with a file of the cut
-known as “dead smooth.” If this file cannot be obtained, pinch a strip
-of the finest sand paper—not emery paper—between the points, and draw
-it gently back and forth, smoothing down first one point and then the
-other. In smoothing platinum points the greatest care should be taken
-to make them flat and true to each other.</p>
-
-<p>After smoothing the points they should be readjusted so that when they
-are separated by the cam they are from ¹/₃₂ to ¹/₆₄ inch apart.</p>
-
-<p>A distributor made with a carbon brush that slides across the contacts
-will require wiping off at least once a month. Carbon dust will rub off
-the brush and collect on the face of the distributor; in the course of
-<span class="pagenum" id="Page_223">[Pg 223]</span>
-time this will cause a short-circuit. The distributor is always made so
-that it can easily be cleaned.</p>
-
-<p>A magneto is timed to an engine so that when the spark control is fully
-retarded, the circuit breaker points are just separating as a piston
-goes over top center. The engine is cranked until one of the pistons
-is at top center; the magneto should be in position, but its coupling
-should be loose, so that the armature can be revolved. The spark
-control is retarded; that is, it is moved as far as possible in the
-direction in which the armature turns. The armature is then revolved
-in the direction in which it will be driven by the engine until it is
-seen that the contact points are beginning to separate; holding the
-armature, the coupling is then made fast.</p>
-
-<p>It will now be found that the distributor brush is touching one of the
-contacts; that contact is to be connected with the spark plug of the
-cylinder that is at top center of the compression stroke. The following
-<span class="pagenum" id="Page_224">[Pg 224]</span>
-distributor contacts are connected to the remaining spark plugs in the
-order in which their cylinders fire.</p>
-
-<p>Should the magneto be suspected of being out of order, the first test
-is to disconnect a wire from its spark plug, and support the tip ⅛ inch
-from the metal of the engine while the engine is cranked briskly; if a
-spark appears, it is evidence that the magneto is operating and that
-the trouble is elsewhere.</p>
-
-<p>If there is no spark, repeat the test with the switch wire disconnected
-from the magneto. This wire and the switch form a circuit from the
-metal of the engine to the insulated part of the circuit breaker;
-when the switch is closed, or in the “off” position, this circuit is
-completed, and as the magneto current flows over it instead of over
-the regular sparking circuit, no spark is produced at the plug. It
-sometimes happens that the switch or wire is defective, and allows
-the current to take that circuit even when the switch is in the open
-or “run” position. If this is the case it will be shown by a spark on
-<span class="pagenum" id="Page_225">[Pg 225]</span>
-cranking the engine with the switch wire disconnected at the magneto,
-and no spark when it is connected.</p>
-
-<p>If the switch and wire are all right, examine the circuit breaker to
-see whether the contact points are clean, and that they touch when the
-cam allows them to; touch the circuit breaker lever to see that it is
-free to move and that its spring is not broken. In some tractors the
-magneto is in such a position that the circuit breaker cannot easily
-be seen; in such a case hold a small mirror in front of the circuit
-breaker and examine the reflection.</p>
-
-<p>If the circuit breaker is in good condition, examine the distributor to
-see whether it is dirty, or the brush broken; if these parts are all
-right, the trouble is of such a character as requires the magneto to be
-returned for repair.</p>
-
-<p>Ignition trouble is usually in the spark plugs. The insulator cracks
-<span class="pagenum" id="Page_226">[Pg 226]</span>
-easily in many makes, which will permit the current to leak across
-without forming a spark; it is frequently the case that the crack does
-not show, and the best test is to replace the suspected plug with a
-plug that is known to be good. If the cylinder fires with one plug and
-not with the other, there is no question as to the cause of the trouble.</p>
-
-<p>The insulator of the plug must be kept clean, for a deposit of carbon
-on it will form a path by which the current can pass without forming
-a spark. A dirty plug can best be cleaned by brushing it with a stiff
-toothbrush dipped in gasoline. A carbon deposit can be softened by
-soaking the plug in gasoline for a few hours, and can then be brushed
-off more easily.</p>
-
-<p>The spark gap of a plug should be from ¹/₃₂ to ¹/₆₄ inch. After
-considerable use the points will be burned off, and the gap will become
-too wide; the points should then be bent to form a proper gap.</p>
-
-<p>Oil and grease will rot rubber, and the ignition wires should therefore
-<span class="pagenum" id="Page_227">[Pg 227]</span>
-be wiped clean. Oil-soaked cables will give trouble, and should be
-replaced with new ones.</p>
-
-<p>It is frequently difficult to locate a leakage of current. If the
-engine is misfiring and losing power, and a leakage of current through
-poor insulation is suspected, the easiest way to detect it is to run
-the engine in the dark. Leaks will show themselves by sparks, which are
-then easily seen.</p>
-
-<h3>COMPRESSION</h3>
-
-<p>In order to deliver its full power a gas engine must have good
-compression, and compression should frequently be tested by cranking
-the engine slowly and steadily with the ignition switched off. If
-compression is good, there will be a springy, elastic resistance
-that becomes greater as a piston approaches the end of a compression
-stroke, and that throws the piston outward as dead center is passed.
-Compression should be the same for all cylinders.
-<span class="pagenum" id="Page_228">[Pg 228]</span></p>
-
-<p>If there is a leakage of compression, the only resistance will be from
-the bearings, and it will be the same for all parts of the stroke.</p>
-
-<p>A compression leak often makes a hissing noise that can be distinctly
-heard, and by which it can be located, but more often it makes no
-sound, and its location must be found by testing. The leak may be at
-any of the openings into the combustion space; at the valves, around
-the spark plugs or piston rings, or at the cylinder head gasket.</p>
-
-<p>To discover whether the gasket leaks, run gasoline along the line of
-the gasket joint with a squirt can while the engine is being cranked
-briskly; at a leaky place it will be sucked in or blown out. The same
-test should be made around the spark plug.</p>
-
-<p>The remedy is to reset the cylinder head, using a new gasket, and being
-sure that the surfaces are clean and free from grit.</p>
-
-<p>Piston ring leaks are usually caused by the rings sticking in their
-grooves through the formation of carbon. To test for piston ring leaks,
-<span class="pagenum" id="Page_229">[Pg 229]</span>
-pour a half pint of cylinder oil into each cylinder, and crank the
-engine slowly. The oil will form a seal around the pistons, and if
-compression is then improved, the rings are shown to be at fault.</p>
-
-<p>To free the rings, pour a few tablespoonfuls of kerosene into each
-cylinder, and spread it by giving the engine a few turns; after
-standing for an hour or so the carbon should be sufficiently softened
-to free the rings.</p>
-
-<p>If the leakage of compression is due to the rings being worn and loose
-in their grooves, they must be replaced.</p>
-
-<p>The most usual cause of compression loss is leaking valves. With its
-continual pounding against its seat, and the heat to which it is
-exposed, a valve and its seat will become rough and pitted, and will
-leak; when in this condition the valve must be ground.</p>
-
-<p>A valve is ground by spreading grinding compound on the seat, and
-turning the valve against it. This requires the valve spring to be taken
-<span class="pagenum" id="Page_230">[Pg 230]</span>
-off; the exact method of doing this depends on how these parts are made.</p>
-
-<p>If the valves are in a removable cylinder head, valve grinding is most
-easily done by taking the cylinder head to a bench. In many designs the
-valve seats are part of the cylinder casting, and the job is done on
-the tractor.</p>
-
-<p>In grinding a valve the valve is not turned around in one direction
-only, for this would cut grooves in the valve and seat. To obtain
-smooth surfaces the valve should be given part of a turn in one
-direction, and then turned equally in the other direction; after every
-few turns the valve should be lifted and dropped to another position on
-the seat. In this way the grinding is made even all around.
-<span class="pagenum" id="Page_231">[Pg 231]</span></p>
-
-<div id="FIG_89" class="figcenter">
-  <img src="images/i_p231.jpg" alt="" width="400" height="470" />
-  <p class="center space-below2"><span class="smcap">Fig. 89.—Grinding
-             Valve in Engine with Fixed Head</span></p>
-</div>
-
-<p>The best tool for valve grinding is a carpenter’s brace with a screw
-driver blade fitting the slot in the valve, as shown in <a href="#FIG_89">Figure 89</a>.
-This drawing illustrates a cylinder with a fixed head; the valve is
-reached by unscrewing the plug from the opening directly above it. When
-grinding valves in an engine of this design the opening between the
-valve pocket and the combustion space should be plugged with a rag or
-<span class="pagenum" id="Page_232">[Pg 232]</span>
-waste to prevent the grinding compound from getting into the cylinder.</p>
-
-<p>With the valve grinding tool in position, swing the handle back and
-forth ten or twelve times; then lift the valve, place it in a new
-position, and repeat. The valve is lifted most easily by a light spring
-placed under the valve disk, as shown in <a href="#FIG_89">Figure 89</a>.</p>
-
-<p>From time to time the valve disk and seat should be cleaned off and
-examined to see whether they are smooth and free from pits and scores.
-If they appear to be, make marks around the valve disk with a lead
-pencil, replace the valve, and give it a complete turn. If this wipes
-off the pencil marks all around the valve, the grinding is complete,
-and the valve may be replaced with its spring and spring retainer. It
-is not necessary to grind until the entire thickness of the valve disk
-and seat are smooth; a narrow band all around will make the valve tight.</p>
-
-<p>After grinding, and before replacing the valve, all traces of the
-<span class="pagenum" id="Page_233">[Pg 233]</span>
-grinding compound should be wiped off, and great care taken that none
-of it gets into the cylinder, valve stem guide, or other working part.</p>
-
-<div id="FIG_90" class="figcenter">
-  <img src="images/i_p233.jpg" alt="" width="500" height="364" />
-  <p class="center space-below2"><span class="smcap">Fig. 90.—Grinding
-             Valve in Detachable Head</span></p>
-</div>
-
-<p>On an engine with a removable head containing the valves, the head
-may be taken to a work bench, which makes grinding easier. This is
-illustrated in <a href="#FIG_90">Figure 90</a>. On an engine in which the valve
-and its seat may be taken out, the seat may be clamped in a vise, as shown in
-<a href="#FIG_91">Figure 91</a>. With valves of either of these types, the grinding
-may be tested by turning the head or the seat so that the disk is down, and pouring in
-<span class="pagenum" id="Page_234">[Pg 234]</span>
-gasoline. If the valve is not tight, the gasoline will leak through,
-and grinding must be continued.</p>
-
-<div id="FIG_91" class="figcenter">
-  <img src="images/i_p234.jpg" alt="" width="600" height="298" />
-  <p class="center space-below2"><span class="smcap">Fig. 91.—Grinding
-           Valve in Detachable Seat</span></p>
-</div>
-
-<p>When a valve seat is very badly worn it must be redressed, which is
-done with a cutting tool to be obtained from the maker of the tractor,
-and illustrated in <a href="#FIG_92">Figure 92</a>. This has a stem fitting the
-valve stem guide which centers the tool and assures a true cut. If a seat is so
-worn as to need redressing, the valve will be in such bad condition
-that it must be discarded and a new one used. This must be ground in
-before the engine is run.</p>
-
-<p>Grinding a valve lowers it in its seat, and usually makes it necessary
-to readjust the push rod. When an engine is cold there is a space of
-<span class="pagenum" id="Page_235">[Pg 235]</span>
-about ¹/₃₂ inch somewhere between the cam and the valve stem; in <a href="#FIG_93">Figure 93</a>,
-this space is shown to be between the valve stem and the rocker arm.
-As the engine heats up the valve stem lengthens, and this space permits
-it to do so.</p>
-
-<div id="FIG_92" class="figcenter">
-  <img src="images/i_p235.jpg" alt="" width="400" height="449" />
-  <p class="center space-below2"><span class="smcap">Fig. 92.—Valve Seat Cutter</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_236">[Pg 236]</span>
-If the space is too small, the stem will come against the rocker arm
-or the push rod, and the valve will be held off its seat, causing
-a compression leak. If the space is too great, the valve will open
-too late and close too early. The space must therefore be carefully
-adjusted, and this is arranged for on practically all makes of tractor engines.</p>
-
-<div id="FIG_93" class="figcenter">
-  <img src="images/i_p236.jpg" alt="" width="250" height="488" />
-  <p class="center space-below2"><span class="smcap">Fig. 93.—“Holt”
-             Valve Arrangement</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_237">[Pg 237]</span>
-One-thirty-second of an inch is the thickness of a 10-cent piece; it
-should just be possible to slip a slightly worn dime into the space
-when the engine is cold.</p>
-
-<h3>VALVE TIMING</h3>
-
-<p>By <i>timing the valves</i> is meant the setting of the cam shaft in
-such a position that the valves are opened at the correct point in the
-stroke. It is necessary to time the valves only when the cam shaft has
-been taken out and must be replaced. The principle of valve timing
-should be understood, however, in order to be able to tell whether an
-engine is timed correctly.</p>
-
-<p>It will usually be found that the face of the flywheel bears letters
-and figures that are indicators of the timing of the valves. This
-arrangement on the E-B engines is shown in <a href="#FIG_94">Figure 94</a>.
-Two lines are cut in the face of the flywheel, one marked ex. cl. 1-4, which
-means exhaust valve closes, cylinders 1 and 4, and the other marked
-<span class="smcap">center</span> 1-4, to indicate that the pistons in
-those cylinders are on center. A straight-edge is held against the
-finished surface of the housing and the crank shaft is turned to bring
-one of the marks in line with it; at that point the valves or pistons
-are as indicated by the lettering.
-<span class="pagenum" id="Page_238">[Pg 238]</span></p>
-
-<div id="FIG_94" class="figcenter">
-  <img src="images/i_p238.jpg" alt="" width="300" height="589" />
-  <p class="center space-below2"><span class="smcap">Fig. 94.—Valve
-            Timing, Using Marks on Flywheel</span></p>
-</div>
-<p><span class="pagenum" id="Page_239">[Pg 239]</span></p>
-<div id="FIG_95" class="figcenter">
-  <img src="images/i_p239.jpg" alt="" width="400" height="421" />
-  <p class="center space-below2"><span class="smcap">Fig. 95.—Valve Timing</span></p>
-</div>
-
-<p><span class="pagenum" id="Page_240">[Pg 240]</span>
-The flywheel is also marked with a dot to indicate the firing point.
-When the dot is in line with the straight-edge, ignition should occur
-with the spark control fully advanced.</p>
-
-<p><a href="#FIG_95">Figure 95</a> shows the valve arrangement of the same engine,
-with the exhaust valve just closing; the point of the cam has passed under the
-lifter or push rod, and has permitted the valve to come to its seat,
-but is still holding the lifter against the valve stem.</p>
-
-<p>To check the valve setting, hold a slip of tissue paper, such as a
-cigarette paper, in the space between the lifter and the valve stem,
-while the engine is cranked slowly. While the cam is holding the valve
-off its seat the paper will be pinched between the lifter and the valve
-stem and held firmly. At the instant when the paper is freed and can
-be moved, the valve is seated and the point of the cam is just passing
-from under; the proper mark on the flywheel should then be in line with
-the straight-edge.
-<span class="pagenum" id="Page_241">[Pg 241]</span></p>
-
-<p>As the cams for all valves are in one piece with the cam shaft, setting
-one valve sets them all and checking the setting of one checks the
-setting of all.</p>
-
-<p>Before taking out a cam shaft, two adjoining teeth of its gear should
-be marked with a prick punch or a small cold chisel, and a similar mark
-should be made on the tooth of the crank shaft gear that comes between
-them. In replacing the cam shaft it is then necessary only to return
-the teeth to the same position. Timing gears are usually marked in this
-way by the manufacturers.</p>
-
-<h3>CARBON</h3>
-
-<p>A kerosene lamp that is turned too high gives a dense black smoke that
-is composed of fine particles of carbon. A piece of paper held in the
-smoke is quickly covered with a deposit of carbon, commonly called
-soot, or lamp-black.</p>
-
-<p>All fuel oils and lubricating oils contain carbon. When these oils burn
-<span class="pagenum" id="Page_242">[Pg 242]</span>
-in the cylinder, they produce carbon, much of which passes out of the
-exhaust, while the rest deposits on the valves and on all parts of the
-combustion space. This deposit hardens, and eventually makes trouble
-through causing preignition.</p>
-
-<p>The deposit is rough, and the heat in the cylinder is sufficient to
-make the outstanding particles glow; they ignite the incoming charge,
-and cause preignition. The sign of carbon trouble is a sharp knocking
-in the cylinder, especially when the engine is under a heavy load. The
-sound is the same as that caused by too great an advance of the spark.</p>
-
-<p>Carbon deposit can be greatly reduced by pouring a few tablespoonfuls
-of kerosene into each cylinder and cranking for a few turns to spread
-it to all parts of the combustion space. This will soften the carbon
-and much of it will be blown out when the engine is next started. Best
-results will be obtained if the kerosene is poured in after a run, when
-the engine is hot.
-<span class="pagenum" id="Page_243">[Pg 243]</span></p>
-
-<p>If the carbon deposit is too hard to be softened by kerosene, it can
-be removed by scraping. This requires the cylinder head to be taken
-off, when the deposit can be scraped and chipped with a screwdriver.
-Care should be taken to keep the carbon crumbs from getting into the
-cylinders, valve stem guides, or other places where it would cause wear.</p>
-
-<p>In taking off the cylinder head the gasket should be handled carefully,
-and protected from denting and bending. A battered or bent gasket is a
-sure cause of compression leaks. In replacing a metal gasket, give it a
-coat of cylinder oil on both sides to improve its seating.</p>
-
-<p>When replacing the cylinder head, set all of the bolts up a little at
-a time, instead of screwing some of them tight while others are loose.
-One bolt drawn tight may tilt the cylinder head slightly, and there
-will be a distortion when another bolt is tightened. This is avoided by
-setting up all of the bolts a little at a time.
-<span class="pagenum" id="Page_244">[Pg 244]</span></p>
-
-<p>Running on too rich a mixture, giving the engine too much oil, and not
-using an air cleaner in dusty work will carbonize an engine rapidly.
-Blue smoke at the exhaust is a sign that too much lubricating oil is
-being used; black smoke indicates too rich a mixture. Carbonizing
-can be greatly reduced by careful adjustment of the lubricator and carburetor.</p>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_245">[Pg 245]</span></p>
-<h2 class="nobreak" id="CHAPTER_XIII">CHAPTER XIII<br />
-<span class="h_subtitle">LOCATING TROUBLE</span></h2>
-</div>
-
-<p>There are many ways in which an engine can give trouble, but these are
-not serious to an operator who understands the action of an engine,
-and who works with his brain as well as with his hands. Each of these
-troubles has a distinct cause; proper care will avoid them, but if they
-come the reasons for them can be determined by simple tests.</p>
-
-<p>In order to develop full power, an engine must be in good mechanical
-condition; that is, the bearings must be free without being loose,
-the gears must run well, the pistons and their rings must not bind or
-be too free, and so on. It must be properly lubricated and cooled,
-compression must be correct, it must get a good mixture, and ignition
-<span class="pagenum" id="Page_246">[Pg 246]</span>
-must take place at the right time. If an engine gives trouble, it is
-because one of these systems is not working properly, and it is not at
-all difficult to locate the cause and to correct it.</p>
-
-<p>If an engine gets a good mixture, which is ignited properly, it will
-run; if it will not give any explosions it is because one or the other
-of these systems is not working properly. An inspection or a simple
-test will show which one is at fault.</p>
-
-<h3>ENGINE WILL NOT START</h3>
-
-<p>If an engine will not start after being cranked a dozen or twenty
-times, it is useless to continue to crank it. It is not getting either
-a proper mixture or an ignition spark, and it saves time and energy to
-find out where the trouble is, rather than to keep on cranking in the
-hope that something may happen.</p>
-
-<p>When a tractor engine refuses to start, the trouble is usually with the
-mixture, and, more often than not, this is due to carelessness or to
-<span class="pagenum" id="Page_247">[Pg 247]</span>
-forgetfulness. The tank may be empty, or the fuel valve may be closed,
-so that the carburetor is dry; see if there is fuel in the carburetor
-bowl. The engine may have been shut down while running on kerosene,
-instead of having been switched to gasoline for the last few minutes of
-its run, so that the carburetor, intake manifold and cylinders contain
-kerosene, which will not vaporize without heat, instead of gasoline,
-which will. In this case the engine must be primed with gasoline.</p>
-
-<p>If too much gasoline has been used for priming, the cylinders may
-contain a mixture that is too rich to ignite; the engine should then be
-cranked briskly with the fuel shut off and the compression relief cocks
-open, to clear out the rich mixture and fill the cylinders with air.</p>
-
-<p>Water in the fuel will make starting difficult or impossible. It is
-easy to forget to shut off the water valve of the carburetor when
-stopping the engine, and when starting, water from this valve will
-<span class="pagenum" id="Page_248">[Pg 248]</span>
-prevent the forming of a mixture and will also interfere with the
-ignition.</p>
-
-<p>If the mixture is apparently all right, the fault may be in the
-ignition. A drop of liquid fuel or of water, for instance, may be on
-the spark plug points; this will short-circuit them and no spark will
-be formed, although the sparking current is passing.</p>
-
-<p>If there is a suspicion that the ignition system is at fault, and that
-the magneto is not producing a sparking current, it should be tested,
-as explained in <a href="#CHAPTER_XII">Chapter XII</a>.</p>
-
-<p>Starting in cold weather is always more difficult than starting when it
-is warm. Helps in cold weather starting are given in <a href="#CHAPTER_XI">Chapter XI</a>.</p>
-
-<p>A leaky inlet manifold will admit an extra amount of air that will
-completely alter the proportions of a mixture. Thus the mixture will be
-wrong, although the carburetor adjustment seems to be correct. Manifold
-<span class="pagenum" id="Page_249">[Pg 249]</span>
-leaks are usually at the joints, but occasionally a manifold is found
-with a hole in it due to poor casting or material, or a crack may develop.</p>
-
-<p>Difficulty in starting due to poor compression caused by stuck valves
-or rings will show its cause by the ease with which the engine can be
-cranked.</p>
-
-<p>If an engine is free enough to turn over, poor lubrication or cooling
-will not interfere with starting it. Faults in these systems show
-themselves only when an engine is running.</p>
-
-<h3>ENGINE LOSES POWER</h3>
-
-<p>An engine will lose power through a defect of compression, carburetion,
-ignition, cooling or lubrication, or because of a mechanical fault.</p>
-
-<p>If the trouble comes from cooling or lubrication, the engine will
-overheat and thus make the cause known. A bearing that binds will
-become very hot, while if the cooling system fails, the engine will
-be hot all over. When the engine is excessively hot, the pistons will
-<span class="pagenum" id="Page_250">[Pg 250]</span>
-expand, and much of the power of the engine will be used up in forcing
-them to move.</p>
-
-<p>An engine that is not hotter than usual, and is having regular and even
-explosions, probably loses power through a loss of compression. This is
-the most usual cause of this trouble, and it is located and remedied as
-explained in <a href="#CHAPTER_XII">Chapter XII</a>.</p>
-
-<p>If compression is good, the loss of power may be due to a clogged
-muffler or exhaust pipe, which will not permit the free escape of the
-burned gases. This condition will prevent full charges of fresh mixture
-from entering the cylinders, and the engine then cannot be expected to
-deliver full power.</p>
-
-<p>Another possible cause of a loss of power with the engine apparently in
-proper condition is the sticking or poor adjustment of the governor.
-The factory adjustment of the governor should not be changed, however,
-until it is definitely proved that that is where the trouble lies.
-<span class="pagenum" id="Page_251">[Pg 251]</span></p>
-
-<p>If the engine misses fire, or runs irregularly, the loss of power
-will be due to faulty carburetion or ignition. The mixture may be
-too rich or too lean; in either case the trouble will be remedied by
-readjusting the carburetor. A mixture that is very much too lean will
-make itself known by <i>backfiring</i>; there will be little explosions
-at the carburetor. This should be remedied at once, for the danger of
-fire from it is very great. Black smoke at the exhaust is a sign of a
-mixture that is too rich.</p>
-
-<p>An engine will not deliver full power if it is run on a retarded
-spark. A loss of power from this cause will be accompanied by general
-overheating of the engine.</p>
-
-<h3>ENGINE STOPS</h3>
-
-<p>The manner in which an engine stops will indicate the reason for it.</p>
-
-<p>A failure of the ignition system that stops the formation of current,
-like the sticking of the circuit breaker lever, will cut off all
-<span class="pagenum" id="Page_252">[Pg 252]</span>
-explosions instantly; the engine will stop abruptly. An engine will not
-stop abruptly from any fault with the mixture; with mixture trouble the
-explosions will become weaker and weaker until they cease.</p>
-
-<p>If an engine stops through a failure of the lubrication or cooling
-systems it will be intensely hot, which will not be the case if the
-fault is with carburetion or ignition.</p>
-
-<p>A running engine will not be brought to a stop by a loss of compression.</p>
-
-<h3>ENGINE MISSES</h3>
-
-<p>A steady or irregular miss in one cylinder is usually due to the spark
-plug’s being cracked or dirty. Carburetor trouble will affect all the
-cylinders; it cannot affect one cylinder only, and missing in one
-cylinder may be put down as ignition trouble. In this case ignition
-trouble does not mean magneto trouble, for if the magneto produces
-sparking current for one cylinder it will produce it for all. Therefore
-ignition trouble in only one cylinder is in those parts of the ignition
-<span class="pagenum" id="Page_253">[Pg 253]</span>
-system supplying that cylinder; that is, in the spark plug or in the
-spark plug cable.</p>
-
-<p>A less likely cause for missing in one cylinder only is poor
-compression. It is usually the case that if compression is poor in one
-cylinder it is poor in them all, but a broken valve or piston ring or a
-weak valve spring will weaken compression in one and not in the others.</p>
-
-<p>A cylinder that misses is cooler than the others, and can be located by
-feeling. It can also be located by short-circuiting the spark plugs one
-at a time; this will make no difference in the dead cylinder, but when
-the spark plug of an active cylinder is short-circuited the speed of
-the engine will drop.</p>
-
-<p>To short-circuit a spark plug, take a wooden-handled screwdriver or
-other tool and rest the blade on the engine near the spark plug; then
-tilt until its shank is close to the spark plug terminal. The spark
-current will then pass to the metal of the engine by way of the tool
-<span class="pagenum" id="Page_254">[Pg 254]</span>
-instead of by the spark plug points. This is also a test of ignition,
-for a spark will pass between the terminal and the tool.</p>
-
-<p>Irregular missing in all cylinders may be due to a fault at one of
-the parts of the ignition system that supplies them all; a dirty
-distributor, for instance, or a sticking circuit breaker lever, or
-rough platinum points. It may also be due to a clogged fuel line, which
-prevents the carburetor from getting a regular and sufficient flow.</p>
-
-<p>Irregular missing will also be caused by loose ignition connections,
-and by loose switch parts.</p>
-
-<h3>ENGINE STARTS; BUT STOPS</h3>
-
-<p>When an engine starts readily but quickly slows down and stops, the
-reason is almost always an insufficient supply of fuel. An obstruction
-in the pipe may prevent the fuel from flowing fast enough to keep the
-carburetor bowl filled when the engine is running; when the engine
-<span class="pagenum" id="Page_255">[Pg 255]</span>
-starts, the fuel is sucked out of the spray nozzle faster than it comes
-in through the float valve, so the carburetor is soon drained and the
-engine stops. The bowl then fills, only to be sucked dry again when the
-engine is next started.</p>
-
-<p>This difficulty is caused by dirt in the fuel, which collects in the
-strainer or the fuel pipe. The strainer is so arranged that it may be
-easily drained and cleaned; to clear out the pipe, shut off the fuel at
-the tank, disconnect the pipe at both ends, and blow through it.</p>
-
-<p>The strainer should be drained every day; it is sufficient to open the
-strainer drain cock for two or three seconds.</p>
-
-<p>Most of the troubles due to dirt in the fuel will be avoided if the
-fuel is strained when filling the tank.</p>
-
-<p>Another thing that will bring an engine to a stop is the clogging of
-the vent holes in the tank filler cap and in the top of the carburetor
-bowl. These holes should be clear, so that air can enter to replace the
-<span class="pagenum" id="Page_256">[Pg 256]</span>
-fuel that is used; if air cannot enter the fuel will not flow, and the
-tank is then said to be <i>air-bound</i>.</p>
-
-<h3>ENGINE OVERHEATS</h3>
-
-<p>An engine may overheat either because it produces more heat than the
-cooling system can take care of, or because the cooling system is not
-taking off all of the heat that it should.</p>
-
-<p>Running an engine with the spark retarded will cause it to overheat; so
-will a failure of the lubrication and an obstruction to the passage of
-the exhaust gases.</p>
-
-<p>If an engine has been taken down and overheats when it is reassembled,
-it may be that the magneto has been wrongly timed, and produces its
-spark too late. If an engine has been running properly but begins to
-overheat, the ignition cause will be the faulty setting of the spark
-control, or the slipping of the spark control rod.</p>
-
-<p>When an engine is run on kerosene, the oil in the crankcase must be
-<span class="pagenum" id="Page_257">[Pg 257]</span>
-frequently drained off and replaced with fresh oil. The reason for
-this is that part of the kerosene that goes to the cylinders does not
-vaporize and burn, but works its way past the pistons and into the
-crankcase, where it thins the lubricating oil. As the oil thins, it
-loses its ability to lubricate, and the engine begins to overheat.</p>
-
-<p>Anything that produces extra friction will cause overheating, as, for
-example, a wrist pin that works endways and rubs against the cylinder
-wall, or a tight bearing.</p>
-
-<p>For a cooling system to work properly it must contain a full supply of
-water, the passages must be clear, sufficient air must pass through the
-radiator, and the pump must be in proper condition.</p>
-
-<p>Hose connections will rot, and a strip of rubber may peel off the
-inside and be drawn across the passage; or if dirty water is used, the
-dirt may choke the fine radiator passages or other channels. If the
-<span class="pagenum" id="Page_258">[Pg 258]</span>
-radiator is covered with mud, air cannot get at the tubes to take the
-heat from the water that they contain.</p>
-
-<p>A very usual cause of overheating is a slipping fan belt; an adjustment
-is provided by which the belt can be tightened when it works loose.</p>
-
-<h3>ENGINE SMOKES</h3>
-
-<p>Black smoke indicates that the mixture is too rich; blue smoke is a
-sign of too plentiful lubrication. Oil that is too thin, or that is
-of a poor grade, will cause smoking; good quality oil of the grade
-recommended by the manufacturer should always be used.</p>
-
-<p>Broken piston rings, or rings stuck in their grooves, will be the cause
-of smoking because they will permit an excess of oil to pass by them.</p>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_259">[Pg 259]</span></p>
-<h2 class="nobreak" id="CHAPTER_XIV">CHAPTER XIV<br />
-<span class="h_subtitle">CAUSES OF TROUBLE</span></h2>
-</div>
-
-<table border="0" cellspacing="0" summary="Trouble-shooting" cellpadding="2" rules="cols">
-  <tbody><tr>
-      <td class="tdc bb2" colspan="2">&nbsp;</td>
-   </tr><tr>
-      <td class="tdl bb" rowspan="3">Engine will not start.</td>
-      <td class="tdl_ws1">No mixture.</td>
-   </tr><tr>
-      <td class="tdl_ws1">No ignition.</td>
-   </tr><tr>
-      <td class="tdl_ws1 bb">No compression.</td>
-   </tr><tr>
-      <td class="tdl bb" rowspan="5">Engine starts,<br />&nbsp;but will not<br />
-                   &nbsp;&nbsp;continue running.</td>
-      <td class="tdl_ws1">Clogged fuel pipe or strainer.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Air-bound tank or carburetor.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Clogged exhaust.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Wet spark plugs.</td>
-   </tr><tr>
-      <td class="tdl_ws1 bb">Governor out of adjustment.</td>
-   </tr><tr>
-      <td class="tdl bb" rowspan="10">Engine loses<br />&nbsp; &nbsp;power.</td>
-      <td class="tdl_ws1">Retarded spark.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Poor compression.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Overheating.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Clogged exhaust.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Incorrect mixture.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Governor out of adjustment.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Tight bearings.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Dragging brake.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Slipping clutch.</td>
-   </tr><tr>
-      <td class="tdl_ws1 bb">Overloaded.
-                         <span class="pagenum" id="Page_260">[Pg 260]</span></td>
-   </tr><tr>
-      <td class="tdl bb">Engine stops suddenly.</td>
-      <td class="tdl_ws1 bb">Ignition trouble.</td>
-   </tr><tr>
-      <td class="tdl bb" rowspan="3">Engine slows down<br />&nbsp; &nbsp;and stops.</td>
-      <td class="tdl_ws1">Clogged fuel supply.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Incorrect Mixture.</td>
-   </tr><tr>
-      <td class="tdl_ws1 bb">Overheated.</td>
-   </tr><tr>
-      <td class="tdl bb">Regular miss in<br />&nbsp; &nbsp;one cylinder.</td>
-      <td class="tdl_ws1 bb">Defective spark plug<br />&nbsp; &nbsp;or wire.</td>
-   </tr><tr>
-      <td class="tdl bb" rowspan="6">Irregular miss in<br />&nbsp; &nbsp;all cylinders.</td>
-      <td class="tdl_ws1">Sticking contact breaker.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Defective distributor.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Clogged fuel line.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Irregular fuel feed.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Water in fuel.</td>
-   </tr><tr>
-      <td class="tdl_ws1 bb">Faulty ignition connections.</td>
-   </tr><tr>
-      <td class="tdl bb" rowspan="5">Engine runs<br />&nbsp; &nbsp; unevenly.</td>
-      <td class="tdl_ws1">Incorrect spark plug gap.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Incorrect mixture.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Binding carburetor float.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Sticking valves.</td>
-   </tr><tr>
-      <td class="tdl_ws1 bb">Sticking governor.</td>
-   </tr><tr>
-      <td class="tdl bb" rowspan="3">Engine overheats.</td>
-      <td class="tdl_ws1">Spark retarded.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Faulty cooling.</td>
-   </tr><tr>
-      <td class="tdl_ws1 bb">Faulty lubrication.
-                              <span class="pagenum" id="Page_261">[Pg 261]</span></td>
-   </tr><tr>
-      <td class="tdl bb" rowspan="4">Engine smokes.</td>
-      <td class="tdl_ws1">Black smoke;<br /><span class="ws2">mixture too rich.</span></td>
-   </tr><tr>
-      <td class="tdl_ws1">Blue smoke; too much oil.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Broken or stuck piston rings.</td>
-   </tr><tr>
-      <td class="tdl_ws1 bb">Poor oil.</td>
-   </tr><tr>
-      <td class="tdl bb" rowspan="2">Engine backfires<br />&nbsp; &nbsp;through carburetor.</td>
-      <td class="tdl_ws1">Mixture too lean.</td>
-   </tr><tr>
-      <td class="tdl_ws1 bb">Sticking inlet valve or<br />&nbsp; &nbsp;weak inlet valve spring.</td>
-   </tr><tr>
-      <td class="tdl" rowspan="3">Explosions in<br />&nbsp; &nbsp;exhaust pipe.</td>
-      <td class="tdl_ws1">Missing spark.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Mixture too rich.</td>
-   </tr><tr>
-      <td class="tdl_ws1">Sticking exhaust valve.</td>
-   </tr><tr>
-      <td class="tdc bt2" colspan="2">&nbsp;</td>
-   </tr>
- </tbody>
-</table>
-
-<hr class="chap x-ebookmaker-drop" />
-
-<div class="chapter">
-<p><span class="pagenum" id="Page_263">[Pg 263]</span></p>
-<h2 class="nobreak" id="INDEX">INDEX</h2>
-</div>
-
-<ul class="index">
-<li class="isub1">Adjusting a carburetor, <a href="#Page_213">213</a></li>
-<li class="isub1">Advance of ignition; theory of, <a href="#Page_18">18</a></li>
-<li class="isub1">Air cleaner or washer, <a href="#Page_71">71</a></li>
-<li class="isub1">Air inlet; extra, <a href="#Page_63">63</a></li>
-<li class="isub1">Armature, <a href="#Page_106">106</a></li>
-<li class="isub1">Atwater-Kent ignition system, <a href="#Page_136">136</a></li>
-<li class="isub1">Automatic carburetor, <a href="#Page_63">63</a></li>
-<li class="isub1">Automobiles and tractors compared, <a href="#Page_1">1</a></li>
-<li class="isub1">Axles; types of front, <a href="#Page_172">172</a></li>
-
-<li class="ifrst">Backfire, <a href="#Page_55">55</a></li>
-<li class="isub1">Balance weights, <a href="#Page_31">31</a></li>
-<li class="isub1">Bearings, <a href="#Page_31">31</a></li>
-<li class="isub1">Bosch magneto; theory of, <a href="#Page_110">110</a></li>
-<li class="isub1">Bosch magneto circuit, <a href="#Page_111">111</a></li>
-<li class="isub1">Bosch magneto windings, <a href="#Page_110">110</a></li>
-<li class="isub1">Bull gear drive, <a href="#Page_165">165</a></li>
-<li class="isub1">Burning point of oil, <a href="#Page_182">182</a></li>
-
-<li class="ifrst">Cam, <a href="#Page_39">39</a></li>
-<li class="isub1">Carbon; formation of, <a href="#Page_56">56</a></li>
-<li class="isub1">Carbonization, <a href="#Page_56">56</a></li>
-<li class="isub1">Carbon; removing, <a href="#Page_242">242</a></li>
-<li class="isub1">Carburetor, <a href="#Page_57">57</a></li>
-<li class="isub1">Carburetor action, <a href="#Page_60">60</a></li>
-<li class="isub1">Carburetor adjustment, <a href="#Page_213">213</a></li>
-<li class="isub1">Carburetor adjustment for two fuels, <a href="#Page_218">218</a></li>
-<li class="isub1">Carburetor; compensating, <a href="#Page_63">63</a></li>
-<li class="isub1">Carburetor connections, <a href="#Page_89">89</a></li>
-<li class="isub1">Carburetor; description of, <a href="#Page_72">72</a></li>
-<li class="isub1">Carburetor; float feed, <a href="#Page_76">76</a></li>
-<li class="isub1">Carburetor; heating the, <a href="#Page_70">70</a></li>
-<li class="isub1">Carburetor; parts of, <a href="#Page_70">70</a></li>
-<li class="isub1">Carburetor; pump feed, <a href="#Page_80">80</a></li>
-<li class="isub1">Carburetor; stopping on gasoline, <a href="#Page_218">218</a></li>
-<li class="isub1">Carburetor strainer, <a href="#Page_89">89</a></li>
-<li class="isub1">Carburetor; trouble with, <a href="#Page_215">215</a></li>
-<li class="isub1">Carburetor; using water in, <a href="#Page_219">219</a></li>
-<li class="isub1">Causes of trouble, <a href="#Page_259">259</a></li>
-<li class="isub1">Centrifugal force, <a href="#Page_94">94</a></li>
-<li class="isub1">Change speed gear; action of, <a href="#Page_152">152</a></li>
-<li class="isub1">Change speed gear; jaw clutch, <a href="#Page_156">156</a></li>
-<li class="isub1">Change speed gear; purpose of, <a href="#Page_6">6</a></li>
-<li class="isub1">Change speed gear; shifting, <a href="#Page_203">203</a></li>
-<li class="isub1">Change speed gear; sliding, <a href="#Page_154">154</a>
-    <span class="pagenum" id="Page_264">[Pg 264]</span></li>
-<li class="isub1">Change speed gear; theory of, <a href="#Page_149">149</a></li>
-<li class="isub1">Choke, <a href="#Page_67">67</a></li>
-<li class="isub1">Circuit; Bosch magneto, <a href="#Page_111">111</a></li>
-<li class="isub1">Circuit breaker; magneto, <a href="#Page_110">110</a></li>
-<li class="isub1">Cleaner; air, <a href="#Page_91">91</a></li>
-<li class="isub1">Clutch; action of, <a href="#Page_144">144</a></li>
-<li class="isub1">Clutch; expanding, <a href="#Page_145">145</a></li>
-<li class="isub1">Clutch; how to use, <a href="#Page_205">205</a></li>
-<li class="isub1">Clutch; plate or disk, <a href="#Page_146">146</a></li>
-<li class="isub1">Clutch; purpose of, <a href="#Page_6">6</a></li>
-<li class="isub1">Cold weather care of tractor, <a href="#Page_207">207</a></li>
-<li class="isub1">Cold weather starting, <a href="#Page_207">207</a></li>
-<li class="isub1">Combustion space, <a href="#Page_11">11</a></li>
-<li class="isub1">Combustion; theory of, <a href="#Page_52">52</a></li>
-<li class="isub1">Compression; importance of, <a href="#Page_16">16</a></li>
-<li class="isub1">Compression leaks; locating, <a href="#Page_228">228</a></li>
-<li class="isub1">Compression stroke, <a href="#Page_16">16</a></li>
-<li class="isub1">Compression; testing the, <a href="#Page_227">227</a></li>
-<li class="isub1">Connecting rod, <a href="#Page_35">35</a></li>
-<li class="isub1">Cooling system, <a href="#Page_46">46</a></li>
-<li class="isub1">Crank shaft, <a href="#Page_30">30</a></li>
-<li class="isub1">Cycle; gas engine, <a href="#Page_11">11</a></li>
-
-<li class="ifrst">Dead strokes, <a href="#Page_12">12</a></li>
-<li class="isub1">Differential; action of, <a href="#Page_161">161</a></li>
-<li class="isub1">Differential; purpose of, <a href="#Page_7">7</a></li>
-<li class="isub1">Differential; theory of, <a href="#Page_158">158</a></li>
-<li class="isub1">Dirt in the fuel, <a href="#Page_215">215</a></li>
-<li class="isub1">Disk clutch, <a href="#Page_146">146</a></li>
-<li class="isub1">Distributor; magneto, <a href="#Page_124">124</a></li>
-<li class="isub1">Dixie magneto action, <a href="#Page_119">119</a></li>
-<li class="isub1">Double bowl carburetor; adjustment of, <a href="#Page_218">218</a></li>
-<li class="isub1">Double opposed engine, <a href="#Page_25">25</a></li>
-<li class="isub1">Drive; master gear or bull gear, <a href="#Page_165">165</a></li>
-<li class="isub1">Drive; purpose of, <a href="#Page_6">6</a></li>
-<li class="isub1">Drive; worm, <a href="#Page_166">166</a></li>
-
-<li class="ifrst">Engine base, <a href="#Page_30">30</a></li>
-<li class="isub1">Engine; double opposed, <a href="#Page_25">25</a></li>
-<li class="isub1">Engine; horizontal, <a href="#Page_25">25</a></li>
-<li class="isub1">Engine; how power is delivered by, <a href="#Page_21">21</a></li>
-<li class="isub1">Engine loses power, <a href="#Page_249">249</a></li>
-<li class="isub1">Engine misses, <a href="#Page_252">252</a></li>
-<li class="isub1">Engine overheats, <a href="#Page_256">256</a></li>
-<li class="isub1">Engine; priming, <a href="#Page_214">214</a></li>
-<li class="isub1">Engine; principle of, <a href="#Page_9">9</a></li>
-<li class="isub1">Engine; purpose of, <a href="#Page_6">6</a></li>
-<li class="isub1">Engine smokes, <a href="#Page_258">258</a></li>
-<li class="isub1">Engine starts; but stops, <a href="#Page_254">254</a></li>
-<li class="isub1">Engine stops, <a href="#Page_251">251</a></li>
-<li class="isub1">Engine trouble; locating, <a href="#Page_246">246</a></li>
-<li class="isub1">Engine; vertical, <a href="#Page_25">25</a></li>
-<li class="isub1">Engine will not start, <a href="#Page_246">246</a></li>
-<li class="isub1">Exhaust stroke, <a href="#Page_20">20</a></li>
-<li class="isub1">Exhaust valve, <a href="#Page_38">38</a></li>
-<li class="isub1">Expanding clutch, <a href="#Page_145">145</a></li>
-<li class="isub1">Extra air inlet, <a href="#Page_63">63</a></li>
-
-<li class="ifrst">Firing order, <a href="#Page_28">28</a></li>
-<li class="isub1">Float feed carburetor, <a href="#Page_76">76</a></li>
-<li class="isub1">Force feed oiling system, <a href="#Page_186">186</a></li>
-<li class="isub1">Frame; purpose of, <a href="#Page_8">8</a></li>
-<li class="isub1">Freezing; to prevent, <a href="#Page_209">209</a></li>
-<li class="isub1">Front axles; types of, <a href="#Page_172">172</a></li>
-<li class="isub1">Fuel; dirt in the, <a href="#Page_215">215</a></li>
-<li class="isub1">Fuel; straining the, <a href="#Page_89">89</a>
-    <span class="pagenum" id="Page_265">[Pg 265]</span></li>
-
-<li class="ifrst">Gas engine cycle, <a href="#Page_11">11</a></li>
-<li class="isub1">Gasket, <a href="#Page_30">30</a></li>
-<li class="isub1">Gasoline mixture, <a href="#Page_57">57</a></li>
-<li class="isub1">Governor, <a href="#Page_94">94</a></li>
-<li class="isub1">Grease cup, <a href="#Page_197">197</a></li>
-<li class="isub1">Grease; when used, <a href="#Page_182">182</a></li>
-<li class="isub1">Grinding valves, <a href="#Page_229">229</a></li>
-<li class="isub1">Grounded circuit or ground return, <a href="#Page_125">125</a></li>
-
-<li class="ifrst">Heat; action of, <a href="#Page_9">9</a></li>
-<li class="isub1">Heat; effect on oil of, <a href="#Page_177">177</a></li>
-<li class="isub1">Heat necessary in forming mixture, <a href="#Page_58">58</a></li>
-<li class="isub1">Heating the carburetor, <a href="#Page_70">70</a></li>
-<li class="isub1">Heating the mixture, <a href="#Page_86">86</a></li>
-<li class="isub1">Horizontal engine, <a href="#Page_25">25</a></li>
-
-<li class="ifrst">Ignition point; changing the, <a href="#Page_103">103</a></li>
-<li class="isub1">Ignition system; Atwater-Kent, <a href="#Page_136">136</a></li>
-<li class="isub1">Ignition system; parts of, <a href="#Page_105">105</a></li>
-<li class="isub1">Ignition; theory of, <a href="#Page_17">17</a>, <a href="#Page_102">102</a></li>
-<li class="isub1">Impulse starter, <a href="#Page_128">128</a></li>
-<li class="isub1">Induction and induced current, <a href="#Page_106">106</a></li>
-<li class="isub1">Inductor magneto, <a href="#Page_115">115</a></li>
-<li class="isub1">Inlet stroke, <a href="#Page_14">14</a></li>
-<li class="isub1">Inlet valve, <a href="#Page_38">38</a></li>
-
-<li class="ifrst">Jack shaft, <a href="#Page_165">165</a></li>
-<li class="isub1">Jaw clutch change speed gear, <a href="#Page_156">156</a></li>
-
-<li class="ifrst">K-W magneto action, <a href="#Page_115">115</a></li>
-<li class="isub1">Kerosene mixture, <a href="#Page_57">57</a></li>
-
-<li class="ifrst">Leaks of compression; locating, <a href="#Page_228">228</a></li>
-<li class="isub1">Lean mixture, <a href="#Page_54">54</a></li>
-<li class="isub1">Loading, <a href="#Page_67">67</a></li>
-<li class="isub1">Lubricating systems, <a href="#Page_184">184</a></li>
-<li class="isub1">Lubrication chart; use of, <a href="#Page_182">182</a></li>
-<li class="isub1">Lubrication; importance of, <a href="#Page_175">175</a></li>
-
-<li class="ifrst">Magnetism, <a href="#Page_105">105</a></li>
-<li class="isub1">Magnet; poles of, <a href="#Page_106">106</a></li>
-<li class="isub1">Magneto action; Bosch, <a href="#Page_110">110</a></li>
-<li class="isub1">Magneto action; Dixie, <a href="#Page_119">119</a></li>
-<li class="isub1">Magneto action; K-W, <a href="#Page_115">115</a></li>
-<li class="isub1">Magneto distributor, <a href="#Page_124">124</a></li>
-<li class="isub1">Magneto distributor; cleaning, <a href="#Page_222">222</a></li>
-<li class="isub1">Magneto inductor, <a href="#Page_115">115</a></li>
-<li class="isub1">Magneto; oiling a, <a href="#Page_221">221</a></li>
-<li class="isub1">Magneto platinum points; care of, <a href="#Page_221">221</a></li>
-<li class="isub1">Magneto safety spark gap, <a href="#Page_127">127</a></li>
-<li class="isub1">Magneto spark; theory of, <a href="#Page_105">105</a></li>
-<li class="isub1">Magneto; theory of Bosch, <a href="#Page_110">110</a></li>
-<li class="isub1">Magneto timer or circuit breaker, <a href="#Page_110">110</a></li>
-<li class="isub1">Magneto timing, <a href="#Page_223">223</a></li>
-<li class="isub1">Magneto trouble; testing for, <a href="#Page_224">224</a></li>
-<li class="isub1">Manifold, <a href="#Page_70">70</a></li>
-<li class="isub1">Master gear drive, <a href="#Page_165">165</a></li>
-<li class="isub1">Mechanical oiler, <a href="#Page_192">192</a></li>
-<li class="isub1">Mixer, <a href="#Page_57">57</a></li>
-<li class="isub1">Mixing chamber, <a href="#Page_70">70</a>
-    <span class="pagenum" id="Page_266">[Pg 266]</span></li>
-<li class="isub1">Mixture changes with engine speed, <a href="#Page_62">62</a></li>
-<li class="isub1">Mixture; formation of, <a href="#Page_53">53</a></li>
-<li class="isub1">Mixture; gasoline and kerosene, <a href="#Page_57">57</a></li>
-<li class="isub1">Mixture; heating the, <a href="#Page_86">86</a></li>
-<li class="isub1">Mixture; heat necessary to form, <a href="#Page_58">58</a></li>
-<li class="isub1">Mixture; rich, <a href="#Page_55">55</a></li>
-<li class="isub1">Mixture; theory of, <a href="#Page_9">9</a></li>
-<li class="isub1">Mixture; thin, or lean, <a href="#Page_54">54</a></li>
-
-<li class="ifrst">Oil affected by heat, <a href="#Page_177">177</a></li>
-<li class="isub1">Oil; burning point and viscosity, <a href="#Page_182">182</a></li>
-<li class="isub1">Oil cup, <a href="#Page_193">193</a></li>
-<li class="isub1">Oiler; mechanical, <a href="#Page_192">192</a></li>
-<li class="isub1">Oiling chart; use of, <a href="#Page_182">182</a></li>
-<li class="isub1">Oiling; importance of, <a href="#Page_175">175</a></li>
-<li class="isub1">Oiling systems, <a href="#Page_184">184</a></li>
-<li class="isub1">Oil pump, <a href="#Page_188">188</a></li>
-<li class="isub1">Oil; varieties used on tractors, <a href="#Page_179">179</a></li>
-
-<li class="ifrst">Piston, <a href="#Page_34">34</a></li>
-<li class="isub1">Piston pin, <a href="#Page_34">34</a></li>
-<li class="isub1">Piston rings, <a href="#Page_37">37</a></li>
-<li class="isub1">Piston rings; care of, <a href="#Page_228">228</a></li>
-<li class="isub1">Plate clutch, <a href="#Page_146">146</a></li>
-<li class="isub1">Poles of magnet, <a href="#Page_106">106</a></li>
-<li class="isub1">Power diagram, <a href="#Page_21">21</a></li>
-<li class="isub1">Power production, <a href="#Page_12">12</a></li>
-<li class="isub1">Power stroke, <a href="#Page_19">19</a></li>
-<li class="isub1">Preignition, <a href="#Page_56">56</a>, <a href="#Page_83">83</a>, <a href="#Page_104">104</a></li>
-<li class="isub1">Priming the engine, <a href="#Page_214">214</a></li>
-<li class="isub1">Pump feed carburetor, <a href="#Page_80">80</a></li>
-<li class="isub1">Push rod, <a href="#Page_42">42</a></li>
-<li class="isub1">Push rod adjustment, <a href="#Page_234">234</a></li>
-
-<li class="ifrst">Radiator, <a href="#Page_48">48</a></li>
-<li class="isub1">Retard of ignition; theory of, <a href="#Page_19">19</a></li>
-<li class="isub1">Rich mixture, <a href="#Page_55">55</a></li>
-<li class="isub1">Rocker arm, <a href="#Page_42">42</a></li>
-
-<li class="ifrst">Safety spark gap, <a href="#Page_127">127</a></li>
-<li class="isub1">Shuttle armature, <a href="#Page_107">107</a></li>
-<li class="isub1">Sliding change speed gear, <a href="#Page_154">154</a></li>
-<li class="isub1">Spark coil; principle of, <a href="#Page_133">133</a></li>
-<li class="isub1">Spark coil; vibrator, <a href="#Page_138">138</a></li>
-<li class="isub1">Spark coil; windings of, <a href="#Page_134">134</a></li>
-<li class="isub1">Spark plug, <a href="#Page_140">140</a></li>
-<li class="isub1">Spark plug gap, <a href="#Page_226">226</a></li>
-<li class="isub1">Spark plugs; trouble with, <a href="#Page_225">225</a></li>
-<li class="isub1">Splash oiling system, <a href="#Page_184">184</a></li>
-<li class="isub1">Spray nozzle, <a href="#Page_57">57</a></li>
-<li class="isub1">Spring support, <a href="#Page_173">173</a></li>
-<li class="isub1">Starter; impulse, <a href="#Page_128">128</a></li>
-<li class="isub1">Starting in cold weather, <a href="#Page_207">207</a></li>
-<li class="isub1">Starting the engine; theory of, <a href="#Page_13">13</a></li>
-<li class="isub1">Steering gear; purpose of, <a href="#Page_7">7</a></li>
-<li class="isub1">Steering; instruction in, <a href="#Page_205">205</a></li>
-<li class="isub1">Storing a tractor, <a href="#Page_210">210</a></li>
-<li class="isub1">Straining the fuel, <a href="#Page_89">89</a></li>
-<li class="isub1">Strangler, <a href="#Page_69">69</a></li>
-
-<li class="ifrst">Tappet, <a href="#Page_42">42</a></li>
-<li class="isub1">Tappet adjustment, <a href="#Page_234">234</a></li>
-<li class="isub1">Temperature; effect of changes on mixture, <a href="#Page_66">66</a>
-      <span class="pagenum" id="Page_267">[Pg 267]</span></li>
-<li class="isub1">Testing for magneto trouble, <a href="#Page_224">224</a></li>
-<li class="isub1">Testing the compression, <a href="#Page_227">227</a></li>
-<li class="isub1">Theory of gas engine, <a href="#Page_9">9</a></li>
-<li class="isub1">Thermo-syphon cooling system, <a href="#Page_48">48</a></li>
-<li class="isub1">Thin mixture, <a href="#Page_54">54</a></li>
-<li class="isub1">Throttle, <a href="#Page_68">68</a></li>
-<li class="isub1">Throws of crank shaft, <a href="#Page_30">30</a></li>
-<li class="isub1">Timer; magneto, <a href="#Page_110">110</a>, <a href="#Page_121">121</a>, <a href="#Page_122">122</a></li>
-<li class="isub1">Timing a magneto, <a href="#Page_223">223</a></li>
-<li class="isub1">Timing the valves, <a href="#Page_237">237</a></li>
-<li class="isub1">Tractor; caring for in cold weather, <a href="#Page_207">207</a></li>
-<li class="isub1">Tractor; difficulties in oiling, <a href="#Page_178">178</a></li>
-<li class="isub1">Tractor driving, <a href="#Page_205">205</a></li>
-<li class="isub1">Tractor; handling a new, <a href="#Page_201">201</a></li>
-<li class="isub1">Tractor inspection, <a href="#Page_203">203</a></li>
-<li class="isub1">Tractors and automobiles compared, <a href="#Page_1">1</a></li>
-<li class="isub1">Tractor; storing, <a href="#Page_210">210</a></li>
-<li class="isub1">Tractor types, <a href="#Page_167">167</a></li>
-<li class="isub1">Transmission; parts of, <a href="#Page_143">143</a></li>
-<li class="isub1">Trouble; causes of, <a href="#Page_259">259</a></li>
-<li class="isub1">Trouble; locating, <a href="#Page_246">246</a></li>
-
-<li class="ifrst">Valve; exhaust, <a href="#Page_38">38</a></li>
-<li class="isub1">Valve grinding, <a href="#Page_229">229</a></li>
-<li class="isub1">Valve; inlet, <a href="#Page_38">38</a></li>
-<li class="isub1">Valve mechanism, <a href="#Page_42">42</a></li>
-<li class="isub1">Valve operation, <a href="#Page_39">39</a></li>
-<li class="isub1">Valve seat; redressing, <a href="#Page_234">234</a></li>
-<li class="isub1">Valve timing, <a href="#Page_237">237</a></li>
-<li class="isub1">Vertical engine, <a href="#Page_25">25</a></li>
-<li class="isub1">Vibrator coil, <a href="#Page_138">138</a></li>
-<li class="isub1">Viscosity of oil, <a href="#Page_182">182</a></li>
-
-<li class="ifrst">Washer; air, <a href="#Page_91">91</a></li>
-<li class="isub1">Water added to mixture, <a href="#Page_58">58</a>, <a href="#Page_83">83</a>, <a href="#Page_219">219</a></li>
-<li class="isub1">Water jackets, <a href="#Page_48">48</a></li>
-<li class="isub1">Windings; Bosch magneto, <a href="#Page_110">110</a></li>
-<li class="isub1">Windings of spark coil, <a href="#Page_134">134</a></li>
-<li class="isub1">Worm drive, <a href="#Page_166">166</a></li>
-<li class="isub1">Wrist pin, <a href="#Page_34">34</a></li>
-</ul>
-
-<div class="transnote bbox space-above2">
-<p class="f120 space-above1">Transcriber’s Notes:</p>
-<hr class="r5" />
-<p class="indent">The illustrations have been moved so that they do not break up
-                  paragraphs and so that they are next to the text they illustrate.</p>
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deleted file mode 100644
index b623432..0000000
--- a/old/67569-h/images/logo.jpg
+++ /dev/null