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 yITY OF CALIFORNIA 
 
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MOTOR VEHICLES 
 
 and THEIR ENGINES 
 
 A Practical Handbook on the 
 CARE, REPAIR and MANAGEMENT 
 
 OF 
 
 MOTOR TRUCKS and AUTOMOBILES 
 
 for Owners, Chauffeurs, Garagemen and Schools 
 BY 
 
 EDWARD S. ERASER 
 
 American Bosch Magneto Corporation; Formerly, Captain, C. A., U. S. A. 
 Instructor Motor Transportation Course, Coast Artillery School 
 
 AND 
 
 RALPH B. JONES 
 
 Willys Overland Company; Formerly, Captain C. A., U. S. A. 
 Instructor Motor TradspgostatiQn, Qpurse, Coas,t, Artillery School 
 
 
 278 ILLUSTRATIONS 
 
 NEW YORK 
 
 D. VAN NOSTRAND COMPANY 
 
 EIGHT WARREN STREET 
 
 1921 
 
P? 
 
 Copyright 1919, by 
 D. VAN NOSTRAND COMPANY 
 
 
 Printed in the U. S. A. 
 
PREFACE 
 
 The following pages represent the result of an attempt to collect 
 in a comparatively small book such elementary, theoretical, and 
 practical information as will assist in the operation, upkeep, and 
 adjustment of the motor vehicles. This book was written with a 
 three-fold purpose; as a guide for the personal instruction of the car 
 owner, as a hand book for chauffeurs, garages, and repairmen, and as 
 a text book for Automobile Schools. The simplest language has been 
 used and technicalities have been reduced to a minimum. The 
 fundamentals of gas motor operation, as well as the care and opera- 
 tion of the principal accessories of the motor vehicles concerned, are 
 discussed in detail and at greater length than is the usual practice. 
 
 To' obtain the maximum economy, efficiency, and life of the 
 apparatus the last four chapters of the book should be studied. 
 These chapters are the result of the authors' observations and expe- 
 rience with the great number of trucks, tractors, automobiles, and 
 motor-cycles operating under their supervision. 
 
 This book is the outgrowth of the authors' former volume " Motor 
 Transportation for Heavy Artillery," which was prepared for use as 
 a textbook in the Coast Artillery School's course in the subject. 
 The valuable experience gained in connection with their work as 
 instructors in this school has been embodied in this second edition so 
 that the book contains all the information necessary to properly 
 operate and care for motor vehicles. 
 
 The authors wish to express their indebtedness to the Norman 
 W. Henley Publishing Company for permission to use figures 6, 7, 
 46, 136, 215, 237, 246, 252, 260, 262, 263, 266 and 268 from Page's 
 " Modern Gasolene Automobile." 
 
 April, 1920. THE AUTHORS. 
 
CONTENTS 
 
 CHAPTER PAGE 
 
 \ I THE GAS ENGINE 1 
 
 i- II PRINCIPLES OF Two AND FOUK-CYCLE ENGINES 8 
 
 ( ( III TIMING 14 
 
 IV ENGINE BALANCE AND FIRING ORDER 21 
 
 V COOLING SYSTEMS 34 
 
 VI FUEL FEED SYSTEMS 48 
 
 VII FUELS 55 
 
 VIII ELEMENTS OF CARBURETION 63 
 
 IX CARBURETORS 72 
 
 X CARBURETORS (Continued) 89 
 
 XI PUDDLE TYPE CARBURETORS 114 
 
 XII MAGNETISM 117 
 
 XIII ELEMENTARY ELECTRICITY 128 
 
 XIV BATTERIES 135 
 
 XV INDUCTION 146 
 
 XVI BATTERY IGNITION SYSTEMS 151 
 
 XVII MAGNETOS: ARMATURE TYPE 172 
 
 XVIII MAGNETOS: ROTOR TYPE 193 
 
 -S XIX DUAL AND DUPLEX IGNITION SYSTEMS 201 
 
 XX STARTING AND LIGHTING SYSTEMS 207 
 
 XXI POWER TRANSMISSION 227 
 
 XXII CLUTCHES 232 
 
 XXIII TRANSMISSIONS 241 
 
 XXIV DRIVES 258 
 
 XXV DIFFERENTIALS 263 
 
 XXVI RUNNING GEAR 270 
 
 XXVII TIRES AND RIMS 289 
 
 XXVIII How TO DRIVE 299 
 
 XXIX ENGINE TROUBLES EXPERIENCED ON THE ROAD 303 
 
 XXX LUBRICATION 309 
 
 XXXI CARE AND ADJUSTMENT. . 317-ltf-l^ 
 
 3T3-<* 
 
 XXXII CARE AND ADJUSTMENT TABLES 329 
 
 INDEX .345 
 
MOTOR VEHICLES 
 
 AND THEIR ENGINES 
 
 CHAPTER I 
 
 THE GAS ENGINE M - *'- - '' 
 
 The term "Gas Engine" is commonly used to designate all types 
 of internal combustion engines regardless of whether they operate 
 on gas or liquid fuel. Liquid fuel is almost universally used in 
 engines adapted for motor transportation. GasolirTe is the most 
 commonly used liquid fuel. Kerosene, alcohol, benzol, and fuel oil 
 are used in internal combustion engines, but in general their use is 
 confined to engines of the stationary type. 
 
 In the internal combustion engine, the fuel is introduced into the 
 cylinder in a combustible mixture and is there ignited. This type 
 of engine is divided into two classes, that in which the combustion 
 takes place gradually and that in which the combustion takes place 
 almost instantaneously. 
 
 The Diesel engine comes under the class in which the combustion 
 is gradual. The liquid fuel is gradually injected into the cylinder 
 which contains only air under high pressure. This air is compressed 
 to such a degree that a temperature far above the ignition point of 
 the fuel is obtained. This causes the fuel to ignite as it is injected 
 into the combustion space. Complete but gradual combustion is 
 obtained in this manner. Engines of this type are not applicable 
 for motor propelled vehicles, largely because of their lack of flexibility. 
 
 In the gasoline engine the fuel is burned almost instantaneously. 
 The air is mixed with the fuel outside of the combustion space (Fig. 1) 
 and the resulting combustible mixture is drawn into the cylinder 
 where it is ignited under compression by some outside source of heat., 
 the electric spark being the one universally adopted. 
 
 Combustion or burning is always accompanied by the production 
 of heat. The temperature produced depends upon the rapidity and 
 completeness of the combustion. The faster the burning the higher 
 the maximum temperature produced. A slow burning fuel produces 
 a more uniform temperature, but not as high as is produced by a 
 fuel burning almost instantaneously. 
 
MOTOR VEHICLES AND THEIR ENGINES 
 
 CRAM SHAFT BMniNG- 
 CflAflK MSF ^HMJrmr CAn 
 fWMSI CM SHAFT GEM 
 
 Fig. 1 Engine Parts 
 
 WORKING PARTS: 
 Pistons 
 
 Piston rings 
 
 Wrist pins 
 Connecting rods 
 
 Connecting rod caps 
 
 Shims 
 
 Connecting rod bearings 
 Crank shaft 
 
 Gear to cam shaft 
 
 Crank arms 
 
 Crank pins 
 
 Journal 
 
 Fly wheel 
 
 VALVE MECHANISM: 
 
 Cam shaft 
 
 Cam shaft gears 
 
 Inlet cams 
 
 Exhaust cams 
 Push rods (lifter rods or tappets) 
 
 Roller or mushroom head 
 
 Adjusting nuts 
 Valves 
 
 Valve stem 
 
 Valve spring 
 
 Valve head 
 
 Valve clearance 
 
ENGINE NOMENCLATURE 
 
 Fan Support 
 Fun tfl<le<i 
 
 Oil Wvll<SsF^ _ fi / 
 
 ~<MT~-r ^^Or^n^ 
 
 Fig. 2 Sectional View of Typical Four-Stroke Cycle, Four-Cylinder 
 
 Motor Truck Engine, Showing Important Internal Parts 
 
 and Their Relation to Each Other 
 
 STATIONARY PARTS 
 
 Cylinder casting 
 
 Water jacket 
 
 Inlet ports 
 
 Exhaust ports 
 
 Valve seats 
 
 Cylinder head 
 
 Combustion space 
 Crank case 
 
 Upper half 
 
 Lower half 
 
 Lifter guides 
 
 Main bearings 
 
 Cam shaft bearings 
 
 Oil reservoir 
 
 Oil pump 
 
 Float 
 
 Gear cover 
 
 Breather tube 
 
 ACCESSORIES: 
 Inlet manifold 
 Exhaust manifold 
 Fan assembly 
 
 Fan 
 
 Pulley 
 
 Belt 
 
 Bracket 
 Starting crank 
 Valve caps 
 Spark plugs 
 
 Compression cocks (priming cocks) 
 Water pumps 
 
 Magneto or timer-distributor 
 Carburetor 
 
4 MOTOR VEHICLES AND THEIR ENGINES 
 
 When gases and most metals are heated they expand, some ex- 
 panding more than others. Gases expand more than metals for a 
 given amount of heat. A definite increase of temperature will cause 
 a gas to expand a certain amount and as the heat is increased the 
 expansion increases in proportion. When the mixture in the cylinder 
 is burned, the resulting heat causes the gases to expand, the amount 
 of this expansion depending upon the temperature. 
 
 When a gas contained in a closed vessel is heated its expansion 
 exerts a pressure equally in all directions. This condition exists in 
 the cylinder of an internal combustion engine after combustion has 
 taken place. The resulting pressure is exerted on the cylinder walls 
 and piston. The piston, being movable, under the force of the 
 expanding gases, moves outward to the full limit of its stroke. 
 
 The energy resulting from this expansion must now be trans- 
 formed into useful work. In order to accomplish this, a construction 
 such as shown in Fig. 3 is used. 
 
 The force exerted on the piston "K" is transmitted through the 
 connecting rod "E" to the crank shaft U H" which is made to revolve, 
 turning through one-half of a revolution as the piston moves out- 
 ward. Attached to the crank shaft is a fly wheel, which stores up 
 energy and its momentum carries the piston through the balance of 
 its motion until it receives another power impulse. In this way the 
 reciprocating motion of the piston is transformed into a rotary 
 motion at the crank shaft. 
 
 The operation of the gasoline engine, as already shown, depends 
 upon the production of heat in the cylinder caused by burning the 
 
 Fig. 3 Engine Operation 
 
THE GAS ENGINE 
 
 .EXHAUST GAS, 
 DIRECT RADIATION 
 
 35.6% 
 
 POWEHOF CAR 
 
 12.5% 
 
 EXCESS POWER FOR 
 ACCELERATION. HILLS. ETC. 
 
 5-4% 
 
 FRONT WHEEL* 
 
 0.6% 
 
 AIR RESISTANCE 
 7.1% 
 
 Fig. 4 Energy Diagram 
 
6 MOTOR VEHICLES AND THEIR ENGINES 
 
 fuel. A given amount of fuel will produce a certain amount of heat 
 when completely burned. However, the total heat value of the fuel 
 cannot be utilized because there are certain losses which must always 
 occur even in the best designed engine. Badly worn engines, im- 
 perfect carburetion, and faulty ignition will add to the necessary 
 losses and decrease the percentage of energy actually available for 
 useful work. 
 
 The highest thermal efficiency attained in the best types of large 
 stationary internal combustion engines (Diesel) is about 35% while 
 few automobile engines ever exceed 20%. The diagram (Fig. 4) 
 shows the dispersion of energy from fuel as it passes through the 
 engine of a high class touring car traveling at a speed of 40 miles 
 per hour on direct drive. 
 
 Referring to Fig. 4, it will be seen that a certain amount of the 
 heat is absorbed by the cooling system. Also a considerable amount 
 of heat is lost in the exhaust gases. Nearly 70% of the total fuel 
 value is lost in this way and this loss cannot be materially reduced 
 below this amount. The loss due to engine friction will vary con- 
 siderably with the design and condition of the engine. The point 
 indicated as " Motor Full Power" represents the amount of energy 
 remaining for useful work. When this energy is applied to driving 
 an automobile, it is consumed as shown in the diagram. This leaves 
 but a small amount of reserve energy, which will be decreased as the 
 speed of the machine is increased. Every design of engine and car 
 of course has a different energy diagram corresponding to the degree 
 of efficiency attained at different speed and loads. 
 
 Engines of all kinds are rated in horse-power the measure of 
 the rate at which they can do work. One horse-power represents 
 33,000 foot-pounds of work per minute. There are two ways of 
 measuring engine power. The power developed by the expansion 
 of the gases in the cylinder can be determined, in which case the 
 INDICATED HORSE-POWER is obtained. By means of a Prony 
 Brake or Dynamometer, the power which the engine actually delivers 
 can be measured and this is called the BRAKE HORSE-POWER. 
 The brake horse-power of an automobile engine will usually be from 
 70% to 85% of its indicated horse-power, the losses being energy 
 consumed in friction and other causes in the engine mechanism. 
 However, in obtaining the horse-power of an engine, formulae are 
 used based on the indicated horse-power assuming certain standard 
 conditions. The horse-power obtained in this manner is often incon- 
 sistent with the actual horse-power developed on test. 
 
 There are a number of quick rules for estimating the power of 
 engines according to their cylinder dimensions and the piston speed. 
 
THE GAS ENGINE 
 
 * 
 
 The one most used for four-cycle engines is given below. The 
 simplest formula is that of the Society of Automobile Engineers: 
 
 .. 
 
 2.5 
 The formula for finding the indicated horse-power of an engine is : 
 
 I. H. P. (for 1 Cylinder) = R A ' S ' 
 
 33,000x4 
 
 Where P = mean effective pressure in pounds per square inch. 
 A = piston area in square inches. 
 S = piston speed in feet per minute. 
 
 Where the engine has more than one cylinder, the result ob- 
 tained from this formula must be multiplied by the number of 
 cylinders. The brake horse-power is obtained by multiplying by the 
 mechanical efficiency of the engine. The complete equation for 
 brake horse-power is: 
 
 BHp= P.A.S.N.E. 
 
 33,000 x 4 
 
 Where N == number of cylinders. 
 E = mechanical efficiency. 
 
 Assuming a mean effective pressure of 90 pounds per square inch, 
 a piston speed of 1,000 feet per minute, and a mechanical efficiency 
 of 75% and substituting these values in the formula for brake 
 horse-power, the following value is obtained: 
 
 D 2 N D 2 N 
 
 B. H. P. = - or approximately - 
 2.489 2.5 
 
 Where D = diameter of piston in inches. 
 
 This is the S. A. E. formula for four-cycle engines 
 
 For two-cycle engines this becomes: 
 
 1.5 
 
CHAPTER II 
 
 PRINCIPLES OF TWO AND FOUR-CYCLE ENGINES 
 
 In order that the operation of the gas engine be continuous, a 
 certain series of events called the cycle must take place which are 
 repeated over and over in the same regular order. In order to clearly 
 understand the events that compose the cycle of an engine, its opera- 
 tion will be compared to the operation of the old style muzzle-loading 
 cannon, which is the simplest form of internal combustion engine. 
 
 Referring to Fig. 5, the first step necessary to fire the cannon is 
 inserting the charge; the corresponding step in the gas engine is the 
 ADMISSION of the charge. The second step is ramming the pro- 
 jectile and powder; the corresponding step in the gas engine is the 
 COMPRESSION of the charge. The third step is lighting the fuse; 
 the corresponding step in the gas engine is the IGNITION of the 
 charge. The fourth step is burning the powder and the fifth step 
 expansion of the gases of combustion due to the heat produced which 
 forces the projectile out of the cannon. The corresponding steps in 
 the gas engine are the COMBUSTION of the charge and EXPAN- 
 SION of the gases. The sixth step in the operation of the cannon is 
 the escape of the burned gases after the projectile has left the muzzle; 
 the corresponding step in the gas engine is the subsequent EXHAUST 
 of the products of combustion. The cannon is now ready to be fired 
 again and the engine to continue its operation. 
 
 The steps comprising the cycle of operation of the gas engine may 
 be summarized as follows : 
 
 1. Admission of the charge. 
 
 2. Compression of the charge. 
 
 3. Ignition of the charge. 
 
 4. Combustion of the charge. 
 
 5. Expansion of the gases. 
 
 6. Exhaust of the gases. 
 
 In the operation of a gas engine the number of strokes required 
 to complete the cycle varies with the type of engine. In the type 
 almost universally used for motor vehicles the cycle is extended 
 through four strokes of the piston or two revolutions of the crank 
 shaft and is therefore called a four-cycle engine. In a few instances 
 the cycle is completed in two strokes of the piston or one revolution 
 of the crank shaft and is therefore called a two-cycle engine. 
 
B 
 
 D 
 
 Fig. 5 Operation of Cannon and Engine Compared 
 
 
 
10 MOTOR VEHICLES AND THEIR ENGINES 
 
 FOUR-CYCLE ENGINES 
 
 In the four-cycle engine, the four strokes are named suction, 
 compression, power, and exhaust in accordance with the operations 
 of the cycle which occur during each particular stroke. 
 
 SUCTION STROKE. During this stroke (Fig. 5-A) the piston 
 is moved outward by the crank shaft which is either revolved by the 
 momentum of the fly wheel or some external starting force. This 
 movement of the piston increases the size of the combustion space, 
 thereby reducing the pressure in it and the higher pressure of the 
 atmosphere outside, forces fresh mixture into the combustion space 
 through the open inlet valve. 
 
 COMPRESSION STROKE. The compression, ignition, and 
 most of the combustion of the charge takes place during the next 
 inward stroke of the piston. The time elapsed between the mixing 
 of the liquid gasoline and air and its admission into the cylinder is 
 too brief to secure a perfect combustible mixture. What passes 
 into the cylinder consists of air, liquid gasoline, and a more or less 
 perfect mixture of the two. The combustion of this mixture would 
 be slow and incomplete resulting in a loss of power and a waste of 
 fuel. In order to obtain a homogeneous mixture, advantage is taken 
 of the heat produced by compression. This renders the gasoline 
 more volatile, while the compression forces it into intimate combina- 
 tion with the air. Even then a perfect mixture may not result for 
 the air and gasoline vapor instead of being thoroughly combined may 
 be in layers. The combustion will then be slow and uneven. When 
 the mixture of air and gasoline vapor are properly proportioned, this 
 difficulty is seldom encountered. The mixture is ignited while 
 under compression and combustion is practically completed at top 
 dead center. 
 
 POWER STROKE. The expansion of the gases due to the heat 
 of combustion exerts a pressure in the cylinder and on the piston. 
 Under this impulse it moves outward. 
 
 EXHAUST STROKE. When the exhaust valve is opened, the 
 greater part of the burned gases escape due to their own expansion. 
 The inward movement of the piston pushes the remaining gases out 
 of the open exhaust valve. The space between the cylinder head 
 and the piston, when it is at its inmost point, is called the clearance 
 and will be filled with the remaining exhaust gases. These will 
 dilute the fresh incoming charge. 
 
 Thus it is seen that in this type of engine four strokes of the piston 
 are required to complete the cycle. 
 
PRINCIPLES OF TWO AND FOUR-CYCLE ENGINES 11 
 
 Fig. 6 Three-Port Two-Cycle Engine 
 
 TWO-CYCLE ENGINES 
 
 The two-cycle type of gasoline engine differs from the four-cycle 
 type just described in that the six events composing the cycle are 
 performed during two strokes of the piston or one revolution of the 
 crank shaft. Power is developed during every outward stroke of 
 the piston instead of alternate outward strokes. 
 
 In order that this result may be attained, the construction of the 
 engine is changed. As shown in Fig. 6, the crank case is utilized as 
 a receiver for the mixture before it passes to the combustion space. 
 The valves are replaced by ports, which are openings into the com- 
 bustion space. These are covered and uncovered by the piston as 
 it slides in the cylinder. The gas inlet port to the crank case is 
 uncovered when the piston is at the inmost point of its stroke ad- 
 mitting the mixture to the crank case. This is air tight and must 
 have a separate compartment for each cylinder. The exhaust port 
 and the intake port are uncovered when the piston is at the outmost 
 point of its stroke. The exhaust port opens first, which permits the 
 burned gases to escape after combustion has taken place. The intake 
 port opens shortly after the opening of the exhaust port and permits 
 a fresh charge to pass from the crank case to the combustion space. 
 
 During an inward stroke, the pressure in the crank case is reduced 
 as the piston moves inward and a fresh mixture is forced into it by 
 the higher atmospheric pressure as soon as the gas inlet is uncovered. 
 This port is covered when the piston makes an outward stroke and 
 the mixture, not being able to escape, is compressed. The tendency 
 
12 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 of the gas to expand causes it to flow to the combustion space when 
 the inlet port is uncovered, and in entering, it strikes a deflecting 
 plate on the piston. This deflects it to the top of the combustion 
 space instead of allowing it to rush across the cylinder and out the 
 open exhaust port. The inward stroke of the piston covers these 
 two ports and compresses the mixture, ignition occurring in the 
 regular manner. The pressure developed by the combustion drives 
 the piston outward. As soon as the exhaust port is uncovered, 
 which is slightly before the uncovering of the inlet port, the gases, 
 which are still expanding, begin to escape. They are further expelled 
 by the fresh charge that enters and drives them before it. Thus the 
 six events of the cycle are performed during an inward and an out- 
 
 Fig. 7 Two-Port Two-Cycle Engine 
 
 ward stroke of the piston. On the lower side of the piston a charge 
 of fresh mixture is drawn into the crank case and forced into the 
 combustion space where it is compressed, ignited, and burned. 
 
 The type of engine just explained is known as the three-port 
 construction of two-cycle engine. There is also a two-port construc- 
 tion of two-cycle engine. This type of engine differs from the three 
 port in that the inlet port to the crank case is replaced by a check 
 valve as shown in Fig. 7. When the pressure in the crank case is 
 reduced due to the piston moving inward, the higher atmospheric 
 pressure opens the valve and forces a fresh mixture into the crank 
 case. The valve is closed by the action of the spring at all other 
 times and is further assisted in closing by compression in the crank 
 
PRINCIPLES OF TWO AND FOUR-CYCLE ENGINES 13 
 
 case. The operation of this engine is identical in all other respects 
 with the three-port construction. 
 
 In all two-cycle engines a screen is placed in the bypass. The 
 object of this is to prevent any possibility of the incoming charge 
 being ignited by the exhaust gases thus causing a back fire into the 
 crank case. 
 
 At slow speeds, two-cycle engines have advantages over the four- 
 cycle in having a power impulse every revolution of the crank shaft 
 and in not having valves and valve mechanism with their weight and 
 possibility of giving trouble. This simplicity makes the two-cycle 
 engine popular for motor boats, where slow and constant speeds are 
 desired. For higher and changing speeds these advantages are out- 
 weighed by disadvantages that show little sign of being overcome. 
 
 With the engine running at high speed, the ports are open for 
 only a brief period during each stroke, and the faster the engine runs, 
 the shorter will be the period during which the gases may enter or 
 leave the combustion space. The inefficiency of two-cycle engines 
 as compared with engines of the four-cycle type is due entirely to the 
 fact that the burned gases have not sufficient time in which to escape 
 from the combustion space, nor the fresh charge time to enter. The 
 fresh charge that does enter is incomplete and contaminated by the 
 portion of the burned gases that have not been able to escape. This 
 results in the "choking up" of the engine, and in the production of 
 lower power than the dimensions and weight of the engine warrant. 
 
 Automobile engineers agree that the four-cycle engine is better 
 for automobile work. It has been developed to a greater degree 
 than the two-cycle and it is easier to keep adjusted and in good 
 running condition. Though the two-cycle engine is undoubtedly 
 the simplest form, it is liable to be erratic in operation and it is some- 
 times difficult to locate the trouble definitely. The following ad- 
 vantages are claimed for the two-cycle engine over the four-cycle: 
 
 (1) absence of poppet valves with their springs, push rods, cam 
 shafts, etc.; (2) fewer parts; (3) better turning effect with the same 
 number of cylinders. Offsetting these, the four-cycle engine has the 
 following advantages over the two-cycle: (1) greater fuel economy, 
 
 (2) greater flexibility. These advantages far over-balance the 
 advantages of the two-cycle over the four-cycle engine and for that 
 reason the two-cycle engine is very rarely used for automobile 
 propulsion. 
 
CHAPTER III 
 
 TIMING 
 
 As explained in the operation of the four-cycle engine, the inlet 
 valve is opened during the suction stroke and the exhaust valve is 
 opened during the exhaust stroke. In this chapter will be shown 
 the exact time at which the valves open and close with reference to 
 the position of the piston. In outlining the timing of the valves, 
 the reason for each operation of the valve will be explained. 
 
 During the inlet stroke, the inlet valve must be open to admit 
 the charge. The charge is forced into the cylinder due to the pres- 
 sure being reduced as the piston moves outward. If the inlet valve 
 were opened at top dead center, the gases would not be forced into 
 the cylinder until the piston had moved out sufficiently to cause a 
 decrease in pressure and the velocity of the incoming gases for some 
 time would be slow. In order to prevent this, the inlet valve remains 
 closed for a certain number of degrees during the downward move 
 ment of the piston. This causes a sufficient decrease in pressure to 
 allow the gases to be forced in with a certain amount of initial velocity. 
 Most manufacturers have adopted this practice as the cylinder will 
 be filled more rapidly. 
 
 The rapid decrease in pressure in the cylinder due to the outward 
 movement of the piston causes the gases to rush in and fill up the 
 space back of the piston. If the piston moves slowly, the mixture 
 will be able to enter fast enough to keep the pressure in the com- 
 bustion space equal to that outside. At the high speed at which a 
 gasoline engine runs, the piston will reach the end of its stroke before 
 a complete charge has had time to enter through the small inlet 
 valve opening. Therefore the pressure in the combustion space will 
 still be below that of the atmosphere. If the inlet valve closed at 
 this point so that no more mixture could enter, the combustion of 
 the partial charge would result in a lower pressure than would be 
 possible with a full charge. The inlet valve should therefore remain 
 open until the piston reaches a point in its next inward stroke at 
 which the pressure in the cylinder equals that outside. The piston 
 moving inward diminishes the space in the cylinder and compresses 
 the gas ahead of it. When under compression, the gas is ready to 
 be ignited and burned. 
 
 The combustion of the inflammable mixture produces a certain 
 amount of heat. The more rapid and complete this combustion, the 
 
 14 
 
TIMING 15 
 
 greater and more sudden will be the rise in pressure. The pressure 
 will be greater when the mixture is contained in a small space than 
 when in a large space. As the combustion space is smallest when 
 the piston is at its inmost point, the greatest pressure will be obtained 
 if combustion is completed at this pointc If the combustion of the 
 mixture were instantaneous, it would be ignited at this point. But 
 even though very rapid, it burns slowly enough to make necessary 
 the ignition of the mixture before the end of the stroke. The com- 
 bustion will then be complete as the piston comes into position to 
 move outward. The instant at which the mixture must be ignited 
 in order to produce this result depends on the speed of the piston. 
 The interval between the ignition of a good mixture and its complete 
 combustion does not vary to any great extent. When the piston is 
 moving slowly, the mixture may be ignited toward the end of the 
 compression stroke, for there will be sufficient time for complete 
 combustion by the time the stroke is ended. When moving at high 
 speed, ignition must occur much earlier in the stroke, as otherwise 
 the piston will have completed the compression stroke and begun to 
 move outward on the power stroke before the mixture is entirely 
 burned. The instant at which ignition occurs also depends on the 
 mixture that is used, since this makes a difference in the rapidity with 
 which it burns. The better the quality of the mixture, the faster 
 and more completely it will burn and ignition may occur later in the 
 stroke than would be possible with a mixture of poorer quality. The 
 instant at which ignition occurs may be controlled by causing the 
 spark to take place earlier or later, this being controlled by the 
 driver. 
 
 When ignition occurs early in the compression stroke, the spark 
 is said to be advanced. A retarded spark takes place when the com- 
 pression stroke is more nearly complete. 
 
 If the spark is advanced too much, combustion will be complete 
 before the piston has reached the end of the compression stroke. It 
 will then be necessary to force the piston inward against the resultant 
 pressure by the momentum of the flywheel, in order that it may get 
 into position to move outward on the power stroke. In such a case, 
 the momentum may not be sufficient to overcome the pressure and 
 the piston will be brought to a stop. 
 
 A retarded spark often results in the complete combustion of the 
 mixture after the piston has begun to move outward on the power 
 stroke. The pressure will then be reduced because combustion takes 
 place in a larger space, the piston consequently being moved with 
 less force. If the spark is still further retarded, the combustion will 
 not be completed by the time exhaust begins. The heat from only 
 
16 MOTOR VEHICLES AND THEIR ENGINES 
 
 a portion of the mixture will then be utilized because the gases will 
 still be burning as they are forced out of the cylinder. 
 
 The position at which the spark occurs should be governed by 
 the speed of the engine. The low pressure that results from a 
 retarded spark moves the piston at low speed, while the high pressure 
 from an advanced spark drives the piston outward with more force 
 and greater velocity. 
 
 While high compression of the charge improves its quality and 
 results in combustion being more rapid and complete, it has limits, 
 and if carried too far the heat generated by the compression will be 
 sufficient to ignite the mixture. This would have a bad effect on the 
 operation of the engine, for the pressure would then be produced at 
 the wrong point in the stroke, retarding instead of assisting the 
 revolution of the crank shaft. 
 
 As the piston is forced outward by the expanding gases, it has 
 been found necessary to open the exhaust valve before the piston 
 reaches the end of its stroke. Even if this wastes some of the force 
 of the expansion, it is amply compensated for by the freedom afforded 
 the piston in commencing the exhaust stroke. By opening the 
 exhaust valve, before the piston reaches the end of its power stroke, 
 the gases will have an outlet for expansion and begin to rush out of 
 their own accord. This removes the greater part of the burned 
 gases, reducing the amount of work to be done by the piston on its 
 return stroke. Obviously it would be wrong to keep the exhaust 
 valve closed up to the very moment when the piston is about to 
 move inward. When commencing the exhaust stroke, the piston 
 would be confronted for an instant with the force which had just 
 driven it down and until the valve was wide open there would be a 
 considerable loss of power. If the exhaust valve opens too early, 
 there will be a waste of power because the gases exhausted could 
 still have exerted a pressure on the piston. During the next inward 
 stroke, the remaining gases are forced out of the open exhaust valve 
 as the pressure in the cylinder exceeds that in the exhaust manifold. 
 This causes a slight compression of the gases ahead of the piston and 
 when it reaches its inmost position there will be a certain amount of 
 compressed exhaust gases in the clearance space. 
 
 If the exhaust valve is closed at this point, a portion of these 
 gases will still be retained in the cylinder. The best results are 
 obtained, not by closing the exhaust valve at the end of the exhaust 
 stroke, but at a short time after the piston has begun to move out- 
 ward. It would appear that this would result in drawing the exhaust 
 gases back into the cylinder. However, this is governed by two 
 conditions: first, the gases under compression exceed the pressure 
 
TIMING 
 
 17 
 
 H^,,,: 
 
 """X 
 
 Fig. 8 Rock of Piston 
 
 in the exhaust manifold and will continue to flow out due to this 
 difference in pressure; second, the piston while at the top of the 
 stroke moves but very little for 10 to 15 degrees movement of the 
 crank shaft. This does not materially increase the combustion 
 space. 
 
 It will be seen that this is true by referring to Fig. 8. When the 
 crank arms are in a position as shown at A, for a certain number 
 of degrees movement of the crank shaft, the piston will move upward 
 for a certain distance. When the crank arms are at point B, for 
 the same number of degrees movement of the crank shaft, the dis- 
 tance moved by the piston will be less. When the crank arms are 
 at point C, for the same number of degrees there is very little 
 upward movement of the piston. Between certain points it can be 
 seen that there is practically no motion of the piston which is called 
 the "rock of the piston." This is usually the amount that the 
 exhaust valve is left open after top dead center. 
 
 Diagrams showing the exact timing of the valves on several en- 
 gines are shown in Figs. 9 to 12, inclusive. From these diagrams, 
 comparisons may be made as to the time the valves open and close 
 in different designs of engine. 
 
 Referring to the valve timing diagrams, it will be seen that the 
 point at which the inlet valve opens is approximately the same on 
 these four standard engines which are designed to run at different 
 speeds and for different kinds of work. On practically all engines, 
 the inlet valves open approximately 11 degrees after top dead center. 
 
 The point at which an inlet valve closes depends upon a great 
 many conditions, the principal ones being the maximum speed for 
 which the engine is designed and the size and location of the valves. 
 The average point for closing the inlet valve is about 35 degrees 
 
18 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 B. AC. 
 
 Fig. 9 
 
 HOLT 
 
 1. Inlet valve opens 10 after T. D. C. 
 
 2. Inlet valve closes 10 after B. D. C. 
 
 3. Exhaust valve opens 30 before B. D. C. 
 
 4. Exhaust valve closes 5 after T. D. C. 
 
 Fig. 10 
 
 DODGE 
 10 after T. D. C. 
 35 after B. D. C. 
 45 before B. D. C. 
 8 after T. D. C. 
 
 T.0.C. 
 
 A AC. 
 
 Fig. 11 
 
 WHITE 
 
 1. Inlet valve opens 10 after T. D. C. 
 
 2. Inlet valve closes 40 after B. D. C. 
 
 3. Exhaust valve opens 40 before B. D. C. 
 
 4. Exhaust valve closes 8 after T. D. C. 
 
 Fig. 12 
 
 F. W. D. 
 
 15 after T. D. C. 
 45 after B. D. C. 
 45 before B. D. C. 
 10 after T. D. C 
 
 The above diagrams each represent the two revolutions of the 
 crank shaft necessary to complete one cycle. 
 
TIMING 
 
 19 
 
 after bottom dead center. The valve closes later on high speed 
 engines and earlier on slow speed engines. 
 
 The point at which the exhaust valve opens also varies consider- 
 ably and depends upon the same conditions as the closing of the 
 inlet valve. The average point for opening the exhaust valve is 
 45 degrees before bottom dead center. It will be earlier on high 
 speed engines and later on slow speed engines. 
 
 The exhaust valves of the engines represented in the timing 
 diagrams all close at approximately the same point. This is true of 
 practically all types of engines, the average point for closing the 
 exhaust valve being 6 degrees after top dead center. This point is 
 limited by the duration of the rock of the piston and hence cannot 
 vary greatly. 
 
 Fig. 13 shows a valve timing diagram made up from the average 
 points at which the valves open and close on engines of American 
 design. It is a good guide for the approximate timing of the valves 
 of an engine in case the exact timing is not known. However, it 
 must never be used for accurately setting the valves on any engine. 
 
 1. Inlet opens 11 after T. D. C. 
 
 2. Inlet closes 35 after B. D. C. 
 
 3. Exhaust opens 45 before B. D. C. 
 
 4. Exhaust closes 6 after T. D. C. 
 Suction 204 
 Compression 145 
 
 Power 135 
 
 Exhaust 231 
 
 ZAC. 
 
 Fig. 13 Valve Timing of Average 
 Engine 
 
 If for any reason it is necessary to disassemble the engine, the 
 timing gears should be punched so as to indicate where they should 
 mesh when they are again assembled in order to have the proper 
 timing of the valves. If an engine is received with the flywheel 
 unmarked, the first duty for the man in charge of the apparatus is to 
 see that the flywheel is marked correctly in order to have some accur- 
 ate method of checking up valve-timing and valve-clearance at all 
 times. Marking the flywheel is a very simple matter and will elimi- 
 
20 MOTOR VEHICLES AND THEIR ENGINES 
 
 nate endless trouble whenever any repairs are made to the engine 
 where disassembling is necessary. 
 
 In case a crank shaft is offset from the center line of the cylinders, 
 the exhaust valves will usually close at top dead center, as the rock 
 of the piston at this point has been eliminated. The reason for such 
 design is that when the maximum expansion occurs at top dead 
 center, there will not be a direct downward thrust on the crank shaft 
 and connecting rod bearings. 
 
CHAPTER IV 
 
 ENGINE BALANCE AND FIRING ORDER 
 
 The term engine balance includes both power balance and me- 
 chanical balance of the engine. An engine has power balance when 
 the power impulses occur at regular intervals in relation to the revolu- 
 tion of the crank shaft. In many types of engines the power impulses 
 do not occur regularly and there is an uneven distribution of power. 
 The power balance of various types of engines will be discussed in this 
 chapter. An engine has mechanical balance when the moving parts 
 are so arranged as to counterbalance in their operation and thereby 
 reduce vibration. 
 
 The difficulty in constructing reciprocating engines is that the 
 weight of the pistons and connecting rods in moving first one way 
 and then the other, produces great vibration. The crank shaft in 
 bringing these parts to a stop at the end of each stroke, is subjected 
 to violent shocks which in time wear it loose in its bearings. With 
 internal combustion engines, this vibration and the shock on the crank 
 shaft are greatly increased by the intensity with which the pressure 
 is exerted on the piston. 
 
 In a well-designed engine, the manufacturer is very careful to see 
 that every piston and connecting rod is of identically the same weight 
 and that the fly wheel and crank shaft have a perfect running balance. 
 By this practice a considerable amount of the vibration will be 
 eliminated. 
 
 In a one-cylinder engine (Fig. 14) there is but one power impulse 
 during two revolutions of the crank shaft. Therefore there will be 
 an uneven distribution of power. Since there is but one piston and 
 connecting rod which reciprocate with no working parts to counter- 
 
 Fig. 14 One-Cylinder Power Balance Chart 
 21 
 
22 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 balance their weight, the engine will not have mechanical balance. 
 The engine can, however, be balanced to some extent by the use of 
 counterweights attached to the crank shaft and also by the use of a 
 fly wheel so heavy that its momentum produces a comparatively 
 steady movement. Fluctuations in the speed of the engine will 
 cause vibration even under the most favorable conditions which 
 makes the one-cylinder engine undesirable for motor vehicles. 
 
 In two-cylinder engines, the vibration may be reduced by ar- 
 ranging the parts so as to have the pistons move in opposite direc- 
 tions, thus counterbalancing each other. This is the plan of con- 
 struction used in the horizontal double opposed engine (Fig. 15). 
 The cylinders are horizontal and arranged on opposite sides of a 
 two-throw 180 crank shaft. That is, there are two pairs of crank 
 
 Fig. 15 Two-Cylinder Opposed Power Balance Chart 
 
 arms projecting from opposite sides of the shaft so that they are one- 
 half a revolution apart. An engine of this construction has good 
 mechanical balance. 
 
 To fully understand the power balance as shown in the table, 
 the order in which the strokes of a four-cycle engine occur must be 
 recalled. The two outward strokes are suction and power and the two 
 inward strokes compression and exhaust. If piston number one is 
 moving outward on power, then piston number two must be moving 
 out on suction, and for the next half revolution or inward strokes of 
 the pistons, number one piston will be exhausting the gases while 
 number two piston is compressing the charge. During the second 
 revolution of the crank shaft, number two piston will move outward on 
 power while number one moves outward on suction and during the in- 
 ward strokes of the pistons, number two is exhausting the burned gases 
 while number one is compressing a fresh charge. In this way, one 
 power impulse is obtained during each revolution of the crank shaft. 
 This engine has both power balance and mechanical balance. 
 
 Two-cylinder engines are also built with vertical cylinders and 
 are classed according to the construction of their crank shafts. One 
 
ENGINE BALANCE AND FIRING ORDER 
 
 23 
 
 has a 180 crank shaft which is identical with that used in the two- 
 cylinder opposed engine. The other has a 360 crank shaft, which 
 has both pairs of crank arms projecting from the same side of the 
 shaft, so that the crank pins are in line. 
 
 Fig. 16 Two-Cylinder 180 Crank Shaft Power Balance Chart 
 
 In the two-cylinder 180 crank shaft construction (Fig. 16) 
 number one piston is moving outward as number two piston is moving 
 inward; in other words, the pistons move in opposite directions. 
 An engine of this construction has good mechanical balance. 
 
 If piston number one is moving outward on power, piston number 
 two can be moving inward either on compression or exhaust. In 
 table one, the power balance is worked out with piston number two 
 moving inward on compression and it is clearly shown that both 
 power impulses occur during the first revolution while there are no 
 power impulses during the second revolution. In table two the 
 power balance is worked out with piston number two moving inward 
 on exhaust. This arrangement gives a power impulse at the begin- 
 ning of the first revolution and at the end of the second, producing 
 the same result as obtained in table one. In either case there is an 
 irregular production of power which sets up strains in the engine 
 which causes it to run unevenly. This results in poor power balance. 
 
 In the two-cylinder vertical engine with a 360 crank shaft, the 
 pistons move up and down together causing bad mechanical balance 
 (Fig. 17). 
 
 With this arrangement the application of power may be evenly 
 distributed for as number one piston moves outward on power, 
 piston number two could move outward on either power or suction. 
 There would be no advantage in having both cylinders firing at the 
 same time, hence number two piston moves outwards on suction. 
 As shown in the table, during the first revolution, number one piston 
 is on power and exhaust while number two piston is on suction and 
 compression. During the second revolution number one piston is 
 
24 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 CMUMffi 
 
 C 
 
 Fig. 17 Two-Cylinder 360 Crank Shaft Power Balance Chart 
 
 on suction and compression while number two piston is on power and 
 exhaust. With this, arrangement there is a power impulse at the 
 beginning of each revolution of the crank shaft and the engine has 
 power balance. 
 
 The defects of two-cylinder vertical engines with either design 
 of crank shaft outweigh any possible advantage of that construction. 
 The horizontal double opposed type with evenly occurring power 
 impulses, mechanical balance, and simplicity of construction is 
 frequently used on small trucks. 
 
 With a four-cylinder engine a 180 crank shaft is always used 
 (Fig. 18). The crank arms for numbers one and four cylinders pro- 
 ject in the same direction and the crank arms for numbers two and 
 three cylinders project from the opposite side of the crank shaft. 
 This arrangement is used in preference to having the cranks projecting 
 alternately, that is, one and three to one side and two and four to the 
 other, because greater vibration and strain on the crank shaft would 
 result with this construction. The form of crank shaft commonly 
 used does not permit a firing order of 1-2-3-4, but gives firing orders 
 in which numbers one and four must fire alternately. The succession 
 in which power strokes occur is called the firing order. 
 
 In the four-cylinder engine numbers one and four pistons are 
 always moving in the opposite direction from numbers two and three. 
 If equal in weight they will balance each other and an engine of this 
 type is said to have good mechanical balance. 
 
 As number one piston is moving outward on power, number four 
 must move outward on suction; number two piston can be moving 
 inward on exhaust or compression and number three will be moving 
 inward on compression or exhaust. Table one shows the power 
 balance with number two piston on exhaust and number three on 
 compression. Table two shows the power balance resulting from 
 number two piston moving inward on compression and number. 
 
ENGINE BALANCE AND FIRING ORDER 
 
 25 
 
 three on exhaust. With either arrangement the power impulses 
 are evenly distributed, that is, they are 180 apart. 
 
 MHM7WN 3 
 
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 C /> 
 
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 /> 
 
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 MWZtflM /> s 
 
 MWtWW c 
 
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 Fig. 18 Four-Cylinder Power Balance Chart 
 
 Each arrangement gives a different firing order. With the 
 arrangement shown in table one the firing orders is 1-3-4-2. With 
 the arrangement shown in table two the firing order is 1-2-4-3. 
 Following are the firing orders of four-cylinder engines in several 
 motor vehicles. It will be noted that the firing order 1-3-4-2 is 
 the most common. 
 
 Four-Wheel Artillery Tractor 1-3-4-2 
 
 F. W. D. 1-3-4-2 
 
 Nash .... 
 White. . . . 
 Dodge 
 
 Standardized "B" 
 Holt .... 
 Packard . 
 Ford . 
 
 1-3-4-2 
 1-3-4-2 
 1-3-4-2 
 1-3-4-2 
 1-2-4-3 
 1-2-4-3 
 1-2-4-3 
 
 Three-cylinder engines are built with 120 crank shafts, that is, 
 the crank arms are J^ of a revolution apart instead of J^ revolution 
 
26 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 as in the 180 crank shafts. With this arrangement as shown in 
 Fig. 19, number one piston moves outward on power, number two 
 piston moves inward finishing its exhaust stroke and starts outward 
 
 CYLINDER 
 
 f 
 
 ^ 
 
 3 
 
 l' T 
 REVOLUTION 
 
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 Fig. 19 Three-Cylinder Power Balance Chart 
 
 on suction, number three piston moves outward finishing its suction 
 stroke and starts inward on compression. As number one piston 
 moves inward on exhaust, number two piston finishes its suction 
 stroke and starts inward OR compression, number three piston finishes 
 its compression stroke and moves outward on power. As number 
 one piston moves outward on suction, number two piston finishes its 
 compression stroke and starts outward on power, number three 
 piston finishes its power stroke and moves inward on exhaust. As 
 number one piston moves inward on compression, number two .piston 
 finishes its power stroke and starts inward on exhaust, number three 
 piston finishes the exhaust stroke and starts outward on suction. 
 From the foregoing it can readily be seen that the power impulses 
 will occur every 240 movement of the crank shaft. An engine of 
 this type has power balance. 
 
 Six-cylinder engines have crank shafts of a similar construction 
 to the three-cylinder; having numbers one and six, two and five, and 
 three and four pistons operating together. With this construction 
 there will be six power impulses during two revolutions which gives 
 very good engine balance. 
 
 In Fig. 20 it will be seen that as numbers one and six pistons are 
 starting outward, numbers two and five are completing their outward 
 strokes, and numbers three and four are on their inward strokes. 
 With this arrangement it is possible to obtain four different combina- 
 tions as shown in tables one, two, three, and four. It is also possible 
 to have numbers three and four pistons finishing their outward strokes 
 as numbers one and six start outward and two and five complete their 
 inward strokes. Combinations as shown in tables five, six, seven, 
 and eight will result. With any of these combinations it can be 
 
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 27 
 
28 MOTOR VEHICLES AND THEIR ENGINES 
 
 readily seen that the power impulses are evenly distributed and are 
 120 apart, the only difference being the order in which the cylinders 
 fire. 
 
 Table 1. Firing Order 1-3-5-6-4-2 
 Table 2. Firing Order 1-4-5-6-3-^- 
 Table 3. Firing Order 1-3-2-6-4-5 
 w Table 4. Firing Order 1-4-2-6-3-5 
 Table 5. Firing Order 1-2-4-6-5-3 
 Table 6. Firing Order 1-5-4-6-2-3 
 Table 7. Firing Order 1-2-3-6-5-4- 
 V Table 8. Firing Order 1-5-3-6-2-4 
 
 Although there are eight possible firing orders there are only 
 four which are commonly used. The following are seldom used: 
 l_2_3_6-5-4, 1-5-4-6-2-3, 1-3-2-6-4-5, and 1-4-5-6-3-2. With 
 any of these firing orders the three-cylinder at one end of the crank 
 shaft fire and then the three at the other end fire, setting up vibration 
 due to the concentration of the power impulses. For this reason, 
 six-cylinder engines are commonly built to fire so that the impulses 
 are. evenly distributed along the crank shaft. 
 
 Eight-cylinder engines for motor vehicles are usually constructed 
 by arranging two four-cylinder engines to operate from a single four- 
 throw 180 crank shaft of the same form used in the four-cylinder 
 engine. The cylinders are set so that their center lines form an angle 
 90 and for this reason such engines are called "V Type." The con- 
 necting rods of the cylinders on the right operate on the same crank 
 pins as the corresponding connecting rods for the cylinders on the 
 left. It must be borne in mind that these connecting rods operate 
 independently of each other. Therefore the operations of the 
 cylinders on the right are always 90 different from the cylinders on 
 the left, that is, when number one piston on the right is at top dead 
 center, number one piston on the left will have completed one-half 
 its stroke (Fig. 21). 
 
 The table showing the power balance is based on the arrangement 
 used in the Cadillac "8." As number one piston on the left is 
 moving outward on power, number four piston on the left is mov- 
 ing outward on suction, number two piston on the left moving in- 
 ward on exhaust, and number three piston on the left moving inward 
 on compression. The movements on the right hand side will be half 
 completed, therefore, number one piston will be completing suction, 
 number four piston will be completing power, number two piston 
 will be completing compression, and number three piston will be 
 completing exhaust. Working out the operations for each 90 move- 
 ment of the crank shaft will give the results shown in the table. 
 
MGHT 
 
 Lcrr 
 
 RIGHT 
 
 CYLINDER 
 
 I 
 
 ^ 
 
 3 
 
 4 
 
 i 
 
 2 
 
 J 
 
 4 
 
 1" 
 
 REVOLUTION 
 
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 REVOLUTION 
 
 3 
 
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 r 
 
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 Fig. 21 Eight-Cylinder Power Balance Chart 
 
 29 
 
30 MOTOR VEHICLES AND THEIR ENGINES 
 
 There is a power impulse for every 90 movement of the crank shaft, 
 giving a firing order as follows : lL-2R-3L-lR-4Lr-3R-2L-4R. The 
 power impulses are regular and very frequent in an engine of this 
 type insuring very good engine balance. 
 
 The twelve-cylinder engine is also a "V Type" and consists of 
 two sets of six cylinders arranged similarly to the "V Type" eight- 
 cylinder engine except that the angle between the center lines of the 
 cylinders is 60. A regular six-throw 120 crank shaft is used, two 
 connecting rods being attached to each crank pin (Fig. 22). The 
 table shown is based on the arrangement used in the Packard Twin 
 Six; starting with number one piston on the right at top dead center 
 and moving the engine 60 or one-third of a complete stroke and 
 showing the changes that take place. This table shows that a fresh 
 power impulse is given the crank shaft for each 60 movement which 
 gives unusually good engine balance. The firing order of this engiue 
 is lR-6L-4R-3L-2R-5L-6R-lLr-3R-4Lr-5R-2L. 
 
 There are many possible firing orders for eight and twelve- 
 cylinder "V Type" engines other than the ones given. The firing 
 order depends upon the arrangement of the cams on the cam shaft 
 and any combination will give equally good power balance. 
 
 The one-cylinder engine having but one power impulse for two 
 revolutions of the crank shaft does not run smoothly or quietly due 
 to the size of the cylinder and time between impulses. This fact led 
 to the adoption of the two, four, and six-cylinder engines and quite 
 recently, the eight and twelve-cylinder engines have come into use. 
 As the number of cylinders is increased, the power impulses increase 
 in frequency. The average power is greater and above^four cylinders 
 there is no period during which some cylinder is not delivering power. 
 This means that in a six, eight, or twelve-cylinder engine there is 
 no time at which the fly wheel must supply all the power required 
 to maintain the engine speed. 
 
 The multi-cylinder engine, therefore, furnishes a practically con- 
 tinuous flow of power with little vibration. The increase in the 
 number of cylinders permits reduction in the size of each cylinder and 
 this combined with the steady operation of the engine makes the 
 modern automobile engine a very quiet, smooth-running, power unit. 
 
 As shown in valve timing, the average length of the power impulse 
 is 145 and from Fig. 23 it can be seen that as the number of cylinders 
 is increased the power impulses extend over a greater range. For 
 engines having more than four cylinders the power impulses are con- 
 tinuous and overlap, the length of overlap increasing with the 
 number of cylinders. 
 
CrUNDtt 
 
 1 
 
 
 
 J 
 
 4 
 
 S 
 
 6 
 
 / 
 
 2. 
 
 J 
 
 4 
 
 5 
 
 e 
 
 /ST 
 
 XEWLI/T/0/V 
 
 P 
 
 3 
 
 
 
 C 
 
 p 
 
 S 
 
 
 
 P 
 
 c 
 
 
 
 3 
 
 c 
 
 P 
 
 C 
 
 
 
 C 
 
 
 
 S 
 
 S 
 
 P 
 
 c 
 
 
 
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 C 
 
 S 
 
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 p 
 
 
 
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 S 
 
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 P 
 
 s 
 
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 S 
 
 c 
 
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 2* 
 xrruvr/w 
 
 S 
 
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 J 
 
 
 
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 y* 
 
 
 
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 Fig. 22 Twelve-Cylinder Power Balance Chart 
 
 31 
 
s0f, 
 
 Fig. 23 Power Overlap Charts 
 
 32 
 
ENGINE BALANCE AND FIRING ORDER 33 
 
 Engines of more than four cylinders will have several possible 
 firing orders. The exact firing order of the engine will depend upon 
 the arrangement of the cams on the cam shaft. Therefore, the firing 
 order can be determined by checking a certain operation of the valves 
 such as the opening of the inlet or the opening of the exhaust, or by 
 checking the compression. The firing order thus obtained will cor- 
 respond to that of the power balance chart worked out for any 
 particular engine. For example, take the power balance chart of a 
 four-cylinder engine, as shown in Fig. 18. If the order in which the 
 suction strokes, the exhaust strokes, or the compression strokes 
 occur is taken the same firing order results. 
 
CHAPTER V 
 
 COOLING SYSTEMS 
 
 As previously shown the internal combustion engine is a machine 
 for transforming heat into mechanical energy. As the heat increases 
 a greater expansion of the gases results and more power is developed. 
 However, there are certain limitations to the degree of heat that can 
 be maintained in the engine and if the temperature were allowed to 
 rise above a certain limit the degree attained would cause mechanical 
 troubles. The intense heat would cause the cylinder to be scored, 
 the valves to warp, and the lubricant to be burned up causing the 
 piston and bearings to bind. It would also cause the incoming 
 charge to become expanded and thereby cause a rarefied mixture. 
 In addition to these things the spark plugs would crack and the 
 temper would be taken out of the valve springs. From this it can 
 readily be seen that some method of cooling the engine must be 
 adopted. 
 
 As shown in the second chapter a considerable amount of heat is 
 lost in cooling but this cannot be materially reduced for the tempera- 
 ture of combustion far exceeds the temperature at which the engine 
 ^^^^^^^^ m could operate. The duty of the 
 cooling system is to keep the en- 
 gine from attaining a tempera- 
 ture which would stop its opera- 
 tion and is not to keep the 
 engine cool, for in so doing it 
 would increase the cooling losses 
 and lower the efficiency. It is 
 a misinterpreted idea in many 
 cases that the cooling system is 
 to keep the engine very cool. 
 It has been found in testing en- 
 gines that they operate best 
 when the water, leaving the 
 water jacket, is over 160 but 
 well under the boiling point. 
 There are two general systems 
 of engine cooling in common use. First, by air which cools the 
 engine by direct radiation. Second, by water which cools the 
 engine and is subsequently cooled by air. 
 
 34 
 
 Fig. 24 Air-Cooled Cylinder 
 
COOLING SYSTEMS 35 
 
 There are certain things which must be taken into consideration 
 when cooling an engine by air. First, the cooling depends upon the 
 amount of surface presented to the air. Therefore in motor cycles 
 the effective outer surfaces of the cylinders are increased by the 
 addition of fins or flanges cast on them and presenting a greater 
 surface for cooling as shown in Fig. 24. Second, the cooling depends 
 upon the amount of air passing over the cooling surface. As the 
 amount of air passing over this surface is increased the cooling will 
 be proportionately increased. On motor-cycles where there is no 
 fan to keep the air in circulation it is essential that the motor-cycle 
 be kept in motion as long as the engine is running, otherwise over- 
 heating of the engine will result. Third, the cooling depends upon 
 the temperature of the air passing over the cooling surface. This 
 results in the engine being kept cooler in cold weather than in warm 
 weather. The rear cylinder of the engine will not be cooled the 
 same amount as the front cylinder. This is because the air becomes 
 heated after passing the front cylinder, therefore, it cannot have an 
 equal cooling effect on the rear cylinder. 
 
 With twin-cylinder motor-cycles difficulty will often be experi- 
 enced with the rear cylinder due to this unequal cooling. There is 
 more probability of carbon being formed in this cylinder which will 
 lead to ignition troubles and engine troubles in general. In case a 
 miss in one cylinder is noted it is best to look first for the trouble in 
 the rear cylinder. 
 
 Because of its simplicity and light weight the air-cooled engine 
 is particularly suitable for motor-cycle engines. The small size of 
 the engine together with its exposed cylinders insures proper cooling 
 and makes this type of cooling ideal for the motor-cycle. 
 
 When water is employed in cooling it must circulate through 
 jackets around the combustion chamber and be kept in motion 
 either by heat or forced circulation. The water is heated by the 
 cylinders and then passes to the radiator where it is cooled by air 
 being drawn through the radiator by a fan. There are three general 
 systems of water cooling in use: the Thermo Syphon, the Force 
 System, and Thermostatic Controlled. 
 
 The THERMO-SYPHON COOLING SYSTEM, shown in Fig. 
 25, is a typical construction. The water enters the cylinder jacket 
 at "A" and upon becoming heated by the combustion within the 
 engine, rises and enters the pipe "B" and passes to the radiator 
 "C" where it is brought into contact with a large cooling surface 
 "D." When water is cooled it becomes heavier and therefore sinks 
 to the bottom of the cooling system. As the water is heated in the 
 cylinder jacket and rises to the top it must be replaced by cool 
 
36 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 water and therefore the water from the lower pipe "A" enters the 
 water jacket. 
 
 Fig. 25 Thermo-Syphon Cooling System 
 
 It can readily be seen that this circulation is proportional to the 
 heat and as the heat increases the circulation becomes faster. This 
 is an ideal condition for keeping the engine at the proper tempera- 
 ture. Since there could be no circulation when the engine is cold the 
 possibility of cold water continuously passing through the water 
 jacket is eliminated, a condition which would keep the engine at a 
 temperature less than should be maintained for proper efficiency. 
 As the circulation depends solely upon the heat it is not positive and 
 a slight amount of foreign matter obstructing the passages would 
 interfere with the circulation. Another objection to the Thermo- 
 Syphon system is that in case enough water evaporates, the water 
 level will fall below the pipe entering the radiator, the circulation 
 will stop, and the engine overheat. To prevent this it is essential 
 that the radiator be kept completely filled. In extremely cold 
 weather freezing of the lower pipe may occur after the car has been 
 on the road for a short time. This is due to the circulation being 
 very sluggish in cold weather and the last point reached by the water 
 warmed in the cylinders is the lower pipe. As soon as freezing takes 
 place circulation stops and overheating results. The water in the 
 jackets is heated and rises to the top but cannot pass down through 
 
COOLING SYSTEMS 
 
 37 
 
 the radiator to be cooled. This trouble arises from not running the 
 engine sufficiently to warm up all the water in the cooling system 
 before starting out. 
 
 Radiator Cap 
 
 Filler Neck 
 
 Top Tank 
 Splash Plate 
 
 Overflow Tube 
 
 Radiator Tubes 
 Rad Inlet Conn 
 
 Cyl. Outlet Hose 
 Hose Clip 
 
 Cyl.nder Head 
 Cylinder Casting 
 Cylinder Inlet Connecuon 
 
 Lower Hose-. 
 
 Lower Hose Clip 
 
 Rad Outlet Conn V Quilei Cona Pipe 
 
 Dram Cock Fan Assb. 
 
 Lower Tank 
 
 Fig. 26 Ford Cooling System 
 
 Fig. 26 shows a typical Thermo-Syphon system. The arrows 
 indicate the course of the water through the water passages. This 
 is one of the few American motor cars that retains the Thermo- 
 Syphon cooling system. 
 
 THE FORCE COOLING SYSTEM shown in Fig. 27 is a typical 
 construction. In this system water leaves the cylinder jackets 
 through the pipe from the cylinder head and enters the radiator 
 through the radiator inlet pipe. The water passes through the radia- 
 tor where it is cooled by the air drawn through the radiator. From 
 the radiator the water passes through the radiator outlet pipe and 
 through the pump to the cylinder jackets. 
 
 While the engine is in operation the pump, being geared to it, 
 causes the water to circulate so that slight obstructions will not clog 
 up the system. In case the radiator is not completely filled the 
 pump will still circulate the water causing it to overflow from the 
 radiator inlet pipe. The only part of the system in which there will 
 be no water will be the upper section of the radiator. The level in 
 
38 MOTOR VEHICLES AND THEIR ENGINES 
 
 the radiator will depend upon the quantity of water in the system. 
 If there is too little water the level will be so low that the efficiency 
 of the radiator in cooling the water will be reduced to such an extent 
 that overheating will often result. Since the water is always in 
 circulation when the engine is running there is little possibility of 
 freezing. 
 
 WAT'SR. HOSE 
 
 Fig. 2? Dodge Cooling System, 
 
 As the pump is positively geared to the engine the circulation will 
 be proportional to its speed and for a given speed the amount of 
 cooling will vary according to the temperature of the air. On a cold 
 day as much water is passed through the water jackets as on a warm 
 day, but the temperature of the water is considerably lower and the 
 engine is kept too cool resulting in considerable loss of efficiency. 
 This is particularly noticeable when starting an engine in cold 
 weather for it causes misfiring due to the cold water being circulated 
 through the water jackets. To prevent excessive cooling of the 
 engine, which reduces its efficiency, the fan may be disconnected 
 thereby reducing the cooling power of the radiator. A more satis- 
 factory method is to cover part of the radiator's cooling surface. The 
 best results are obtained when an adjustable device or shutter is used. 
 
 Natural circulation is of practically no assistance in the Force 
 Cooling System; it depends entirely upon the pump for circulation. 
 This permits the use of smaller water jackets and piping and as it is 
 the practice to construct the engine as light as possible, these are 
 made as small as practicable. In case any difficulties arise which 
 stop the operation of the pump, natural circulation cannot be de- 
 
COOLING SYSTEMS 
 
 pended upon to sufficiently cool the engine as it does in the Thermo- 
 Syphon System, where large water jackets and pipes are used. 
 
 THE THERMOSTATIC CONTROLLED COOLING SYSTEM. 
 A Thermostatic device is introduced in this system in order to 
 overcome the difficulties which arise in the Forced Cooling System 
 when cooled water is circulated through the water jackets. The 
 temperature of the liquid circulated by the pump is under Ther- 
 mostatic control. The purpose of this is to permit water circulating 
 through the water jackets of the cylinders and carburetor intake 
 manifold to warm up to the temperature at which the engine operates 
 best, very soon after the engine is started and to prevent the tem- 
 perature dropping below this point while the engine is running. To 
 explain the operation of the Thermostatic Controlled Cooling System, 
 those used on the Cadillac and Packard will be described. 
 
 On the Cadillac the circulation through each cylinder block is 
 independent of that through the other, two separate pumps being 
 provided. Two centrifugal pumps are located at the front end of 
 the crank case, on each side, and are driven from the crank shaft 
 through helical gears. A housing containing a Sylphon Thermostat 
 
 and a valve controlled by the 
 
 Thermostat are located on the 
 cover of each water pump. The 
 Thermostat "A" (Fig. 28) is 
 accordion shaped. It contains 
 a liquid which is converted 
 into gas when heated. The 
 resulting pressure elongates the 
 Thermostat, forcing the valve 
 "B" from its seat. A drop in 
 temperature changes the gas to 
 a liquid, reducing the pressure 
 in the Thermostat and allowing 
 it to contract, bringing the valve 
 "B" back to its seat. 
 
 When the temperature of 
 the water in the water jackets 
 on the cylinders and intake 
 manifold is below a predeter- 
 mined point the valve "B" is 
 held tightly closed by the Ther- 
 mostat which prevents water being drawn from the radiator. When 
 the temperature of the water tends to rise above the predetermined 
 point the valve "B" is forced open by the Thermostat, permitting 
 
 Fig. 28 Thermostat Regulator 
 on Cadillac 
 
40 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 the water pump "P" to draw water from the radiator. Provision 
 is made for forcing the valves operated by the Thermostat from 
 their seats. This is necessary to drain the radiator. 
 
 S F K P H 
 
 Fig. 29 Cadillac Cooling System 
 
 When the engine is first started and is cold the valves operated 
 by the Thermostats are held tightly on their seats. This prevents 
 the water pumps from drawing water from the radiator. Under 
 these conditions the water is circulated as follows: From the water 
 pump "P," (Fig. 28 and 29) through the hose "F" to the water 
 jackets on the cylinders, from the water jackets on the cylinders 
 some of the water returns to the pump "P" through the hose "C" 
 and the Thermostat housing "E," and the remainder is carried by a 
 small pipe "N" to the water jacket around the intake manifold and 
 from the intake manifold to the pump "P" through the pipe "D" 
 and the Thermostat housing "E." 
 
 After the engine has become warm and the valves between the 
 pumps and radiator have been forced from their seats by the Thermo- 
 stats the circulation is as follows: Water is drawn from the radiator 
 through the hose "G" and forced to the water jackets on the cylinders 
 through the hose "F," from the water jackets the water returns to 
 
COOLING SYSTEMS 41 
 
 the radiator through the hose "M" connecting the cylinder block 
 and radiator. Water is still forced to the water jackets on the intake 
 manifold through the small pipe "N" and from the intake manifold 
 to the pump "P" through the pipe "D" and the Thermostat housing 
 "E." Some of the water still flows back to the pump through the 
 hose "C" and the Thermostat housing "E." 
 
 As the temperature of the water returning to the pump through 
 the pipe "D," hose "C," and Thermostat housing "E" rises or falls, 
 the Thermostat expands or contracts, opening or closing the valve, 
 thereby admitting a larger or smaller amount of cooled water from 
 the radiator. A condenser, the purpose of which is to prevent the 
 loss of the cooling medium by evaporation particularly when an 
 alcohol solution is used, is attached to the right-hand side of the 
 frame just beneath the front floor boards. A pipe "S" (Fig. 29) 
 connected to the overflow tube of the radiator leads to the 
 condenser. 
 
 The condenser acts in this manner. The vapor rising from the 
 heated liquid in the radiator passes through the overflow tube to the 
 condenser. As it passes into the liquid in the condenser the vapor is 
 condensed. When the engine has stopped the cooling of the radiator 
 and its contents results in the contraction and condensation of the 
 vapor left in the upper part of the radiator. The partial vacuum 
 thus caused allows the atmospheric pressure in the condenser to 
 force condensed vapor back into the radiator. The proper operation 
 of the condenser requires an air-tight joint at the radiator filler cap. 
 To make it possible to screw down and tighten the cap without injury 
 to the rubber gasket, two metal washers are interposed between the 
 head of the cap and the gasket. It is important that nothing be 
 installed on the radiator filler cap which might cause a leak at the 
 cap or which might make necessary the elimination of the steel 
 washers or the cutting of a hole through the rubber gasket. 
 
 In the Thermostatic Controlled Cooling System as used on the 
 Packard (Fig. 30) there are two paths through which the water may 
 circulate. The water is forced by the pump through the cylinder 
 water inlet manifold, thence through the water jackets, and out 
 through the pipe at the top of the cylinder block. From here it 
 has two paths through which it may return to the pump. It may 
 pass through the bypass manifold directly to the pump or through 
 the radiator returning to the pump by the lower pipe. 
 
 The path which the water takes is regulated by the Thermostat 
 which operates a valve in the pipe leading to the radiator. The 
 operation of the Thermostat is identical with that on the Cadillac, 
 the only difference being its location. 
 
COOLING SYSTEMS 
 
 43 
 
 The great advantage of a Thermostatic Controlled Cooling 
 System is its efficient operation in cold weather in preventing cold 
 water being circulated through the water jackets and cooling the 
 engine below an efficient running temperature. There is little possi- 
 bility of the radiator freezing because the length of time required 
 to heat the small quantity of water in the jackets is very short. This 
 results in sending a quantity of heated water almost immediately 
 into the radiator. The Thermostat will gradually permit the 
 heating of the water in the entire system always maintaining the 
 water in the jackets at approximately the same temperature. 
 
 Fig. 31 Phantom View of Centrifugal Pump 
 
 PUMPS. There are several constructions of pumps used for 
 water circulation, the most common of these being the centrifugal 
 and gear types. omer 
 
 In the centrifugal 
 type (Fig. 31) the water 
 enters at the center of 
 the pump and is caught 
 by the rotating blades 
 and thrown to the out- 
 side by centrifugal force. .' 
 The casing limits its out- \ 
 ward motion, but allows \ 
 the blades to impel it in 
 circular motion, the pres- 
 sure against the casing 
 increasing until the out- 
 let pipe is reached. Here 
 the resistance to its out- Fig. 32 Gear Pump 
 
44 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 ward motion is removed and the stored-up energy forces the water 
 through the discharge pipe to the water jackets. 
 
 In the gear pump (Fig. 32) the water takes the path indicated by 
 the arrows. The gear teeth pick up the water and carry it around in 
 the spaces between the teeth, the pump casing making a tight joint. 
 The teeth of the two gears meshing at the center prevent any water 
 being carried down between them, hence a steady stream of water 
 will be forced out the discharge pipe. 
 
 RADIATORS. The purpose of a radiator is to present a large 
 amount of cooling surface to the air In order to accomplish this 
 
 Fig. 33 Tubular Radiator Sections 
 
 there are many constructions varying in design in accordance with 
 the manufacturer's ideas. All radiators may be classed as either 
 
 tubular or cellular. The so- 
 called honeycomb radiator may 
 , v ,, ?: be either tubular or cellular 
 (though generally the latter) and 
 <"- gets its name from its appearance. 
 The tubular radiator is one 
 in which the upper and lower 
 tanks are connected by a series 
 of tubes through which the water 
 must pass. The tubes may be 
 arranged vertically or in a zig-zag 
 fashion which materially in- 
 creases the cooling surface. 
 Fig. Z^Tubular Radiator In FJg 33 ^.^ ^^ 
 
 constructions are shown, that in the lower left-hand corner being 
 a honeycomb type. 
 
COOLING SYSTEMS 
 
 45 
 
 In Fig. 34 a straight vertical tube type of radiator is shown and 
 is typical of the construction used for trucks. To increase the 
 radiating surface fins are employed on the tubes. 
 
 The cellular radiator (Fig. 35) is composed of a large number of 
 individual air cells which are surrounded by water and the course of 
 the water through the radiator is not confined to any definite vertical 
 
 Fig. 35 Cellular Radiator Sections 
 
 or angular course. Because of its appearance the cellular type is 
 usually known as a "honeycomb" radiator. 
 
 Since the water passes through all of the tubes of a tubular 
 radiator, if one tube becomes clogged the cooling effect of the entire 
 tube is lost. In the cellular construction the clogging of any passage 
 results in a loss of but a very small part of the total cooling surface as 
 compared to the loss of a whole tube in the tubular type. For this 
 reason the cellular or commonly called " honeycomb " radiator is 
 more efficient but is more expensive to construct. 
 
 FANS. In order to cool the water sufficiently a fan driven by a 
 belt or chain from the engine is placed back of the radiator so that 
 in its operation it will draw air through the radiator. In many con- 
 structions of radiators the mere motion of the car could not force 
 sufficient air through the radiator but, by placing a fan behind it, 
 sufficient air will be drawn through for cooling purposes. It is a 
 misinterpreted idea that a fan is used to cool the engine, its function 
 being solely to assist in cooling the water in the radiator. In some 
 constructions it may assist slightly in cooling the engine. 
 
 The fan bracket is so constructed that the tension on the belt is 
 adjustable. At all times the belt should be under sufficient tension 
 to prevent slippage. Fans require but little power and usually run 
 at a speed two or three times as great as that of the crank shaft and 
 are mounted on ball-bearings to reduce friction as much as possible. 
 
46 MOTOR VEHICLES AND THEIR ENGINES 
 
 ANTI-FREEZING MIXTURES. In order to prevent the water 
 in the cooling system from freezing in extremely cold weather when 
 the engine is not in operation there is provided at the bottom of the 
 radiator, at the lowest points in the water jackets, and at the pump, 
 drain cocks through which the water can be removed. Water in 
 freezing expands and if confined in the cooling system would cause 
 the water jackets, pipes, or radiator to break. As an assurance in 
 freezing weather that the cooling system of a car has been drained 
 and as an indication that it must be filled before operating the car, 
 a card marked DRAINED in black letters about three inches high 
 should be conspicuously displayed. This is usually done by sus- 
 pending the card across the radiator from the filler cap. As it is 
 often found undesirable to remove the water from the cooling system 
 fluids with very low freezing points are often employed. These 
 are called anti-freezing mixtures. The ideal requirements for an 
 anti-freezing mixture are as follows: 
 
 1. It should cause no harmful effect to any part of the cooling 
 system with which it comes in contact. 
 
 2. It should be easily dissolved or combined with water. 
 
 3. It should be reasonably cheap. 
 
 4. It should not waste by vaporization, that is, its boiling point 
 should be as high as that of water. 
 
 5. It should not deposit any foreign matter in the jackets or 
 pipes. 
 
 The materials which are most commonly used are alcohol, mix- 
 tures of alcohol and glycerine, kerosene oil, and calcium chloride. 
 The most common of these are solutions of alcohol and water in the 
 following proportions: 
 
 WATER 
 
 80% 
 70% 
 60% 
 
 The above table is based on the use of denatured alcohol but if 
 wood alcohol is used, slightly lower temperatures can be reached with 
 the same proportions of alcohol and water. In these solutions, the 
 alcohol being more volatile than water, will evaporate making it 
 necessary to continually add more alcohol. The use of this solution 
 is very unsatisfactory because the only method of being positive that 
 the alcohol is present is by measuring the specific gravity of the 
 solution. 
 
 There are certain solutions of glycerine, alcohol, and water which 
 are more stable because the glycerine holds the alcohol in solution. 
 
 ALCOHOL 
 
 SPEC. GRAY. 
 
 FREEZING POINT 
 
 20% 
 
 .975 
 
 14 
 
 30% 
 
 .964 
 
 - 1 
 
 40% 
 
 .954 
 
 -20 
 
COOLING SYSTEMS 47 
 
 The following table shows the percentage of each and the freezing 
 points of the solutions : 
 
 ALCOHOL GLYCERINE WATER FREEZING POINT 
 
 12% 12% 76% 10 
 
 15% 15% 70% - 5 
 
 17% 17% 66% -15 
 
 These solutions are very satisfactory as they are dependable, but 
 it often happens that the glycerine will gum up the radiator and stop 
 the circulation of the water through some section thus reducing the 
 cooling. 
 
 Calcium Chloride or alkali solutions are often recommended, 
 their freezing points being very low. The great objection to the use 
 of these is that they form a scale in the water jackets and radiator 
 which in time interferes with the circulation. When Calcium 
 Chloride is used it must be chemically pure as the commercial chloride 
 of lime sets up electrolytic action. The following solutions are used : 
 
 CALCIUM CHLORIDE WATER SPEC. GRAY. FREEZING POINT 
 
 20% 80% 1.119 
 
 22% 78% 1.200 - 9 
 
 24% 76% 1.219 -18 
 
 Kerosene has the advantage of a high boiling point so that it does 
 not evaporate readily but it has the disadvantage of not making a 
 good mixture with water and will not absorb heat as rapidly. Kero- 
 sene should not be used where there is any rubber in the system for 
 it attacks the rubber hose and gaskets and causes them to deteriorate 
 rapidly. 
 
 Whenever an anti-freezing mixture is used it is essential that it 
 be removed from the cooling system as soon as the weather moderates. 
 If this is not done the engine will overheat. 
 
 If the water in the cooling system should freeze through neglect 
 of ordinary precaution do not attempt to thaw it by starting the 
 engine, but thaw by putting the car in a warm place or by draining 
 the system and then adding hot water. It has been stated that 
 solutions of Calcium Chloride deposit a scale in the water jackets 
 and radiator and therefore should not be used. There are many 
 places in which the drinking water contains a considerable amount 
 of lime which will cause the same result. To prevent scale it is 
 always best to fill the cooling system with rain water. 
 
CHAPTER VI 
 
 FUEL FEED SYSTEMS 
 
 Provision must be made on motor-propelled vehicles for storing 
 gasoline and supplying it to the carburetor. There are three systems 
 in common use for supplying liquid fuel to the carburetor from the 
 storage tank, the Gravity System, the Force Feed System, and the 
 Vacuum System. 
 
 GRAVITY SYSTEM. In the gravity fuel feed system the storage 
 tank must be placed above the carburetor so that the gasoline will 
 flow from it to the carburetor by gravity. A typical system of this 
 kind is shown in Fig. 36. It is very simple and has but a few parts. 
 The storage tank has a filler cap in the top with an air vent through 
 it and a gasoline outlet at the bottom which leads to a sediment well 
 
 r.ASOLINE TAKK COVCR 
 SHUT OFF. VALVE. 
 
 AUXILIARY AIR 
 ADJUSTMENT 
 
 THROTTLE LEVER 
 .BELL-CRANK 
 
 OPERATING 
 A ;o- IN TAKE VALVE 
 
 ruOAT-CHAMBER CAP. 
 LOW SPEED 
 
 ADJUSTMENT 
 
 GASOLINE MD OPE 
 
 Fig. 36 Gravity Fuel Feed System 
 
 and drain plug. The feed pipe to the carburetor takes off from the 
 top of this well and is as straight and short as possible. A stop cock 
 for shutting off the supply of gasoline from the tank is provided in 
 the outlet underneath the tank or a needle valve is used inside the 
 tank which can be controlled from the top. Automatic gauges are 
 sometimes provided on the storage tank to show the amount of fuel 
 in the tank. 
 
 Because of the simplicity of construction they are not apt to get 
 out of order. On the other hand they have several drawbacks. 
 The pressure varies with the relative height of tank and carburetor 
 and since this is usually not very great the resulting pressure will be 
 low. When ascending or descending grades the relative height of 
 tank and carburetor will change which correspondingly varies the 
 pressure. Since the tank must be above the carburetor for this 
 
 48 
 
FUEL FEED SYSTEMS 49 
 
 system to be operative its location is very limited and it generally 
 has to be placed at some point not readily accessible. This fact also 
 makes it hard to shut off the supply of gasoline and in case fire occurs 
 at the carburetor. The result may be serious if the supply of gasoline 
 is not immediately shut off. 
 
 PRESSURE SYSTEM. When the pressure fuel feed system is 
 employed the storage tank may be placed at the most convenient 
 and accessible point on the machine usually at the extreme rear of 
 the chassis. When installed in this manner it is necessary to force 
 gasoline out of the tank by air pressure since the gasoline tank is 
 lower than the carburetor. Pressure is maintained by a small air 
 pump automatically controlled and driven by the engine. An 
 auxiliary hand pump gives enough initial pressure to force gasoline 
 to the carburetor for starting. A safety valve in the pressure system 
 prevents the pressure from rising beyond a safe limit. The tank must 
 be airtight and the filler cap screwed tight with a wrench to hold the 
 
 Fig. 37 Pressure Fuel Feed System 
 
 pressure. A gasoline gauge is provided to show how much gasoline 
 the tank contains. Two pipes run from the tank, one being the 
 pressure line and the other the gasoline line (Fig. 37). The gasoline 
 line runs from the lowest point in the tank directly to the carburetor. 
 The pressure line is connected to both the engine driven pump and 
 the hand pump. The hand pump is shut off by means of a valve at 
 its lower end when not in use. A pressure gauge may be attached 
 to this line near the hand pump to show the pressure in the system 
 at all times. Some systems have the pressure gauge attached to the 
 gasoline line. 
 
 Since a constant pressure is maintained in the tank at all times 
 the gasoline is fed uniformly to the carburetor and its flow is inde- 
 pendent of the relative position of tank and carburetor. In addition 
 to this the location of the tank is not limited, permitting it to be 
 

 50 
 
FUEL FEED SYSTEMS 51 
 
 o* 
 
 placed in an accessible position where gasoline may be put in with the 
 greatest facility. Should fire occur at the carburetor the supply of 
 gasoline can immediately be shut off at the dash by turning the cock 
 at the hand pump so that the pressure in the system can escape to 
 the air. Trouble may be experienced in this system with leaks in the 
 various pipes, valves, or filler cap and the pumps must be in proper 
 working order for constant operation. In addition the pressure is 
 liable to interfere with the operation of the carburetor float and 
 prevent the needle valve from seating properly. However, the pressure 
 feed system has been so highly perfected that few mechanical diffi- 
 culties are apt to be experienced. 
 
 VACUUM SYSTEM. In this system the gasoline is drawn from 
 a supply tank in the rear of the car by suction to a small auxiliary 
 vacuum tank near the engine from which it flows by gravity to the 
 carburetor. The vacuum tank is installed under the hood and con- 
 nected by tubing to the intake manifold, gasoline storage tank, and 
 carburetor (Fig. 38). The suction created by the pistons on their 
 outward strokes in the engine causes a suction in the vacuum tank 
 through the connection to the intake manifold. This draws gasoline 
 from the main supply tank into the vacuum tank through the tubing 
 from the gasoline supply tank. 
 
 The Stewart Vacuum Gasoline Tank consists of two chambers. 
 The upper is the filling chamber and the lower is the emptying 
 chamber. Between these two chambers is a partition in which is 
 placed a valve. The suction of the pistons on the intake stroke 
 creates a vacuum in the upper chamber and this vacuum closes the 
 valve between the two chambers and also sucks or pumps up the 
 gasoline from the main supply tank into this upper chamber. As the 
 gasoline flows into this upper chamber it raises a float. When the 
 float has risen to a certain point, it operates a valve which shuts off 
 the suction and at the same time opens an air valve. This admission 
 of outside air releases the vacuum causing the valve leading into the 
 lower chamber to open, through which the gasoline immediately 
 commences to flow into the lower or emptying chamber. This lower 
 chamber is always open to the outside air so that nothing can ever 
 prevent the gasoline in it from feeding through its connection to the 
 carburetor in an uninterrupted flow. 
 
 DESCRIPTION OF STEWART VACUUM TANK 
 
 "A" is the suction valve for opening and closing the connection 
 to the manifold and through which a vacuum is extended from the 
 engine manifold to the gasoline tank, 
 
AIR' 
 
 FROM 
 
 GASOLINE 
 SUPPLY TANK 
 
 TO CARBU- 
 RETOR 
 
 Fig. 39 Stewart Vacuum Tank 
 
 52 
 
FUEL FEED SYSTEMS 53 
 
 "B " is the atmospheric valve and permits or prevents atmospheric 
 pressure in the upper chamber. When the suction valve "A" is 
 open and the suction is drawing gasoline from the main reservoir 
 this atmospheric valve "B" is closed. 
 
 "C" is the pipe connecting the tank to manifold of the engine. 
 
 "D" is the pipe connecting the vacuum tank to main gasoline 
 supply tank. 
 
 "E" is the lever to which the two coil springs "S" are attached. 
 This lever is operated by the movement of the float "G." 
 
 "F" is a short lever which is operated by the lever "E" and 
 which in turn operates the valves "A" and "B." 
 
 "G" is the float. 
 
 "H" is the flapper valve in the outlet "T" (Fig. 39). This 
 flapper valve is held closed by the action of the suction whenever 
 the valve "A" is open, but it opens when the float valve has closed 
 the vacuum valve "A" and opened the atmospheric valve "B." 
 
 "J" is a plug in the bottom of the tank which can be removed 
 for draining or cleaning the tank. This plug can be replaced with a 
 pet cock to be used for drawing off gasoline for priming or cleaning 
 purposes. 
 
 "K" is the line to the carburetor extended on inside of the tank 
 to form a pocket for trapping water and sediment. 
 
 "L" is the channel space between the inner and outer shells and 
 connects with the air vent "R," thus maintaining an atmospheric pres- 
 sure in lower chamber at all times. This insures an even flow of 
 gasoline to the carburetor. 
 
 "R" is an air vent over the atmospheric valve. The effect of 
 this is the same as if the whole tank were elevated and is for the pur- 
 pose of preventing an overflow of gasoline if the storage tank became 
 higher than the vacuum tank. Through this tube also the lower or 
 reservoir chamber is continually open to atmospheric pressure so 
 that the flow of gasoline from this lower chamber to the carburetor 
 is always an uninterrupted flow. This outlet is located at the bottom 
 of the float reservoir in which is the flapper valve "H." 
 
 The simple durable construction used in the manufacture of the 
 Stewart Vacuum Tank makes it unlikely that it will ever be neces- 
 sary to make internal repairs. However, some of the following 
 troubles may possibly be experienced. The vent tube may overflow 
 and if it does this regularly the trouble may be: 
 
 1. The air hole in main gasoline tank filler cap may be too small 
 or may be stopped up. 
 
 2. Vacuum tank may not be placed high enough above the 
 carburetor. 
 
54 MOTOR VEHICLES AND THEIR ENGINES 
 
 If faulty feed is due to the vacuum system it may result from one 
 of the following causes: 
 
 1. Gasoline strainer may be clogged and should be examined 
 first if the tank fails to operate. 
 
 2. The float may leak allowing gasoline to be drawn into the mani- 
 fold which will choke down the engine. 
 
 3. Flapper valve may not seat properly. 
 
 4. Manifold connection may be loose allowing air to be drawn 
 into it. 
 
 5. Tubing may have become stopped up. 
 
 This system supplies gasoline at a constant pressure but low 
 enough not to interfere with the action of the carburetor float. This 
 system does not limit the location of the supply tank but eliminates 
 the trouble giving pumps and valves of the pressure system and 
 permits the final supply of gasoline to the carburetor by gravity. 
 
 CARE OF GASOLINE. Gasoline being a volatile liquid is very 
 dangerous if not properly handled but is quite safe if the proper 
 precautions are taken. It should never be exposed in a closed room 
 as it will evaporate, mixing with air and forming an explosive gas. 
 Open lights should never be used where gasoline vapor is apt to be 
 encountered. When it is necessary to handle gasoline at night in 
 the open an electric light should be used and under no circumstances 
 should a flame be brought near the gasoline. When an open flame is 
 used at some distance from gasoline, it should always be placed above 
 the gasoline. Gasoline should be stored in an underground tank or 
 in an air-tight container in a separate building used especially for 
 that purpose. 
 
 In putting out a gasoline fire, water should never be used as the 
 gasoline, being lighter than water, floats on it, resulting in spreading 
 the fire. The only successful method of extinguishing a gasoline 
 fire is to smother it with sand, sawdust, or a blanket or by the use of 
 a chemical fire extinguisher. Each piece of motor equipment should 
 be provided with a small chemical extinguisher for this purpose. 
 
CHAPTER VII 
 
 FUELS 
 
 The crude oils from which gasoline is derived occur in various 
 parts of the world and manifest a variety of properties. Thus the 
 "paraffine base," Pennsylvania and Ohio oils yield 60 to 70 percent 
 of kerosene and lubricating oils, while the "asphaltum base," Cali- 
 fornia, Oklahoma, or Texas oil, furnishes practically nothing of either 
 of these products. It is much heavier than Pennsylvania oil, and 
 Mexican oil is usually still heavier. Crude oils having an asphaltum 
 base are heavy and dark-colored and when distilled down leave a 
 black tarry residue. If a crude oil has a paraffine base it is lighter 
 in weight and color, and the residue after distillation yields (by 
 pressure and refrigeration) the white paraffine wax. Either kind of 
 crude oil will yield good gasoline. A large proportion of the world's 
 supply of crude petroleum comes from American wells. These 
 variations are indicated by the density, which varies from a maximum 
 of 50 with Pennsylvania crude down to 12 or less with California 
 crude. The lower the density, the less is the proportion of gasoline 
 obtainable from the crude oil. 
 
 The density of liquids lighter than water (like fuel oils and their 
 products) is indicated by 
 
 140 
 specific gravity = 
 
 where B is the hydrometer reading. The specific gravity is the weight 
 of the liquid as compared with the weight of an equal bulk of water. 
 Hence water would give an hydrometer reading of 10. Water 
 weighs 8^ Ibs. per gallon at normal temperature. 
 
 Crude oils are too heavy and viscious for use as fuels in internal 
 combustion engines without special preparatory treatment. They 
 require heating and may liberate poisonous or explosive gases which 
 are heavier than air. They contain, as impurities, free carbon, 
 sulphur, silt, and moisture, in widely varying proportions. 
 
 When crude oil is subjected to moderate heat those of its con- 
 stituents which have low^boiling points are boiled off. By condensing 
 their vapors, highly inflammable gasoline is obtained. After this a 
 somewhat higher temperature may be applied and lower grade 
 gasoline collected in a separate condenser. By successive increases 
 
 55 
 
56 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 GAS61WC. BMZ/*/C, AW 
 
 of temperature, with separa- 
 tion of products condensed, a 
 considerable series of products 
 is derived. 
 
 It would be commercially 
 inadmissible to treat crude oil 
 with a view to deriving gaso- 
 line only. This process is 
 called "fractional distillation," 
 and is the basis of petroleum 
 refining. As the temperature 
 of distillation increases, the 
 products become lighter (hav- 
 ing a higher hydrometer read- 
 ing and less fluid and inflammable. Fig. 40 shows the composition 
 of a sample of American crude oil. 
 
 Fig. 40 Composition of Crude Oil 
 
 AVERAGE FRACTIOXATION OF CRUDE PETROLEUMS (ROBINSON) 
 
 AMERICAN OIL 
 
 CONSTITUENT 
 
 PERCENT. 
 OBTAINED 
 
 BOILING 
 POINT, DEG. 
 FAHR. 
 
 HYDROMETER 
 READING, 
 DEG. 
 
 Gasoline 
 
 0-10 
 
 32-265 
 
 58-107 
 
 Kerosene 
 
 12-55 
 
 300-700 
 
 44-49 
 
 Fuel oil (gas oil) 
 
 variable 
 
 
 35 
 
 Lubri eating oil 
 
 17^ 
 
 
 22-28 
 
 Paraffin and residue 
 
 2-10 
 
 
 
 
 
 
 
 RUSSIAN OIL 
 
 Gasoline 
 
 5-16 
 
 
 53-63 
 
 Kerosene 
 
 40-52 
 
 
 33-41 
 
 Lubricating oil 
 
 3-40 
 
 
 22-31 
 
 Residue (fuel oil) ... . 
 
 10-15 
 
 
 17-25 
 
 
 
 
 
 The boiling point of any liquid varies according to the pressure 
 to which it is subjected. If the boiling temperature at atmospheric 
 pressure is less than the resisting temperature, the liquid will vaporize 
 until a pressure is created equal to that at which boiling occurs at the 
 existing temperature. The lighter gasolines therefore are always 
 boiling off from the crude oils which contain them. Loss and danger 
 can be avoided only by confining such oils. 
 
FUELS 
 
 57 
 
 PRESSURES AND BOILING POINTS 
 
 Boiling Point, Deg. Fahr 
 
 70 
 
 80 
 
 90 
 
 100 
 
 110 
 
 120 
 
 140 
 
 
 
 
 
 
 
 
 
 Pressure, f Ordinary gasoline 
 inches I Kerosene, poor* 
 
 8.9 
 1.0 
 
 10.0 
 1.2 
 
 11.8 
 1.4 
 
 13.8 
 1.5 
 
 16.4 
 1.6 
 
 19.6 
 1.8 
 
 2^3 
 
 of ordinary 
 
 0.6 
 
 0.7 
 
 0.8 
 
 0.9 
 
 1.1 
 
 1.3 
 
 1.7 
 
 Mercury [ water white. . . 
 
 0.6 
 
 0.6 
 
 0.6 
 
 0.7 
 
 0.7 
 
 0.8 
 
 1.0 
 
 *Poor for use as an iUuminant, because volatile and therefore unsafe. The 
 most dangerous illuminating kerosenes, are, however, the best as fuels for internal 
 combustion engines. 
 
 To convert pressure in inches of mercury to Ib. per sq. in., mul- 
 tiply by 0.49. Thus, if gasoline is vaporized at 120 F. its vapor 
 pressure is 9.6 Ib. per sq. in. The lower the pressure, the lower the 
 temperature at which vaporization occurs. Suction, therefore, 
 facilitates carburetion. 
 
 The proportions of the various products obtainable from re- 
 fining any particular crude oil cannot be changed by the refiner. 
 In getting 5 percent of gasoline, for example, he is compelled to 
 accept 40 percent of kerosene, say. If the demand for kerosene is 
 slight, while the demand for gasoline is brisk, he may have to sell 
 the former at a loss and protect himself by charging an excessive 
 price for gasoline. There is no such thing as "cost of production 11 
 chargeable against any one of the products. When any one is cheap, 
 others must be dear. If gasoline is cheap at any time it is because 
 there is relatively a greater demand for other products. About 1903 
 kerosene was cheaper than gasoline in some sections. Recently it 
 has been twice as costly. 
 
 The average gasoline consists mainly of carbon and hydrogen: 
 From 83J^ to 85 parts of the former to 15 to 15 J^ of the latter by 
 weight. Good commercial gasoline should show an hydrometer read- 
 ing between 67 and 73. Grades down to 50 are sometimes offered. 
 They are, of course, not true gasoline, but may be used in warm 
 weather without difficulty. This density is about the same as that 
 of some of the best samples of Pennsylvania crude oil. At 68 the 
 specific gravity is 140 -^ 198 = 0.71. Since water weighs 8.33 Ib. per 
 gal., this gasoline weighs 0.71X8.33 = 5.91 Ib. per gal. Petroleum 
 products are always sold by bulk; the gallon or the 42-gal. barrel. 
 It would be fairer if they were sold by weight. 
 
 The weight per measured gallon is an exact indication of the 
 density. If w = weight per gallon, B = hydrometer density, then 
 
 1 -t r>rj 
 
 B = - -130. Thus if the weight per gallon is 5.835 Ib., B = 70. 
 It will be noted that some slight amounts of the lighter gasolines 
 
58 MOTOR VEHICLES AND THEIR ENGINES 
 
 are obtained by distillation at temperatures as low as 32 F.; i.e., 
 without any heat at all. In fact, as much as IK percent of some 
 American crude oils will distil off at temperatures below 150 F. 
 These products are highly inflammable and dangerous. It is not 
 always possible to market them. By blending them with rather light 
 kerosene a substance is produced which may be regarded as gasoline, 
 for it has the density of the latter. It has different properties, how- 
 ever, notably with respect to igniting point and vapor pressure. 
 
 Gasoline may be produced from natural gas by the combined 
 effects of pressure and cooling. Improved methods of distillation 
 (Burton and Rittman processes,* etc.) increase the gasoline yield 
 from crude oil, but usually at the cost of some impairment to quality. 
 
 Average gasoline must be supplied with air in the ratio 15 to 1 
 by weight for complete combustion. This means that 1 Ib. of fuel 
 requires 200 cu. ft. of air at 62 F. Gasoline vapor weighs 0.24 Ib. 
 per cu. ft. at atmospheric pressure and 32 F., or is about three times 
 as heavy as air. About 50 cu. ft. of air are required to make a 
 perfect combustible mixture with 1 cu. ft. of gasoline vapor. These 
 ratios may be considerably varied without preventing ignition, but 
 if varied the power and efficiency are influenced unfavorably. 
 According to Lucke, limits are as follows: 
 
 RATIO OP GASOLINE VAPOR TO 
 TOTAL MIXTURE, BY VOLUME 
 
 86 Gasoline " 0.0154 to 0.0476 
 
 71 Gasoline 0.0154 to 0.0476 
 
 65 Gasoline 0.0131 to 0.0476 
 
 If these limits are passed, the mixture will not ignite explosively 
 (at atmospheric pressure, by electric spark). As has been shown, 
 the best value is about & or 0.02. A rich mixture causes failure to 
 ignite less promptly than does a weak mixture. 
 
 The heat value of a fuel is expressed in British thermal units 
 (B. t, u.). One B. t. u. is the quantity of heat necessary to raise 
 the temperature of 1 Ib. of water 1 F. It is equivalent to 778 ft. Ib. 
 of mechanical energy. Since 1 horse power = 33,000 ft. Ib. per min., 
 it is also equal to 33,000 -f- 778 = 42.42 B. t. u. per min. Average 
 gasoline contains from 19000 to 21000 B. t. u. per Ib. In general, 
 for all petroleum distillates, 
 
 B. t. u. per lb. = 18650+40 (B-10). 
 Thus for 68 gasoline, B. t. u. per lb. = 20970. The lighter the dis- 
 
 *The Burton process involves the obtaining of gasoline by redistillation of 
 less volatile products under pressure. The Rittman process, developed by the 
 United States Bureau of Mines, is similar, but the operation is conducted con- 
 tinuously instead of in batches. 
 
FUELS 59 
 
 tillate the higher the heat value. One horse power is 42.42 B. t. u. 
 per min. or 42.42X60 = 2545 B. t. u. per hr. The gasoline con- 
 sumption of a perfect engine would be 2545 -T- 20970 = 0.121 Ib. per 
 hour per horse power. Actually it is four to seven times this or more, 
 on account of the inefficiency of the engine. High compression 
 which follows low clearance reduces the fuel consumption. 
 
 The fuel consumed per mile depends on the traction force exerted, 
 the efficiency of engine and driving mechanism, and the speed. If 
 p = average pressure in the cylinder during the power stroke, d = 
 diameter of cylinder and n the number of cylinders, the total pressure 
 continuously maintained in a four-cycle engine is P = ?rd 2 np. If 
 the stroke is s and the engine makes r rev. per min., and if the 
 efficiency from cylinder to wheels is e, the horse power exerted at the 
 wheels if H = Pesr-J- 198000. If the gear ratio is g (engine speed 
 divided by wheel speed) and the wheel diameter is D in., the speed 
 of the truck is V = nDr ^- 1056 g. The tractive force is T = 375 H + 
 V = 2 Pesg-r-7rD, which is practically independent of the engine 
 speed. Take p = 70, d = 5, n = 4 : then P = 1375. Take s = 7, r = 700, 
 e = 0.70. Then H = 23.8. Take g = 5, D = 34: then V=14.2 miles 
 per hour, and T = 629 Ibs. When working at full traction, H is 
 about nd 2 -j-2.5 and the fuel consumption about 0.7 H Ib. per hour. 
 
 If gasoline is used composed of 84 parts of carbon to 16 of hydro- 
 gen, by weight, about 15.22 Ibs. of air will be the correct amount per 
 Ib. of fuel. More air will give more power, but at a sacrifice of 
 efficiency. Suppose the truck to make 5 miles per gallon of gasoline. 
 If the liquid fuel were stretched out along the road in a pipe, the tube 
 of fuel containing one gallon or 231 cubic inches would be 5 miles or 
 316800 inches long, and its diameter would be about % 3 of an inch. 
 A similar pipe full of air would contain 1130 cu. ft., or the diameter 
 would be 2.8 inches. This illustrates the point that most of what 
 goes into the cylinder under any condition is nothing but air. 
 
 Since 1 Ib. of gasoline produces about 200 cu. ft. of combustible 
 mixture, the mixture contains about 20970 -T- 200 = 105 B. t. u. per 
 cu. ft. This is reduced if the temperature is higher than 62 F., 
 because 200 cu. ft. at 62 F. will occupy a larger volume at higher 
 temperatures. 
 
 Efforts are constantly being made to find acceptable substitutes 
 for gasoline. The most important substitutes may be grouped in 
 three classes: Lower grade distillates, including kerosene; alcohol; 
 and coal-distillation products, such as benzol. The study of sub- 
 stitutes has until recently been carried on much more thoroughly in 
 Europe than in this country, because there are no readily accessible 
 supplies of gasoline from the commercial centers of the continent. 
 
60 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 KEROSENE has very nearly the same percentage composition 
 as gasoline, but its density being greater, its heat value is less. It 
 requires more air for combustion, and the heat value per cu. ft. of 
 combustible mixture is less. The lower heat value is not an objection ; 
 in fact, it is in one way an advantage. Low heat values mean a high 
 igniting temperature. This permits of more compression without 
 danger of pre-ignition, and high compression increases both power 
 and efficiency. However, a high ignition temperature does itself 
 introduce difficulties. 
 
 The essential objection to kerosene is the difficulty of vaporizing 
 it. The table shows that its boiling point is 300 F. or more. Gas- 
 oline may be vaporized either by pure evaporation in a slow current 
 of warm air, or by spray-injection. Kerosene needs heat. This 
 may be supplied externally, at the carburetor; or the fuel may be 
 delivered to the cylinder in liquid form by a pump and vaporized by 
 contact with a hot (un jacketed) cap or plate forming a part of the 
 cylinder. This is the method of the Hornsby-Akroyd stationary 
 engine, but the timing of ignition is uncertain, especially under 
 variable loads. For motor cars, carburetor heating is more prom- 
 ising. 
 
 Kerosene is not necessarily more apt to form carbon deposits. 
 These will result from any blended fuel in which the free carbon of 
 the heavier constituents has not been thoroughly filtered out, or 
 from any fuel at all under appropriate conditions of carburation and 
 cooling. 
 
 Alcohol as a fuel has had considerable attention. There are two 
 kinds, methyl or wood alcohol, and ethyl or grain alcohol. The 
 former contains half the carbon and two-thirds the hydrogen of the 
 latter. It has only about three-fourths the heat value and requires 
 less air for combustion. Unlike petroleum distillates, both of the 
 alcohols contain oxygen. Commercial alcohols always contain water. 
 This does not destroy their value as fuels. The following table 
 shows the effect. The B. t. u. per Ib. are adjusted values, which 
 
 Percent of Alcohol in Mixture, 
 by Weight 
 
 93 8 
 
 87 8 
 
 81 8 
 
 76 1 
 
 70 5 
 
 65 
 
 Specific Gravity 
 
 0.805 
 
 815 
 
 826 
 
 836 
 
 846 
 
 856 
 
 B. t. u. per Ib 
 
 10880 
 
 10080 
 
 9360 
 
 8630 
 
 7920 
 
 7200 
 
 
 
 
 
 
 
 
 are comparable among themselves, but not with those given for 
 petroleum distillates. For the latter purpose, the heat value of pure 
 ethyl alcohol may be taken at 12800 B. t. u. per Ib. Denatured 
 alcohol is a mixture of pure ethj r l alcohol, 90 parts; water, 10 parts; 
 
FUELS 61 
 
 methyl alcohol, 10 parts; and benzine, J/ part; by volume. Alter- 
 natively, the last two constituents may be replaced by methyl alcohol, 
 2 parts, and pyridin bases, Y^ part. Denaturing makes alcohol unfit 
 for use in connection with beverages. 
 
 One cubic foot of, alcohol vapor requires 14J/ cu. ft. of air for 
 complete combustion. It will ignite when the air volume is any- 
 where between 7 and 25 cu. ft. If the air supply is seriously deficient, 
 the combustion products will contain acetic acid, which causes 
 rusting and corrosion. The igniting temperature of alcohol vapor at 
 atmospheric pressure is 950 F. The alcohols are intermediate 
 between gasoline and kerosene in their readiness of vaporization, 
 and methyl alcohol is particularly close to gasoline in its vaporizing 
 properties. Moderate heating at the carburetor is required in cold 
 weather. Higher compression is necessary than with gasoline, for 
 the same power and efficiency, and the engine must be specially 
 designed for such high compression. Tests have shown that where 
 70 Ibs. compression pressure was used for both fuels, the alcohol 
 engine consumed 50 percent more fuel than that burning gasoline. 
 By raising the compression of the former engine to 180 Ibs., its fuel 
 consumption became the same as that of the gasoline engine: 0.10 
 gallon per hour per horse power. Unfortunately the present methods 
 for distillation of alcohol from vegetable substances have not yet 
 produced that fuel at a price competitive with that of gasoline. 
 
 Benzol is a by-product of the distillation of soft coal, for the 
 manufacture of coal gas or coke. It appears both in the gas and in 
 the liquid tar, and is derived only when by-products or retort ovens 
 are used. It ignites at 970 F. at atmospheric pressure. Its specific 
 gravity is 0.88 and its heat value about 18000 B. t. u. per Ib. About 
 13}/ Ib. of air are required for combustion of 1 Ib. of benzol, or about 
 
 36 cu. ft. of air for 1 cu. ft. of benzoL Ignition is possible with 15 to 
 
 37 volumes of air, but weak mixtures are very uncertain. Benzol 
 has been used in three ways. While somewhat less volatile than 
 gasoline, it has been vaporized in an ordinary carburetor, after 
 starting on gasoline. By adding benzol to alcohol there is less danger 
 of corrosion from acetic acid formation. In Europe, a mixture of 
 equal parts of benzol and alcohol has frequently been employed as a 
 motor fuel. The mixture had a heat value of 14200 B. t. u. per Ib. 
 Commercial benzol has been charged with excessive carbon formation, 
 but so has commercial gasoline of the present day. 
 
 There seems to be little possibility of the direct use of crude oil, 
 coal tar (a by-product from coal-gas distillation) or tar oil (by-pro- 
 duct from tar distillation) in the cylinders of motor-car engines. 
 Even in stationary engines of the hot-cap type they have been un- 
 
62 MOTOR VEHICLES AND THEIR ENGINES 
 
 satisfactory. Extremely high compression and still higher fuel- 
 injection pressures, usually complicated by an air blast, have thus far 
 been necessary. The engines have been heavy and costly and in 
 many instances unreliable. Kerosene is the most promising cheaper 
 fuel, but the kerosene problem will not be solved until the starting 
 problem, as well as the running problem, is solved. There seems to 
 be no good ground for apprehension that the substitution of kerosene 
 will leave us where we are now, as far as cost is concerned. The yield 
 of kerosene is very much greater than that of high-grade gasoline. 
 In fact, kerosene is simply low-grade gasoline. Circumstances are 
 compelling the use of lower and lower grades, so that a gradual 
 approximation to kerosene as fuel seems both the most probable and 
 the easiest direction for progress. The necessary modifications of 
 equipment have in a measure been already anticipated by such 
 devices as water-jacketed and hot-air-jacketed carburetors, etc. 
 
CHAPTER VIII 
 
 ELEMENTS OF CARBURETION 
 
 Pure gasoline vapor must be combined with oxygen in order to 
 render it inflammable. The simplest manner of effecting this is to 
 mix air with gasoline. When the correct proportions are obtained 
 the oxygen supplied by the air will be sufficient to result in the com- 
 plete combustion of the gasoline vapor without a surplus of either 
 of the ingredients. This mixing is called carburetion and the air is 
 said to be carbureted. 
 
 The carburetor is a metering device whose function is to blend 
 mechanically a liquid fuel with a certain amount of air to produce 
 as nearly a homogeneous mixture as possible and in such proportion 
 as will result in as perfect an explosive mixture as can be obtained. 
 
 With a liquid fuel such as gasoline it is difficult to obtain this 
 perfect mixture especially with low test gasoline. If it were possible 
 to transform a liquid fuel into its vapor, the vapor would act as a 
 gas and would mix easily with the air to form a homogeneous mixture. 
 The carburetor should be so designed as to atomize the fuel and break 
 it up into as small particles as possible so every minute particle of 
 the fuel is surrounded by the correct proportion of air as it enters 
 the inlet manifold of the engine. To facilitate the vaporization of 
 these minute particles of fuel it is advisable to heat the air taken 
 into the carburetor. 
 
 There is a range of proportions of air to vapor for a given fuel 
 between which combustion will result. This range* extends from 
 that proportion known as the UPPER LIMIT OF COMBUSTION 
 to that known as the LOWER LIMIT OF COMBUSTION. The 
 upper limit is reached when the ratio of air to vapor is a maximum 
 at which combustion will take place, any further addition in air 
 rendering the mixture non-combustible. The lower limit is reached 
 when the ratio of air to vapor is a minimum at which combustion 
 will take place, any decrease in air below this point producing a non- 
 combustible mixture. It should be remembered that the limits of 
 combustion are dependent upon the temperature and pressure. 
 
 The limits of combustion of gasoline (70 Sp. Gr.) can be taken 
 approximately as follows: Lower limit, 7 parts air (by weight) to 1 
 part of gasoline; upper limit, 20 parts air to 1 part gasoline. Under 
 given temperature and pressure the ratio at which a combustible 
 
 63 
 
64 MOTOR VEHICLES AND THEIR ENGINES 
 
 mixture will burn depends upon the ratio of air to vapor. This rate 
 of burning is known as the RATE OF FLAME PROPAGATION and 
 it is desirable to obtain a mixture whose rate of flame propagation 
 is a maximum because the expansion will depend upon the rapidity 
 with which the entire mixture- is completely burned. 
 
 Rich mixtures have a greater proportion of fuel vapor and are 
 slow burning and sluggish. They also cause carbon to be deposited 
 in the combustion space because of their incomplete combustion. 
 Mixtures that have too great a proportion of air are very erratic in 
 their combustion. The mixture in the cylinders is often formed in 
 layers and as each layer burns independently of the other the rate of 
 burning is slow. The term LEAN MIXTURE is often used to desig- 
 nate not only this type of mixture, but those which have not reached 
 the upper limit. These mixtures have a high rate of flame propa- 
 gation. When mixtures are too lean they cause misfiring of the 
 engine and also cause back firing into the carburetor. 
 
 A carburetor must be constructed to maintain the proper pro- 
 portions of gasoline and air under all conditions. To accomplish 
 this several designs and principles have been evolved which will be 
 discussed in the following chapters. Types of carburetors which 
 are not commonly used will not be discussed because the principle 
 upon which they are based has not proven satisfactory for motor 
 vehicles. 
 
 Before taking up any of these types it is necessary to study the 
 basic principles underlying carburetion. These will be most clearly 
 understood when applied to a simple carburetor of the spray nozzle 
 
 type. The gasoline supply from 
 the storage tank enters the float 
 chamber "F" of the carburetor 
 and as the gasoline level rises the 
 float presses against the levers at 
 the top of the float chamber (Fig. 
 41). These levers are pivoted so 
 that their outer ends are raised 
 by the float. Their inner ends 
 working in a collar or recess, press 
 the float needle valve downward 
 into its seat. This shuts off the 
 
 Fig. 41 Simple Carburetor su PP ! y of gasoline when the level 
 
 in the float chamber has reached 
 
 the proper height. The height at which this gasoline should be main-, 
 tained is governed by the nozzle or jet "G." The level must stand 
 approximately % below the top of this nozzle. The gasoline is fed 
 
ELEMENTS OF CARBURETION 65 
 
 to the nozzle "G" from the float chamber through the pipe "E." 
 The inlet valve being open when the piston moves outward in the 
 cylinder on its suction stroke, air will be drawn through the carburetor, 
 as indicated by the arrows in Fig. 41, passing the nozzle on its way 
 to the cylinders. The suction created by the rush of air past the 
 spray nozzle causes the gasoline to be delivered to the mixing chamber 
 in a fine spray. Since the suction depends upon the velocity of the 
 air passing the nozzle, a Venturi tube "X" is used. 
 
 A Venturi tube is a tube which is narrowed at the center so that 
 the area through which the air must pass is considerably decreased. 
 As the same amount of air must pass through every point in the tube 
 its velocity will be greatest at the narrowest point. The more this 
 area is reduced the greater will be the velocity of the air and the 
 suction will be proportionally increased. 
 
 The sp^-ay nozzle should be located where the suction is greatest 
 which is just above the narrowest part of the Venturi tube. The 
 spray of gasoline from the nozzle and the air entering through the 
 Venturi tube are mixed together in the mixing chamber, that portion 
 of the tube immediately above the spray nozzle. This produces a 
 combustible mixture which passes through the intake manifold into 
 the cylinders. 
 
 The speed of the engine is controlled by the use of the throttle 
 "T" which is a form of damper placed between the mixing chamber 
 and intake manifold. The more the throttle is closed the greater 
 will be the obstacle placed in this passage and the greater will be 
 the opposition to the filling of the cylinder at each stroke. This 
 gives a less powerful impulse to the piston and the engine's speed 
 is correspondingly reduced. 
 
 As the throttle is opened the speed of the engine increases and 
 with wide open throttle attains its maximum speed which for this 
 discussion will be assumed to be 1,600 revolutions per minute. 
 The cylinder fills as freely as possible and a large quantity of air 
 passes through the carburetor while the gasoline jet delivers its 
 maximum. 
 
 As the load on the engine is increased as will be the case when a 
 hill is encountered, the speed is gradually diminished, say to 400 
 R. P. M. It is obvious that the air does not pass through the car- 
 buretor with the same velocity as before and the suction is greatly 
 reduced, although the throttle is still wide open. It is evident the 
 throttle does not wholly control the speed of the engine; the load is 
 also a factor that must be considered. In actual test with wide open 
 throttle the engine suction has decreased over nine times between 
 1600 R. P. M. and 400 R. P. M. The throttle is simply a means to 
 
MOTOR VEHICLES AND THEIR ENGINES 
 
 prevent the engine from pulling in a full charge of mixture each 
 suction stroke and thus regulates its power. 
 
 As the speed of the engine increases the suction increases. The 
 flow of liquids is governed by definite laws and the flow from a jet 
 increases under suction faster than the corresponding flow of air. 
 With a simple construction of nozzle the mixture becomes richer as 
 the speed increases. As it is essential to have practically the same 
 proportions of air and gasoline at all speeds it is necessary to construct 
 the carburetor to maintain this proportion as the suction increases. 
 
 To overcome rich mixtures the carburetor must be adjustable so 
 that less gasoline or more air will be supplied. The gasoline supply is 
 controlled by the size of the spray nozzle opening. For a given 
 suction the quantity of gasoline delivered varies directly as the cross 
 sectional area at the nozzle. In some carburetors the nozzle, which 
 is of fixed size, may be replaced by a smaller or larger nozzle depending 
 upon the regulation desired. 
 
 Fig. 42 Types of Needle Valves 
 
 In other carburetors the opening at the nozzle is adjustable by 
 means of a needle valve (Fig. 42). As the needle is screwed into its 
 
 seat the nozzle area is 
 reduced resulting in leaner 
 mixtures. 
 
 The air supply may be 
 controlled by employing an 
 automatic air valve (Fig. 
 43). This consists of a 
 valve held in its seat by a 
 spring whose tension is 
 adjustable. This valve is 
 opened automatically by 
 Fig. 43 Auxiliary Air Carburetor atmospheric pressure which 
 
ELEMENTS OF CARBURETION 67 
 
 will overcome the tension of the spring allowing air to enter the 
 mixing chamber. As the tension in the spring is increased greater 
 suction will be required to open the valve regulating the point at 
 which the valve opens and the amount it opens. 
 
 The auxiliary air entering the mixing chamber does not pass 
 through the Venturi tube hence it dilutes the rich mixture resulting 
 from the increased suction. In this manner the proportions of air 
 and gasoline are kept constant at variable speeds. 
 
 PRECAUTIONS WHEN ADJUSTING CARBURETOR. Before 
 attempting to put a carburetor in proper adjustment certain con- 
 ditions must prevail. 
 
 1. The engine must be warm. 
 
 2. The adjustment must be made under actual operating 
 conditions. 
 
 3. There must be no leaks allowing air which does not pass 
 through the carburetor to enter the combustion space. 
 
 4. All choking devices must be wide open. 
 
 5. All gasoline passages must be free from obstructions. 
 
 6. The ignition system must be properly timed and in working 
 order. 
 
 In making carburetor adjustments it is desirable to obtain as 
 lean a mixture as will give proper results. Hence, it is imperative 
 first to diminish the proportions of gasoline to air until so lean a 
 mixture is obtained that missing of the engine and possibly back 
 firing in the carburetor results. The proportion should then be 
 gradually increased until the missing is overcome and the engine 
 runs smoothly. 
 
 When making any changes in adjustment it is necessary that only 
 slight changes be made at a time. After every change of adjustment 
 sufficient time must be given for this change to effect the operation 
 of the engine before further changes are made. This will eliminate 
 any possibility of making unnecessary changes. The greatest care 
 must be observed in this respect when overcoming a lean mixture 
 since a mixture richer than necessary may result. This would not 
 be noticed in the running of the engine but would increase the fuel 
 consumption materially. 
 
 Carbon monoxide, a deadly poisonous gas, is present in the 
 exhaust of gasoline engines. Increasing the proportion of gasoline 
 to air in the mixture increases the amount of carbon monoxide given 
 off at the exhaust pipe. Because of the presence of carbon mon- 
 oxide it is very dangerous to run the engine for any length of time 
 while the car is in a small closed garage. If the doors and 
 windows are open the danger is very much lessened, but it is far 
 
68 MOTOR VEHICLES AND THEIR ENGINES 
 
 safer if an adjustment of the carburetor is being made to run the 
 car outside. 
 
 Serious personal injury may be caused by the presence of carbon 
 monoxide in a garage if the percentage of it in the air is greater than 
 a very small fraction of one per cent. Unconsciousness may result 
 without warning. It is reported that no indication of danger is 
 given by personal discomfort until too late. Deaths resulting from 
 the presence of carbon monoxide in garages have been reported. 
 
 During the final test of all motor apparatus by the manufacturer 
 the carburetor is very carefully adjusted and this adjustment should 
 not be changed unless it is absolutely necessary because of greatly 
 changed climatic conditions or grade of fuel used. After the car- 
 buretor is adjusted to operate under these conditions there should 
 be no necessity for further change. 
 
 Engine troubles arise from many sources and it is very seldom 
 that the trouble is due to the carburetor adjustment. It must be 
 borne in mind that a properly adjusted carburetor cannot get out of 
 adjustment unless tampered with. It is the tendency of inexperi- 
 enced men to adjust the carburetor no matter what the trouble 
 without first endeavoring to locate the real difficulty. This leads to 
 the adjusting devices becoming worn and inaccurate. Make it an 
 inflexible rule to try to locate engine troubles at all other possible 
 sources before touching the carburetor. 
 
 In case the suction through the carburetor is suddenly increased 
 by quickly opening the throttle, the air, being lighter than gasoline, 
 will respond almost instantly and its flow will be accelerated very 
 suddenly. The gasoline particles owing to that characteristic known 
 as "inertia," will not respond so rapidly due to their heavier weight 
 and the flow of gasoline will not accelerate as rapidly as the air. 
 This will result in the air rushing ahead of the gasoline particles and 
 the proportion of air to gasoline will be greater until the inertia has 
 been overcome and the gasoline particles have responded completely 
 to the increased suction. This condition will take place unless some 
 provision is made against it. That is, a sudden opening of the 
 throttle will tend to produce a very lean mixture at the engine due 
 to the lagging of the gasoline. A lean mixture at this time, when 
 acceleration is desired, will be detrimental. It is at this particular 
 time that additional gasoline is most desired in order to compensate 
 for this lagging and maintain the proper mixture at the engine. The 
 device which accomplishes this result is known as an "accelerating 
 well." The construction or arrangement of this device will be 
 explained as each type of carburetor is taken up. 
 
ELEMENTS OF CARBURETION 69 
 
 A rich mixture is required when starting an engine, especially 
 when cold. The additional gasoline may be supplied in several ways ; 
 by priming through the priming cocks, by " flooding" the carburetor, 
 by the use of chokes, or by a dash control which increases the gasoline 
 supply temporarily. 
 
 The practice of priming should not be resorted to unless all other 
 methods fail, since the continued addition of liquid gasoline to the 
 cylinders cuts the lubricant, causing loss of compression and permits 
 the gasoline to run past the pistons into the crank case. The result 
 of over-priming makes it almost impossible to start the engine because 
 of the abnormally rich mixture obtained. If an explosion does result 
 the power will not be sufficient to rotate the engine until another 
 power impulse is obtained. 
 
 Pet cocks are made with a cup which will hold sufficient gasoline 
 for proper priming. This cup should be filled, the cock opened, and 
 again closed. The common practice of priming without regard to 
 the amount of gasoline used generally results in over-priming. Before 
 starting an engine which has been over-primed the pet cocks should 
 be opened and the engine cranked until the piston and cylinder walls 
 have been lubricated. Turning the engine over for some time also 
 frees the combustion space of the overrich mixture. This must be 
 done as the liquid gasoline adheres to the piston and cylinder walls 
 enriching each incoming charge. 
 
 Flooding the carburetor causes the float chamber to be filled with 
 gasoline above the level at which it ordinarily stands. Gasoline 
 will overflow from the spray nozzle by gravity and be picked up by 
 the primary air and carried into the cylinders. 
 
 Rich mixtures for starting may also be obtained by the use of 
 chokes. These are placed in the air passages making it difficult to 
 draw air, the suction being satisfied by an increased amount of 
 gasoline vapor. Choking devices are provided on some carburetors 
 to cut down the supply of air until the engine is heated. 
 
 All liquids vaporize when heated sufficiently and while gaso- 
 line will vaporize at ordinary temperatures, increased heat improves 
 this vaporization. This tends to reduce the percentage of liquid 
 gasoline in the mixing chamber causing a more intimate combina* 
 tion of the air and gas. This heat may be obtained several ways; 
 by passing air heated by the cylinder or exhaust pipe through 
 the carburetor, by water jacketing the mixing chamber of the car- 
 buretor, by water jacketing the inlet manifold, or by combining the 
 inlet and exhaust manifolds so that the exhaust gases heat the 
 incoming charge. 
 
70 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 There are two common types of float chambers; the concentric 
 in which the float chamber is placed around the Venturi tube and is 
 concentric with it, the eccentric in which the float chamber is placed 
 by the side of the Venturi tube. 
 
 Fig. 44 Effect of Grades on Eccentric Type Carburetor 
 
 Fig. 44 shows an eccentric type float chamber and the normal 
 gasoline level is shown by the line in "A." When the carburetor is 
 tilted due to the car ascending or descending a grade the level will be 
 changed as shown in "B " or "C." This causes too much or too little 
 
 gasoline to be supplied by the 
 nozzle giving imperfect mixtures. 
 To prevent lean mixtures when 
 ascending grades a carburetor 
 with this type of float chamber 
 should be attached with the 
 float chamber towards the 
 radiator. This difficulty will 
 not be experienced with a 
 concentric float type of car- 
 buretor. The level at the 
 nozzle always remains constant 
 as shown in Fig. 45 by the 
 
 Fig. 45 Effect of Grades on 
 Concentric Type Carburetor 
 
 different levels A-A, B-B, and 
 C-C. This accounts for the 
 usage of concentric float car- 
 buretors on motor cycles, tractors, or other motor vehicles which are 
 not designed for the ordinary road work. 
 
ELEMENTS OF CARBURETION 71 
 
 GOVERNORS. In order to automatically limit both the vehicle 
 and engine speed at all times, a governor is provided. It consists 
 of a grid or butterfly valve in the inlet manifold controlled by the 
 action of movable weights attached by levers to the driven shaft and 
 valve mechanism. Centrifugal force which results from whirling 
 the weights around the shaft causes them to pull away. This action 
 moves the valve in the intake manifold cutting down the supply 
 of gas. 
 
 The position of these weights will depend upon the speed of the 
 engine and at approximately 1200 R. P. M. the gas supply will be 
 cut off, restricting the engine and consequently the vehicle speed. 
 This governing limits the speed of the machine to about 15 miles 
 per hour. 
 
 The drive is thru a flexible shaft. It is driven by a set of gears 
 from the cam shaft or by the fly wheel. An adjustment is provided 
 for varying the setting of the governor. 
 
CHAPTER IX 
 
 CARBURETORS 
 
 The operation and adjustment of the various types of carburetors 
 most commonly used will be outlined giving the particular points 
 in which they vary. 
 
 SCHEBLER MODEL "E" 
 
 This carburetor is a concentric float auxiliary air type and is a 
 very simple carburetor. The primary air inlet is through an air 
 bend at the bottom of the carburetor passing the spray nozzle and 
 the auxiliary air inlet, controlled by the usual type of valve, is pro- 
 vided at the top of the mixing chamber. The spray nozzle is regu- 
 lated by the needle valve (Fig. 46). 
 
 Air Valve Sprl< 
 Leather Air Value Dk 
 
 Auxiliary Air Port 
 Throttle Levef 
 
 Throttle Disc 
 Oas Outlet 
 
 Lock Spring 
 Loch Nut 
 
 Air Value Adjusting 
 Sere iv 
 
 Primary Air Inlet 
 Air Bend 
 
 Float Valve 
 
 'nlon Nut 
 Union Nipple 
 
 \ 
 
 Reversible Union Ell 
 
 Needle Valve Packing Nut 
 Gasoline AdjustingNeedle Value 
 
 Fig. 46 Sehebler Model E 
 
 72 
 
CARBURETORS 73 
 
 LOW SPEED ADJUSTMENT. Have the auxiliary air valve 
 spring tension tight, then adjust by the needle valve turning to the 
 right until the mixture is too lean, and then turn gradually to the 
 left until the missing of the engine is eliminated and the engine runs 
 smoothly. 
 
 HIGH SPEED ADJUSTMENT. Release the tension on the 
 auxiliary air valve spring until so much air is supplied that missing 
 of the engine results and then tighten the spring tension until the 
 engine runs smoothly. With these settings the increasingly rich 
 mixture of the primary should be compensated for by the extra 
 auxiliary air at all speeds. 
 
 THE SCHEBLER MODEL "H" 
 
 This carburetor is for motor-cycle use and is of the auxiliary air 
 type having a "lift needle valve." The supply of gasoline is con- 
 trolled by a needle "E" and cam adjustment, which insures the 
 proper amount of gasoline at all speeds. As the throttle is opened 
 the needle rises from its seat. 
 
 An air elbow is attached to the primary air passage of the car- 
 buretor so that it can be turned to any convenient angle in order to 
 draw warm air off the cylinders (Fig. 47). 
 
 LOW SPEED ADJUSTMENT. See that the leather air valve 
 "A" seats lightly and then turn knurled button "I" to the right until 
 the needle "E" seats in the spray nozzle cutting off the flow of gasoline. 
 Now turn "I" to the left about three turns and open low speed air 
 adjusting screw "L" about three turns and then open throttle about 
 half way to start the engine. After starting the engine close the 
 throttle and turn needle valve adjusting screw "I" to the right until 
 the mixture becomes so lean that the engine back fires or misses. 
 Then turn adjusting nut "I" to the left slowly, notch by notch, until 
 the engine runs smoothly. If, with this low speed adjustment, the 
 engine runs too fast turn low speed adjusting screw "L" to the right 
 thus ^increasing the size of the throttle opening. 
 
 HIGH SPEED ADJUSTMENT. The carburetor is now ready 
 for high speed adjustment and the throttle should be opened and the 
 spark advanced. The machine should be run at high speed on the 
 road. The adjustment is now made by the pointer "Z" which, as 
 it moves from "1" toward "3," increases the supply of gas as it 
 allows the needle valve "E" to be raised higher out of the nozzle. 
 Moving the indicator "Z" from "3" towards "1" cuts down the 
 supply of gasoline as it raises the cam and does not allow the needle 
 to move as far out of the nozzle. When the indicator reaches the 
 
74 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 correct point the engine will run without missing or back firing. If, 
 when lever " Z" is turned to "3 " the mixture is still too lean, causing 
 the engine to miss and back fire, increase the tension of auxiliary 
 air valve spring by turning adjusting screw "12" to the left. 
 
 Fig. 47Schebler Model H 
 
 The air lever on the side of the mixing chamber should be opened 
 when extremely high speed is desired. Be sure to shut this port 
 before the engine is stopped because difficulty will be experienced in 
 starting if this port is left open. 
 
 STARTING. To facilitate easy starting of the engine pull out 
 the knurled button "12" and turn to the right or left so that it 
 cannot fall back in the recess. This tightens the spring on the 
 auxiliary air valve preventing a large quantity of cold air rushing 
 past this valve. The cold air admitted to the carburetor will come 
 only through the primary air passage past the nozzle insuring a rich 
 mixture which will facilitate easy starting. 
 
 After the engine starts the knurled button "12" should be turned 
 back to release the spring tension. Just after the engine starts it 
 
CARBURETORS 
 
 75 
 
 will often be inclined to back fire which is caused by the parts being 
 cold. In this case the knurled button "12" should be dropped into 
 recess marked "2" until the engine warms up. 
 
 KINGSTON MODEL "E" 
 
 This is an auxiliary air type of carburetor with concentric float 
 chamber. The construction is shown in Fig. 48. 
 
 Fig. 48 Kingston Model E 
 
 The principle involved, while simple, requires some explanation. 
 Gasoline is admitted at connection "24" and continues to flow until 
 valve "22" is seated due to the proper height of gasoline being 
 obtained. From the float chamber the gasoline passes to the spray 
 nozzle the shape of which should be particularly noticed as it forms 
 a cup around the needle valve above its seat, the level being 1 / 32 // below 
 the top of the cup. 
 
 When starting this excess of gasoline is drawn up with the primary 
 air and furnishes a very rich mixture. As the speed increases this 
 cup is emptied, the supply being drawn from and regulated by the 
 adjustment of needle valve "7" at its seat. 
 
 Both primary and auxiliary air are drawn from a common source 
 passing controller or choke "11." The primary air passes down the 
 primary air passage "3" and up through the Venturi tube. 
 
 The auxiliary air in this carburetor is not controlled by a valve 
 but by five balls "2" which are lifted from their seats by suction. 
 These balls are seated at different depths and as the suction increases, 
 they permit a greater amount of air to pass by them. There is no 
 adjustment, their action being automatic and arranged by the 
 manufacturer* 
 
76 MOTOR VEHICLES AND THEIR ENGINES 
 
 The only adjustment on this carburetor is the needle valve which 
 should be set to give the proper results at the speed which the ap- 
 paratus will be habitually used. The needle valve when turned to 
 the right, gives leaner mixtures and when turned to the left gives 
 richer mixtures. The action of the auxiliary air should compensate 
 for any change in speed. 
 
 PACKARD 
 
 This carburetor is of the auxiliary air type with eccentric float 
 chamber. The gasoline flows into the float chamber through a 
 needle valve and then into the nozzle "40" (Fig. 49). 
 
 The mixing chamber is surrounded by a water jacket through 
 which passes warm water taken from the water circulation system. 
 This maintains a uniform temperature and insures efficiency in mixing 
 the sprayed gasoline with air. The air has two paths through which 
 it can enter the carburetor, the primary air inlet "33" and the 
 auxiliary air inlet "26." The primary air in passing the nozzle picks 
 up the gasoline. The auxiliary air does not pass the nozzle and there- 
 fore enters the mixing chamber as pure air. 
 
 It is important that the mixture of air and gasoline be kept at a 
 constant proportion. Although the primary air inlet valve is large 
 enough to supply air for all conditions, the proportion of air and gas 
 does not remain constant as the suction increases, therefore auxiliary 
 air is necessary. The auxiliary air inlet valve is controlled by springs 
 so that while the valve opens slightly at low speed the increased 
 suction at high speed opens it still more, admitting a greater amount 
 of air, thus compensating for the rich mixture through the primary. 
 
 The primary air intake is from around the outside of the exhaust 
 pipe. This provides a supply of warm air which prevents condensa- 
 tion in the carburetor and in cold weather materially assists in the 
 vaporization of the gasoline. There is a regulator "30" so that the 
 proportion of warm and cold air may be regulated. 
 
 AUXILIARY AIR VALVE. The valve is controlled by the tension 
 of two springs one within the other. The tension of the springs is 
 regulated by a wedge underneath them. This wedge is connected 
 to the control board and when it is moved towards the word "gas" 
 the tension of the springs is increased causing richer mixtures. 
 This assists in starting especially in cold weather and the lever 
 should be kept more to the side "gas" than "air" until the engine 
 warms up. This is the only regulation on this carburetor. 
 
 To further facilitate starting in cold weather there are chokes in 
 both primary and auxiliary air intakes. 
 
Si/.. i 
 
 77 
 
78 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 PEERLESS 
 
 This carburetor is of the auxiliary air type with eccentric float 
 chamber (Fig. 59). The gasoline enters the float chamber passing 
 through the screen "1107." The level at which the gasoline is 
 maintained in the float chamber is controlled by the float "1100" 
 which operates the levers "1096" which in turn operate the needle 
 valve "1101." From the float chamber the gasoline passes directly 
 to the nozzle "1110" which supplies gasoline to the mixing chamber. 
 
 Fig. 50 Peerless Carburetor 
 
 Air enters the mixing chamber from two sources: the primary 
 air entering at the primary air intake, passing the nozzle located at 
 the center of the Venturi tube "1112," picking up gasoline from the 
 spray nozzle; the auxiliary air enters at the automatic air intake 
 valve " 1079 " which is held in its seat by spring " 1081." The auxili- 
 
CARBURETORS 79 
 
 ary air enters the mixing chamber as pure air compensating for the 
 rich mixture from the primary at high speed. 
 
 The mixing chamber is water jacketed which assists materially 
 in vaporizing the gasoline and producing a more nearly homogeneous 
 mixture. 
 
 The throttle is not of the usual butterfly construction, but con- 
 sists of a valve having two seats. Before leaving the factory the 
 seat "1065" is so adjusted that it will allow the proper amount of 
 mixture to enter the cylinders when idling. The throttle "1064" 
 is controlled by the throttle lever at the top of the steering column 
 or by the accelerator pedal. 
 
 To adjust this carburetor the tension on the auxiliary air valve 
 spring is changed. When nut "1085" is turned to the right, it 
 increases the tension on the spring, thus reducing the amount of 
 auxiliary air entering the mixing chamber for a given amount of 
 suction causing the mixtures to become richer. When nut "1085" 
 is turned to the left it weakens the tension on the spring, thus causes 
 leaner mixtures. 
 
 To limit the maximum amount that the auxiliary air valve can 
 open, an adjusting nut "1086" is placed on the lower side of the 
 auxiliary air valve. By turning this to the left it will limit the 
 maximum amount that the valve can open, thereby reducing the 
 amount of air which enters at high speed. This adjustment should 
 be made so that it does not effect the operation at any point except 
 extremely high speed. 
 
 FIERCE-ARROW 
 
 This carburetor (Fig. 51) is of the auxiliary air type with eccentric 
 float chamber. Gasoline enters the float chamber from the tank, 
 the level being controlled in the usual way. Valve "P" is operated 
 by levers "M" which in turn are operated by the float. From the 
 float chamber gasoline passes direct to the nozzle "A-I." The 
 primary air enters through the tube "K-l," passing through the 
 small Venturi tube "L-l," picking up gasoline from the nozzle, and 
 carrying it to mixing chamber "L." The auxiliary air is admitted 
 through the carefully calibrated reed valves "Q-l" and "N-l." 
 There is no method of regulating auxiliary air. The only regulation 
 on this carburetor affecting the mixture is by the needle valve "D-l." 
 When screwed to the right it will give leaner mixtures and when 
 screwed to the left it will give richer mixtures. 
 
 This carburetor is equipped with an adjustment for regulating 
 the temperature of the air passing through the primary air inlet. 
 
80 
 
CARBURETORS 
 
 81 
 
 Cold air regulator "I" is located at the rear of the carburetor; in 
 warm weather the pointer of the regulator should be set to read 
 "open," in cold weather it should be set to read "closed." Any 
 intermediate adjustments can be made according to the temperature. 
 There is also a hot water jacket "T-l" around the mixing chamber. 
 It is connected by pipe "D" from the carburetor to the outlet water 
 pipe and is equipped with a cock. In warm weather this may be 
 closed partially or entirely. By the use of these two adjustments 
 incorrect mixtures encountered because of the lower grades of gasoline 
 can be overcome as vaporization depends upon temperature. 
 
 STROMBERG MODEL "G" 
 
 This is an auxiliary air type of carburetor with eccentric float 
 chamber. The gasoline enters the float chamber and passes to the 
 two nozzles "C" and "J." 
 
 Fig. 52 Stromberg Model G 
 
 When the engine is idling^ir is drawn through the primary intake 
 passes around the primary nozzle "C" from which a jet of gasoline is 
 spraying. Under load the air valve "E" allows additional air to be 
 sucked in past the auxiliary nozzle "J," producing a mixture which 
 
82 MOTOR VEHICLES AND THEIR ENGINES 
 
 unites with the primary mixture formed in the Venturi tube and 
 passes by the throttle valve to the inlet manifold. 
 
 There are only two simple adjustments that ever need attention, 
 "A" the low speed adjusting nut and "B" the high speed adjusting 
 nut (Fig. 52). To adjust this carburetor precede as follows: 
 With the engine at rest set the high speed nut "B" so there is at 
 least Vie of an inch clearance between the spring "G" and the nut 
 "X" above it. This is imperative. Set the low speed nut "A" so 
 the air valve "E" is seated lightly. 
 
 Start the engine, first closing the choke valve "R" in the air horn 
 by the control provided. Open this as soon as the engine starts and 
 keep open while engine is running. If engine does not start on the 
 third or fourth turn of the crank open this valve and engine should 
 then run. 
 
 LOW SPEED. Do not adjust carburetor until engine is thor- 
 oughly warmed up. When engine is warm and with spark retarded, 
 adjust nut " A" up or down until engine runs smoothly at low speed. 
 To determine proper adjustment open the air valve with finger by 
 depressing "X" slightly. If this causes the engine to speed up 
 noticeably it indicates too rich a mixture and "A" should be turned 
 down notch by notch. If this causes the engine to die suddenly 
 when slightly opening the air valve it indicates too lean a mixture, 
 and "A" should be turned up until this is overcome. Once properly 
 set for idling do not change this adjustment when making the high 
 speed adjustment. 
 
 HIGH SPEED. Advance the spark to the normal position and 
 open the throttle gradually. If engine back fires through the car- 
 buretor it is a positive indication of too lean a mixture and nut "B" 
 should be turned up notch by notch until this is overcome. 
 
 If mixture is too rich as indicated by " galloping" of the engine 
 and heavy black smoke from the exhaust, turn "B" down until engine 
 operates properly. A further test for the correct mixture at high 
 speed can be made by depressing the air valve when the engine is 
 running at this speed. If engine speeds up it indicates too rich a 
 mixture, if engine runs slower too lean a mixture. 
 
 Turning either adjusting nut up means a richer mixture or more 
 gasoline; down means a leaner mixture or more air. 
 
 TO FIND PROPER NOZZLE SIZE. Carburetors are equipped 
 with the proper size nozzle before leaving the factory and on changes 
 should be made unless absolutely necessary. Before changing 
 examine all manifold and valve head connections for air leaks. It 
 is absolutely impossible to make the carburetor operate properly if 
 there are any air leaks in the engine. 
 
CARBURETORS 83 
 
 DOUBLE JET TYPE. If after following the instructions given 
 for adjustment with the engine running idle at low speed the air 
 valve "E" remains tightly seated it indicates too small a primary 
 nozzle "C" and a larger one should be substituted. 
 
 If with the proper adjustment and after stopping the engine the 
 air valve "E" hangs off the seat the primary nozzle is too large and 
 a smaller one should be used. 
 
 To change primary nozzle remove pet cock or plug at "P," insert 
 screwdriver, and unscrew nozzle. 
 
 If the mixture on low speed is correct but to get the proper high 
 speed adjustment it is necessary to turn nut "B" up so far that the 
 spring "G" is in contact with "X" above it, after the engine is shut 
 down, it indicates that the auxiliary nozzle "J" is too small and a 
 larger one should be used. 
 
 If the mixture on high speed is correct but to get the proper 
 adjustment it is necessary to turn nut "B" down so that there is 
 more than y% of an inch clearance between "G" and "X," when 
 the engine is shut down, it indicates too large an auxiliary nozzle 
 "J" and a smaller one should be used. 
 
 To change auxiliary nozzle " J" move air horn to one side, remove 
 plug "A-P," insert screwdriver, and unscrew "J." Nozzles are 
 numbered according to drill gauge sizes; for instance, -No. 59 is 
 larger than No. 60. 
 
 SEASON ADJUSTMENT. Open shutter "T" in summer, 
 close in winter. To get best results from this carburetor warm air 
 should be supplied to the hot air horn of the carburetor from around 
 the exhaust manifold. 
 
 CADILLAC 
 
 This is an auxiliary air type carburetor with concentric float 
 chamber. The gasoline enters the float chamber through the gasoline 
 inlet passage passing the gasoline inlet needle valve. The air is 
 supplied from two sources; the primary air enters at the primary 
 air inlet passing the nozzle at the Venturi tube, the secondary air 
 enters at the auxiliary air valve entering the mixing chamber as 
 pure air. 
 
 A leaning device, sometimes called a "gas-saver," is provided 
 which may be adjusted to cause a mixture in which the proportion 
 of gasoline to air is cut down for ordinary driving speeds. The 
 mixture is not affected by the leaning device at the closed or nearly 
 closed position of the throttle, or at the open or nearly open position. 
 The leaning device is adjusted at " G " (Fig. 53) . When the adjusting 
 
84 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Cadillac Carburetor 
 
 AUTOMATIC THROTTLE 
 
 THROTTLE 
 'AUXILIARY AIR VAtvt 
 
 I 
 
 FLOA 
 
 CATCH BASIN 
 DRAIN PIPE 
 
 GASOLINE INLET 
 PASSAGE 
 
 GASOLINf INLEl 
 NEEDLE VALVE 
 
 -THKOTTtE PUMP 
 
 !H- DRAIN PIPE 
 
 Fig. 53 Cross-Section of Cadillac Carburetor 
 
CARBURETORS 85 
 
 screw "G" is screwed in as far as it will go the leaning device has no 
 influence on the mixture at any throttle position. 
 
 The leaning device consists of a shutter attached to the right 
 hand end of the throttle shaft which covers a slot in the carburetor 
 body when the throttle is opened slightly and then uncovers the slot 
 when the throttle is opened wide or nearly so. A hole is drilled 
 through the carburetor body from the mixing chamber to the slot 
 and another hole is drilled from the float chamber to the slot. When 
 the slot is covered by the shutter, a passage is formed from the mixing 
 chamber to the float chamber. The partial vacuum in the mixing 
 chamber causes a lowering of the air pressure in the float chamber 
 resulting in less gasoline being fed through the spray nozzle. When 
 the shutter uncovers the slot the partial vacuum in the mixing 
 chamber has no effect on the air pressure in the float chamber and 
 the amount of gasoline fed through the spray nozzle is not affected. 
 
 This carburetor is equipped with a device to force gasoline 
 through the spraying nozzle when the throttle is opened quickly for 
 acceleration and is called the "throttle pump." It is so arranged 
 that when opening the throttle slowly it will have no effect on the 
 mixture but when sudden acceleration is desired the plunger will be 
 forced down suddenly as the throttle is opened. In this way the 
 gasoline is forced out of the spray nozzle. As the throttle is closed 
 the chamber below the plunger fills up. 
 
 The carburetor is equipped with an automatic throttle (Fig. 53) 
 controlled by a spring. Its purpose is to prevent pulsations of air 
 in the intake manifold from causing the auxiliary air valve to flutter 
 when the engine is running slowly with the throttle fully opened. 
 The automatic throttle is adjusted when the carburetor is assembled 
 and requires no further attention. 
 
 METHOD OF ADJUSTMENT. Move the spark lever to the 
 extreme left to retard the spark on the sector and the throttle lever 
 to a position which leaves the throttle in the carburetor slightly 
 open. Adjust the air valve screw "A" to a point which produces 
 the highest engine speed. Turning the screw "A" in a clockwise 
 direction increases the proportion of gasoline to air in the mixture 
 and vice versa. 
 
 Close the throttle (move it to the extreme left on the sector) and 
 adjust the throttle stop screw "B" to a point which causes the engine 
 to run at a speed of about 300 revolutions per minute. The spark 
 lever should be at the extreme left on the sector when this adjustment 
 is made. 
 
 With the spark and throttle levers at the extreme left on the 
 sector adjust the air valve screw "A" to a point which produces the 
 
86 MOTOR VEHICLES AND THEIR ENGINES 
 
 highest engine speed. Open the throttle until the shutter attached 
 to the right hand end of the throttle shaft just covers the slot in the 
 carburetor body. Then adjust the screw " G " to a point which pro- 
 duces the highest engine speed or to a point where the engine misses 
 from too lean a mixture, then overcome the missing by turning the 
 screw "G" in a clockwise direction increasing the proportion of gaso- 
 line to air in the mixture. 
 
 During very cold weather when a slightly richer mixture is de- 
 sirable it may be found best to turn the adjusting screw "G" further 
 in a clockwise direction. 
 
 SETTING OF CARBURETOR FLOAT. After the carburetor 
 has been in use for sometime there may be a slight amount of wear 
 at the point of the inlet needle and its seat. If this should occur 
 the height of the gasoline in the carburetor bowl will rise. 
 
 To determine if the float is properly set remove the carburetor 
 from the engine and the bowl from the carburetor. Raise the float 
 until the inlet needle valve is just closed. The dimension "A" 
 (Fig. 53) should then be one-half inch. The setting may be corrected 
 by slightly bending the arm to which the float is attached. 
 
 MARVEL 
 
 This is an auxiliary air type of carburetor with eccentric float 
 chamber. The spray nozzle opening is regulated by a needle valve 
 which constitutes the gasoline adjustment of the carburetor and it 
 is surrounded by the Venturi tube, through which a portion of the 
 incoming air passes at high velocity, picking up gasoline from the 
 end of the spray nozzle. 
 
 The mixing chamber also contains the air valve and the high 
 speed nozzle. The auxiliary air valve is held to its seat by an adjust- 
 able spring which forms the air adjustment. At a high rate of speed 
 the suction increases. This causes the auxiliary air valve to lift 
 from its seat admitting additional air mixed with gasoline drawn 
 from the high speed nozzle (Fig. 54). 
 
 The air enters the carburetor through a three-way valve connected 
 to the air regulator on the instrument board. By means of this valve 
 the air can be taken from the heater under the exhaust manifold or 
 directly from the atmosphere. In the " choke" position this valve 
 partly closes the air intake causing the engine to draw excessively 
 rich charges for starting. 
 
 The opening between the mixing chamber and the intake manifold 
 is controlled by a butterfly valve. This is connected to the throttle 
 lever on the steering wheel and thus regulates the amount of mixture 
 being fed to the engine. 
 
87 
 
88 MOTOR VEHICLES AND THEIR ENGINES 
 
 The upper end of the mixing chamber and the Venturi tube are 
 surrounded by jackets through which some of the hot exhaust gas 
 passes to keep the carburetor warm and assist vaporization of the 
 fuel. A damper in the jacket opening is connected to and controlled 
 by the throttle lever so as to increase the amount of heat as the 
 throttle is closed. In warm weather the diamond-shaped shutter 
 on the bottom of the carburetor should be opened to allow the hot 
 exhaust gas to escape before it overheats the nozzle. 
 
 ADJUSTMENT OF THE CARBURETOR. Turn gasoline ad- 
 justment to the right until needle valve is completely closed. Set 
 air adjusting screw so that end of the screw is even with the point 
 of the ratchet spring just above it. Open gasoline adjustment by 
 giving needle valve one full turn. Start engine as usual and allow 
 it to run a few minutes with air regulator turned to "hot" until 
 engine is thoroughly warmed up. 
 
 With the spark lever fully retarded turn gasoline adjustment to 
 the right, closing needle valve until engine misses and then turn to 
 left until engine idles smoothly. 
 
 Advance the spark lever and turn air adjustment screw to the 
 left, a little at a time, until the engine misses indicating too much 
 air and then turn it to the right until the engine runs smoothly. 
 
 To test the adjustment leave spark lever advanced and open 
 throttle quickly. The engine should accelerate instantly. If it 
 skips or pops back open gasoline adjustment slightly by turning 
 needle valve to the left. Do not touch air adjustment again unless 
 it appears absolutely necessary. The best possible adjustment has 
 been secured when gasoline adjustment is turned as far as possible 
 to the right and air adjustment is turned as far as possible to the left. 
 This allows engine to idle smoothly and accelerate quickly when 
 throttle is opened. 
 
CHAPTER X 
 
 CARBURETORS (continued) 
 
 The carburetors explained in this chapter do not employ auxiliary 
 air valves. The methods used to keep the proportion of air and gas 
 constant at varying speeds is explained as each carburetor is discussed. 
 
 STEWART MODEL 25 
 
 This carburetor is of the metering pin type, that is, it meters out 
 the proper amount of gasoline for each speed. The action of the 
 carburetor is as follows: The suction created in the inlet manifold 
 draws air into the mixing chamber through air ducts, drilled holes 
 "H H" (Fig. 55). The same suction draws a fine spray of gasoline 
 through the aspirating tube "L" into the mixing chamber and the 
 air becomes impregnated with the gasoline vapor. In order that the 
 proportions of air and gasoline vapor may be correct for all engine 
 speeds provision is made by means of a valve "A" for the automatic 
 admission of larger quantities of both air and gasoline vapor at high 
 engine speed. The passages "H H" are open at all times, but the 
 valve " A" is held to its seat by its weight until the suction, increasing 
 as the engine speed increases, is sufficient to lift it and admit a greater 
 amount of air by passing around "A" at "L" The valve "A" is 
 joined to the tube "L" hence the latter is raised when the valve is 
 lifted and the increase of proportionally larger quantities of gasoline 
 is made possible. This is accomplished by means of a tapered meter- 
 ing pin "P " normally stationary, projecting upward into the tube 
 "L." The higher the tube rises the smaller is the section of the 
 metering pin even with its opening and the greater is the quantity of 
 gasoline which may be taken into the tube. The taper of the me- 
 tering pin being carefully designed, the carburetor thus automatically 
 produces the correct mixture and quantities for all engine speeds. 
 
 There is one adjustment which can be made on this carburetor 
 but which should not be changed unless it is known absolutely that 
 the adjustment is incorrect. The height of the metering pin relative 
 to the opening of the aspirating tube can be changed. To change the 
 fixed " running" position of the pin turn the stop screw to the right 
 or left. Turning this screw to the right lowers the position of the 
 metering pin and turning to the left raises it. As the pin is lowered 
 
A Air Valve 
 B Air Valve Seat 
 C Float Chamber 
 D Dash Pot 
 E Combining Tube 
 F Metal Float 
 G Gasoline Inlet Valve 
 H Drilled Holes 
 I Air Passage 
 K Air Valve Guide 
 L Aspirating Tube 
 M Dash Control Pinion 
 N Metering Pin Carrier 
 
 and Rack 
 
 O Mixing Chamber 
 P Metering Pin 
 Q Gasoline Valve Cap 
 S Gasoline Passage 
 V Throttle Valve Lever 
 Z Filler Screen 
 
 AA Air Inlet 
 
 CC Filter Cap 
 
 Fig. 55 Stewart Model 25 
 90 
 
CARBURETORS 91 
 
 more gasoline is admitted to the aspirating tube at a given engine 
 speed thus enriching the mixture. A wider range of adjustment of 
 the position of the metering pin may be made by releasing the clamp 
 "M" of the pinion shaft lever and changing its position with relation 
 to the shaft. This requires very careful work and should only be 
 made in extreme cases. The metering pin is also subject to control 
 from the dash and when making any of the foregoing adjustments the 
 dash adjustment must be all the way in. 
 
 In starting the engine, especially in cold weather, some difficulty 
 may be experienced. To overcome this difficulty a very rich mixture 
 is required temporarily. To obtain this without disturbing the regu- 
 lar carburetor adjustment a control is provided with an operating 
 plunger on the dash or instrument board. Pulling out the plunger 
 operates the pinion shaft at "M" on the carburetor and lowers the 
 metering pin. This permits more gasoline to be drawn through the 
 aspirating tube than normally. Though the quantity of air drawn 
 into the mixing chamber remains the same a richer mixture results. 
 A mixture of this character ignites much more readily than one 
 having a greater proportion of air, but the resulting explosion does 
 not produce any more power. Therefore, as soon as the engine starts 
 the plunger at the dash should be pushed down. 
 
 In very cold weather, the dash adjustment should not be pushed 
 all the way down after the engine starts but should be pushed part 
 way back and left there until the engine warms up. This is necessary 
 because the gasoline does not vaporize as readily in the cold weather. 
 
 To prime the carburetor remove Gasoline Valve Cap, "Q" and 
 lift the float needle valve. 
 
 HUDSON 
 
 This carburetor is of the metering pin type with eccentric float 
 chamber. The gasoline enters the gasoline feed regulator and passes 
 up the "V" groove in the measuring pin. As the measuring pin is 
 lifted it causes a larger opening supplying an increased amount of 
 gasoline. The suction of the engine draws air through the air intake 
 and also from the air chamber above the piston (Fig. 56). As the 
 air is drawn from the air chamber it causes the piston to rise and 
 lift the measuring pin. As the suction increases the greater will be 
 the amount that the piston is raised, proportionately increasing the 
 gasoline supply. As the piston rises a larger area for the air is 
 provided, therefore, the velocity does not necessarily increase with 
 the increased amount of air passing. If the amount of air passing 
 increases and the velocity does not materially increase it will require 
 
<i 
 
 IO 
 
 to 
 
 
 
 2:5 
 
 55 
 
 UlX 
 
 fi 
 
 
 5 
 wf 
 
 > 
 
 a 
 
 z 
 
 LU 
 
CARBURETORS 93 
 
 a larger opening at the measuring pin to keep the proper propor- 
 tions. This is automatically controlled by the piston at the same 
 time. 
 
 In case the resulting mixture is not correctly proportioned the 
 gasoline feed regulator can be adjusted. If it is lowered it will cause 
 richer mixtures and if it is raised it will cause leaner mixtures. This 
 adjustment is made by the feed regulator lever which is attached to 
 a dash control. 
 
 If found necessary to enrich the mixture for starting purposes do 
 not forget to readjust it to the lean position as soon as the engine 
 warms up. Do not have the air control lever in the "choke" or 
 "hot" position after the engine is warm. The increased resistance 
 to the air intake causes a proportionately greater throttle opening 
 than is necessary for the power developed and this results in excessive 
 gasoline consumption. 
 
 The only attention necessary on this type of carburetor is to see 
 that the filter under the float chamber is not clogged up, thereby 
 restricting the flow of gasoline, and that the needle valve is seating 
 properly and does not allow the gasoline level to increase and over- 
 flow at the regulating sleeve. It is also advisable to note the action 
 of the carburetor to make sure that the piston valve is acting smoothly 
 and responds to the speed of the engine. It is possible that this 
 piston valve may stick in the cylinder through an excessive accumu- 
 lation of dust which may be caused by driving on a much frequented 
 road. Provided the strangler is used for starting it is very likely 
 this will not be noticed as it is possible to operate this carburetor 
 without any valve action at all. However, if the car is used by an 
 experienced driver who counts upon quick acceleration and good 
 hill climbing abilities the difference will be noticed. This will be 
 especially noticeable if driving without the strangler particularly in 
 cold weather. 
 
 To free the valve it is only necessary to remove the cover at the 
 top of the cylinder, withdraw the valve from its place, and clean it 
 with a little gasoline. In putting it back a few drops of kerosene 
 on the top of the piston will help in flushing down any sediment or 
 grit which the gasoline may have left. 
 
 STROMBERG MODEL "M" 
 
 This carburetor is of a plain tube construction in which both the 
 air and the gasoline openings are fixed in size. The gasoline is 
 metered automatically without the aid of moving parts by the suction 
 of air velocity past the jets (Fig. 57). 
 
94 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 N 
 
 M 
 
 AIR 
 
 Fig. 57 Stromberg Model M 
 
 To maintain the proper proportion of gasoline and air at variable 
 engine speeds an AIR BLED JET is used (Fig. 58). The principles 
 
 of the Air Bleeder are as follows : 
 The gasoline leaves the float 
 chamber, passes the point of the 
 high speed adjusting needle, and 
 rises through the channel "B." 
 Air is taken in through the Air 
 Bleeder "C" and discharged 
 into the gasoline channel through 
 small holes "D." It should be 
 noted that this air is discharged 
 
 into the gasoline before the latter 
 reacheg ^ je( . holeg ^ ^ smal , 
 
 Venturi tube "E." As the suction of the engine increases drawing a 
 proportionately greater amount from the holes at "E" the propor- 
 tions are kept constant because of the amount of air bled with the 
 gasoline in the channel "B." 
 
 The accelerating well (Fig. 59) operates as follows: The action 
 is based upon the principle of the ordinary U-tube. If a U-tube 
 
 Fig. SS-Air Bleeder 
 
CARBURETORS 
 
 95 
 
 contains a liquid and suction is applied to one end of the tube the 
 liquid will rise in that arm and will drop in the other arm. Referring 
 to Fig. 59, the space "F" forms one arm of the U-tube and the space 
 "B" the other arm. These spaces communicate with each other 
 through the holes "G" thus forming a modified form of U-tube. 
 
 When the engine is 
 idling or retarding in 
 speed the accelerating 
 well or space "F" fills 
 P with gasoline. When the 
 
 / throttle is opened increas- 
 
 m ^ ne suction in the 
 Venturi tube the following 
 takes place: Atmospheric 
 pressure in the space "F" 
 is exerted through the 
 bleeder forcing the liquid 
 down to join the regular 
 flow from "H" passing up 
 the space "B" and out 
 into the high velocity air 
 stream through the small 
 Venturi tube. While the 
 well acts the flow of gaso- 
 line is more than double 
 the normal rate compen- 
 sating for the lagging of 
 the gasoline due to inertia. 
 Upon close observation it will be noticed that there is a series of 
 small holes down the wall of the well. Referring to the analogy of 
 the U-tube these holes directly connect the two arms of the U-tube. 
 It is obvious that the smaller and fewer these holes, the faster the 
 well will empty due to the U-tube suction, and the larger and more of 
 these holes, the slower the well will empty. It is therefore apparent 
 that the rate of discharge of the well can be regulated, as required 
 by different engines, different grades of gasoline, different altitudes, 
 etc., by inserting wells of different drillings. The action of tjie well 
 is also dependent upon the size of the hole in the bleeder because the 
 area of the hole of the bleeder relative to the areas of the holes in 
 the well determines the rate at which the well will empty. 
 
 The operation and arrangement for idling is shown in Fig. 60. 
 Concentric and inside of the passage "B" is located the IDLING 
 TUBE "J." When the engine is idling, that is when the throttle is 
 
 B 
 
 Fig. 59 Accelerating Well 
 
 H 
 
MOTOR VEHICLES~AND THEIR ENGINES 
 
 practically closed, the action which takes place is as follows: The 
 gasoline leaves the float chamber, passes through the passage "H" 
 into the idling tube through the hole "I," thence up through the idling 
 
 jet "L." Air is drawn through 
 the hole "K" and mixes with 
 the gasoline to form a finely 
 divided mist which passes on 
 to the jet "L." This jet 
 directs the mist, of gasoline and 
 air into the manifold just above 
 the lip of the throttle valve. 
 In as much as this throttle 
 valve is practically closed, the 
 vacuum created at the entrance 
 of the jet "L" is very high and 
 exceeds 8 pounds per square 
 inch. 
 
 It is obvious, therefore, with 
 this condition, that the gasoline 
 will be drawn into the manifold 
 in a highly atomized state. It 
 is well to call attention here to 
 the fact that the LOW SPEED 
 ADJUSTING SCREW "F" 
 operates a needle valve which 
 controls the amount of air pas- 
 sing through the hole "K" and 
 it is the position of this needle 
 
 valve which determines the 
 Fig. QO-Idling Jet idjing mixture . 
 
 As the throttle is slightly opened from the idling position a suction 
 is created in the throat of the small Venturi tube as well as at the 
 idling jet. When idling, the suction is greater at the idling jet, and 
 when the throttle is open the suction is greater at the small Venturi 
 tube. At some intermediate position of the throttle there is a time 
 when the suction at the idling jet is equal to that at the small Venturi 
 tube, therefore, at this particular time the gasoline will follow both 
 channels to the manifold. This condition (Fig. 61) lasts but a very 
 short while because as the throttle is opened wider the suction at the 
 small Venturi tube rapidly becomes greater than that at the idling 
 jet. The result is that the idling tube and idling jet are thrown 
 entirely out of action and the level of the gasoline in the idling tube 
 drops (Fig. 62) when the throttle is wide open, in which case all of 
 
 H 
 
CARBURETORS 
 
 97 
 
 Fig. 61 Operation at Slow Speed 
 
 Fig. 62 Operation at High Speed 
 
98 MOTOR VEHICLES AND THEIR ENGINES 
 
 the gasoline enters the manifold through the holes in the Venturi 
 tube. With the throttle in this position the accelerating well has 
 emptied, and there is a direct passage for air from the Bleeder to the 
 gasoline in the main passage, giving the "AIR BLED JET" feature 
 explained before. 
 
 TO ADJUST THE CARBURETOR. Turn both high and low 
 speed adjusting screws "A" and "B" completely down so that the 
 needle valves just touch their respective seats. Then unscrew 
 (anti-clockwise) the high speed adjustment "A" about three turns 
 off the seat, and turn low speed adjusting screw "B" (anti-clockwise) 
 about one and one-half turns off the seat. The air-horn choke valve 
 should be closed and the engine is set for starting. After the engine 
 has warmed up and the air-horn choke valve is wide open the car- 
 buretor is ready for adjustment. 
 
 To adjust the high-speed adjustment "A" proceed as follows: 
 Advance the spark to the position for normal running. Set the gas 
 lever on the steering-wheel quadrant at such a position corresponding 
 to an engine speed of approximately 750 R. P. M. Then turn down 
 (clockwise) on the high-speed screw "A" gradually, notch by notch, 
 until a missing of the engine results. Then turn up or open the same 
 screw (anti-clockwise) until the engine runs at the highest rate of 
 speed for that particular setting of the throttle. This gives an 
 approximate setting of the needle " A." 
 
 To adjust the low-speed adjustment "B" proceed as follows: 
 Retard the spark fully and close the throttle as far as possible without 
 causing the engine to come to a stop. If upon idling the engine tends 
 to "roll" or "load" it is an indication that the mixture is too rich 
 and therefore the low-speed adjusting screw "B" should be turned 
 away from the seat (anti-clockwise) thereby permitting the entrance 
 of more air into the idling mixture. This rolling of the engine might 
 also be due to uneven compression in the cylinders, or to the lack of 
 compression in one or more of the cylinders. The low-speed adjust- 
 ment is best made by carefully observing the smoothness with which 
 the engine revolves when idling, and can be properly obtained by 
 turning the screw "B" up or down, notch by notch, until the best 
 idling prevails. It is safe to say that the best idling results will exist 
 when the screw "B." is not much more or less than one and one-half 
 turns off the seat 
 
 After satisfactory adjustments have been made with the motor 
 vehicle stationary it is most important and advisable to take the 
 vehicle out on the road for further observation and finer adjustments. 
 If upon rather suddenly opening of the throttle the engine backfires 
 it is an indication that the high-speed mixture is too lean and in this 
 
CARBURETORS 
 
 99 
 
 case the adjusting screw "A" should be opened one notch at a time 
 until the tendency to backfire ceases. On the other hand if when 
 running along with open throttle the engine " rolls" or "loads" it is 
 an indication that the mixture is too rich and this is overcome by 
 turning the highspeed screw "A" down (clockwise) until this loading 
 is eliminated. 
 
 ZENITH MODEL "L" 
 
 This carburetor is of the compound nozzle type and to fully under- 
 stand its operation a detailed description of the principle upon which 
 it is constructed will be given. 
 
 As was explained with a simple construction of carburetor having 
 no regulation (Fig. 41) when the suction increases the air and 
 gasoline increases but the proportion of gasoline increases a greater 
 amount than the air, therefore, the mixture becomes richer. 
 
 F 
 
 Fig. 63 Constant Flow Nozzle 
 
 If a jet such as shown in Fig. 63 be used in which the opening 
 at "I" is smaller than the opening at the nozzle "H" the follow- 
 ing condition will exist. When the car has been standing the well 
 "J" and nozzle "H" will fill up to the level in the float chamber 
 "F." Although the suction is not high at ordinary speeds say 400 
 R. P. M. yet it could take up more gasoline from "H" than is 
 permitted to flow through "I." Air is also drawn up through the 
 nozzle from the open well and the mixture is too lean for proper 
 results. 
 
 As the speed of the car increases the suction is greater and the 
 quantity of air increases while the gasoline remains the same because 
 
100 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 the tiny stream at "I" is independent of the suction at "H" (the 
 suction at "H" is not transmitted to "I" because the open well 
 "J" allows air to satisfy this suction). The mixture becomes leaner 
 and leaner as the speed or suction increases, the action being directly 
 opposite to that of the simple jet construction. 
 
 E K' 
 
 Fig. 64 Compound Jet 
 
 In Fig. 64 a construction is shown with the jets combined showing 
 the level of the gasoline when the engine is at rest. The simple jet 
 "G" is supplied through the pipe "E" and compounded with the 
 jet "H" which is supplied by the pipe "K" from open well "J" and 
 compensator "I." 
 
 E 1 K 1 
 
 Fig. 65 Operation at Low Speed 
 
 Fig. 65 shows the condition when the engine is under load at 400 
 R. P. M. with wide open throttle. This suction is not very strong, 
 but it is lifting gasoline from nozzle #W. and also from nozzle "H," 
 
 ft* 
 
CARBURETORS 
 
 101 
 
 the latter being fed from open well "J." "T&e action of "the com- 
 pensator "I" has held down the supply algasqllntf &$ifap av^l has 
 emptied. 
 
 Fig. 66 shows the condition 
 with the engine turning 1600 
 R. P. M. The suction has 
 greatly increased as shown by 
 the arrows drawing more gaso- 
 line from nozzle "G," nozzle 
 "H" however, still gives the 
 same measured amount because 
 of the action of the compensa- 
 tor "I." 
 
 The compound nozzle re- 
 ceives its gasoline from two 
 sources. At any speed both 
 sources of supply are in action. Fig. 66 Operation at High Speed 
 The main jet "G" (the one 
 
 controlled by suction) is selected of the proper size to give 
 just about enough gasoline at high suction. At low suction it will, 
 of course, be deficient. This unavoidable defect of one nozzle, start- 
 ing poor and growing richer until it is almost right at high suction, is 
 compensated for by the peculiarity 
 of the other jet "H" which also 
 starts poor and keeps growing 
 poorer. The compensator " I " sup- 
 ports the main nozzle "G" at low 
 suction when it is most needed. 
 One supplements the other so that 
 at every engine speed there is a 
 constant ratio of air and gasoline 
 to stimulate efficient combustion. 
 
 IDLING DEVICE. At low 
 speed when the butterfly throttle 
 valve "T" is nearly closed the 
 main jet and cap jet gives but little 
 or no gasoline, but as there is con- 
 siderable suction on the edge of the 
 butterfly, the gasoline is drawn 
 through the idling device. This 
 device (Fig. 67) consists of the 
 idling tube "J" within the secondary 
 well "P" inserted in the first well Fig. 67 Idling Device 
 
102 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 at the bottom of whic^the compensator "I" is located and which 
 is openitkxjat^spbpi-e pressure through holes "A." 
 
 Gasoline from the compensator "I" flows through the calibrated 
 hole in the bottom of the secondary well "P" which in turn is ad- 
 justably open to the air through the idling screw "O." The idling 
 tube "J" leads to a hole located at the edge of the butterfly throttle 
 valve where the suction is most strongly felt. This suction lifts the 
 gasoline through the idling tube and, in combination with the air 
 passing the butterfly valve, forms the idling mixture. 
 
 There are four adjustments which are possible with this type of 
 carburetor. 
 
 1. Choke tube "X." 
 
 2. Main jet "G." 
 
 3. Compensator " I." 
 
 4. Regulator screw "0." 
 
 CHOKE TUBE TOO LARGE. The "pick up" will be defective 
 and cannot be bettered by the use of a larger Compensator. Slow 
 
 Fig. 68 Zenith Model L 
 
CARBURETORS 103 
 
 speed running will not be very smooth. The engine will have a 
 tendency to "load-up" under a hard pull and at high speed the 
 exhaust will be of an irregular nature. This "loading-up" will be 
 much worse if the manifold is too cold. 
 
 CHOKE TUBE TOO SMALL. The effect of a small Choke Tube 
 is to prevent the engine from taking a full charge with the throttle 
 opened wide. The "pickup" will be very good but it will not be 
 possible to get all the speed of which the car is capable. Remember 
 that when the Choke (Venturi tube) is increased more air is admitted 
 and the mixture is correspondingly thinned. The influence of the 
 Main Jet is mostly felt at high "speed. 
 
 MAIN JET TOO LARGE. At high speed on a level road it will 
 give the usual indications of a rich mixture; irregular running, 
 characteristic smell from the exhaust, firing in the muffler, sooting 
 up at the spark plugs, and low mileage. 
 
 MAIN JET TOO SMALL. The mixture will be too lean at high 
 speed and the car will not attain its maximum speed. There may 
 be back-firing at high speed, but this is not probable especially if the 
 Choke and main jet are according to the factory setting. This back- 
 firing is more often due to large air leaks in the intake or valves or to 
 defects in the gasoline line. 
 
 The compensator size is best tried out on a long gradual hill of 
 such a slope that the engine will labor rather hard to make it on high 
 gear. A long, even, hard pull of this sort taxes the efficiency of the 
 Compensator to the utmost and will indicate readily the correctness 
 of its size. 
 
 COMPENSATOR TOO LARGE. This will cause too rich a 
 mixture on a hard pull. It will give the same indication as for rich 
 mixture at high speed on the level. 
 
 COMPENSATOR TOO SMALL. This will cause too lean a 
 mixture making the engine liable to miss and give jerky action of 
 the car on a hard pull. 
 
 IDLING DEVICE IS TOO SMALL. It will be impossible to 
 obtain a satisfactory mixture except by turning the Idling (adjusting) 
 Screw all the way in. In this event put in a larger Idling Device. 
 
 IDLING DEVICE IS TOO LARGE. It will be impossible to 
 obtain a satisfactory mixture unless the Idling Screw is turned out as 
 far as possible. In this case put in a smaller Idling Device. 
 
 It has been found from practice that it is rarely necessary to make 
 adjustments on this carburetor as the conditions are carefully cal- 
 culated when installing the carburetor by the engine manufacturer, 
 however, in a few cases where the climatic conditions or the grade of 
 
104 MOTOR VEHICLES AND THEIR ENGINES 
 
 gasoline vary greatly from the ordinary standards, the Compensator 
 "I" and the Jet "G" may have to be changed. 
 
 RAYFIELD 
 
 The Rayfield carburetors are made in two types, models G and 
 L. The difference is that model G is water-jacketed (Fig. 69). 
 These carburetors are of the mixed type, having both auxiliary air 
 valves and metering pins. The gasoline supply enters through the 
 gasoline intake passing the needle valve which is operated by the 
 float. Gasoline is supplied from the float chamber to the two 
 nozzles, marked in Fig. 69 as "spray nozzle" and " metering pin 
 nozzle." 
 
 Air enters the mixing chamber from three sources: Through a 
 constant air opening which is a hole in the side of the carburetor so 
 that the air in entering the mixing chamber passes the spray nozzle. 
 Air also enters through the upper automatic air valve, this air passing 
 the metering pin nozzle. The lower air valve admits air directly to 
 the mixing chamber and is operated by levers which are controlled 
 by the automatic air valve. 
 
 The operation of this carburetor is as follows: With a closed 
 throttle and the engine idling, air enters through the constant air 
 opening picking up gasoline at the spray nozzle. As the speed is 
 increased and the throttle opened wide, the increased suction will 
 cause the automatic air valve to open. This valve in opening causes 
 the lower air valve to open and at the same time forces down the 
 metering pin which increases the opening at the metering pin nozzle, 
 causing a greater amount of gasoline to be supplied. When suddenly 
 accelerating the operation is as follows: The automatic air valve 
 opening suddenly causes the dash-pot piston to force gasoline out 
 of the metering pin nozzle, thus enriching the mixture which will 
 compensate for the lag of the gasoline due to inertia. 
 
 ADJUSTING LOW SPEED. With throttle closed, dash control 
 down, close nozzle needle by turning low speed adjustment to the 
 left until block "U" slightly leaves contact with cam "M." Then 
 turn to the right about 3 complete turns. Start engine and allow 
 it to run until warmed up. Then with retarded spark close throttle 
 until engine runs slowly. With the engine thoroughly warm make 
 final low speed adjustment by turning low speed screw to left until 
 engine misses and then turn to right a notch at a time until engine 
 idles smoothly. If the engine does not throttle low enough turn 
 stop arm screw "A" to the left until the engine runs at the lowest 
 number of revolutions desired. 
 
HIGH SPEED 
 ADJUSTMENT 
 
 TURN TO RIGHT FOR. 
 
 MORE GAS 
 
 LOW SPEED 
 ADJUSTMENT 
 
 (LOWER AIR VALVE] 
 MODEL G 
 
 Fig. 69 Rayfield Carburetor 
 
 105 
 
106 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 ADJUSTING HIGH SPEED. Advance spark about one-quarter. 
 Open throttle rather quickly. Should engine miss, it indicates a 
 lean mixture. Correct this by turning high speed adjustment screw 
 to the right one notch at a time until the throttle can be opened 
 quickly without the engine missing. If "loading" or "choking" is 
 experienced when running under heavy load with throttle wide open, 
 it indicates too rich a mixture. This can be overcome by turning 
 high speed adjustment to the left. 
 
 TO START ENGINE WHEN COLD. First, close throttle and 
 pull dash control all way up. Second, when engine starts open 
 throttle slightly and push dash control J4 way down. Third, as 
 engine warms up push control down gradually as required. When 
 thoroughly warm push dash control all way down. When engine is 
 warm it is necessary to pull dash control only part way up for starting. 
 
 SCHEBLER MODEL A, SPECIAL 
 
 This carburetor is of the plain tube type with eccentric float 
 chamber. All the air enters at "I" and passes through the Venturi 
 tube past the nozzle to the inlet manifold (Fig. 70). The gasoline 
 supply enters at "12" passing through the screw "11" and enters 
 the float chamber. The proper level is maintained in the usual 
 manner by a float "15" operating a needle valve "13." From the 
 float chamber the gasoline has two paths; one is past Idle adjusting 
 needle valve "9" to passage "7," the other is past main fuel adjusting 
 needle valve "14." 
 
 When starting, the choke should be closed (Fig. 71), especially in 
 cold weather and the throttle "19" nearly closed. This shuts off 
 the air supply and the suction causes gasoline to be drawn through 
 
 passage "7" and out the 
 opening just above the 
 throttle. Some gasoline will 
 also be drawn from the three 
 holes "21" and the lip "6." 
 This gives a rich mixture 
 which makes starting easy. 
 When running idle the 
 throttle is closed. This only 
 permits a small amount of 
 air to pass through the 
 Venturi tube, its velocity not 
 being sufficient to draw gaso- 
 Fig. 71 Operation Choked line from the main jet. The 
 
107 
 
108 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 72 Operation Running Idle 
 
 Fig. 73 Operation Under Partial 
 Load 
 
 greatly restricted area at the throttle creates a suction at the open- 
 ing of passage "7." Some of the air entering will pass under the 
 edge of the Venturi tube (Fig. 72) into passage "18," thence through 
 passage "7" mixing with the gasoline. This mixture is delivered 
 through the opening just above the throttle. 
 
 As the throttle is opened the amount of mixture drawn through 
 the Venturi tube is increased. The velocity of the air now being 
 sufficient to cause a suction which will draw fuel through the three 
 holes "21" (Fig. 73). The incoming air strikes the projecting lip 
 
 on the nozzle housing and due 
 to its velocity enters the hole 
 "6." Due to the U-tube con- 
 struction contained in the 
 nozzle housing, the level of 
 gasoline in the arm connected 
 to the opening "6" will be 
 lowered uncovering holes be- 
 tween this arm and arm "20." 
 As these holes are uncovered 
 the air passes through them 
 mixing with gasoline in passage 
 "20." Instead of pure gaso- 
 
 Fig. 74 Operation Under Full Load line bein S delivered at holes 
 
 "21," a spray of air and gasoline 
 
 is delivered which mixes with the air being drawn through the 
 Venturi tube. Some mixture may be delivered by the idling jet, 
 decreasing as the throttle is opened. 
 
 When the throttle is wide open (Fig. 74) the increased amount of 
 air passing through the Venturi tube causes a much greater suction 
 
CARBURETORS 109 
 
 at the holes ".21," likewise the pressure at the hole "6" is increased 
 causing the level to be lowered still further in the U-tube. This 
 permits more air to be drawn through the communicating holes 
 mixing with the gasoline in the passage "20." Thus the proportion 
 of air and gasoline delivered to the mixing chamber is kept constant 
 as an increasing amount is drawn through the holes "21." If only 
 pure gasoline was drawn the mixture would become richer but as 
 both air and gasoline are drawn from holes "21," this air bleeding 
 keeps the mixture constant at all speeds. 
 
 ADJUSTMENT. There are but two adjustments on this car- 
 buretor both of which control the amount of gasoline supplied. The 
 idle adjusting needle valve "9" regulates the supply of gasoline for 
 idling and the main needle valve "14" regulates the amount of 
 gasoline supplied to the main fuel nozzle "4." 
 
 Screw out both Adjusting Needles several turns. Start the en- 
 gine with the throttle slightly open. Slowly turn the Idle Adjusting 
 Head "17" to the right or towards the "less gas" position as indi- 
 cated by the dial until the engine runs smoothly. Adjust the engine 
 speed for running idle by means of the throttle lever Stop Screw on 
 the throttle lever. Open the throttle wide allowing the governor to 
 regulate the engine speed and with a retarded spark turn the Main 
 Gas Adjusting Head "16" toward the "less gas" direction until the 
 engine begins to miss or backfire. Turn the adjusting head in the 
 "more gas" direction just sufficient to stop the engine missing or 
 backfiring. These adjustments should produce a good mixture. 
 
 For starting or warming up with the present day fuel it is almost 
 always necessary to use the air choke until proper operating tem- 
 perature is obtained. The engine will start readily with the choke 
 closed one-half to three-quarters of the way. When the weather is 
 very cold it may be necessary to close the choke entirely, but this 
 should be done only for an instant, as it cuts off all the air and delivers 
 practically raw gasoline. 
 
 WHITE 
 
 The White is an eccentric float, multi-jet type of carburetor (Fig. 
 75). Air enters at opening "47," which is .provided with a choke 
 "42." The gasoline flows from the float chamber to the low speed 
 nozzle "29" and high speed nozzle "28." A small drilled hole "62" 
 in the side of low speed nozzle "29" near its base supplies gasoline 
 to a passage leading to a vertical well "64" in the side of the car- 
 buretor body. 
 
 The nozzles are incased in nozzle sheaths "34" and "33." Low 
 speed nozzle sheath "34" is open at the top but closed at the bottom 
 
110 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 to air entering at "47." High speed nozzle sheath "33" is open at 
 the top and drilled with holes "63" at the bottom permitting some 
 of the air to be drawn up inside the sheath discharging at its top. 
 Ths starting nozzle "65" dips into the vertical well "64" and sup- 
 
 34 33 
 
 Fig. 75 The White Carburetor 
 
 plies gasoline through a small drilled hole just above the throttle 
 valve. Screened hole "106" opening into the top of the well, main- 
 tains atmospheric pressure at all times. The throttle valve "2" is 
 of the barrel type, consisting of a metal cylinder with twin openings 
 cut through it of the proper shape to admit mixture. As the throttle 
 is revolved on its axis the opening from the low speed nozzle is 
 gradually uncovered. At a certain point the opening to the high 
 speed nozzle is uncovered and at wide open throttle position, both 
 passages are completely uncovered. A screw "36" is provided 
 regulating the amount of air supplied with the throttle closed and 
 the engine idling. 
 
A IDLE 
 
 S L P 
 
 B Low SPEED 
 
 C MEDIUM SPEED 
 
 H L P 
 
 D HIGH SPEED 
 
 Fig. 76 Operation of White Carburetor 
 ill 
 
112 MOTOR VEHICLES AND THEIR ENGINES 
 
 Referring to the diagrams in Fig. 76 the operation of the car- 
 buretor is as follows: 
 
 For idling or starting the throttle is completely closed (Fig. 76 A). 
 Suction in the intake manifold causes a reduction in pressure above 
 the throttle "T." Atmospheric pressure exerted at the top of well 
 " W" causes gasoline to rise in the starting nozzle "N." At the same 
 time, air is drawn past the regulating screw (not shown) and through 
 the drilled hole "D" producing a mixture for starting and idling. 
 The choke must be closed when starting, reducing to a minimum the 
 amount of air drawn through "D." 
 
 ' For low speed the throttle is turned so that the low speed passage 
 is partially uncovered (Fig. 76B). A considerable volume of air is 
 drawn past the low speed nozzle sheath "S" causing low speed 
 nozzle "L" to deliver gasoline which passes out the opening at the 
 top of the sheath and mixes with the incoming air. The well "W" 
 is almost immediately emptied, a small quantity of air probably 
 being drawn in through the passage "P." The high speed nozzle 
 "H" is still completely covered. 
 
 As the throttle is turned to the medium speed position, the low 
 speed passage is further uncovered and the high speed passage is 
 uncovered slightly (Fig. 76C). The low speed nozzle "L" functions 
 as before, the increased suction causing it to deliver more mixture. 
 Additional air and gasoline is supplied through the partially un- 
 covered high speed passage, air passing in at the bottom of the sheath 
 "R." 
 
 As the throttle is turned to the high speed position, both low and 
 high speed passages are completely uncovered, bringing both nozzles 
 fully into action (Fig. 76D). The maximum volume of air is drawn 
 through both the low and high speed openings. Low speed nozzle 
 "L" draws as much air as possible through passage "P" and high 
 speed nozzle "H" delivers its maximum. It is probable that the 
 air passing through the sheath "R" increases the suction on high 
 speed nozzle "H." If the throttle is suddenly opened wide a large 
 volume of air will rush in past "R" before a flow of gasoline from 
 "H" is established. This will cause the engine to "die." 
 
 ADJUSTMENT. The only adjustment on this carburetor is 
 made by the Idle Adjusting Screw "36" with the engine running 
 and the car standing still. If there is too much air, this screw should 
 be turned to the right or in. If there is not enough air, it should be 
 turned to the left or out. Further regulation of the quantity of 
 air and gasoline for every position of the throttle valve is automatic. 
 Too rich a mixture may be caused by dirt in the air inlet screens. 
 These should be kept clean. 
 
CARBURETORS 113 
 
 In extreme cases, the nozzles "34" and "33" may be replaced by 
 others of different drillings. Both the hole at the top of low speed 
 nozzle "34" and hole "62" in its side near the base vary in size. 
 The high speed nozzle "33" is seldom changed. 
 
 The air coming in at "47" is supplied through a tube running 
 to a stove on the exhaust pipe. A shutter "45" is provided to regu- 
 late the temperature of this air. This shutter should be closed in 
 winter and open in summer. Additional heat is supplied by pumping 
 warm water through the jacket on the inlet manifold "50." 
 
CHAPTER XI 
 
 PUDDLE TYPE CARBURETORS 
 
 The carburetors explained in the preceding chapters are of the 
 sprayer type, that is, a nozzle is used to supply the gasoline to the 
 mixing chamber in the form of a spray. There are certain types of 
 carburetors which do not use a nozzle but allow the incoming air to 
 pass over the surface of a puddle of gasoline and draw off vapor 
 carrying it to the mixing chamber. For this reason they are called 
 the puddle type of carburetor. The most common of these types 
 will be explained in this chapter. 
 
 KINGSTON MODEL "Y" 
 
 This carburetor was used on Ford Cars and is of the puddle type. 
 The gasoline enters the float chamber passing the gasoline supply 
 valve until the proper level is attained. The gasoline from the float 
 chamber passes the valve and fills the recess directly around it 
 (Fig. 77). 
 
 The mixing chamber is of a peculiar form, so designed that all 
 the primary air must pass over the small pool of gasoline at the 
 bottom of the mixing chamber before it reaches the engine. The 
 amount of gasoline supplied to the mixture may be varied by regu- 
 lating the needle valve. 
 
 At low speed all the air entering passes through the main air inlet 
 (primary air) and picks up the gasoline carrying it to the cylinders. 
 As the speed increases this mixture becomes richer and additional 
 air must be supplied which does not pass over the puddle of gasoline. 
 The additional air is admitted through the auxiliary air duct passing 
 the auxiliary air valves of the ball type and entering the inlet mani- 
 fold. These balls are so arranged that as the suction increases they 
 lift in turn from their seats admitting a greater amount of air. 
 
 The only adjustment on this carburetor is the needle valve which 
 when turned to the right causes the mixture to become leaner and 
 when turned to the left causes richer mixtures. 
 
 HOLLEY MODEL "S" 
 
 This carburetor is of the puddle type with concentric float (Fig. 
 78). The gasoline enters the gasoline inlet pipe (Fig. 79) passing 
 
 114 
 
PUDDLE TYPE CARBURETORS 
 
 115 
 
 NEEDLE VALVE 
 
 COCKING SCREW 
 
 CHOKE 
 
 THROTTLE 
 
 LEVER 
 
 AUXILIARY 
 AIR DUCT 
 
 OCKING SCREW 
 ADJUSTING SCREW 
 THROTTLE LEVER 
 
 OVERFLOW TUBE 
 
 DRAIN COCK 
 
 Fig. 77 Kingston Model Y 
 
 6 A SO L 
 
 NEEDLE VALV. 
 
 TH e rue L ANQ A.IA 
 TAKf/V THROUGH THE 
 
 T(J0.QLjr 
 TO THROTTLf. 
 
 Fig. 1%Holley Model 
 
116 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 the float needle valve in entering the float chamber. From the float 
 chamber the gasoline passes through the holes "E" to the needle 
 valve "F." The float level is so set that the gasoline rises past the 
 needle valve and sufficiently fills the cup "G" to submerge the lower 
 end of the small copper tube "H." 
 
 Fig. 79 Side View of Holley 
 
 The air enters from only one source, the air intake, there being no 
 auxiliary air valves in the carburetor. All the air entering the car- 
 buretor must pass over the surface of the puddle of gasoline at 
 "G." The needle valve "F" regulates the amount of gasoline 
 supplied to this well. 
 
 The tube "H" conducts gasoline from the well "G" to a point 
 just beyond the throttle valve. This arrangement assists in supply- 
 ing a mixture for running idle with closed throttle. 
 
 For facilitating starting in cold weather a choke is placed in the 
 air passage to cause a slightly richer mixture. 
 
 The only adjustment on this carburetor is the needle valve and 
 when turned to the right will cause leaner mixtures and when turned 
 to the left will give richer mixtures. 
 
CHAPTER XII 
 
 MAGNETISM 
 
 In order to thoroughly understand ignition, starting, and lighting 
 systems, a preliminary knowledge of magnetism and elementary 
 electricity is necessary. Only the most simple and fundamental 
 electrical principles will be taken up but it will be necessary that this 
 and the following chapter be thoroughly understood or trouble will 
 be encountered when the electrical apparatus used on a motor 
 vehicle is studied. The preliminary discussion will be divided into 
 two parts, a chapter on Magnetism and a chapter on Elementary 
 Electricity. 
 
 The name magnet was first applied to certain brown colored 
 stones taken from the earth which possessed the peculiar property 
 of attracting small pieces of iron ore. When freely suspended by a 
 string at the center this stone possessed the important property of 
 pointing north and south, hence, it was given the name of "lode- 
 stone" (meaning leading stone). Hence, a magnet may be defined 
 as a piece of steel or other substance which possesses the properties 
 of attracting other pieces of steel or iron, and of pointing north and 
 south when freely suspended in a horizontal position. 
 
 The compass needle is nothing more than a small bar magnet 
 pivoted at the center so that it is free to turn in any direction like 
 the lodestone. It will always point north and south, the same end 
 pointing north each time. The ends of a magnet are termed its 
 poles. The point midway between them is known as the neutral 
 point. The end of a compass needle which points to the north is 
 termed the north pole while the opposite end is called the south pole. 
 The north pole of a magnet is generally marked in some manner to 
 distinguish it from the south pole. 
 
 Magnets are of two kinds, permanent and temporary. Per- 
 manent magnets are either bar or horseshoe, the names arising from 
 their shape. A permanent magnet must be a piece of steel which 
 has been magnetized and which retains its magnetism indefinitely. 
 A temporary magnet may be a piece of iron under the influence of a 
 permanent steel magnet or temporarily magnetized by electric 
 current (electro-magnet). 
 
 There is a distinction between substances which are magnetic 
 and which are nonmagnetic. Iron and steel are the only two sub- 
 
 117 
 
118 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 stances which manifest these properties to any great extent. Two 
 other metals, nickel and cobalt, are very slightly magnetic. For prac - 
 tical purposes all other substances such as copper, lead, gold, brass, 
 bronze, wood, rubber, glass, etc., cannot be magnetized and are there- 
 fore nonmagnetic. Magnetic influences will take place through these 
 substances. 
 
 A distinction must also be made between magnets and magnetic 
 substances. A magnet attracts only at its poles, each of which pos- 
 sesses opposite properties. A piece of iron will be attracted by a 
 magnet no matter what part of it is approached to the magnet but 
 it does not possess fixed poles or a neutral point while a magnet 
 always has two poles and a neutral point. 
 
 Fig. 80 Field Surrounding a Bar Magnet 
 
 Surrounding any magnet there exists what is known as the mag- 
 netic field. It is invisible and in fact is not perceptible to any of the 
 senses. That it does exist can be proved by placing a piece of paper 
 over the magnet and sifting iron filings over it. The magnetic force 
 which permeates the space immediately surrounding the magnet 
 causes the filings to arrange themselves in a certain definite manner 
 indicating the nature of the force, its direction, and distribution. 
 The magnetic force is not the same at all distances but decreases as 
 the distance from the magnet increases. Fig. 80 shows the magnetic 
 field existing about a bar magnet while Fig. 81 shows the magnetic 
 field of a horseshoe magnet. 
 
 It is assumed that the magnetic lines of force (Figs. 80 and 81) 
 emanate from the north pole of the magnet, pass through the sur- 
 rounding medium, re-enter at the south pole and complete the circuit 
 by passing from the south to the north pole through the magnet 
 itself. Every line of magnetic force must have a complete circuit, 
 
MAGNETISM 
 
 119 
 
 hence, it is impossible to have a magnet with only one pole. Mag- 
 netic lines of force complete their circuits independently and never 
 cut across or merge into each other. The fact that all the lines of 
 force pass through the magnet itself accounts for the concentration 
 of magnetic force at the poles. 
 
 Fig. 81 Field Surrounding a Horseshoe Magnet 
 
 Lines of magnetic force will pass through some substances more 
 readily than through others. When a piece of iron is placed in a 
 magnetic field the lines of force are bent out of their natural paths 
 and pass through the iron. There are now more lines of force passing 
 through the space occupied by the iron than when this space was 
 occupied by air only. The property of any substance for con- 
 ducting magnetic lines of force is termed its "permeability." 
 
 As shown in Fig. 82 a bar of iron placed in a magnetic field will 
 cause distortion of the lines of force, many of which will pass through 
 
 Fig. 82 Permeabilities Compared 
 
120 MOTOR VEHICLES AND THEIR ENGINES 
 
 the iron. Magnetic lines of force always take the path of least re- 
 sistance. If the piece of iron is arranged free to move in the field it 
 will take up such a position as to accommodate through itself the 
 greatest possible number of lines of force. If instead of being a 
 magnetic body it is a magnet, it will move under the influence of the 
 magnetic field in which it is placed, not only so as to accommodate 
 through itself the lines of force of the field but also in a particular 
 direction so that its lines will be in the same direction as those of the 
 field. Thus a magnet always tends to place itself so that lines of 
 magnetic force enter its south pole and leave at its north pole. 
 
 Magnetic substances have the greatest permeabilities but the 
 permeability of every magnetic substance is different. If a piece 
 of steel is substituted for the soft iron (Fig. 82) fewer lines of force 
 will pass through the same space showing that the conducting power 
 of iron is greater than that of steel. The permeability of iron may 
 be as high as two thousand times that of air, that is, two thousand 
 times as many lines of force will pass through the same space when 
 occupied by iron as when occupied by air. 
 
 The path taken by magnetic lines of force in passing from any 
 pole of the magnet through the surrounding medium and back to the 
 same pole again is known as a magnetic circuit. The simple magnetic 
 circuit is composed of a magnetic substance throughout its entire 
 length, as for example, a magnetized iron ring or a horseshoe magnet 
 with a keeper across its poles. A compound magnetic circuit is one 
 in which the lines of force must pass through both magnetic and non- 
 magnetic substances, as for example, a horseshoe magnet without 
 its keeper. 
 
 If two bar magnets are placed side by side and the resultant 
 magnetic field is obtained by sifting iron filings on a paper covering 
 
 Fig. 83 Field Resulting with Like Poles Adjacent 
 
MAGNETISM 
 
 121 
 
 them. It will be seen that the arrangement of the lines of force will 
 depend upon whether opposite poles or like poles are adjacent. 
 
 When like poles are adjacent (Fig. 83) the lines of force striking 
 against each other are distorted from their natural paths and com- 
 pressed into a small space. This causes the magnets to be mutually 
 repelled since the lines of force try to return to the regular positions 
 that they normally occupy. 
 
 Fig. 84 Field Resulting with Unlike Poles Adjacent 
 
 If unlike poles are adjacent (Fig. 84) the lines of force flowing 
 from the north pole of each will enter the adjacent south pole since 
 the steel offers a better path than air due to its greater permeability; 
 This causes the lines of force to be stretched out of their regular 
 positions and mutual attraction results since the lines of force tend 
 to return to their normal positions. Thus it is seen that the like 
 poles of magnets repel while unlike poles attract, both of which are 
 the direct result of distortion of the magnetic field. 
 
 It is the same phenomenon that causes a piece of iron to be 
 attracted by a magnet. When a piece of iron or steel is near enough 
 
 Fig. 85 How Magnet Attracts Iron 
 
122 MOTOR VEHICLES AND THEIR ENGINES 
 
 to a magnet to be in its magnetic field the lines of force stretch out 
 and pass through the piece of iron. This causes a distortion of the 
 magnetic field and results in the iron or steel being drawn to the 
 nearest pole of the magnet (Fig. 85). While this is taking place the 
 flow of lines of force through the piece of hpn or steel causes it to 
 become a temporary magnet. When any body is magnetized by the 
 influence of a magnet it is said to be due to magnetic induction. 
 Contact between the inducing magnet and the body magnetized is 
 not necessary and may take place through all nonmagnetic substances 
 whether solids, liquids, or gases. 
 
 From the foregoing the following laws of magnets have been 
 deduced : 
 
 1. Unlike poles of magnets are mutually attracted. 
 
 2. Like poles of magnets are mutually repelled. 
 
 3. Magnetic lines of force always take the path of least resistance. 
 If the polarity of a magnet is unknown it may be tested by using 
 
 a compass needle or other small magnet of known polarity in ac- 
 cordance with the laws just stated. 
 
 The molecular theory of magnetism explains why a piece of iron 
 or steel can be magnetized. All substances are composed of minute 
 particles which are called molecules. The molecules composing iron 
 or steel are each individual magnets. When the iron or steel is not 
 magnetized then the molecules arrange themselves promiscuously in 
 the material, but according to the law of attraction between unlike 
 poles local magnetic circuits are formed internally and there is no 
 resulting external magnetism. Fig. 86A illustrates the possible 
 
 A B 
 
 Fig. 86 Molecules in Magnetic Substance 
 
 positions in which the particles composing a magnetic substance may 
 arrange themselves when there is no external magnetism. It must be 
 remembered that there may be as many as a million or more variously 
 arranged magnetic circuits in even a very small piece of iron or steel. 
 When the piece of iron or steel is placed in a magnetic field each little 
 magnetized particle tends to place itself so that its axis is parallel 
 to the direction of the magnetic field with its north pole pointing so 
 that the lines of force must pass out at that end. This causes the 
 closed magnetic circuits to be broken up and the particles to arrange 
 themselves parallel to each other with their north poles all pointing 
 in the same direction (Fig. 86B). The iron or steel now manifests 
 
MAGNETISM 123 
 
 external magnetism and will continue to do so as long as the mole- 
 cules stay in this arrangement. 
 
 When under the influence of a strong magnetic field soft iron 
 possesses greater attractive force than steel. When the magnetic 
 field is removed, however, the steel possesses far superior attractive 
 properties to the iron which it retains for the most part permanently. 
 The soft iron is very slightly magnetized and what remains is com- 
 monly known as " residual magnetism. " This difference is easily 
 explained by the molecular theory of magnetism. The molecules of 
 iron and steel offer considerable resistance to the force tending to 
 turn them on their axes, the resistance "of the steel molecules being 
 much greater. It is difficult to turn them around but once being 
 turned around it is equally as difficult for them to return to their 
 original positions due to the friction between themselves, hence, the 
 resulting permanent magnetism in steel. On the other hand the 
 molecules of soft iron turn very readily when under the influence of a 
 magnetic field but resume their original positions when the magnetic 
 field is removed as the friction between the molecules is much less, 
 accounting for the temporary magnetism in iron. Not all of the 
 molecules regain their exact original positions which is shown by the 
 slight trace of magnetism always found in any piece of iron after 
 having been magnetized. 
 
 It is impossible to see the molecules of iron or steel changing their 
 relative positions under the influence of magnetism but by experiment 
 this theory has been found to be correct. It is assumed that the 
 molecules composing the iron or steel are regularly disposed, which 
 necessarily has to be the case. When local magnetic circuits are 
 formed, magnetization turns the molecules on their axes until they 
 are arranged symmetrically. When they have all been turned 
 around the bar is said to be saturated or completely magnetized. 
 No matter how much additional magnetic force is available the mag- 
 netism of the bar cannot be further influenced. 
 
 Since magnetism depends upon the arrangement of the molecules 
 in the magnetic substance their displacement will cause the partial 
 or total loss of external magnetism. Any vibration tends to destroy 
 permanent magnetism. For this reason permanent steel magnets 
 must never be dropped or struck. Slight shocks are sufficient to 
 demagnetize soft iron; steel retains with tenacity the properties of 
 a magnet but its magnetic strength is impaired by shocks and will 
 be entirely destroyed by a sufficient vibration. 
 
 Vibration may be produced in a substance by heat which causes 
 the molecules to become more widely separated and reduces the 
 internal friction between them. When sufficient heat is applied to a 
 
124 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 magnet it will entirely lose its magnetism because its molecules have 
 become disarranged by the resulting vibration. For this reason heat 
 must never be applied to permanent magnets. 
 
 When current flows through a conductor an electromagnetic field 
 is set up about it. Every wire carrying a current possesses this 
 magnetic field, which can be proved by bringing a compass needle 
 near the wire. The magnetic field of the wire acts on the magnetic 
 field of the compass needle causing it to be deflected. If a wire 
 through which current is flowing is passed through paper upon which 
 iron filings are sifted they will arrange themselves in concentric 
 
 Fig. 87 Field About Current Carrying Conductor 
 
 circles with the wire at the center as shown in Fig. 87. Thus, it is 
 seen that the magnetic field around a straight wire carrying a current 
 consists of a cylindrical whirl of circular lines, their intensity decreas- 
 ing as the distance from the wire increases as shown in Fig. 88. As is 
 true of all lines of magnetic force these magnetic whirls do not 
 merge, cross, or cut each other, but complete their circuits independ- 
 ently around the wire. 
 
 The direction of the magnetic whirls about the wire depends upon 
 the direction the current is flowing through it. If the thumb of the 
 right hand is placed along the wire in the direction in which the cur- 
 rent is flowing the curved fingers will indicate the direction of the 
 magnetic whirls about the wire. This may be checked by placing 
 a compass needle near the wire which will show the direction of the 
 lines of force by its deflection. 
 
 Fig. 88- Magnetic Whirls 
 
MAGNETISM 
 
 125 
 
 If a wire is arranged as shown in Fig. 89 so that it describes a 
 half circle above the cardboard its magnetic field will be shown by 
 
 sifting iron filings on the 
 cardboard. When current is 
 passing through the wire the 
 iron filings arrange themselves 
 circularly around the wire. 
 It is seen that the magnetic 
 lines of force pass down 
 through the center of the 
 loop, which can be confirmed 
 by applying the right hand 
 
 Fig. 89 Direction of Field Through 
 Loop of Wire 
 
 rule. 
 
 If a wire is bent into a circular loop and current sent through it 
 (Fig. 90) all the magnetic whirls about the wire will pass in through 
 
 one side of the loop and out 
 the other. If a compass needle 
 is brought near the loop it 
 will be attracted by the mag- 
 netic field of the loop just as it 
 would be by a bar magnet. 
 This is due to the fact that 
 the side of the loop from 
 which the magnetic whirls 
 emerge acts as the north pole 
 while the other side manifests 
 south polarity. 
 
 If a coil of wire is wound 
 into a helix and current sent 
 Fig. 90 Whirls About Loop of Wire through it, the result will be as 
 
 shown in Fig. 91. Magnetic 
 
 whirls are set up about each turn of the helix but the turns of wire 
 being so near each other, the whirls instead of completing separate 
 
 Fig. 91 Field About Helix 
 
 circuits join together looping all the turns composing the helix 
 resulting in a continuous magnetic field. The total field is the 
 
126 MOTOR VEHICLES AND THEIR ENGINES 
 
 sum of the magnetic lines of each individual turn, since it is the 
 result of the whirls about adjacent conductors joining together and 
 the sum of all the turns constitutes the field or total number of 
 lines of force passing through the coil. The field set up by the coil 
 is shown in Fig. 91 and it will be seen that one end of the coil is the 
 north pole while the other end is the south pole, just as was true of 
 the two sides of the single loop of wire through which current was 
 flowing. If the curved fingers of the right hand are placed about 
 the coil of wire in the direction the current is flowing the thumb 
 will indicate the north pole of the coil. 
 
 When a great many turns of wire are wound on a wooden or brass 
 spool similar to the winding of a spool of thread the resulting coil is 
 called a "solenoid." 
 
 An iron or steel bar inserted in a solenoid through which current 
 is flowing is a much better conductor of the magnetic lines of force 
 inside the solenoid than the air, so that the strength or attractive 
 force of the solenoid is materially increased though the magnetizing 
 
 Fig. 92 Electro-Magnet 
 
 current is the same as before. An iron core introduced into a sole- 
 noid carrying a current becomes strongly magnetized and is called 
 an electro-magnet (Fig. 92). The direction of the lines of force 
 through the iron core of the solenoid is the same as their natural 
 direction through the solenoid alone so that the laws of polarity of 
 the solenoid hold for the electro-magnet. The molecular theory of 
 magnetism explains how magnetism is produced in the iron bar by 
 passing current around it. The solenoid's magnetic field acts upon 
 the molecules composing the iron bar causing them to arrange them- 
 selves producing an external field about the core. The magnetic 
 field set up by the current simply makes evident the latent magne- 
 tism of the iron. This molecular action also accounts for the per- 
 manent magnetism produced in a piece of steel, inserted in a solenoid 
 
MAGNETISM 127 
 
 after the current ceases, since the friction between the molecules 
 prevents many of them resuming their original positions. 
 
 If a coil of wire is wound around an iron ring, and current sent 
 through it, lines of magnetic force will flow around through the iron 
 ring. If a small air gap is made in the ring by sawing out a section 
 a compound circuit is formed and lines of force are compelled to 
 pass through the air gap to complete their circuit so that north and 
 south poles are produced. The lines of force through the iron part 
 of the circuit are not nearly so dense as before, since the resistance of 
 the circuit has been increased by introducing an air gap. If the 
 removed section of the ring is now replaced and the ring covered with 
 iron filings, while it is magnetized, a great many filings will be attracted 
 at the two joints. This illustrates magnetic leakage. When mag- 
 netic leakage takes place with permanent magnets their strength is 
 impaired. This should be guarded against especially when dis- 
 mounting the magnets of magnetos. 
 
CHAPTER XIII 
 
 ELEMENTARY ELECTRICITY 
 
 The term electricity has been applied to an invisible force known 
 only by the effects it produces. Its exact nature is not known but 
 the laws governing it are clearly understood and defined. These 
 can best be explained by comparing its flow to that of water to which 
 it is similar. However, it must be remembered that electricity is 
 not a liquid and is only compared to water to better understand its 
 flow. 
 
 Fig. 93 Water Analogy to Flow of Current 
 
 Fig. 93 shows two tanks "A" and "B" at the same level ("A" 
 being filled with water) connected by a pipe in which is placed a 
 valve. When the valve is opened slightly the water will flow from 
 "A" into "B" until the level of water in both tanks is the same. 
 If the valve had been opened wider, the flow of water would have 
 been faster because the larger opening offers less resistance to its 
 flow. Had air been pumped into the top of tank "A" until a high 
 pressure was obtained the flow of water through the pipe into tank 
 "B" would have been still faster. Although the rate at which the 
 water flows from tank "A" into tank "B" may vary, the quantity 
 that flows is independent of the rate and depends only upon the 
 difference in pressure between the two tanks. It is seen that pressure 
 is required to cause water to flow and the rate of flow may be in- 
 creased by reducing the resistance to its passage or by increasing the 
 pressure. 
 
 In Fig. 94 the two terminals "A" and "B" of the dry cell are 
 connected by a wire through the switch "C." This may be com- 
 pared to the two tanks connected by a pipe; the positive terminal 
 
 128 
 
ELEMENTARY ELECTRICITY 
 
 129 
 
 "A" corresponding to the full tank, the negative terminal "B" 
 corresponding to the empty tank, the wire to the pipe, and the switch 
 
 "C" to the valve. When the 
 switch is closed current flows 
 from "A" to "B" through the 
 wire. The water flows from 
 tank "A" to tank "B" be- 
 cause there is greater pressure 
 at "A" than at "B." Current 
 flows from terminal "A" to 
 terminal "B" because there is 
 greater electrical pressure at 
 "A" than at "B." 
 
 Water pressure is usually 
 measured in pounds per square 
 inch, electrical pressure is meas- 
 ured in volts. The amount of 
 water that flows may be meas- 
 
 Fig. 94 Simple Electric Circuit 
 
 ured in gallons or barrels, the amount of current that flows is 
 measured in amperes. The smaller or longer the pipe the less will 
 be the water flowing through it due to the increased resistance; 
 similarly, the smaller or longer the wire the less will be the 
 current flowing through it due to the increased resistance and this 
 electrical resistance is measured in ohms. 
 
 The pound and the gallon are definite units of pressure and quan- 
 tity both of which are familiar due to their common usage. Years 
 ago in order to decide upon similar units for measuring electricity a 
 committee was appointed made up of prominent scientists of the 
 time. Dr. Ohm was chairman of this committee which met in his 
 laboratory to decide the units by which electrical pressure, current, 
 and resistance should be measured. 
 
 It was decided that the amount of pressure given by a certain cell 
 should be the standard unit to which all other electrical pressure 
 should be compared. The cell chosen was the Voltaic Cell and the 
 amount of pressure this cell gave was named the "Volt." A six volt 
 battery is one having six times the pressure of the Voltaic cell. 
 
 To obtain the unit of resistance it was decided to take a certain 
 conductor and call its resistance the standard to which all others 
 should be compared. The one chosen was a tube of mercury of 
 definite size and length and the amount of its resistance to the flow 
 of current through it was named the "Ohm." A conductor which 
 has three ohms resistance is one that offers three times as much resist- 
 ance to the flow of current as the original tube of mercury. 
 
130 MOTOR VEHICLES AND THEIR ENGINES 
 
 To obtain the unit of current it was decided to take this cell 
 giving one volt pressure and connect its terminals with the tube of 
 mercury and the amount of current that flowed was named the 
 " Ampere." A circuit which has 10 amperes flowing through it is 
 one in which the current is 10 times as great as that caused to flow 
 by a pressure of one volt through one ohm resistance. 
 
 Referring to Fig. 93 if the pressure is increased and the pipe size 
 and length remains the same more water will flow; the same is true 
 of electricity. If the pressure (voltage) is increased, more current 
 (amperes) will flow through the circuit provided the resistance is 
 not changed. If the pressure remains the same but the size of the 
 valve opening is made smaller or the pipe decreased in size or in- 
 creased in length, less water will flow; the same is true in electric 
 circuits. If the pressure (voltage) remains the same and the wire is 
 decreased in size or increased in length, increasing the resistance 
 (ohms), less current (amperes) will flow. 
 
 By experiment it has been found that the flow of electricity 
 always depends upon the pressure and resistance of the circuit and 
 that definite laws govern the amount of change in the flow of elec- 
 tricity for a given change of either of these. The relation between 
 electrical pressure, current, and resistance is known as Ohm's Law 
 and is as follows : 
 
 First: The strength of current flowing in any circuit is equal to 
 the pressure in volts divided by the resistance of the circuit in ohms. 
 
 Second: The strength of current in any circuit increases or 
 decreases directly as the pressure increases or decreases when the 
 resistance is constant. With a constant pressure the current in- 
 creases as the resistance is decreased and decreases as the resistance 
 is increased. 
 
 n Pressure 
 
 Current = 
 
 Resistance 
 
 Volts 
 
 Amperes = 
 
 Ohms 
 R~ 
 
 Problem 1. 
 
 With a six-volt battery and a circuit of two ohms resistance, how 
 many amperes of current will flow in the circuit? 
 
 T E 6 Q 
 
 I = = =3 amperes. 
 
 R 2 
 
 Problem 2. 
 
 If the voltage is increased to 12 volts and the resistance is the 
 same, how many amperes of current will flow? 
 
ELEMENTARY ELECTRICITY 131 
 
 T E 12 
 
 I = = = 6 amperes. 
 
 This proves that as the voltage increases, the current increases. 
 
 Problem 3. 
 
 If the resistance is increased to 3 ohms and the voltage is the same, 
 how many amperes of current will flow? 
 
 E 6 
 
 I = = = 2 amperes. 
 R 3 
 
 This proves that as the resistance is increased the current is decreased. 
 
 If the two tanks "A" and "B" (Fig. 93) are connected by a 
 solid rod, no water can flow, a hollow rod or pipe is necessary to permit 
 water to pass through it. If the terminals "A" and "B" (Fig. 94) of 
 the dry cell were connected by a glass rod no current could flow, a met- 
 al rod or wire is necessary to permit electric current to pass through it. 
 For this reason metals and other substances that electricity flows 
 through easily, due to their low resistance, are called CONDUCTORS. 
 
 To retain water, a pipe must be made of strong enough material 
 to withstand the pressure exerted by the water passing through it. 
 Similarly, to retain the current passing through it a wire must be 
 surrounded by some material through which current cannot pass. 
 Materials which offer considerable resistance to the passage of cur- 
 rent through them are called non-conductors or INSULATORS. 
 
 All conductors do not conduct electricity equally well since the 
 resistance of every substance is different. Silver, copper, aluminum, 
 steel, and iron are all good conductors and offer but little resistance 
 to the flow of current. Materials such as glass, porcelain, rubber, 
 silk, cotton, fiber, wood, and air offer a great deal of resistance to 
 the flow of current and are classed as insulators. As in the case of 
 conductors, all insulators do not resist the flow of current equally 
 well. 
 
 Ohm's Law proves that the pressure in an electric circuit deter- 
 mines the amount of current that will flow. In other words pressure 
 can overcome resistance and force current to flow. For this reason 
 when the pressure is high in a circuit an insulator of much higher 
 resistance must be used than would be necessary if the pressure 
 were low. 
 
 For electric current to flow a path consisting of conductors must 
 be provided. A break in the circuit will cause the current to cease 
 flowing and it is said to be "open circuited." 
 
 The common circuits used in ignition, lighting, and starting work 
 are series and parallel. 
 
132 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 SERIES CIRCUIT : When electric lamps are connected as shown 
 i n Fig. 95 they are said to be in series because the current flows through 
 
 0-0-On 
 
 LAMPS 
 
 Fig. 95 Series Circuit 
 
 each lamp to the next succeeding one, returning from the last one 
 to the battery. In a circuit of this kind the resistance increases as 
 the number of lamps is increased, decreasing the current if the 
 pressure remains the same. 
 
 O 
 
 2S477Z7BK 
 
 LAMPS 
 
 Fig. 96 Parallel Circuit 
 
 PARALLEL CIRCUITS. When electric lamps are connected as 
 shown in Fig. 96 they are said to be connected in parallel. All the 
 
 Fig. 97 Water Analogy to Parallel Circuit 
 
ELEMENTARY ELECTRICITY 133 
 
 
 
 current in this case does not have to flow through every lamp but 
 part of it flows through each and back to the battery through the 
 common return wire. 
 
 If two tanks "A" and "B" are connected as shown in Fig. 97 
 and valve "C" is opened, a certain amount of water will flow between 
 them. If valve "D" is opened more water will flow because another 
 path has been opened, reducing the total resistance. If valve "E" 
 is opened a still greater quantity of water will flow. 
 
 This is the same arrangement as shown in Fig. 96 and as more 
 lamps are added the total resistance of the circuit is reduced and more 
 current flows if the pressure remains the same. 
 
 Lights on cars are usually connected in parallel since turning on 
 additional lights will not require a change of voltage. Also, the 
 burning out of one light will not put out any of the others. 
 
 In making up wiring diagrams certain electrical symbols are used. 
 Fig. 98 shows those adopted by common usage. 
 
LCCTft/CAL SYMBOLS 
 
 US0 /Af Hf/MAfff 0/A6/tAMS 
 
 + 
 
 ros/T/rss/tr on rt/tM/WL 
 
 
 
 MffAT/nr S/tf Oft rMffM4L 
 
 -A/WW 
 
 PR/MA/tr W/MDING 
 
 -AA/WWV 
 
 3CCOA/OARY W//VD/NG 
 
 * 
 
 6/T0W/0 
 
 -HWtt- 
 
 A77TZ/tr 
 
 -- 
 
 AM*fT/l 
 
 (y) 
 
 VOLTMETER 
 
 -& Hl- 
 
 CWOCMSC/t 
 
 -"-- 
 
 SW/TCH 
 
 -* 
 
 3/XRK GAP 
 
 = 
 
 CONTACT /VWTS 
 
 i 
 
 TWO W/fiS*/O/Af0 
 
 T 
 
 f 
 
 W/ACS NOT S0/NZD 
 
 D=Q <\J 
 
 swse 
 
 E: 
 
 SHW/T W/N0/NG 
 
 cT^ 
 
 3/t/CS W/NMN& 
 
 
 COA/W/M0 W/MD/Afff 
 
 r^^ 
 
 Fig. 98 
 
 134 
 
CHAPTER XIV 
 
 Fig. 99 Simple Cell 
 
 BATTERIES 
 
 The simplest method of producing electric current is by chemical 
 means. A simple primary cell may be made by placing two dis- 
 similar metals in an acid or alkaline solution. Fig. 99 shows a plate 
 of zinc and a plate of copper 
 placed in a glass jar containing 
 a solution of sulphuric acid. If 
 the plates are connected by a 
 piece of wire a chemical reaction 
 takes place between the zinc 
 plate and the acid causing the 
 zinc to be gradually wasted 
 away. This causes the terminal 
 at the copper plate to be posi- 
 tively charged, resulting in a 
 flow of current from the termi- 
 nal at the copper plate through 
 the wire to the terminal at the 
 zinc plate. This action will 
 continue as long as any of the zinc is left or until the acid has become 
 so weak that its power to attack the zinc is exhausted. If the con- 
 nection between the plates is broken at any time the chemical 
 reaction stops and will only continue when the circuit is again made. 
 This is the simplest form of chemical cell and illustrates the funda- 
 mental principle underlying the operation of all chemically produced 
 electric current. 
 
 There are many kinds of cells for chemically producing electric 
 current but there are only two which are applicable for ignition on 
 motor-propelled vehicles. These are the Dry Cell and Storage Cell 
 and are the only types which will be discussed in this chapter. 
 
 DRY CELL. The active elements of the dry cell consists of a 
 zinc shell "1" in the center of which a carbon rod "3" is placed 
 (Fig. 100). Next to the zinc shell is placed blotting paper "2" 
 which is soaked with the active chemical (usually salamoniac or 
 zinc chloride) called the electrolyte. The carbon rod is surrounded 
 by some depolarizing material (usually manganese dioxide) and the 
 space between is filled with a compound "4" usually kept secret by 
 
 135 
 
136 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 the manufacturer. To make the cell watertight it is sealed at the 
 
 top with pitch "5." 
 
 The zinc shell is attacked by the active chemical and is eaten 
 
 away. During this chemical action hydrogen gas is liberated and I 
 
 collects on the carbon rod in small 
 bubbles. These would insulate it if it 
 were not for the action of the depolari- 
 zer which combines with the hydrogen 
 to form water. The voltage of a dry 
 cell of the kind just described is ap- 
 proximately \y^ volts on open circuit 
 when new and in good condition 
 irrespective of the size of the cell. A 
 large cell of the same construction will 
 give more current than a small one but 
 the voltage will not be increased. The 
 ordinary size of dry cell will giva 20 to 
 35 amperes of current when the circuit 
 is first closed. The cell will deliver this 
 maximum amount of current for only a 
 very short length of time. For this 
 reason dry cells are only suitable for 
 intermittent circuits. 
 
 A battery consists of two or more 
 cells which are connected together to 
 obtain suitable voltage and current. 
 The arrangement or connection will 
 depend upon the requirements of the 
 
 circuit for which the battery is to supply current. 
 
 There are three methods of connecting dry cell to form batteries; 
 
 series, parallel, and series-parallel. 
 
 Fig. 100 Cross-Section 
 Through Dry Cell 
 
 Fig. 101 Cells in Series 
 
 Fig. 101 shows a battery composed of dry cells connected in series. 
 The positive terminal of one cell is connected to the negative of the 
 next succeeding cell and the line is connected to the remaining 
 
BATTERIES 
 
 137 
 
 terminals. When cells are connected in series the voltage of the 
 battery is equal to the sum of the voltages of all the cells. That is, the 
 voltage of a battery is the voltage of one cell times the number of 
 cells when each cell has the same voltage. The amperage of the 
 battery will be equal to the amperage of one cell. For example, if 
 each cell in Fig. 101 has a strength of 1J^ volts and 25 amperes, the 
 strength of the battery will be 9 volts and 25 amperes. 
 
 Fig. 102 Cells in Parallel 
 
 Fig. 102 shows a battery of dry cells connected in paraUel. The 
 positive terminals of all the cells are connected to one line and all the 
 negative terminals to the other line. When cells are connected in 
 parallel it is necessary that every cell be of the same voltage. The 
 voltage of the battery will be equal to the voltage of one cell. The 
 amperage will be equal to the sum of the amperes of all the cells. 
 That is the amperage of the battery is equal to the amperage of one 
 cell times the number of cells when the amperage of each cell is the 
 same. For example, if the cells in Fig. 102 are each of 1J^ volts and 
 25 amperes the strength of the battery will be 1J^ volts and 150 
 amperes. 
 
 These two methods of connecting cells to form batteries are the 
 most common; however, when increased voltage and amperage are 
 both desired the cells must be 
 connected in series-parallels. 
 
 Fig. 103 shows a battery of 
 dry cells connected in series- 
 parallel. It is made up of sets 
 of cells connected in series, each 
 of these sets being connected in 
 parallel. The voltage of this 
 battery is equal to that of each 
 set of cells connected in series. 
 The amperage is equal to the 
 sum of the amperes delivered 
 by each set. For example, if 
 the cells in Fig. 103 are each of Fig. 103 Cells in Series-Parallel 
 
138 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 volts and 25 amperes the strength of each set in series will be 
 6 volts and 25 amperes. The strength of the battery will therefore 
 be 6 volts and 100 amperes. 
 
 STORAGE BATTERIES. These batteries are almost without 
 exception the only kind used on modern motor-propelled vehicles. 
 The reason for this is the adoption of starting and lighting systems 
 as standard equipment on most motor vehicles. 
 
 In the storage cell the current results from chemical action the 
 same as in the simple primary cell. The plates or electrodes are 
 usually built upon grids which are perforated as shown in Fig. 104. 
 
 The group of plates connected to 
 the positive terminal of the cell 
 consists of grids filled with a paste 
 of lead peroxide characterized by its 
 brown color. The group of plates 
 connected to the negative terminal 
 of the cell consists of grids filled 
 with metallic lead of a spongy 
 nature and is dull gray in color. 
 These plates are arranged in the 
 cell so that the positive and the 
 negative plates alternate. Between 
 the plates are placed separators 
 which are to prevent the plates of 
 the positive and negative groups 
 from coming in contact. The 
 separators must be porous to allow 
 the solution to pass through freely 
 and are usually made of specially treated wood or hard rubber. 
 The jar or container in which the plates are placed is usually made of 
 hard rubber which is not affected by the acid. The assembly of 
 plates and separators (Fig. 105) is placed in this jar or container and 
 a solution of sulphuric acid and distilled water is added until the level 
 of the liquid in the jar covers the tops of the plates. The cell is 
 sealed by a cover of hard rubber through which the positive and 
 negative terminals project (Fig. 106). A filler cup is provided 
 through which an air vent is left for the escape of gas which may be 
 formed in the cell. 
 
 Storage cells are connected in series to form batteries which will 
 give higher voltage. The voltage of a storage cell is usually con- 
 sidered two volts since this is the average value. If greater amperage 
 is desired the size of the cell is increased. The rating of storage 
 batteries is usually given in volts and ampere hours. Ampere 
 
 *S8|lip| 
 
 Fig. 104 Grid 
 
BATTERIES 
 
 139 
 
 Fig. 105 Plate Assembly 
 
 UNSCREW 
 THIS CAP 
 
 Fig. 106 Cross-Section Through Storage Cell 
 
140 MOTOR VEHICLES AND THEIR ENGINES 
 
 hours means that if the battery is discharged at a certain definite 
 rate it will give a certain current for so many hours. If 10 amperes 
 was the rate of discharge upon which it was rated, a 6 volt 120 ampere- 
 hour battery would be one having 3 cells connected in series and would 
 give 10 amperes of current for 12 hours. If the battery was dis- 
 charged at a high rate, 20 amperes, it would not last for 6 hours and 
 likewise if discharged at a low rate, 5 amperes, it would usually last 
 much longer than 24 hours. Therefore, the ampere-hour life of a 
 battery is governed by the rate at which it is discharged. 
 
 When a storage battery is discharging a chemical reaction takes 
 place. The sulphuric acid (H 2 S0 4 ) is broken up into two parts, H 2 
 and SC>4. The hydrogen is liberated at the lead peroxide plates 
 (Pb02) reducing them to lead oxide (PbO) which combines with 
 part of the sulphuric acid to form lead sulphate (PbSO^ and water 
 (H 2 0). The SC>4 is liberated at the spongy lead plates (Pb) and 
 combines with them to form lead sulphate (PbS04). During this 
 process the electrolyte grows less concentrated because of the ab- 
 sorption of S(>4 by the spongy lead plates. 
 
 When the battery is being charged by passing current through it 
 in the opposite direction the chemical action just described is re- 
 versed. The lead sulphate on one plate is converted back to lead 
 peroxide, the lead sulphate on the other plate is reduced to spongy 
 lead, and the electrolyte becomes more dense due to the increased 
 amount of sulphuric acid. The following is the chemical reaction 
 which takes place in a storage cell while discharging and being 
 charged. 
 
 DISCHARGING 
 
 Positive plate Pb0 2 + H 2 + H 2 S0 4 = PbS0 4 + 2 H 2 
 
 t 
 
 Negative plate Pb + S0 4 = PbS0 4 
 
 CHARGING 
 
 Positive plate PbS0 4 +0 + H 2 = Pb0 2 + H 2 S0 4 
 
 I 
 
 Negative plate PbS0 4 +H 2 = Pb -f H 2 S0 4 
 
 The current in a storage cell results from chemical action just as 
 in any other cell. When a dry cell is exhausted it is thrown away 
 while the storage cell is restored to normal condition by passing direct 
 current through it from some outside source. By this process the 
 chemical reaction which took place upon discharge is reversed 
 restoring the elements to their original condition. It is erroneous 
 to say that electricity is stored in a storage cell. The storage cell is 
 
BATTERIES 
 
 141 
 
 noo 
 
 7200 
 
 a means of converting electrical energy into chemical energy during 
 charge and chemical energy into electrical energy during discharge. 
 
 During discharge some of the sulphuric acid combines with the 
 plates causing the solution to have a greater proportion of water 
 to sulphuric acid, this proportion increasing as the discharg- 
 ing continues. The relative 
 amounts of acid and water can 
 be determined by reading the 
 specific gravity of the solution. 
 This is accomplished by the use 
 of an instrument called a hydro- 
 meter contained in a syringe 
 (Fig. 107). The electrolyte is 
 drawn up into the syringe by 
 the bulb and the hydrometer 
 will sink to a greater or less 
 amount depending upon the 
 amount of sulphuric acid in the 
 solution. If the hydrometer 
 reads 1.280 it indicates that the 
 liquid is 1.280 times as heavy as 
 water. The scale of the hydro- 
 meter is read on the stem at the 
 surface of the liquid when the 
 hydrometer is floating in it 
 (Fig. 107). 
 
 The readings of the hydrometer shows the condition of the battery 
 in accordance with the following table: 
 
 Fig. 107 Hydrometer and Syringe 
 
 READING 
 
 1.280-1.300 
 
 1.250 
 
 1.215 
 
 1.180 
 
 1.150 
 
 CONDITION 
 Full charge 
 34 Discharged 
 J/ Discharged 
 % Discharged 
 Discharged 
 
 During the chemical reaction which takes place in charge and 
 discharge heat is generated and causes the loss of some of the water 
 but there is no loss of sulphuric acid. For this reason when the solu- 
 tion in the cells gets below the top of the plates more distilled water 
 must be added. When adding distilled water care must be taken 
 not to fill the cell full. This is apt to result in the loss of some of the 
 solution through the vent, the acid attacking the metal parts causing 
 
142 MOTOR VEHICLES AND THEIR ENGINES 
 
 them to become corroded and eaten away. If acid is spilled or slops 
 out on the battery box it will soon be destroyed. In addition to 
 this if some of the solution is spilled there is no way to determine 
 how much acid has been lost and it cannot be replaced with certainty. 
 
 Never take readings of the specific gravity of a cell immediately 
 after adding water to a cell. When taking a hydrometer reading with 
 a syringe be sure to return the solution to the same cell from which 
 it was taken. Under no circumstances should acid of any kind be 
 added to a cell which has once been put in operation. 
 
 When a bettery is to be prepared for service remove the black 
 hard rubber vents which are standard equipment and remain on the 
 battery when in service. The cells should be filled to the bottom of 
 the vent holes with 1.275 specific gravity electrolyte at 70 degrees 
 Fahrenheit. 1.275 specific gravity electrolyte consists of approx- 
 imately two and one-half parts by volume of distilled water and one 
 part by volume of chemically pure sulphuric acid. The acid should 
 be poured into the water and allowed to cool below 90 degrees 
 Fahrenheit before being used. Never fill the battery with electrolyte 
 above 90 degrees Fahrenheit. 
 
 Allow the battery to stand for twelve hours and add more 1.275 
 specific gravity acid if necessary to bring the level up to the bottom 
 of vent holes. Then start charging at the finish rate stamped on the 
 name plate for not less than 72 hours or until the specific gravity 
 of the electrolyte stops rising. At the end of charge each cell 
 should be gassing freely and the voltage should read at least 2.4 
 volts per cell. 
 
 While charging add distilled water to replace any electrolyte lost 
 by evaporation. If during the charge the temperature in any one 
 cell exceeds 110 degrees Fahrenheit the current must be reduced 
 until the temperature falls below 100 degrees Fahrenheit. This 
 will necessitate a longer time to complete the charge, but must be 
 strictly adhered to. 
 
 The batteries are now completely charged and the specific gravity 
 of the electrolyte should be between 1.290 and 1.310 in each cell. 
 If above 1.310 remove a little electrolyte and add the same amount of 
 distilled water while the battery is left charging (in order to thor- 
 oughly mix the solution) and after three hours if the electrolyte is 
 within the limits, the cell is ready for service. If the specific gravity 
 is below 1.290 remove a little electrolyte and add the same amount 
 of 1.400 specific gravity electrolyte and leave on charge as before 
 1.400 specific gravity electrolyte consists of seven parts chemically 
 pure sulphuric acid and nine parts distilled water by volume. The 
 acid should be poured into the water and allowed to cool below 90 
 
BATTERIES 143 
 
 degrees Fahrenheit before being used. The standard vent plugs are 
 now inserted and the battery is ready for service. 
 
 A storage battery requires constant care and attention and if 
 treated properly will give most satisfactory service but if neglected 
 will cause constant trouble and soon become unserviceable. A 
 battery should be held rigid in the battery box to prevent spilling of 
 the solution. There should be an air space between the battery and 
 the battery box for ventilation. The interior of the battery box must 
 be kept clean and dry and the terminals should be coated with vase- 
 line or grease. If any acid is spilled on the battery wipe it up 
 with waste wet with ammonia. Never lay waste on top of a battery 
 since this practice is apt to cause short circuit between the cells. 
 
 A battery should be inspected once each week in warm weather 
 and once every two weeks in cold weather to ascertain its condition. 
 If the solution is low distilled water should be added to cover the 
 tops of the plates. Be very careful not to add too much water. At 
 each inspection several hydrometer readings of each cell must be 
 taken before adding any water. After testing the electrolyte be sure 
 to replace it in the cell to which it belongs. If the specific gravity 
 of one cell shows it to be considerably lower than the others at several 
 successive readings this indicates the cell is out of order. Likewise, 
 if one cell requires more water than the other it shows that the jar 
 is cracked. 
 
 Never allow the battery to get completely discharged because it 
 will sulphate the plates in the battery. If the generator on the car 
 does not keep the battery up to a reading of 1.200, at least part of 
 the time, the battery should be removed and charged by some outside 
 source. 
 
 If it is found that the batteries read very high at several successive 
 readings it is best to use some of the current either by running the 
 engine for a few minutes with the starting motor or by leaving the 
 lights turned on until the battery is partially discharged. 
 
 If for any reason an extra charge is needed and the battery is 
 charged from some outside source only direct current can be used. 
 Limit the current to the proper charging rate by connecting a suitable 
 resistance in series with the battery. Incandescent lamps are 
 suitable for this purpose. Connect the positive battery terminal to 
 the positive charging wire and the negative to the negative wire. 
 If reversed, serious injury to the battery will result. The proper 
 charging rates are generally marked on the name plate of a battery. 
 When charging start at the starting rate and continue to charge at 
 this rate until the cells gas freely. Then reduce the charging to the 
 finish rate and continue for 6 hours. The specific gravity at the end 
 
144 MOTOR VEHICLES AND THEIR ENGINES 
 
 of the charge should read 1.280 to 1.300. If it does not reach this 
 point continue the charge at the finish rate until the specific gravity 
 stops rising. If the specific gravity still does not reach 1.280 it 
 indicates that the battery needs special attention, the trouble prob- 
 ably resulting from loss of acid or sulphating or buckling of one or 
 more plates. If during charging the tefnperature of any cell exceeds 
 110 degrees Fahrenheit the charging rate must be reduced. 
 
 During warm weather the temperature of the battery must be 
 watched and if the solution is found to be 110 degrees Fahrenheit the 
 lights should at once be turned on so as to reduce the current passing 
 into the battery. Batteries overheat when nearly fully charged if a 
 high rate of charge is maintained. 
 
 During extremely cold weather it is essential that the battery be 
 kept fully charged in order to prevent freezing of the solution The 
 f ollowing table shows the temperature afr which electrolyte of different 
 specific gravity will freeze. 
 
 SP. GRAVITY FREEZING PT. 
 
 1.150 20 above 
 
 1.180 
 
 1.215 20 below 
 
 1.250 60 below 
 
 When a battery is not to be used for a short period of time, such 
 as one or two months, it should be given a fresh charge once a month 
 and a thorough charge before being put back into active service. In 
 case a battery is to be shipped it should be fully charged, the electro- 
 lyte emptied out, and the plates thoroughly washed in distilled water 
 and dried. It is put in operation again as previously described. 
 
 Fig. 108 shows a very good charging board which is suitable for 
 charging a storage battery from 110 volt direct current mains. The 
 charging is controlled by the number of lamps in the circuit. The 
 lamps being connected in parallel, more current will flow as the 
 number of lamps is increased. 
 
 Batteries are constructed for the particular service for which they 
 are to be used. A battery constructed for lighting purposes only, 
 should never be used with starting systems, as the heavy discharge 
 rate will cause serious damage to the battery. 
 
BATTERIES 
 
 145 
 
 Line 
 
 Fuses not less 
 than 10 Amperes, 
 
 Lamps 
 
 o 
 -o- 
 
 o 
 o 
 
 -o 
 
 -gj. 
 
 c Double Pole 
 
 Single Throw 
 
 Switch 
 
 For Charging use 
 
 8.110 Volt -32 C. P. (100 Watt) 
 
 Carbon Filament Lamps 
 
 or 
 
 16-110 Volt-16^.P. (50 WatO 
 Carbon Filament Lamps 
 or 
 
 20- 110 Volt. 10 Watt 
 Tungsten Lamps 
 
 32-110 Volt-25 Watt 
 Tungsten Lamps 
 
 Fig. 108 Charging Board 
 
CHAPTER XV 
 
 INDUCTION 
 
 When electricity is produced by chemical means the voltage is 
 low and therefore is not suitable for ignition systems unless the 
 voltage is increased in some manner. High voltages are obtained by 
 electro-magnetic induction and this method of obtaining higher 
 voltages is applied to ignition systems. To thoroughly understand 
 ignition it is necessary to study the elementary principles under- 
 lying induction which will be taken up in this chapter. 
 
 The exact nature of magnetism and electricity is still unknown 
 but much has been discovered concerning the relation existing 
 between them. It has been shown that whenever there is a current 
 of electricity flowing there is always a magnetic field present. This 
 magnetic field lasts as long as the current continues to flow showing 
 that there is a definite relation existing between magnetism and 
 electricity. Since electricity produces magnetism it is reasonable to 
 expect magnetism to produce electricity and it has been found by 
 experiment that this is true. 
 
 Fig. 109 Electro-Magnetic Induction 
 
 If a magnetic field is present and a loop of wire is moved so as 
 to cut the magnetic lines of force (Fig. 109) a current is caused to 
 flow through the conductor. Currents generated in this way are 
 known as induced currents and the phenomenon termed electro- 
 magnetic induction. The same result is obtained if the conductor 
 is kept stationary and the magnetic lines of force moved so as to 
 be cut by the conductor. 
 
 146 
 
INDUCTION 
 
 147 
 
 Fig. 110 Right-Hand 
 Rule 
 
 The direction of the flow of the induced current in the conductor 
 will depend upon the direction of the lines of force and the direction 
 in which the magnetic field is cut. A simple method of determining 
 this when the direction of motion and direction of the lines of force 
 are known is by means of the right hand rule. Place the thumb, the 
 first, and the second fingers of the right 
 hand all at right angles to each other (Fig. 
 110) and in such relation to the conductor 
 that the first finger points in the direction 
 of the lines of force, and the thumb in the 
 direction of motion. The second finger will 
 then indicate the direction of the induced 
 current. Applying this rule to Fig. 110 in 
 which the wire is being moved upward and 
 the lines of force flow from the north pole 
 as indicated, the current is found to flow through the conductor as 
 indicated by the arrow. 
 
 The strength of the induced voltage in a conductor when it is 
 cutting lines of force is proportional to the rate at which the lines of 
 force are cut. If a circuit of several turns of wire is substituted for 
 the single loop used in Fig. 109 the induced voltage will be greater. 
 This results because each loop now cuts as many lines of force as 
 were cut by a single loop increasing the total number of lines of force 
 cut. If the strength of the magnet is increased it will cause more 
 lines of force to be set up so that the same number of turns moving 
 through the field would cut a greater number of lines of force thus 
 causing an induced current of higher voltage. The induced voltage 
 will, therefore, depend upon the following factors: 
 
 1. The strength of the magnetic field. 
 
 2. The speed or rate of cutting lines of force, 
 
 3. The number of turns of wire cutting the lines of force. 
 
 Fig. Ill Self Induction 
 
148 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 SELF INDUCTION. If a coil of wire is placed about a core of 
 soft iron, and current sent through the coil, magnetic lines of force 
 will be set up. If the circuit is broken by opening the switch "A" 
 (Fig. Ill) the current ceases to flow and the magnetic field will 
 collapse. In collapsing the lines of force cut the winding of the coil 
 inducing current in the coil which is called self induction. Self 
 induction is defined as "the cutting of a wire or coil by the lines of 
 force set up by the current flowing through it." Applying the right 
 hand rule it will be seen that the direction of flow of the induced 
 current is in the same direction as the interrupted flow of current. 
 When applying the right hand rule do not take the motion of the 
 lines of force as the direction of motion but take the equivalent 
 motion of the conductor. 
 
 The induced voltage will be much higher than that of the current 
 which set up the magnetic field. When the switch is opened this 
 high induced voltage causes an arcing between the separating con- 
 tacts. When self induction is present in an ignition system the 
 induced voltage is approximately 200 volts, which is not sufficiently 
 high to jump a fixed air gap of any appreciable size but will cause a 
 following arc between separating points. 
 
 When the circuit is made the magnetic field building up also cuts 
 the winding. By applying the right hand rule it will be seen that the 
 induced current opposes the flow of the current setting up the field. 
 This is termed counter electro-motive-force and its opposition to the 
 increasing current in the coil causes the field to build up very slowly. 
 
 Fig. 112 Mutual Induction 
 
 MUTUAL INDUCTION. If two coils of wire are placed about an 
 iron core and current caused to flow through one of them (Fig. 112) 
 a magnetic field will be built up about the core. The coil through 
 
INDUCTION 149 
 
 which this current is caused to flow is known as the primary and the 
 other coil is called the secondary. If the switch " A " is now suddenly 
 opened this magnetic field collapses and both windings are cut by 
 the lines of force. This causes currents to be induced in both the 
 primary and secondary windings, that in the secondary is said to be 
 mutually induced current. Mutual induction is defined as "the 
 cutting of a wire or coil by lines of force set up by current flowing 
 through another wire or coil." There is no electrical connection 
 between the primary and secondary windings. By applying the 
 right hand rule it will be seen that the induced current in the second- 
 ary flows in the opposite direction to the inducing current in the 
 primary when the primary circuit is made and in the same direction 
 when the primary circuit is broken. 
 
 When the primary circuit is made a counter E. M. F. results 
 which tends to oppose the building up of the field. The mutually 
 induced current in the secondary sets up a field which tends to 
 strengthen this counter E. M. F., further retarding the building up 
 of the magnetic field. Thus the current flowing in the primary 
 has to overcome the counter E. M. F. due to the induced current. 
 Hence the rate at which the field builds up is slow and the resulting 
 voltage in the secondary will be correspondingly low. When the 
 primary circuit is broken, however, there is no counter E. M. F. 
 in the primary; the result is a sudden collapse of the field and a 
 consequently high voltage is induced in the secondary. 
 
 When high voltages are desired, they may be obtained by mutual 
 induction, employing a much greater number of turns of wire in the 
 secondary winding than in the primary. The voltages in the primary 
 and secondary windings vary directly as the number of turns of wire 
 in each while the current varies inversely as the number of turns of 
 wire. For this reason fine wire is used for the secondary winding and 
 much heavier wire for the primary. 
 
 Fig. 113 shows a simple vibrator which is used for making and 
 breaking the circuit. It consists of a coil wound about a soft iron 
 core "A"; opposite one end of this core is placed a small piece of 
 soft iron "B" attached to a spring "C." An adjusting screw "D" 
 is in contact with the spring when in its normal position. 
 
 One side of the battery is grounded while the other is connected 
 through the switch " S ' ' to the coil, the other end of the coil is attached 
 to the spring. "C" and the screw "D" is grounded. 
 
 When the switch is closed a magnetic field is set up magnetizing 
 the core. This attracts the iron "B" breaking the circuit at "D." 
 This causes the core to be demagnetized and the spring "C" returns 
 to its normal position, again closing the circuit. This operation will 
 
150 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 113 Simple Vibrator 
 
 be repeated over and over as long as the switch "S " is closed. Thus 
 the circuit is automatically made and broken. 
 
 When the circuit is broken 
 the collapse of the magnetic 
 field induces a current in the 
 winding. The voltage of this 
 self-induced current is sufficient 
 to cause an arc to follow the 
 separating points at "D" each 
 time the current is broken. 
 This arcing burns and pits the 
 contact points increasing the 
 resistance of the circuit. To 
 prevent this a condenser "K" 
 is connected in parallel with the 
 contact points as shown in 
 Fig. 113. When the circuit is 
 broken the flow of induced 
 current passes into the conden- 
 ser charging it. This momen- 
 tarily diverts the flow of current from the contact points allowing 
 them to separate sufficiently to prevent a following arc. 
 
 A condenser is usually constructed of sheets of silver, tin, or lead 
 
 foil, alternate sheets being 
 connected to common ter- 
 minals and separated from each 
 other by some insulating ma- 
 terial such as mica or specially 
 treated paper (Fig. 114). 
 
 The capacity of a conden- 
 ser depends upon the total 
 area of the plates and the 
 distances these plates are sepa- 
 rated by the insulating mater- 
 ial. When a condenser is used 
 on ignition systems it is neces- 
 sary to have it of proper capa- 
 city. This is governed by the 
 amount of self -induced current in the circuit in which it is placed. 
 
 Fig. 114 Condenser 
 
CHAPTER XVI 
 
 BATTERY IGNITION SYSTEMS 
 
 After experimenting for many years with different systems of 
 ignition it has been found that the most reliable and satisfactory 
 is the high tension "jump spark" system. There are many means 
 employed to produce the necessarily high voltage required to jump 
 a set gap, all of which are based on the principle of mutual electro- 
 magnetic induction. Ignition systems are classified under two 
 general headings, Battery Ignition Systems and Magneto Ignition 
 Systems. Battery ignition systems employ a coil to obtain the neces- 
 sary voltage receiving the current for the primary from some outside 
 source. This type of ignition system will be discussed in this chapter. 
 
 Fig. 115 Induction Coil 
 
 Fig. 115 shows a core "A" wound with a primary and secondary 
 winding, one end of the primary being connected to the battery, the 
 other side of which is grounded. The other end of the primary is 
 connected to ground through a switch " S . " One end of the secondary 
 is grounded and the other end led to a spark gap "G," the other side 
 of which is grounded. 
 
 When the switch is closed a magnetic field is set up about the core 
 which collapses when the switch is opened, causing a mutually induced 
 current to flow in the secondary. In ignition coils a great number 
 of turns of wire are used on the secondary to obtain sufficient voltage 
 to jump set air gaps. 
 
 As already explained in timing the spark must occur at a certain 
 definite time during the operation of the engine. This requires that 
 the primary circuit be made and broken to obtain the mutually 
 
 151 
 
152 MOTOR VEHICLES AND THEIR ENGINES 
 
 induced current in the secondary at the proper time. To accomplish 
 this some circuit breaking device positively driven by the engine and 
 timed with it must be used. Such a device is known as "Timer" 
 and its object is to make and break the primary circuit at the proper 
 time. 
 
 Fig. 116 Closed Circuit Timer Fig. Ill Open Circuit Timer 
 
 There are two types of timers, that shown in Fig. 116 where the 
 contacts are together except when separated by the cam, and that 
 shown in Fig. 117 where the contacts are separated except when 
 closed by the cam. The first type allows the current to flow through 
 the primary except for the short period when the circuit is broken. 
 The circuit being closed the greater part of the time the current con- 
 sumption will consequently be large. The other type allows current 
 to flow through the primary only for an instant which materially 
 reduces the current consumption. When the circuit is made in this 
 construction the flow of the current through the primary is opposed 
 by the counter E. M. F. resulting from self-induction and the com- 
 plete building up of the magnetic field takes a definite length of time. 
 At slow speed there will be enough time elapsed before the circuit is 
 again broken for the complete building up of the field. As the speed 
 increases there is not sufficient time and the field will still continue 
 to build up due to the inertia of the current after the circuit has been 
 broken. Therefore, the collapse of the field and consequent mutual 
 induction in the secondary does not occur for some time after the 
 primary circuit has been broken. This is known as "electrical lag" 
 and is measured in degrees of revolution of the crank shaft between 
 point of break and point of spark. On some ignition systems this 
 lag has been measured and found to be as great as 35 at 2,000 
 R. P. M. of the engine. 
 
 If the cams (Figs. 116 and 117) are turned clockwise and the 
 housing carrying the contact points is turned anti-clockwise the 
 
BATTERY IGNITION SYSTEMS 
 
 153 
 
 circuit will be broken earlier. This will advance the time at which 
 the spark takes place in the cylinder and is termed "advancing the 
 spark." If the housing were moved in a clockwise direction it would 
 cause the circuit to be interrupted later and consequently the spark 
 would take place later in the cylinder. This is termed "retarding 
 the spark." The general rule is that when the housing is turned in 
 the opposite direction to the rotation of the cam the spark is advanced 
 and when turned in the same direction the spark is retarded. 
 
 It will be remembered from valve timing that ignition is advanced 
 in accordance with the speed of the engine. Hence, it is necessary 
 to limit the movement of the timer housing. The method of ac- 
 complishing this varies with the type of timing connection employed. 
 
 The cam used in a timer may have any number of noses but it 
 generally has as many as the engine has cylinders. This makes it 
 necessary to drive the timer at half engine speed on a four-cycle 
 engine. To determine the speed at which any timer should be driven- 
 the following formulae are used: 
 
 For four-cycle engine, 
 
 Number of Cylinders 
 Speed = - 
 
 2 x number of noses on cam. 
 
 For two-cycle engines, 
 
 * , _ Number of Cylinders 
 
 Number of noses on cam. 
 
 Applying the formula for four-cycle to a four-cylinder engine 
 having a four-nosed timing cam : 
 
 Speed = - - = engine speed. 
 
 Fig. 118 Induction Coil with Timer and Condenser 
 
 In Fig. 118 the switch has been replaced by a timer and a con- 
 denser has been connected in parallel with it. The condenser is 
 
154 MOTOR VEHICLES AND THEIR ENGINES 
 
 necessary just as in the case of a vibrator the self-induction otherwise 
 causing arcing at the contact points. 
 
 If continued arcing at the contact points were permitted burning 
 and pitting would result which would increase the resistance of the 
 primary circuit. Any increased resistance in the primary circuit 
 reduces the amount of current flowing, thus weakening the magnetic 
 field. This reduction of the lines of magnetic force will correspond- 
 ingly reduce the induced voltage of the secondary and material re- 
 duction of the secondary voltage will affect the spark or stop it 
 altogether. Low secondary voltage is generally traceable to the 
 primary circuit. 
 
 For the timer to operate properly it is necessary that the contact 
 points be in proper adjustment. The gap should be 0.5 mm. or 
 0.020 inch when the points are fully separated. If the gap is too 
 small arcing will take place causing pitting of the contact points. 
 
 The timer controls the instant at which the spark occurs and must 
 operate in synchronism with the engine. However, if the system is 
 to be used on a multi-cylinder engine some provision must be made 
 to distribute the secondary current to the spark plugs in their proper 
 firing order. To accomplish this a distributor is used. 
 
 Fig. 119 Flush Segment Distributor 
 
 Fig. 119 shows one common construction of distributor. The 
 current is led to the center terminal which is in contact with the 
 rotor. This rotor is made of insulating material and has a brass tube 
 running through it in which fits the carbon brush which conducts the 
 current to the segments. The housing is made of insulating material 
 with brass segments inserted in it and flush with the inner circum- 
 ference with which the carbon brush of the rotor makes contact. 
 The segments are connected by brass tubes through the insulating 
 material to the terminals on the outer surface of the distributor. As 
 the rotor revolves it makes contact with the segments in order and 
 the terminals connected to these segments are wired to the spark 
 plugs in their proper firing order. It is necessary to have this rotor 
 positively driven by the engine and at such a speed that it will be 
 
BATTERY IGNITION SYSTEMS 155 
 
 on the proper segment when the primary circuit is broken by the 
 timer. 
 
 As it is necessary to have a segment for each cylinder the speed is 
 figured by using the same formulae as employed in determining the 
 speed of a timer. It will be found that the rotor always turns half 
 engine speed on a four-cycle engine and engine speed on a two-cycle 
 engine. 
 
 As previously stated timers are usually designed with cams having 
 the same number of noses as there are cylinders. This permits the 
 timer and distributor to be driven at the same speed so that they can 
 be incorporated in one unit and driven by the same shaft. This 
 arrangement is called a timer-distributor and the rotor of the dis- 
 tributor is superimposed on the timer cam so that it fits only in one 
 position and the distributor housing is keyed to the timer housing. 
 This construction assures the proper relation of timer and distributor 
 but it must be borne in mind that there is no electrical connection 
 between them. 
 
 When a carbon brush distributor is used the brush is always 
 in contact with the inner surface of the distributor, part of which is 
 insulating material between the segments. This continual rubbing 
 of the carbon brush over the surface often causes a carbon deposit to 
 be formed which short-circuits the segments allowing the current 
 to flow to the spark plug in the cylinder which offers the least re- 
 sistance. This will cause misfiring of the engine. 
 
 Fig. 120 Raised Segment Distributor 
 
 Fig. 120 shows a distributor having* metal segments raised above 
 the insulation and employing a metal brush. This design eliminates 
 short circuiting of the segments. 
 
 Fig. 121 shows a distributor placed in the secondary circuit and 
 connected to the spark plugs. This completes the wiring of a 
 typical battery ignition system for a four-cylinder engine. 
 
156 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 121 Wiring of Battery Ignition System 
 
 SPARK PLUGS. On high tension ignition systems it is necessary 
 to have some device in each cylinder to maintain & gap of definite 
 size across which the secondary current must jump to complete its 
 circuit. This device is known as a spark plug. 
 
 Fig. 122 shows a typical spark plug in cross 
 section. The central electrode should be made 
 of some material which will not pit easily from 
 the heat of the spark, such as chrome nickel- 
 steel. This is insulated from ground by insu- 
 lating material which may be composed of 
 porcelain, mica, or steatite. The insulator 
 must perform three functions: First, it must 
 have sufficient dielectric efficiency to insulate 
 the central electrode from the ground; second, 
 it must present a surface in the combustion 
 chamber to which carbon will not readily 
 adhere; third, it must not crack under the 
 intense heat in the cylinder. Insulators are 
 finished with a highly polished surface which 
 should not under any circumstances be scraped 
 as tn * s wou ^ permit carbon to adhere to the 
 Section of Spark surface. Some plugs are made so that the 
 Plug insulators can be removed for replacement, in- 
 
 spection, or cleaning (Fig. 123). 
 
 This necessitates a gas-tight joint between the insulator and shell 
 which is usually obtained by screwing a bushing down against a 
 gasket. When porcelain insulators are used there must be enough 
 "give" at this joint to allow for expansion of the insulator or it will 
 
 Fig. 122 Cross- 
 
BATTERY IGNITION SYSTEMS 
 
 157 
 
 RUBY INDIA 
 MICA INSULATION 
 LATERALLY WOUND 
 
 COPPER .J 
 
 ASBESTOS GASKET \ 
 POSITIVE GAS TIGHT f 
 JOINT 
 
 SMALL 
 
 COMPRESSION 
 SPACE 
 
 Green Jacket 
 
 UNSCREW HERE 
 -*- FOR CLEANING 
 
 EXTRA HEAVY 
 SPARKING POINTS 
 
 Fig. 123 Plug with Removable 
 Insulator 
 
 be cracked. The body of the plug is usually made of steel, the lower 
 part of which is threaded to fit the thread in the cylinder. These 
 threads are made up in three 
 sizes: the half-inch, with ta- 
 pered pipe thread; the % inch 
 S. A. E. standard, with straight 
 thread; the 18 mm. metric, 
 with straight thread. On the 
 % inch and metric plugs a 
 shoulder is provided the pur- 
 pose of which is to tighten 
 down on a gasket when the 
 plug is screwed into the cy- 
 linder. This is not necessary 
 with a half-inch plug because 
 of the tapered thread which 
 becomes gas tight as it is 
 screwed into the cylinder. At- 
 tached to the body of the plug 
 is a small electrode which 
 governs the size of the spark 
 gap. By bending this elec- 
 trode toward or away from t^ie central electrode the size of the 
 gap is regulated to give the best results. For battery ignition 
 this gap should be between l /w and 1 / 3 2 of an inch and for magneto 
 ignition between 1 / 6 4 and l / 5Q of an inch. 
 
 The results obtained from an engine are largely dependent upon 
 the location of the spark plugs. When two independent ignition 
 systems are used, that is, battery ignition for starting and magneto 
 ignition for running, using two separate spark plugs, the one that is 
 nearest the inlet valve should be connected to the magneto ignition 
 system. The usual installation of plugs for this type of ignition is 
 to place one directly over the inlet valve and the other over the ex- 
 haust valve. As the best mixtures will be nearest the inlet valve the 
 system which should be used for continuous running should be 
 wired to these plugs, while the other should be wired to the system 
 used for starting. 
 
 Fig. 124A shows a spark plug properly installed in a recessed 
 spark plug cap. It can be seen that the electrodes project slightly 
 into the combustion chamber and the best results are obtained 
 under these conditions. 
 
 Fig. 124B shows a standard plug installed in an unrecessed spark 
 plug cap. It is seen that the electrodes of the plug do not extend 
 
158 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 124 Spark Plug Locations 
 
 into the combustion chamber and a pocket is formed. After a charge 
 has been fired and the piston comes up on the exhaust stroke it will 
 compress burned gases in this pocket. Therefore, on the following 
 compression stroke some of the fresh mixture will be compressed in 
 this pocket where it will mix with the pocketed exhaust gas causing 
 a very poor mixture. The mixture is so poor in some cases that it 
 will not ignite and causes misfiring of the engine. If the charge does 
 ignite the rate of flame propagation will be reduced causing a loss of 
 power. 
 
 Fig. 125 Vibrating Induction Coil 
 
BATTERY IGNITION SYSTEMS 159 
 
 Fig. 124C shows a spark plug passing directly through the water- 
 jacket without a recessed spark plug cap being used. Although the 
 electrodes project into the combustion space this installation is not 
 entirely satisfactory because it is necessary to have a special design 
 of plug for each engine. Many times it is impossible to obtain exact 
 length of plug necessary to bring the electrodes flush with the cylinder 
 walls. This makes it imperative to use either spark plug caps that 
 will take standardized plugs or else use a special plug designed for 
 that particular engine. 
 
 If a second winding of a great many turns of fine wire is wound on a 
 simple vibrator coil such as shown in Fig. 113 a spark coil is obtained. 
 Fig. 125 shows such a coil, one end of the secondary being grounded 
 while the other is led to a spark gap "G," the other side of which is 
 grounded. When the switch "S" is closed the vibrator " V" rapidly 
 makes and breaks the primary circuit as already explained. This 
 causes a magnetic field to be alternately built up and broken down 
 inducing a current of high voltage in the secondary which can jump 
 the spark gap to the ground. 
 
 If this spark gap is inside the cylinder of an engine the explosive 
 mixture will be fired when the switch "S" is closed which will cause 
 a spark to jump the gap. In this way the spark coil is used for igni- 
 tion purposes. It was applied to early ignition systems and still 
 may be found on a few machines. 
 
 Fig. 126 shows a four-unit coil system in which four separate spark 
 coils are used. One side of the battery "B" (or other source of 
 current) is grounded while the other is connected to the primary 
 windings of the coils "C," "D," "E," and "F." The other ends of 
 the primaries are connected through the vibrators "V" to the con- 
 tact segments of a revolving switch "S" sometimes called a "com- 
 mutator." Across each of the vibrators is connected a condenser "K." 
 The rotor "R" of the switch "S" is positively driven by the engine 
 and is connected to ground, successively completing the circuits 
 through the contact segments. Since there are as many segments 
 as there are cylinders it must be driven at half engine speed. One 
 end of each secondary is connected to its primary through which it 
 is grounded, while the other end is wired to a particular spark plug, 
 depending upon the firing order of the engine. When the revolving 
 rotor touches one of the contacts, current from the battery flows 
 through the coil connected to it, causing its vibrator rapidly to make 
 and break the primary circuit. This induces high voltage impulses 
 of current in the secondary and sparks jump the gap at the spark 
 plug to which the secondary is connected. This is identical with the 
 
160 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 126 Four-Unit Coil Ignition System 
 
 Fig. 127 1 Four-Unit Coil System with Master Vibrator 
 
BATTERY IGNITION SYSTEMS 
 
 161 
 
 Ford system in which the current is supplied by a low tension 
 magneto instead of a battery. 
 
 This system eliminates the necessity for a distributor but makes 
 four separate spark coils necessary, each with a vibrator to be kept 
 in adjustment and contacts to clean. It is practically impossible to 
 adjust all the vibrators so that the spring tension is the same on each. 
 This causes the sparks in the different cylinders to vary in intensity 
 and uneven running of the engine results. 
 
 To remedy this difficulty a Master Vibrator may be installed in 
 the system. This consists of a vibrating coil having but one winding 
 which is connected in the primary circuit as shown in Fig. 127. All 
 the spark coils are non-vibrating or if vibrating coils are installed the 
 contact screws should be screwed down so they hold the springs 
 tight against the iron cores of the coils. 
 
 When the rotary switch "S" touches one of the contacts, current 
 flows from the battery "A" through the master vibrator "M" 
 and coil "A," "B," "C," or "D," depending upon which contact is 
 touched. The vibrator "V" makes and breaks the primary circuit, 
 inducing current in the secondary winding of the spark coil just as 
 when it had its own vibrator. This makes it possible to get the same 
 intensity of spark in all the cylinders with but one vibrator to adjust. 
 
 NORTHEAST IGNITION SYSTEM 
 
 The complete ignition system consists essentially of three self- 
 contained units; the single unit coil, the timer and distributor 
 
 Fig. 128 Unit Assembly 
 
162 MOTOR VEHICLES AND THEIR ENGINES 
 
 assembly, and the automatic advance. Each of these three units is 
 constructed so as to be easily removed for repairs and replacement 
 (Fig. 128). 
 
 The coil is constructed to operate on 12 volts. It differs from the 
 ordinary coil in having both ends of the primary brought out to 
 terminals on the coil housing. As usual, one end of the secondary is 
 grounded while the other is connected to a stud on the side of the 
 coil and this stud is connected to an insulated binding post on the 
 side of the coil housing. Around this post is a raised section of the 
 housing designed to act as a safety spark gap. If at any time the 
 resistance between this post and the ground at the spark plug be- 
 comes greater than that of this air gap the current will jump from 
 the post to the housing, relieving the pressure in coil so that the insula- 
 tion will not be broken down. When sparking occurs at this point 
 it is usually an indication of a broken or disconnected cable or too 
 wide a gap at the spark plug. 
 
 Fig. 129 Timer with Condenser 
 
 The timer (Fig. 129) is typical of the construction used for 
 saturated coils. Both contacts of this timer are insulated from the 
 ground and the condenser is wired in parallel with the contact points 
 and contained in the timer housing. This makes the condenser 
 accessible and easy to replace, but it must be remembered that the 
 condenser must be of a certain capacity which is determined by the 
 coil. Therefore, when replacing a condenser one designed for this 
 coil must be used. 
 
BATTERY IGNITION SYSTEMS 
 
 163 
 
 Fig. 130 Automatic Spark 
 Advance 
 
 The distributor is of the flush segment type using a metal brush. 
 The rotor is superimposed upon the timer cam both being driven by 
 the same vertical shaft. 
 
 There are two methods for advancing and retarding the spark on 
 this system. The manual control moves the housing carrying the 
 contact points, this movement being limited so that further advance 
 must be accomplished by the automatic device. The automatic 
 control (Fig. 130) is operated by cen- 
 trifugal action so that as the speed 
 increases, the shaft operating the 
 timer cam is advanced with respect 
 to the operation of the engine, the 
 reverse taking place as the speed is 
 diminished. Since the timing of the 
 ignition is partially dependent upon 
 the speed of the engine this dual control proves very satisfactory. 
 
 Fig. 131 is a wiring diagram showing the internal wiring of this 
 system as applied to the Dodge Car and Fig. 132 shows the actual 
 external connections. One end of the primary is connected to the 
 ignition switch while the other end is connected to one of the timer 
 terminals. The switch is arranged so there are two "on" and two 
 "off" positions. In one "on" position the current passes through 
 the primary of the coil, then through the timer and back to the 
 switch where it is grounded. In the other "on" position the cur- 
 rent passes through the timer and then through the primary winding 
 in the opposite direction returning to the switch where it is grounded. 
 The object of a switch of this kind is to cause the current to pass 
 through the primary in the opposite direction each time the switch 
 
 position. If the current flows through a 
 
 STABTING SWITCH 
 
 Fig. 131 Internal Wiring Diagram 
 
164 
 
BATTERY IGNITION SYSTEMS 
 
 165 
 
 primary each time in the same direction the soft iron core will retain 
 some of its magnetism after the circuit is broken. This prevents a 
 complete breaking down of the magnetic field and will lower the self 
 and mutually induced voltage. This is prevented by building up 
 the field each time in the opposite direction. 
 
 DELCO IGNITION SYSTEM 
 
 This ignition system is made up of two self-contained units, the 
 coil assembly and timer-distribution assembly with automatic 
 
 To 
 
 W//f3 
 
 Fig. 133 Unit Assembly 
 
 advance. The coil housing can easily be attached to the timer 
 distributor housing as shown in Fig. 133. 
 
 The coil is wound for 6 volts but has a resistance connected in 
 series with the primary so that it may be used on a 12-volt circuit. 
 There are four terminals on the coil housing. The ends of the primary 
 are connected to two of these, one side of the condenser is connected 
 to a third, and the ungrounded end of the secondary is connected 
 
166 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 to the fourth. The condenser is contained in the coil housing and 
 connected in parallel with the contact points. 
 
 The timer is of the construction used with a saturated coil both 
 contacts being insulated from the ground. The distributor is super- 
 imposed upon the timer and is of the flush segment type, the rotor 
 being driven by the same shaft as the timer cam. 
 
 This system has both manual and automatic spark advance. The 
 manual advance is accomplished in the usual manner by moving 
 the housing carrying the contact points. The automatic advance is 
 of the usual centrifugal construction advancing the cam with relation 
 to the operation of the engine, the amount of the advance being 
 controlled by the speed of the engine. 
 
 Fig. 8 
 
 Fig. 134 Internal Wiring Diagram 
 
 Fig. 134 is a wiring diagram showing the internal wiring of this 
 system as applied to the Dodge Car and Fig. 135 shows the actual 
 external connections. One side of the battery is grounded and the 
 other side is connected to the ignition switch passing to the starting 
 switch and through the ammeter. From this point the current will 
 flow through the ignition system in two ways and is governed by the 
 position of the switch when in the "on" position. The switch is so 
 arranged that it causes the current to flow first in one direction and, 
 in the other "on" position, in the opposite direction. One path is 
 as follows: The current flows to the coil passing through the re- 
 sistance and then through the primary winding the other end of the 
 primary winding being connected to the timer. From the timer the 
 current flows back to a terminal on the coil housing, this being con- 
 nected to one side of the condenser the other side of which is connected 
 to the end of the primary leading to the timer. From this binding 
 post the current is lead back to the switch where it is grounded. 
 When the switch is turned "off" and then "on" again the current 
 
W) 
 
 E 
 
 167 
 
168 MOTOR VEHICLES AND THEIR ENGINES 
 
 takes the same path but flows in the opposite direction. This is 
 accomplished by the switch for in one position the lead from the coil 
 is connected to the battery terminal and the lead from the timer is 
 grounded. In the other position of the switch these connections are 
 reversed. 
 
 As the current passes through the primary of the coil in a different 
 direction every time the engine is operated it eliminates the pos- 
 sibility of the soft iron core becoming magnetized thus weakening 
 the strength of the induced current. It also prevents excessive wear 
 on one of the contact points. 
 
 REMY IGNITION SYSTEM 
 
 This system consists of two units mounted on one bracket, the 
 coil assembly and the timer-distributor assembly (Fig. 136). Both 
 ends of the primary winding are led to binding posts on the top of the 
 coil housing, one of these being connected to the battery and the 
 other to the tuner. One end of the secondary is internally grounded 
 the other being lead out to a binding post on the side of coil housing. 
 The condenser is contained in the timer housing, one side being 
 grounded and the other connected to the primary lead wire at the 
 tuner. This coil may or may not be equipped with a resistance to 
 reduce the amount of current flowing through the primary. 
 
 The timer is of the construction used for saturated coils. Only 
 one of the contacts is insulated the other being internally grounded. 
 
 The distributor is of the raised segment type with a metal contact 
 segment on the rotor. It is superimposed on the timer cam and is 
 driven by the same shaft. Advanced and retarded ignition are 
 accomplished by manual control in the usual manner by turning the 
 timer-distributor housing. 
 
 This is a typical one-wire system using a ground return. Fig. 137 
 shows a wiring diagram of the internal connections. 
 
 ATWATER-KENT SYSTEM 
 
 This system consists of two separate self-contained units, the 
 coil assembly and the time-distributor assembly with automatic 
 spark advance. 
 
 The coil is usually placed on the dash and is wound for 6 volts. 
 Both ends of the primary and secondary windings are brought out 
 to binding posts on the coil box. 
 
 The timer is so constructed that the coil is non-saturated thus 
 reducing the current consumption. Both contacts are insulated 
 
BATTERY IGNITION SYSTEMS 
 
 169 
 
 Secondary Cable - 
 
 .Leads h Plugs 
 
 'Distributor Cover 
 
 Oiler 
 
 ; Drive Shaft 
 
 Fits Standard 
 Magneto Base Bracket"" ' 
 
 Oilers 
 
 Fig. 136 Unit Assembly 
 
 ,^^ 
 
 Fig. 137 Internal Wiring Diagram 
 
170 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 and the condenser is connected in parallel with them and enclosed 
 in the timer housing. 
 
 The distributor is of the raised segment type having a metal 
 segment on the rotor which is superimposed on the timer cam and 
 driven by the same shaft. 
 
 Both manual and automatic spark advance are employed in this 
 system each being independent of the other. The manual control 
 moves the housing carrying the contact points and is controlled from 
 
 Fig. 138 Automatic Advance Mechanism 
 
 the steering wheel. The automatic advance is of centrifugal con- 
 struction (Fig. 138) advancing the position of the cam with respect 
 to the rotation of the shaft as the speed increases. 
 
 Fig. 139 shows a wiring diagram of the internal connections of 
 this system. One side of the battery "K" is connected to "C" while 
 the other is connected to terminal "B" of the switch. Terminal 
 "A" is connected to one side of the primary winding while "D" is 
 connected to one of the timer contacts. The other side of the primary 
 winding is connected to the remaining timer contact. One side of 
 the secondary winding is grounded and the other connected to the 
 central distributor terminal. The current flows through the primary 
 circuit in either direction depending upon the position of the switch. 
 When in the position as shown by the heavy lines the current passes 
 from the battery through the primary winding to the timer and back 
 through the switch to the battery. When the switch is in the 
 position shown by the dotted lines the current flows to the timer 
 and through the primary in the opposite direction. This prevents 
 residual magnetism in the core and excessive wearing away of one 
 contact. 
 
BATTERY IGNITION SYSTEMS 
 
 171 
 
 Fig. 139 Internal Wiring Diagram 
 
 Practically all makes of Battery Ignition Systems of the non- 
 vibrating type are like one of those just described. The saturated 
 coil is nearly always used and the reverse current switch is quite 
 common. The tendency now seems to be toward placing the con-- 
 denser in the timer housing rather than placing it inside the coil 
 housing where it is hard to get at. The combined timer-distributor 
 is used almost without exception and a compact unit with short 
 direct connections is the predominating construction. The recent 
 wide adoption of battery ignition systems has resulted in many 
 improvements and excellent results are obtained. 
 
CHAPTER XVII 
 
 MAGNETOS 
 ARMATURE TYPE 
 
 Before electrical generators were used on motor vehicles a great 
 deal of trouble was experienced with battery ignition systems since 
 the source of current was not always dependable. If the battery 
 was composed of dry cells it was effected by dampness and was short- 
 lived. If a storage battery was used the machine was put out 
 of operation every time it became necessary to recharge the battery. 
 This resulted in constant trouble and annoyance. 
 
 To eliminate this unreliability the magneto was developed and 
 the high tension magneto has been adopted for ignition, since it is 
 more reliable, being a self-contained unit. The efficiency of operation 
 of the battery ignition system depends upon the current flowing 
 through the primary winding and the rapidity of collapse of the field. 
 Difficulties are encountered due to additional resistance in the primary 
 circuit or the reduction of the battery voltage. These difficulties 
 are not experienced with the magneto as all connections are internally 
 made and an outside source of current is not depended upon to 
 magnetize the core. 
 
 The iron core of the spark coil is magnetized by current by some 
 outside source such as a battery. The magneto eliminates this, the 
 armature core becoming magnetized by being placed between the oppo- 
 site poles of strong permanent magnets so that it forms a part of a com- 
 pound magnetic circuit. The armature core is of the socalled " shuttle" 
 
 or "anchor" type and is mounted upon a 
 horizontal axis so that it can be revolved 
 between the pole shoes of the permanent 
 horseshoe magnets (Fig. 140). It is so 
 shaped that wire may be wound upon it. 
 The air gaps across which the magnetic 
 lines of force must flow are made as short 
 as possible. The bearings upon which 
 the armature shaft is mounted must be 
 in good condition since proper results will 
 not be obtained if the armature core is 
 allowed to rub either of the pole shoes. 
 
 172 
 
 Fig. 140 Armature in 
 Place Between Magnets 
 
(d) 
 
 (9) 
 
 (*) (I) 
 
 Fig. 141 Change of Magnetic Flux in Revolving Armature 
 
 173 
 
174 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 141 shows several positions of the armature core of a magneto 
 with relation to the pole shoes during one revolution. Starting with 
 the armature core at position A all the lines of force flow in at "H" 
 and through the core neck in passing from the north to the south 
 poles of the horseshoe magnets. If the core is revolved clockwise 
 as indicated by the arrow, it will next reach the position B and fewer 
 lines of magnetic force will flow through the core neck since less of 
 the curved sides of the core are now opposite the pole pieces. When 
 the core has revolved to position C still less of the curved portion is 
 opposite the pole pieces and the number of lines of force passing 
 through the core neck is still further decreased. When the core has 
 reached vertical position D all the lines of force flow through the 
 curved sides and none through the neck of the armature core. The 
 reason for this is because the magnetic lines of force take the path 
 offering the least resistance. As the armature core is revolved to 
 position E a few lines of force start to flow through the core neck 
 again but in the opposite direction leaving it at "H." As the arma- 
 ture core is revolved through the position F the number of lines of 
 force flowing through the core neck increases until it reaches a 
 maximum when the core is revolved to the position G. During the 
 next half revolution as the armature revolves through positions H 
 
 to L exactly the same changes of 
 magnetic flux take place through 
 the core neck as during the first 
 half revolution. 
 
 When the armature core is 
 rotated at a uniform speed the 
 magnetic flux flowing through the 
 core neck changes from a maxi- 
 mum at A to zero at D, to a 
 maximum in the reversed direc- 
 tion at G, and to zero at J or 
 from a maximum to zero twice 
 during one revolution. The rate 
 of change is not uniform and is 
 greatest as the armature core 
 approaches the vertical position. 
 This is shown graphically in 
 Fig. 142. 
 
 Fig. 142 Curve Showing Flux Varia- If a P rim ary and secondary 
 tions During One-half Revolution winding is wound on a soft iron 
 
MAGNETOS, ARMATURE TYPE 175 
 
 ring (Fig. 143) and the amount of current flowing through the primary 
 is varied the magnetic flux flowing around through the iron ring will 
 be varied accordingly. When the number of lines of magnetic force 
 threading through the secondary is 
 changed a current will be induced in it. 
 The more rapid the rate of change the 
 greater will be the induced voltage. This 
 electrical principle of induction is ex- 
 pressed in Faraday's Law and is stated 
 as follows: "The induced E. M. F. is 
 proportional to the rate of change of the Fig ' l-*nv Transformer 
 magnetic lines of force or flux threading through a coil." This 
 principle is employed in the operation of a magneto since the mag- 
 netic flux flowing through the armature core, about which the 
 conductors are wound, varies in intensity. 
 
 If a coil of insulated wire is now wound about the armature core 
 neck (Fig. 141) to form a complete circuit, current will be induced in 
 the winding when the armature is revolved between the pole pieces. 
 This is due to the change in magnetic flux through the armature core. 
 The induced voltage will be proportional, or nearly so, to the rate of 
 change of the magnetic flux through it. In Fig. 144 a complete 
 electric circuit is obtained by grounding both ends of the insulated 
 wire to the core. These connections are indicated by black spots 
 "l"and"2." 
 
 When the armature is at A (Fig. 144) it is in one of the positions 
 where the flux is a maximum.' through the armature core neck. As 
 the armature revolves through the first quarter revolution from posi- 
 tion A to D the magnetic flux through the core neck decreases, 
 slowly at first but at an increasing rate until position D is reached. 
 The decrease of magnetic flux through the core neck causes an 
 induced electric current to flow as indicated through the insulated 
 wire of the winding. The path of the current is from "2" through 
 the insulated wire to " 1 " and thence through the metal of the core 
 from " 1 " to "2." The current flow beginning at zero keeps increas- 
 ing during the first quarter revolution and reaches its maximum at 
 position D of the armature. As the armature is revolved from 
 position D the current decreases in value until it drops to zero again 
 when the armature has reached position G. During the second half 
 revolution from G to L similar variations in the current take place 
 but the current now flows from "1" toward "2" since the direction 
 of the magnetic flux through the core neck has been reversed. 
 
 Starting from position A the current increases from zero to a 
 maximum at D and back to zero again at G. It then increases in the 
 
Fig. 144 Electro-magnetic Induction in Primary Circuit 
 
 176 
 
MAGNETOS, ARMATURE TYPE 
 
 177 
 
 opposite direction to a maximum at J and back to zero again at A. 
 An electric current of the kind just described is called an alternating 
 current. 
 
 The induced current in the primary winding depends upon the 
 rate of change of flux through the armature core neck. If the speed 
 of rotation of the armature is increased the rate of change will be 
 proportionately increased. Therefore, the induced voltage depends 
 upon the speed at which the magneto is driven. 
 
 In order to start an engine on magneto sufficient speed of rotation 
 must be attained to produce current in the primary. If a powerful 
 engine is cranked by hand, especially a heavy duty type such as is 
 used on tractors, sufficient speed will not be attained to produce 
 the desired current. This difficulty is overcome by the use of an 
 impulse starting device (Fig. 145). 
 
 It is so designed that a catch holds the magneto armature (or 
 rotor) during 80 degrees of travel and then is tripped throwing the 
 
 Fig. 145 Impulse Starter 
 
 armature ahead at the rate of approximately 500 R. P. M. by means 
 of a coil spring, assuring a good spark properly timed with the engine. 
 By pressing down on the back end of ratchet catch lock "TS-8," 
 ratchet catch "TS-11" will be released. This allows it to engage 
 with the notch on ratchet "TS-4," which is keyed to the armature, 
 holding it stationary while case "TS-1" turns through 80 degrees com- 
 pressing the coil spring "TS-23." When the lug on case "TS-1" 
 revolves far enough to lift catch "TS-11," the armature is thrown 
 ahead with a rush by the compressed spring. This produces the 
 desired induced current even though the engi^ is being turned over 
 slowly. The armature when released is thrown to position D (Fig. 
 141) so that it passes quickly through the point where the maximum 
 rate of change of flux takes place. The same thing takes place 
 during the second half-revolution of the armature. 
 
 When the armature is in positions A and G (Fig. 141) it accom- 
 modates itself to the greatest number of lines of force and, there- 
 
178 MOTOR VEHICLES AND THEIR ENGINES 
 
 fore, resists being turned from these positions. If a flexible shaft 
 coupling is provided the armature will lag behind the shaft causing 
 tension in the coupling. When the tension has become sufficient 
 the armature will be forced to rotate. The stored-up energy then 
 turns the armature with increasing speed causing it to catch up with 
 the shaft. This results in the armature rotating through the vertical 
 position at a rate exceeding the speed of the shaft, thus increasing 
 the induced voltage. For this reason flexible couplings are ad- 
 vantageous and often used. 
 
 The voltage induced in a single winding on a revolving armature 
 core will not be sufficiently high (approximately 200 volts) to jump 
 a fixed air gap and for this reason a magneto of such construction is 
 called a low tension magneto. It is still necessary to send the cur- 
 rent through a spark coil in order to obtain sufficient voltage for 
 ignition purposes; hence, all the parts of the battery ignition system 
 remain except the battery which has now been replaced by a low 
 tension magneto. This arrangement will still be found in a few 
 ignition systems used for motor-propelled vehicles. 
 
 High-voltage current can be obtained directly from the magneto 
 by the addition of a secondary winding. This is wound on top of the 
 primary winding on the armature core just as the secondary of a 
 spark coil is wound on top of its primary winding. As the armature 
 is revolved current is built up in the primary winding due to the 
 rapid change of magnetic flux through the armature core. This 
 current reaches a maximum when the armature has reached ap- 
 proximately a vertical position D or J (Fig. 144). During the same 
 part of a revolution current is also induced in the secondary winding 
 but the voltage is not sufficiently high to cause a spark to jump an 
 air gap. If the primary circuit is suddenly broken as the armature 
 moves just beyond these positions the magnetic field set up by the 
 current flowing through the primary will be broken down. Just as 
 in the spark coil this induces a current of high voltage in the secondary 
 (approximately 5000 volts) which will jump a fixed air gap. 
 
 Since it is necessary for the primary circuit to be broken at certain 
 definite positions of the armature an interrupter is used driven by 
 the armature shaft. Li this way the rotation of the armature and 
 interrupter are kept perfectly synchronized. 
 
 Fig. 146 shows all the necessary parts of a high tension magneto 
 and diagrammatically illustrates how they should be connected. 
 The interrupter on a magneto will normally have two cams since the 
 primary circuit can ordinarily be broken but twice during one revolu- 
 tion. This is because there are but two positions of the armature in 
 
MAGNETOS, ARMATURE TYPE 
 
 179 
 
 I '^Ground' 
 
 Fig. 146 Typical Wiring Diagram of High Tension Magneto 
 
 common constructions of magnetos at which the induced primary 
 current is at a maximum. 
 
 A condenser is connected in parallel with the breaker points to 
 prevent arcing and is generally mounted in the end of the armature, 
 revolving with it. 
 
 A switch is provided which will continuously ground the primary 
 circuit when closed. This prevents the interrupter from interrupting 
 the primary circuit consequently preventing a current of high voltage 
 from being induced in the secondary. By closing this switch the 
 ignition is "shut off." 
 
 One end of the secondary is grounded through the primary, while 
 the other is connected to a distributor just as was done in a battery 
 ignition system. The same types of distributors are found on mag- 
 netos as are used on battery ignition systems, there being as many 
 contact segments as there are cylinders. For this reason the dis- 
 tributor will always be internally geared so as to run at one-half engine 
 speed (on four-cycle engines). 
 
 The ordinary construction of magneto with "shuttle" type of 
 armature produces two sparks during each revolution equally spaced 
 or 180 degrees apart. This is because there are but two points where 
 the rate of change of magnetic flux through the armature is greatest. 
 When magneto ignition is used for twin-cylinder motor-cycles with 
 "V" type cylinders a special construction is necessary to obtain 
 two sparks not equally spaced. This is required because the cylinders 
 are set_at an angle varying from 42 degrees to 47 degrees, depending 
 
180 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 upon the manufacturer. Assuming the angle is 45 degrees, No. 2 
 cylinder fires 315 degrees of engine revolution after No. 1 while the 
 engine turns through 405 degrees of revolution after No. 2 fires before 
 No^l fires again. Since the magneto gives two sparks per revolution 
 it is driven at half engine speed, therefore, the sparks it delivers must 
 be spaced 157J/ degrees and 202^ degrees of magneto revolution 
 apart. This is accomplished by advancing the second spark (nor- 
 mally occurring 180 degrees after the first spark) 22^ degrees. This 
 is done by moving the point of maximum change of flux ahead a 
 similar amount. Since the relative positions of pole shoes and 
 armature determines this point the desired result may be obtained 
 by altering the shape of the pole shoes and armature. 
 
 Fig. 147 shows the pole shoes 
 and armature of the Bosch Mag- 
 neto designed for twin-cylinder 
 motor-cycle ignition. The tips 
 of the diagonally opposite halves 
 of each pole shoe are cut away 
 and opposite sides of each half 
 of the armature core are almost 
 Fig. 147 Bosch Pole Shoes and entirely removed. 
 
 Armature for Motor Cycles when ^ armature core ig in 
 
 the position shown at A (Fig. 148) the lines of force flow from the 
 north pole across the small air gap "A" and through the core dia- 
 gonally. They enter the south pole by flowing across the similarly 
 small air gap "A" at the opposite (far) end of the armature core. 
 They do not pass straight through the armature core because the 
 large air gaps "B" offer a much harder path. 
 
 The point of maximum current B in the primary will be when 
 the armature has just cleared the trailing pole tips "C" and "D" 
 as in the usual construction. 
 
 When the armature core has reached the position C the lines of 
 force flow from the cut away part of the north pole shoe across the 
 small air gap "A" diagonally through the armature core. They then 
 pass into the cut away south pole shoe by flowing across the similarly 
 small air gap "A" at the opposite (near) end of the armature core. 
 They do not pass straight through the armature because of the large 
 air gaps "B." 
 
 The second point of maximum induced current in the primary will 
 be when the armature has just cleared the cut-away trailing pole 
 shoe tips at "E" and "F." In this case, however, the impulse of 
 current will come earlier with respect to the movement of the arma- 
 ture than in the first case by the amount that the pole tips are cut 
 
MAGNETOS, ARMATURE TYPE 
 
 181 
 
 away. This amount may be varied and in the case just considered 
 would have to be equivalent to 22J/2 degrees of armature rotation. 
 
 Fig. 148 Change of Magnetic Flux in Motor Cycle Magneto Armature 
 
 Thus the second spark is moved up 22J/ degrees nearer the first 
 spark which is the proper amount for a 45-degree "V" type twin- 
 cylinder engine. 
 
 Other methods of producing this same result have been devised 
 with varying degrees of success. One common construction is to 
 cover part of the pole shoes with brass which cuts off the lines of 
 force emanating from that particular part. Another is to cut a narrow 
 groove in the pole shoes which produces almost the same effect when 
 the armature leaves the edge of the groove as when it leaves the pole 
 shoe tip. Fig. 149 shows this construction employed in the Berling 
 Magneto. In this way impulses of induced current are obtained at 
 two different points, the primary being broken first at one and then 
 
182 
 
 MOTOR^VEHICLES AND THEIR ENGINES 
 
 at the other. The distance between the grooves in the pole shoes and 
 the pole shoe tips depends upon the angle be- 
 tween the cylinders of the engine. 
 
 BOSCH MAGNETOS 
 
 Bosch magnetos are manufactured in many 
 types and are designated by a combination of 
 letters and numbers engraved on the base plate of 
 the magneto. The letters represent the general 
 construction, the number specifying the engine 
 with which the magneto is to be used. For ex- 
 ample: Du4, the letters represent the type and 
 the "4" specifies that it is for a four-cylinder 
 engine. A few of the typical constructions will be 
 
 Fig. IWBerling 
 
 Construction for 
 
 Motor Cycles 
 
 explained so as to gain a general knowledge of these types of mag 
 netos. The principle upon which they are constructed is the same 
 as any shuttle type of armature. 
 
 The most common types in use are the "Du" magnetos con- 
 structed for engines of from one to six cylinders. The four-cylinder 
 design is shown in Fig. 150. The six-cylinder type differs only in 
 
 Fig. 150 Bosch Du4 Magneto 
 
 that it has a distributor arranged with six segments and terminals 
 and the internal gearing so arranged that the distributor is driven 
 at half engine speed when the magneto is properly installed on the 
 engine. 
 
 Fig. 151 shows a cross section of this magneto and the solid black 
 represents insulating material. Fig. 152 shows the wiring of the 
 magneto and in explaining the path of the primary and secondary 
 
MAGNETOS, ARMATURE TYPE 
 
 183 
 
 1 116 u 2 117 
 
 Fig. 151 Cross-section of Bosch Magneto 
 
 S 3 4 
 
 Fig. 152 Internal Wiring of Bosch Magneto 
 
184 MOTOR VEHICLES AND THEIR ENGINES 
 
 circuits the numbers of the parts in Fig. 151 will be used to give a 
 clear conception of the path the current takes. 
 
 PRIMARY CIRCUIT. One end of the primary winding which 
 consists of a few turns of heavy wire is in metallic connection with 
 the armature core. The other end is connected to the condenser 
 plate "1." The interrupter fastening screw "2" which screws into 
 plate "1" conducts the primary current to the insulated contact 
 block supporting the long platinum screw "G-2" of the magneto 
 interrupter. The interrupter lever carrying the short platinum 
 contact "G-3" is mounted on the interrupter disc which is elec- 
 trically connected to the armature core. The primary circuit is 
 complete when the two platinum points are brought together and 
 interrupted whenever these points are separated. The separation 
 of the platinum points is controlled by the action of the interrupter 
 lever as it bears against the steel segments screwed to the inner 
 surface of the interrupter housing (timing lever housing). There 
 are two segments in this housing so that the circuit is broken at the 
 two points of maximum current in the primary. The condenser 
 "9" is connected acorss the interrupter points so as to stop the 
 arcing. One side is connected to the condenser plate "1" and the 
 other side is connected to the armature core. 
 
 SECONDARY CIRCUIT. The secondary winding is composed 
 of a great number of turns of fine wire. One end is connected to the 
 primary and the other end to the insulated current collector ring 
 (slip-ring) "10" mounted on the armature at the driven end. The 
 slip ring is made of insulated material with a continuous brass seg- 
 ment inserted. In contact with this segment is the carbon brush 
 " 11 " held by the carbon holder " 12." On top of the carbon holder 
 there is a terminal " 13 " from which the current is conducted by the 
 insulating bar "14" to the brass segment "18" in the center of the 
 distributor. A brush holder " 15 " is mounted on a gear which meshes 
 with a gear on the armature shaft so that the operation of the dis- 
 tributor will be in perfect ^synchronism with the armature. Carbon 
 holder "15" contains a carbon brush "16" which conducts the cur- 
 rent from the brass segment "18" to the segments which are em- 
 bedded in the distributor plate "17." These segments are connected 
 with the terminal studs on the face of the distributor plate and the lat- 
 ter are connected by cables to the spark plugs in the various cylinders. 
 In the cylinders the high tension current produces a spark and the 
 current then returns through the engine to the magneto armature 
 
MAGNETOS, ARMATURE TYPE 185 
 
 core, completing the secondary circuit. To protect the armature 
 and other current carrying parts a safety spark gap "K" is provided, 
 connected between the terminal "13" and dust cover "22." This 
 gap is so arranged as to have more resistance than the gap at the 
 spark plug under compression. Under ordinary conditions the cur- 
 rent will flow through its normal path but if for any reason the 
 resistance in the secondary circuit is increased to a high point, as 
 when a cable becomes disconnected or the gap is too wide at the 
 spark plugs, the high tension current will discharge across the safety 
 spark gap. In this way the possibility of breaking down the in- 
 sulating material of the instrument itself will be eliminated. 
 
 CUTTING OUT THE IGNITION. Since high tension current 
 is generated only on the interruption of the primary circuit, it is 
 evident that in order to cut out the ignition it is necessary merely to 
 divert the primary current to a path which is not effected by the 
 action of the magneto interrupter. This is accomplished as follows: 
 Spring "118" being in contact with screw "2" leads the current to 
 the insulated binding post "24" and if this binding post is connected 
 to a switch having the other side grounded the primary in the mag- 
 neto will be grounded at both ends when the switch is closed. There- 
 fore, the operation of the interrupter will not break down the current 
 flowing through it and consequently there will be no secondary 
 current. 
 
 The ZR type of magneto is arranged for four and six-cylinder 
 engines and is identical in operation with that of the Du4 and the 
 path of the current is identically the same. It differs in that it is 
 a water-tight construction. When speaking of water-tight magnetos 
 it is to be borne in mind that this does not imply that the magneto 
 can be submerged in water for 
 any length of time. It will with- 
 stand damaging effects of rain, 
 moisture, or a stream of water 
 squirted on it when the car is 
 being washed. This is accom- 
 plished by the special construc- 
 tion of end plates and distributor 
 with special terminal nuts as 
 shown in Fig. 153. The edges of 
 the oil covers are bent down and 
 felt inserts used. Between the 
 
 magnets there are strips of paper 
 
 f - ,, Fig. 153 Bosch ZR6 Magneto 
 
 and felt washers. 
 
186 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 154 ZR4 Magneto Partially Disassembled 
 
 Fig. 154 shows the distributor and timing lever removed from the 
 magneto showing carbon brush and holder on the distributor gear 
 wheel as explained in the Du4 construction. 
 
 The LT4 type magneto is designed for four cylinder engines. It 
 is in reality a modified ZR4 magneto, all electrical circuits being 
 identical and water-proof construction being used. This type was 
 especially designed for the Government, a distributor adopted as 
 "standard" being employed. Other dimensions, such as height 
 of shaft, taper of shaft, and dimensions of base platejare in 
 accordance with Government specifications. This standardization 
 permits of interchangeability of magnetos on Government apparatus 
 regardless of manufacture, without tools or special equipment being 
 used. This is of great assistance in the field, since a very quick change 
 can be made and the necessity of carrying as spare equipment extra 
 magnetos of each make is eliminated. Fig. 155 shows this magneto 
 with the distributor and timer lever cover removed. 
 
 The ZEV type of magneto (Fig. 156) is for a twin cylinder motor- 
 cycle engine and is a water-tight construction. As this magneto is 
 used for motor-cycles which require the spark to occur at unequal 
 intervals. The pole shoes and armature are cut away as previously 
 explained. In every other respect the magneto is identical with the 
 other Bosch Magnetos. In Fig. 156 the interrupter cover is removed 
 showing that the cams are not set an equal distance apart, but are 
 
MAGNETOS, ARMATURE TYPE 
 
 187 
 
 170 
 
 263 
 
 205(11) 
 
 Fig. 155 Bosch Magneto Standardized for Military Purposes 
 
 arranged to interrupt the circuit at the proper time to compensate 
 for the cylinders being set at an angle. 
 The primary circuit in this mag- 
 neto is the same as in all other Bosch 
 Magnetos. The secondary circuit is 
 slightly different. One end of the 
 secondary is grounded through the 
 primary winding and the other end is 
 connected to the segment of the slip 
 ring. The slip ring in this type has a 
 short segment instead of one that is 
 continuous. In contact with this slip 
 ring are two carbon brushes and 
 holders which are placed one on each 
 side of the magneto. In this manner 
 the segment of the slip ring is in con- 
 tact with only one brush when the 
 
 primary circuit is interrupted during either half revolution. Cables 
 connect the spark plugs to these carbon holders so that the cur- 
 rent is first led to one plug and then to the other. As the sparks 
 are not equally spaced care must be taken to connect the proper 
 carbon holder to the spark plug in No. 1 cylinder. Fig. 157 shows 
 the proper wiring from the carbon holders to the spark plugs in the 
 cylinders. 
 
 20W1) 
 
 455 W5 
 
 Fig. 156 Bosch ZEV 
 Magneto 
 
188 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 n 
 
 Fig. 157 Wiring Diagram of a Twin Cylinder Motor 
 with a "ZEV" Magneto 
 
 EISEMANN MAGNETO 
 
 The G-4 magneto is designed for four-cylinder engines and is 
 made up in two general constructions, Edition I (Fig. 158) and 
 Edition II (Fig. 159) The later model is used more extensively 
 
 Fig. 160 Internal Wiring of Eisemann Magneto 
 
 than the Edition I. Fig. 160 shows the internal wiring of these 
 magnetos. 
 
DISTRIBUTOR PLATE 
 
 CABLE FOR CUTTING 
 OFF IGNITION 
 
 DISTRIBUTOR 
 CARBONS 
 
 END CAP 
 
 SETTING SCREW 
 
 DISTRIBUTOR DISC 
 
 CARBON B'RUSH PICKING UP 
 CURRENT FROM COLLECTOR RING 
 
 SETTING MARKS 
 
 FIBRE 
 CAMS 
 
 COPPER BRUSH FOR SHORT 
 CIRCUITING IGNITION 
 
 Fig. 158 Eisemann G-4 Ed I 
 
 DISTRIBUTOR PLATE 
 
 WITH 
 AUR-PROOF CABLE FASTENINGS 
 
 INDICATOR POINT 
 
 FOR SETTING MAGNETO 
 
 TO MOTOR 
 
 SETTING 
 MARKS 
 
 CARBON BRUSff 
 
 DISTRIBUTOR *VTO PIC K UP 
 
 CARBON BRUSHES 1 *CURRENT FROM 
 COLLECTOR RING 
 
 CABLE CONNECTION 
 FOR CUTTING OFF 
 MAGNETO IGNITION 
 
 WAILK-PROOF ENt 
 CAP FOR BREAKER 
 
 TIMING LEVER BODY 
 
 IAGNETO CONTAC1 
 BREAKER POINTS 
 
 Fig. 159 Eisemann G-4 Ed II 
 
 189 
 
190 MOTOR VEHICLES AND THEIR ENGINES 
 
 PRIMARY CIRCUIT. One end of the primary is metallicall: 
 connected to the core and the other end is brought out and splicec 
 to a piece of cable. One end of the cable leads to the condensei 
 which is installed at the driven end of the magneto in the armatui 
 housing, the other end being connected to the insulated terming 
 block "J" carrying the adjustable long platinum screw. In contacl 
 with this there is a short platinum stud which is attached to a spring 
 fastened in a post which is grounded by the carbon brush "CB." 
 This makes a metallic return to the armature core of the primary 
 circuit. When the platinum points are closed the circuit is made 
 and when the platinum points are separated due to the action of the 
 cam, the circuit is broken. 
 
 SECONDARY CIRCUIT. The secondary winding consists of a 
 great number of turns of fine wire. One end is connected to the 
 primary and the other end is connected to an insulated collector ring 
 at the interrupter end of the magneto. The distributor is placed 
 directly above the slip ring and has a carbon brush in contact with it. 
 This carbon brush is metallically connected to a carbon brush in the 
 center of the distributor. There are also four carbon brushes which 
 are connected to the cables leading to the spark plugs. On the 
 distributor gear wheel there is mounted an insulating plate with a 
 brass segment embodied in it. This gear is meshed with the gear on 
 the armature shaft so that they synchronize. The segment revolving 
 with the distributor gear conducts the current from the center brush 
 of the distributor to the four brushes in order. These carbon brushes 
 being connected by cables to the spark plugs fastened in the engine 
 which is in metallic connection with the armature core, make a 
 complete path for the secondary current. 
 
 In the Edition I the interruption of the primary circuit is accom- 
 plished by fiber cams inserted in the timer lever body. In the Edi- 
 tion II the interrupter is of a different construction (Fig. 158). The 
 interruption is made by the use of steel segments attached to the 
 timer lever body. 
 
 The method of short-circuiting the primary winding to put the 
 magneto out of operation is as follows: A copper brush in the end 
 of the screw holding the contact breaker in place is metallically con- 
 nected to the end cap terminal which, when connected to ground 
 through a switch, will short-circuit the primary winding. In the 
 Edition II this varies slightly in that the carbon brush is in the end 
 cap and bears against the interrupter fastening screw. 
 
 A few things to be noted about this magneto are that the con- 
 densor is so installed that it can be disconnected without interfering 
 with the primary circuit. A grounded condenser could easily be 
 
MAGNETOS, ARMATURE TYPE 
 
 191 
 
 detected by breaking this connection. Arranging the slip ring so 
 that it is directly below the distributor eliminates several connections 
 and makes the instrument more compact. Another point in favor of 
 this location is that it is more protected than when located at the 
 driven end of the magneto. Slip rings located at the driven end are 
 often broken by inexperienced men when prying off gears or couplings. 
 
 BERLING MAGNETO 
 
 Berling Magnetos are manufactured in many types. The most 
 commonly used are the F-41 for four-cylinder engines and B-21 for 
 twin-cylinder motor-cycles. Fig. 161 shows diagrammatically the 
 internal wiring of the F-41 type. 
 
 Fig. 161 Internal Wiring of Berling F-41 
 
 PRIMARY CIRCUIT. One end of the primary is grounded and 
 the other end is led to the condenser plate. The interrupter fastening 
 screw conducts the current from condenser plate to the insulated 
 block of the interrupter carrying one of the interrupter contacts. 
 The other contact is connected to ground and completes the circuit 
 for the primary when the interrupter points are together. The 
 separation of the points is accomplished by the lever as it bears 
 against cams pressed in the surface of the timing lever housing. The 
 condenser is connected across the interrupter points, one side being 
 
192 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 connected to the condenser plate and the other to a wire which is 
 grounded to the armature core. 
 
 SECONDARY CIRCUIT. One end is connected to the primary 
 to obtain its ground return, the other end is brought out and con- 
 nected to the slip ring. The slip ring has a continuous segment so 
 that the brush which is held by the carbon holder is always in contact 
 with it. From here the current is conducted to the rotor which is 
 mounted on the distributor gear in mesh with a gear on the armature 
 shaft so that they are in synchronism. The distributor is connected 
 
 Fig. 162 Internal Wiring of Berling B-21 
 
 to the spark plugs by cables; thus the complete secondary circuit is 
 made. 
 
 Fig. 162 shows diagrammatically the internal wiring of the type 
 B-21. The only difference in this wiring is that the slip ring has a 
 short segment instead of a continuous segment as in the F-41. In 
 contact with the slip ring are two carbon brushes so that the current 
 generated in the first half revolution flows to one carbon brush and 
 in the next half revolution to the other brush. Each of these brushes 
 must be connected to the proper spark plug as previously explained 
 (Fig. 157). 
 
 As this magneto is used on an engine which has the cylinders 
 set at an angle it uses a special construction of pole shoes and also 
 has the segments in the interrupter set to interrupt the circuit at the 
 proper time. 
 
 The magnetos described in this chapter are typical of all Revolv- 
 ing Armature constructions. Except for minor details other mag- 
 netos of this type do not differ from those explained. 
 
CHAPTER XVIII 
 
 MAGNETOS 
 ROTOR TYPE 
 
 Ail the magnetos discussed in the preceding chapter were con- 
 structed so that their windings revolved requiring insulated moving 
 wires, collector rings, brushes, and moving contacts. In the revolving 
 rotor type the windings are stationary, the rotor or inductor revolving 
 between the pole pieces of the magnets conducting the lines of mag- 
 netic force through the soft iron core about which the stationary 
 windings are placed. 
 
 Fig. 163 Rotor and Winding 
 
 Fig. 163 shows a rotor or inductor of the construction commonly 
 used on this type of magneto. It consists of a steel shaft carrying 
 laminated soft iron arms fastened to the shaft and projecting in 
 opposite directions. These arms are shaped so as to reduce the air 
 gap between them and the pole shoes to a minimum just as is done 
 in the shuttle type armature. 
 
 Fig. 164 shows several positions of the rotor with relation to the 
 pole shoes during one revolution. Starting with the rotor at position 
 A, all the lines of force flow from the North Pole to the arm "R," 
 then at right angles through the shaft and out through the other arm 
 to the South Pole. If it is revolved clockwise it will next reach 
 position B and fewer lines of magnetic force will flow through the 
 rotor shaft. When it has revolved to position C the number of 
 lines of force passing through the rotor shaft is still further decreased. 
 When it has reached the vertical position D all the lines of force 
 
 193 
 
Fig. 164 Change in Flux Through Revolving Rotor 
 
 194 
 
MAGNETOS, ROTOR TYPE 195 
 
 flow directly across from the north to the south pole through 
 the soft iron arms and none flow through the steel shaft. This is 
 because the magnetic lines of force take the path of least resist- 
 ance. As the rotor is revolved to position E, the lines of force 
 start to flow through it again but in the opposite direction, leaving 
 the rotor at arm "R." As the rotor is revolved through the position 
 F the number of lines of force flowing through it increases until it 
 reaches a maximum when the rotor has reached position G. During 
 the next half revolution as the armature revolves through positions 
 H to L the same changes of magnetic flux through the rotor take place 
 as during the first half revolution. 
 
 If the speed of rotation is uniform the rate of change of magnetic 
 flux through the rotor is greatest as it approaches positions D and J. 
 As already shown in chapter 18 current is induced in a winding by 
 causing a rapid change in the strength of the magnetic flux threading 
 through it. This principle is applied in this type of magneto since 
 the necessary varying flux is obtained by rapidly revolving the rotor. 
 
 If a stationary coil of insulated wire is wound about the steel 
 rotor shaft, between the two soft iron arms as shown in Fig. 163, cur- 
 rent will be induced in it whenever the rotor is revolved. Just as 
 in the revolving armature type of magneto the maximum voltage 
 induced in the winding will be when the rotor has just passed posi- 
 tions D and J (Fig. 164). The two maximum valves will be equal 
 but the flow of current will be in opposite directions. This is due to 
 the reversal of the direction of magnetic flux through the rotor. 
 Hence this type of magneto also generates alternating current. 
 
 If but one winding is used the resulting voltage will be low in 
 value and for that reason magnetos of this construction are called 
 Low Tension Magnetos. 
 
 When a secondary winding is wound on top of the stationary 
 primary winding high tension current may be obtained from this 
 type of magneto. The interrupter is in the primary circuit breaking 
 it when the rotor is just beyond the vertical position. This breaks 
 down the field due to the current in the primary and induces a high 
 tension current in the secondary. 
 
 THE K-W MAGNETO 
 
 The K-W is a high tension magneto of the inductor type. The 
 only revolving part in this magneto is the rotor (Fig. 165). This 
 rotor differs from the one shown in Fig. 163 as the rotor arms are 
 placed at right angles to each other and project from both sides of 
 
196 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 165 K-W Rotor and Windings 
 
 the shaft. The same effect is obtained as if two rotors were used, 
 that is, four impulses are induced per revolution instead of two. 
 
 Fig. 166 shows how this is accomplished. The arrows indicate 
 the path of the magnetic flux through the rotor at different positions. 
 It will be noticed that the rotor in this construction does not revolve 
 between the pole shoes but directly below them. 
 
 ABC 
 Fig. 166 Path of Flux in K-W Magneto 
 
MAGNETOS, ROTOR TYPE 
 
 197 
 
 The windings are stationary and composed of a primary and 
 secondary concentric with the rotor shaft (Fig. 165). The inter- 
 rupter is wired in the primary circuit as usual and the condenser is 
 connected across the contact points. The condenser is located inside 
 the magnets at the shaft end of the magneto. The interrupter 
 normally has a two-nosed cam, driven by the rotor shaft, so that the 
 current is interrupted in the primary at but two of the four points 
 where it is a maximum. Therefore, it must be driven at the same 
 speed as a revolving armature type of magneto. 
 
 The current from the secondary passes directly to the insulated 
 terminal on top of the windings. From this point the high tension 
 lead conducts it to the central terminal of the distributor which dis- 
 tributes it to the various cylinders of the engine. The safety spark 
 gap is also connected to this terminal and is located just above the 
 condenser. 
 
 Fig. 167 Cross-section of K-W. Magneto 
 
 Fig. 167 shows a cross section of the K-W magneto, the various 
 windings and connections being shown. 
 
 There are several K-W magnetos, the models being designated by 
 letters in the usual manner. When the letter K is part of the desig- 
 nation it indicates that the magneto is equipped with an impulse 
 starter such as already explained in chapter 18. 
 
 THE DIXIE MAGNETO 
 
 The Dixie is a high tension magneto of the inductor type. The 
 rotor as usual is the only revolving part, but it differs considerably 
 in construction from those previously described. 
 
198 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 168 Magnets and Rotor of 
 Dixie Megneto 
 
 Fig. 168 shows the arrangement of the magnets and rotor. One 
 arm of the rotor always conducts magnetic flux from the north pole 
 of the magnets while the other conducts it to the south pole. To 
 prevent magnetic flux from flowing between the arms of the rotor the 
 central part is made of brass which is a non-magnetic substance. 
 The rotor revolves between pole shoes "F" and "G" of soft iron 
 connected by a core "C" upon which the windings are placed. 
 
 Fig. 169 Path of Flux in Dixie Magneto 
 
 When the rotor is in the position shown at A (Fig. 169) the mag- 
 netic flux takes the following path. From the north magnetic pole 
 through the rotor arm "N," pole shoe "G," core "C," pole shoe 
 " F," rotor arm " S," to the south magnetic pole. When the rotor has 
 turned to the position shown at B, the path of the magnetic flux is as 
 follows: From the north pole of the magnet through the rotor 
 
MAGNETOS, ROTOR TYPE 199 
 
 arm "N," to both pole shoes "F" and "G," directly to the rotor 
 arm "S," and thence to the south pole of the magnet. With the 
 rotor in this position none of the lines of force set up by the per- 
 manent magnets flow through the core "C." When the rotor has 
 turned to the position shown at C the magnetic flux takes the same 
 path as at A but passes through the pole shoes and core in the reverse 
 direction. Thus a rapid change of flux through the core "C" is 
 obtained which induces a current in the primary winding. This 
 current will be a maximum when the rotor has just passed the vertical 
 position. If the primary circuit is interrupted when the current is a 
 maximum, a current of high voltage will be induced in the secondary. 
 Since there are but two points at which the current is at a maximum 
 during each revolution the interrupter will have a two-nosed cam 
 which gives two sparks per revolution. 
 
 Fig. 170 Dixie Magneto 
 
 Fig. 170 shows the waterproof covering and one magnet removed 
 from a Dixie Magneto. When the timing lever is moved in advancing 
 or retarding the spark the pole shoes and coil are moved a correspond- 
 ing amount. In this manner the primary circuit is always interrupted 
 at the point of maximum current. 
 
 The interrupter cam is driven by the same shaft as the rotor. 
 One contact is grounded and the other connected to the ungrounded 
 end of the primary. The condenser is located on top of the windings 
 and is connected across the contact points. One end of the secondary 
 is grounded through the primary and the other is connected to the 
 rotor of the distributor. Fig. 171 shows diagrammatically the internal 
 wiring of the Dixie Magneto. 
 
 The Dixie Magneto constructed for use on twin-cylinder motor- 
 cycles has no changes in its pole shoe or rotor construction. The 
 
200 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 171 Internal Wiring of Dixie Magneto 
 
 interrupter cam is arranged to break the primary circuit at unevenly- 
 spaced intervals to compensate for the angle at which the cylinders 
 are placed. This causes one spark to be delivered when the rotor is 
 just leaving the trailing pole shoe while the other occurs after the 
 rotor has turned a considerable distance beyond the trailing pole 
 shoe. This same relation is always maintained whether in the 
 advanced or retarded position because of the movable pole pieces in 
 the magneto. 
 
CHAPTER XIX 
 
 DUAL AND DUPLEX IGNITION SYSTEMS 
 
 When a magneto is used on a heavy engine which cannot be 
 turned by hand at a sufficiently high speed to produce a spark and 
 the engine does not employ an electric starter, a battery ignition 
 system may be used to obtain a spark at low speeds. This led to 
 the adoption of two independent ignition systems employing a bat- 
 tery ignition system for starting and a magneto for continuous 
 operation. With this arrangement two spark plugs were required 
 in each cylinder, one for the battery ignition system and one for the 
 mageto ignition system. As the battery plugs were not used while 
 operating on the magneto they became sooted and short-circuited 
 so that they would not operate when desired for starting. 
 
 To overcome this difficulty systems have been designed in which 
 the magneto and battery ignition system use the same set of plugs. 
 These are called Dual or Duplex systems of ignition. In some cases 
 a low tension magneto is used with a high tension coil, the primary 
 of which is supplied with current either from the magneto or battery. 
 In other types a high tension magneto is used and a separate induc- 
 tion coil for the battery. The only part used in common is the dis- 
 tributor of the magneto. A few types called Dunlex employ a high 
 tension magneto and a low tension vibrator coil which is wired in 
 series with the primary of the magneto. 
 
 REMY 
 
 This is a low tension magneto using a high tension coil, the 
 primary of which is supplied with current either from the magneto or 
 from the battery. 
 
 Fig. 172 shows diagrammatically the internal and external wiring 
 of the Remy Dual ignition system. When the dash coil is switched to 
 the "off" position all circuits are open. When the switch is turned 
 to the "M" (Magneto) position the battery circuit is open and 
 the current is furnished by the magneto. In this position the switch 
 is making connection between "A" and "B." 
 
 The primary circuit is as follows: The current from the magneto 
 primary winding, one side of which is grounded, flows from "G" at 
 the magneto to "G" at the coil which is connected to the switch at 
 
 201 
 
202 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 172 Internal Wiring of Remy Dual System 
 
 "A" and then across the switch plate to "B." From here it flows 
 through the primary of the coil to terminal "Y" on the coil which 
 is connected to terminal "Y" on the magneto. The interrupter is 
 connected between terminal "Y" and ground. When the points 
 are together the circuit is made and when separated the circuit is 
 interrupted, causing a breakdown of the magnetic field set up by 
 the primary of the coil, inducing current in the secondary. The 
 secondary circuit is as follows: One end is grounded at "R" on the 
 magneto. The other end of the secondary winding of the coil is 
 connected to the center terminal of the distributor from which it is 
 distributed to the terminals wired to the plugs. 
 
 When the switch is turned to the "B" (Battery) position, the 
 current is supplied to the primary at the coil from the battery instead 
 of the magneto, the switch now connecting "C" and "B." 
 
 The primary circuit is as follows: The current flows from the 
 positive of the battery to a terminal "P" on the coil. Then it flows 
 through a jumper in the coil to terminal "R" which is connected by 
 cable to "R" on the magneto which is the ground terminal. One 
 side of the interrupter being grounded and the other side connected 
 to "Y" the current takes this path when the interrupter points are 
 closed. It flows to terminal "Y" on the coil which is connected to 
 the primary of the coil. The other end of the primary is connected 
 
DUAL AND DUPLEX IGNITION SYSTEMS 
 
 203 
 
 to "B." As "B" and "C" are connected the current flows to the 
 terminal "N" and back to the battery making a complete circuit. 
 When the interrupter points are separated the circuit is broken 
 causing a collapse of the field set up by the primary of the coil thus 
 inducing the secondary current. The secondary circuit is the same 
 as when operating on magneto. 
 
 This is the typical arrangement when a low tension magneto is 
 used for dual ignition and all other systems vary but little from this 
 in any respect except switch connections. 
 
 BOSCH DUAL 
 
 In this system a high tension magneto is used and also a high 
 tension coil with battery. They work independently of each other 
 except that they both employ the same distributor. 
 
 Fig. 173 shows diagrammatically the internal wiring of the coil 
 and magneto of the Du-4 Dual ignition system as well as the external 
 connections from the magneto to the coil. At A is shown the in- 
 
 Fig. 173 Internal Wiring of Bosch Dual System 
 
 ternal wiring of the coil and its connections to the movable switch 
 plate "X." At B is shown how the segments in the movable switch 
 plate connect the terminals of the fixed switch plate "Y" when in 
 different operating positions. At C is shown the internal connec- 
 
204 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 tions of the magneto and how they are wired to the fixed switch 
 plate "Y" of the coil. It is to be noted that the magneto has two 
 interrupters as shown in Fig. 174. One is for the magneto and one 
 
 ^, Lock nut 
 ^-Contact block 
 .^Segment 
 ,_ Long platinum screw 
 :>^ Fastening screw for spring 
 ^ Short platinum, screw 
 >- Interrupter lever 
 >- Auxiliary spring 
 ^ Spring post 
 ^Fastening screw for spring, 
 y Screw plate 
 
 ^.Spring for magneto interrupter 
 nj-Sprinp for battery interrupter^ 
 /V. Interrupter fastening screw < 
 -+~ Screw plate 
 
 Fig. 174 Dual Interrupters 
 
 for the battery ignition system, each being electrically independent 
 of the other. 
 
 When the coil is switched to the "M" (Magneto) position the 
 battery circuit is broken as the "5" terminal is not in contact with 
 any segment on the movable switch plate. The primary circuit of 
 the magneto is as follows: One end of the primary winding is 
 grounded. The other end is lead to the interrupter contact point 
 "P" which is in connection with contact "Q" which is grounded. 
 
 The secondary circuit is as follows: One end of the secondary 
 winding is connected to the primary and the other end is connected 
 to the slip ring. Carbon holder "3," the brush of which is in contact 
 with the slip ring, is connected to terminal "3" on the switch plate 
 of the coil. A segment of this movable switch plate connects term- 
 inals "3" and "4" so that the current is lead to the distributor and 
 then to the plugs. The battery or coil windings do not enter into 
 the circuits when operating on magneto. 
 
 If the switch is turned to the "off" position shown at B the 
 movable switch plate makes connection between terminals "2" and 
 "6" which short-circuits the primary of the magneto putting it out 
 of operation. The battery circuit is still broken as the terminal 
 "5" is not connected to any segment of the movable switch plate. 
 Therefore, the battery system is out of operation. 
 
 When the coil is switched to the "B" (Battery) position number 
 "2" terminal is still connected to ground so that the magneto is out 
 of operation. Terminal "5" is now connected to the segment shown 
 as a square on the movable switch plate. The battery current 
 
DUAL AND DUPLEX IGNITION SYSTEMS 205 
 
 passes through the primary of the coil and to terminal "1" of the 
 switch plate which is connected to the battery interrupter on the 
 magneto. The secondary winding of the coil has one end attached 
 to the segment of the movable switch plate which is in contact with 
 terminal "6" and is grounded. The other end of the secondary 
 winding is connected to the segment on the movable switch plate 
 which is now in contact with terminal "4." This terminal is con- 
 nected to the distributor of the magneto from which the current is 
 lead to the spark plugs. 
 
 The only part used in common for the magneto and battery 
 system is the distributor so that in reality two complete ignition 
 systems exist independent of each other except that they use the 
 same distributor and plugs. This condition is ideal and it gives two 
 separate systems so that if one goes dead the other can easily be 
 used. This design is typical of all systems employing a high tension 
 magneto in a dual system of ignition. 
 
 VIBRATING DUPLEX SYSTEM 
 
 In order to obtain a system which would be simple and not require 
 a separate high tension coil, a construction called the vibrating duplex 
 system has been designed and used by many ignition manufacturers. 
 It consists of a switch and a low tension vibrator coil which is wired 
 in series with the primary of the magneto. In this way the battery 
 supplies the necessary current to the primary of the magneto and the 
 vibrator interrupts it so as to get the induced secondary current. 
 
 The connections in this system are made as shown hi Fig. 175. 
 One side of the battery is connected to the coil and the other side is 
 connected to the terminal "C" of the switch. Terminal "D" is 
 connected to ground and terminal "B" is connected to the other 
 terminal of the coil. Terminal "A" is connected to the short-cir- 
 cuiting terminal of the magneto. When the switch is in the "off" 
 position it connects "A" to "D" which short-circuits the primary 
 of the magneto. Terminal "C" is free so that the battery circuit 
 is broken. 
 
 When the switch is turned to the "battery" position terminals 
 "C" and "D" are connected and likewise "A" and "B." The 
 current from the battery now passes through the vibrator coil and 
 to terminal " S " at the magneto. If the interrupter points are closed 
 the current will be grounded through them and the vibrator will 
 vibrate but the primary of the magneto does not receive any of the 
 battery current. When the interrupter points are separated the 
 current must pass through the primary of the magneto to get to 
 
206 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 ground and every time that the vibrator interrupts the circuit an 
 induced current will be set up in the secondary. In this way a spark 
 or series of sparks will be produced even if the magneto is at a stand- 
 still or revolving slowly. 
 
 Fig. 175 Internal Wiring of Duplex System 
 
 When the switch is turned to the magneto position all the con- 
 tacts at the switch are open so that the battery circuit is broken and 
 the magneto is not grounded. It will thus operate as an inde- 
 pendent high-tension magneto. 
 
 With this system the advantage of having battery ignition for 
 starting and magneto for operating has been obtained but its entire 
 operation depends upon the magneto so that any trouble with the 
 magneto puts the entire system out of operation. 
 
CHAPTER XX 
 
 STARTING AND LIGHTING SYSTEMS 
 
 One of the greatest improvements in the equipment of modern 
 motor vehicles has been the adoption of electric starting and lighting 
 systems. The unhandy and troublesome lights formerly used have 
 been replaced by efficient electric lights ready to illuminate the road 
 at a moment's notice. The task of cranking the engine by hand 
 which was always laborious, and sometimes dangerous, has been 
 eliminated and the engine is now spun easily whenever desired by an 
 electric cranking motor. 
 
 Starting and lighting systems are generally divided into two 
 classes: first, single-unit systems; second, two-unit systems. In the 
 first a single piece of electrical apparatus, a motor-generator, fur- 
 nishes the current for charging the storage battery, for ignition, and 
 for operating the lights and also acts as a motor for cranking the 
 engine. The two-unit system has a generator for furnishing the 
 current and a separate motor for cranking the engine. 
 
 In order to understand the operation of motors and generators 
 a brief explanation of the principles upon which they operate will 
 first be given. 
 
 The generator does not actually create electrical energy as might 
 be implied from its name. It simply generates or produces an elec- 
 tro-motive force by means of electro-magnetic induction which 
 causes current to flow. The electrical output of a generator depends 
 upon the mechanical energy supplied to drive it. Hence a generator 
 is a piece of electrical apparatus for transforming mechanical energy 
 into electrical energy in the form of induced electro-motive force. 
 This force causes electricity to flow through the external circuit from 
 the positive terminal or point of high potential to the negative 
 terminal or point of low potential, just as water flows from a higher 
 to a lower level. In the internal circuit electricity flows from a lower 
 to a higher potential due to the induced electro-motive force just 
 as water is pumped from a lower to a higher level. 
 
 Generators and motors are classified according to their design and 
 mechanical construction. 
 
 1 . Direct current machines. 
 
 2. Alternating current machines. 
 
 The current in the internal circuit is always alternating just as in 
 the magneto but may be made direct current in the external circuit 
 
 207 
 
208 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 by employing suitable moving contacts called a commutator. Since 
 only direct current machines can be used for starting and lighting 
 systems because of the storage battery, alternating current machines 
 with the exception of the Ford magneto will not be discussed in this 
 chapter. 
 
 The simplest form of generator may be made by revolving a 
 closed loop of wire in a magnetic field. Fig. 176 shows a loop of 
 
 wire mounted on a shaft which 
 may be revolved in the magnetic 
 field existing between the north 
 and south poles as shown. If 
 the loop is revolved as indicated 
 by the arrow the following will 
 result. In the position shown 
 there will be no induced electro- 
 motive force in the loop since all 
 the lines of force thread through 
 it. As it turns through one-quar- 
 ter of a revolution the number 
 of lines of force threading through 
 Fig. 176 Principle of Generator the loop are diminished at a 
 
 constantly increasing rate until 
 
 it reaches the dotted position where no lines of force thread through 
 it. The induced electro-motive force depends upon the rate of 
 change of the lines of force threading through the loop and will 
 therefore be greatest when the loop is moving across the pole faces 
 with a maximum value when the loop is in the dotted position. 
 Applying the right hand rule (Fig. 110) the direction of the current 
 flow is that indicated by the arrows in Fig. 176. During the second 
 quarter revolution the lines of force thread through the opposite 
 side of the loop. The rate of change and consequently the electro- 
 motive force decreases until both are zero again when one-half 
 revolution has been completed. During the next half revolution the 
 same variations in the induced electro-motive force occur but in the 
 opposite direction. The current is reversed twice each revolution, 
 an alternating current flowing around the loop. 
 
 To utilize the current flowing in a closed loop when it is rotated 
 in a magnetic field some mechanical device must be used to lead the 
 current from the rotating loop so it will flow through an external 
 circuit. This is accomplished by attaching the ends of the loop to 
 metal contacts against which are held stationary pieces called 
 brushes. If each brush is connected first with one end and then 
 with the other end of the revolving loop and the change is made at the 
 
STARTING AND LIGHTING SYSTEMS 
 
 209 
 
 Fig, 177 Simple 
 Commutator 
 
 instant the current in each side of the loop is reversing the current 
 in the outside circuit will always flow in the same direction. This 
 is accomplished by means of a commutator 
 (Fig. 177). 
 
 The simplest form of commutator consists 
 of a split ring the segments "S-l" and "S-2" 
 being insulated from each other and also from 
 the shaft. The brushes " B-l " and " B-2 " rest 
 on the commutator at diametrically opposite 
 points collecting the current and delivering it 
 to the lamps "L." 
 
 Assuming that the current in "C-l " is flow- 
 ing to the brush "B-l" the current in "C-2" 
 must be flowing in the opposite direction or away from brush 
 "B-2." Hence "B-l" is positive and "B-2" negative. The brush 
 "B-l" bears on the segment "S-l" as long as the current in 
 "C-l" continues to flow in this direction. At the instant the cur- 
 rent in "C-l" starts to flow in the opposite direction the segment 
 "S-l" leaves this brush and "S-2" just makes contact with "B-l." 
 The current in "C-2" has also reversed and now flows to segment 
 "S-2." Hence "S-2" now delivers current to brush "B-l" which 
 still continues to be the positive brush. In the same way brush 
 "B-2" is always the negative brush and the current delivered to 
 the lamps always flows in the same direction. 
 
 When but a single loop of wire is used the induced electro-motive 
 force will necessarily be low. By increasing the number of turns, 
 the induced electro-motive force is increased proportionately. With 
 a single loop, the current delivered will not be steady although always 
 in the same direction. The variations in the current flow are due to 
 the change in the induced electro-motive force from a maximum to 
 zero as the loop is revolved. If another loop is placed at right 
 angles to that shown in Fig. 176 the current flow in this loop will be 
 a maximum when it is zero in the other loop. As the two loops are 
 revolved the current flow in one increases as that in the other de- 
 creases giving a less pulsating current in the external circuit. Fig. 
 178 shows graphically the difference between the current delivered 
 by a single loop and that delivered by two loops at right angles to 
 
 i* \4 Vr \4 rf/ 
 
 |f lHwolMtion J 
 
 Fig. 178 Graphic Representation of Current in External Circuit 
 
210 MOTOR VEHICLES AND THEIR ENGINES 
 
 each other. By equally spacing a great number of coils a continuous 
 current output and high electro-motive force is obtained. 
 
 To concentrate the magnetic field between the poles of the field 
 magnets and also to support the coils of wire a laminated armature 
 of soft iron is used. 
 
 Fig. 179 Drum Type Armature 
 
 The armature may be ring-shaped with the coils wound around 
 it or it may be of the slotted-drum type (Fig. 179). The latter is the 
 type of armature universally used on starting motors and lighting 
 generators. Although the armature coils are all connected in series 
 with each other there must be a commutator segment for every coil 
 of wire wound on the armature. This is necessary so that the cur- 
 rent flowing in any particular coil has a path through the brushes 
 to the outside circuit at the instant the current flowing in it is a 
 maximum. 
 
 Commutators are built up of copper segments insulated from 
 each other by mica inserts the segments projecting slightly above the 
 mica. The commutator is finished by being turned true so that the 
 carbon brushes always make good contact with its surface. 
 
 In order to set up a strong magnetic field between the pole pieces, 
 the field magnets of motors and generators are electro-magnets. 
 Part or all of the current generated in the armature is sent through 
 coils of wire wound on the field pieces. Of course no current would 
 be generated in the armature at starting if there was not some mag- 
 netic field existing between the pole pieces. The soft iron field 
 pieces retain sufficient "residual" magnetism to set up a weak field 
 which in turn generates a weak current. This current flows through 
 the field windings increasing the magnetic field which in turn in- 
 creases the generated current. In this way the machine " builds 
 up" until it has reached its normal operating condition. 
 
 Field windings may be arranged in any of the following ways* 
 series shunt, or compound. 
 
STARTING AND LIGHTING SYSTEMS 
 
 211 
 
 Fig. 180 shows a simple two-pole machine in which all the current 
 generated in the armature passes through the field coils. Hence, 
 heavy wire is used to carry the current and but a small number of 
 turns are necessary to give the desired strength of magnetic field. 
 This is known as a series wound machine. Generators of this de- 
 
 Fig. 180 Series Generator 
 
 scription are not used for lighting motor vehicles. This is because 
 the voltage varies greatly when the resistance of the external circuit 
 is changed hence they are only suitable for supplying practically 
 constant current. Series wound motors, however, are always used 
 because of the great starting torque obtained. This will be discussed 
 more fully later in this chapter. 
 
 Fig. 181 shows the field windings so arranged that only part of 
 the current generated in the armature flows through them. Hence, 
 
 Fig. 181 Shunt Generator 
 
 fine wire is used and a great many turns are necessary to produce 
 the desired strength of magnetic field. This is known as a shunt 
 wound machine. A shunt generator "builds up" in the same way a 
 series generator does. The voltage of a shunt wound generator falls 
 off as the load on it is increased but when used as a lighting generator 
 the storage battery carries any extra load keeping the voltage con- 
 stant on the line. Shunt wound starting motors are not used because 
 of their low starting torque. 
 
212 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 
 Fig. 182 shows a two-pole compound wound machine. The field 
 windings are made up of both shunt and series coils. When the field 
 windings are arranged so that they oppose or "buck" each other 
 
 Fig. 182 Compound Generator 
 
 the machine is said to be "differentially wound." When the field 
 windings are so arranged that they aid each other the machine is 
 said to be "cumulative." 
 
 The operation of the motor depends upon the resultant field set 
 up when a conductor through which current is flowing is placed in a 
 strong magnetic field. 
 
 A B 
 
 Fig. 183 Field About a Current Carrying Conductor 
 
 Fig. 183A shows the field existing about a wire when current is 
 flowing through it and Fig. 183B, the field resulting when it is placed 
 in a uniform field flowing from left to right. The lines of force above 
 the wire flowing to the right join those of the field flowing to the right 
 and thus strengthen the field above the wire. Those below the wire 
 flowing to the left neutralize some of the lines of force flowing to the 
 right and weaken the field below the wire. Thus a strong field is 
 
STARTING AND LIGHTING SYSTEMS 213 
 
 built up above the wire and a weak field below it resulting in a force 
 which causes the wire to move down due to the elastic action of the 
 lines of force. 
 
 Fig. 184 shows the effect of sending current through a loop of 
 wire free to revolve between opposite poles of a magnet. When 
 current flows in at "A" and out at "B" the field is weakened below 
 "A" and above "B." This causes the loop to revolve in a counter 
 clock-wise direction. When the number of loops and the strength of 
 current passing through them is increased the turning force will be 
 
 Fig. 184 Principle of Motor 
 
 greatly increased. When the field between the poles is strengthened 
 by placing the coils on an armature and spacing them equally an 
 even torque is obtained. This is identical with the construction 
 used on generators. Sending current through the armature of a 
 generator causes it to revolve and the machine becomes a motor. A 
 motor, therefore, is a machine for transforming electrical energy into 
 mechanical energy. 
 
 To determine the direction of rotation the left hand should be 
 held as shown in Fig. 110 the middle finger indicating the direction 
 the current is flowing through the coil and the forefinger the direction 
 of magnetic flux. The thumb will then indicate the direction of 
 rotation. When run as a motor current is always sent through the 
 armature of a machine in the opposite direction to its flow when 
 operating as a generator. The direction of rotation of the machine 
 will be the same when running as a motor as when driven as a gener- 
 ator. This can be proved by applying the left hand or motor rule. 
 
 Motors and generators used for starting and lighting purposes 
 are almost always four-pole machines. The field magnets are made 
 as compact as possible so as to concentrate the magnetic field. The 
 magnets are supported by an iron case which completes the magnetic 
 circuit and encloses all windings, brushes, and armature protecting 
 them from dampness and dirt. 
 
 Due to the great variation in the speed at which the engine of a 
 motor vehicle runs the voltage of a generator will necessarily vary. 
 
214 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Most generators are designed to start charging the storage battery 
 at a car speed of 8 or 10 miles per hour. As the speed is increased 
 the voltage unless regulated in some manner will become excessive, 
 resulting in burned-out lights, excessive sparking at the commutator, 
 and too high a charging rate. Therefore, some form of regulation 
 must be employed to keep the voltage or current supplied constant 
 at the higher speeds. 
 
 Several methods of accomplishing regulation are employed and 
 those used on the systems discussed in this chapter are explained as 
 each system is described. 
 
 Fig. 185 Lighting System Without Cutout 
 
 Fig. 185 shows a wiring diagram of a compound wound generator 
 "G" connected to charge a storage battery "B" and furnish current 
 for lights "L." As long as the speed of the engine driving the gener- 
 ator is high enough the voltage at the generator will be greater than 
 that of the battery causing current to flow as indicated by the heavy 
 arrows. However, if the engine speed is reduced the voltage at the 
 generator will fall off and the voltage of the battery will exceed that 
 at the generator. This will cause current to flow in the direction 
 indicated by the dotted arrows. The battery discharges through the 
 generator causing it to run as a motor. To prevent the battery 
 from discharging when the engine is slowed down or stopped an auto- 
 matic cut-out is placed in the circuit. 
 
 Fig. 186 shows a simple single-unit starting and lighting system 
 with a cut-out. The current from the generator flows through the 
 potential coil "P" having a great many turns of fine wire, causing 
 the soft iron core "G" to become magnetized. When the voltage 
 at the generator becomes sufficient, enough current will be forced 
 through the high resistance potential coil "P" to make the core "G" 
 
STARTING AND LIGHTING SYSTEMS 
 
 215 
 
 Fig. 186 Starting and Lighting System With Cutout 
 
 so strongly magnetic that the soft iron disc " D " is drawn to it against 
 the action of the spring "R." This causes the contact points "C" 
 to close, the current flowing through the low resistance series coil 
 "S" to the battery "B" and lights "L." Only a little current con- 
 tinues to flow through "P" when the cut-out closes but the series 
 coil "S" keeps the core "G" sufficiently magnetized to hold the cut- 
 out closed. If the voltage at the generator falls off until it is less 
 than that of the battery, current from the battery will start to flow 
 in the opposite direction through the coil "S." Coil "P" tends to 
 keep the core "G" magnetized, though the current flowing through 
 it has decreased, but coil "S" now tends to magnetize the core "G" 
 in the opposite direction. This results in a weakening of the magnetic 
 strength of "G" so that it cannot hold "D" against the pull of the 
 spring "R." The cut-out opens separating the contact points "C" 
 and prevents the battery current from flowing back through the 
 generator. The lights are now supplied by the battery until the 
 voltage at the generator becomes great enough to close the cut-out. 
 When the engine stops current is drawn from the battery by closing 
 the switch "A." The current flows through the generator in the 
 opposite direction causing it to turn as a motor and crank the engine. 
 
 NORTH EAST 
 
 The North East system consists of a single unit motor-generator 
 which furnishes current for charging the storage battery, lights, 
 ignition, and cranks the engine when starting. The machine is four- 
 
216 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 3SS.4-G-1 STTE 
 
 JFTAffTlM* 
 
 pole compound wound and is driven by a silent chain from the crank 
 shaft at three times engine speed. 
 
 Fig. 187 shows the internal wiring of the North East motor- 
 generator installation on the Dodge car. The shunt and series field 
 windings are clearly shown and also the windings on the cut-out. A 
 fuse is provided which protects the shunt field windings. 
 
 It will be noticed that one end of the shunt field winding is at- 
 tached to a third brush. This brush is the voltage regulating device 
 
 used on this system. As the 
 speed at which the generator 
 is driven increases the voltage 
 in the armature coils between 
 the third brush and negative 
 brush falls causing less current 
 to be forced through the shunt 
 field. This correspondingly 
 reduces the strength of the 
 magnetic field and compen- 
 sates for the increased speed 
 at which the machine is being 
 driven. Charging starts at a 
 car speed of about 10 miles 
 per hour, the maximum charg- 
 ing rate of 6 amperes being 
 reached at a speed of about 
 17 miles per hour. At ex- 
 tremely high speeds the charg- 
 ing rate falls off becoming as 
 low as 3 amperes. 
 
 To increase the charging rate the third brush is moved in the 
 direction the armature rotates. This setting should never be changed 
 unless the battery charge is habitually low or the charging rate too 
 high. Too high a charging rate is indicated by the battery requiring 
 a too frequent addition of water. 
 
 Fig. 188 shows the complete wiring of the North East single unit 
 system of starting and lighting on the Dodge car. When running 
 10 miles per hour or faster the cut-out is closed and the generator 
 furnishes current for charging the battery, the head lights, tail lights, 
 dash light, ignition system, and the electric horn when the push 
 button is pressed. 
 
 The ammeter on the dash reads " charge " when current is passing 
 into the battery. When the speed is reduced sufficiently the cut-out 
 opens and the battery furnishes the current the ammeter reading 
 
 Fig. 187 Internal Wiring of 
 North East 
 
\ 
 
 217 
 
218 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 "discharge." To start the engine the starting switch is closed which 
 draws current from the battery causing the motor-generator to revolve 
 as a motor and crank the engine. This heavy current does not pass 
 through the ammeter so the windings will not be burned out. 
 
 LEESE-NEVILLE 
 
 The Leese-Neville starting and lighting system consists of two 
 units, a shunt wound four-pole generator and a series wound motor. 
 The generator furnishes current for charging the storage battery, 
 lights, and ignition and the motor cranks the engine drawing current 
 from the storage battery. 
 
 The generator, running at approximately engine speed, is driven 
 by a chain from the crank shaft. Third brush regulation is 
 used which has already been explained. An automatic cut-out is 
 provided to prevent the battery from discharging through the genera- 
 tor at low engine speeds and is of the usual construction. 
 
 CIRCUIT BREAKER 
 
 FUSE 
 
 GENERATOR 
 
 B.-4 
 
 Fig. 189 Internal Wiring of Leese-Neville 
 
 Fig. 189 shows the internal wiring of the generator and circuit 
 breaker or cut-out. In the grounded system the brush connected 
 to "A-2" is internally grounded and only one cable comes from the 
 cut-out. The charging rate is controlled by the position of the third 
 brush. The shunt field is protected by a 10-ampere fuse. 
 
 The motor is attached to the crank case and drives the flywheel 
 of the engine through the gear teeth cut in its circumference by 
 means of a small pinion directly driven by the motor armature shaft. 
 
STARTING AND LIGHTING SYSTEMS 
 
 219 
 
 The armature shaft carries a worm gear (Fig. 190). The pinion 
 "P" has a female thread which fits on the worm and when the arma- 
 ture shaft revolves the pinion tends to stand still and is screwed out 
 
 Fig. 190 Bendix Drive 
 
 engaging with the teeth on the flywheel. When the engine starts 
 it turns the pinion at a greater rate of speed than the armature shaft 
 is turning causing the pinion to be screwed back to its former position 
 disengaging the flywheel gear. This method is called the Bendix 
 drive. 
 
 Fig. 191 Wiring on White 
 
 Fig. 191 shows the complete wiring of the starting and lighting 
 system installed on the Staff Observation Car. The motor is sup- 
 plied with current from the storage battery when the starting switch, 
 which is located on the floor boards of the car, is closed. The gen- 
 erator charges the battery and supplies the lights with current when 
 the cut-out is closed and the battery supplies the lights when the 
 
220 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 cut-out opens. A circuit-breaker is provided in the lighting cir- 
 cuit which takes the place of fuses opening when there is a ground 
 on the line. 
 
 BIJUR 
 
 The Bijur Lighting System as installed on the Nash Trucks con- 
 sists of a shunt wound generator driven by a silent chain from the 
 pump shaft. 
 
 Fig. 192 is an internal wiring diagram showing all circuits except 
 the connections to the lights. A cut-out is provided which operates 
 
 Fig. 192 Internal Wiring of Bijur 
 
 in the usual manner the storage battery furnishing current when the 
 cut-out is open. 
 
 The voltage regulator is of the vibrating variable resistance type. 
 The voltage regulating unit as shown in Fig. 192 at "B" consists of 
 a core having a single winding connected in parallel with the arma- 
 ture. The current in the winding and the resulting magnetic pull 
 of the core will depend upon the pressure developed by the generator. 
 Opposite one end of the core is a vibrating armature which is spring 
 retracted from the core. When the armature is retracted it makes 
 contact so that there is a by-pass around the resistance "D" which 
 is in series with the field winding of the generator. With the vibra- 
 ting armature in this position the shunt field winding receives the 
 full pressure developed by the generator. With increasing generator 
 speed the voltage increases until the armature develops 7.75 volts, 
 and at this electrical pressure the regulator begins to function and 
 
STARTING AND LIGHTING SYSTEMS 221 
 
 will maintain this voltage across the generator brushes at all higher 
 speeds. 
 
 With increasing generator speed the voltage will tend to rise 
 above 7.75. However, if this value is exceeded by a very small 
 amount, the increased pull on the armature of the regulating unit 
 will overcome the spring pull and the armature will be drawn towards 
 the core, thus opening the contacts and inserting the resistance "D" 
 in the generator field circuit. The added resistance in the field 
 circuit decreases the exciting current in the field winding and the 
 voltage developed by the armature tends to drop below the normal 
 value. If the voltage drops slightly below the normal the pull of 
 the spring on the regulator armature predominates and this armature 
 moves away from the core and closes the cut-out which short-circuits 
 the resistance and permits the exciting field current to increase. 
 This cycle of operations is repeated at rapid intervals and maintains 
 the generator voltage constant at all speeds above the critical value 
 at which it develops 7.75 volts with the resistance cut out of the 
 field circuit. 
 
 The rapidity of vibration depends to a large extent upon speed, 
 but in general the regulator armature vibrates at the rate of one 
 hundred to one hundred and fifty times per second. The actual 
 voltage developed by the generator is made up of a series of very 
 small impulses the mean value of which is 7.75 volts. This is the 
 constant value for which the regulator is adjusted. 
 
 It is obvious that increasing the tension of the regulator spring 
 will increase the constant voltage which the generator will maintain. 
 Under no circumstances should the regulator spring tension be 
 increased in an attempt to have the generator charge at a higher rate 
 at low speed. The generator cannot begin to charge until the cut- 
 out has closed and the closing of the cut-out is independent of the 
 action of the regulator. This cut-out closes after the generator 
 reaches a speed at which it develops 6.5 volts, and no adjustment 
 of the regulator or cut-out can change the charging rate at low speed. 
 Increasing the tension of the regulator spring so that the generator 
 will develop a constant voltage in excess of 7.75 volts will result in 
 excessive current to the battery overcharging it or causing the 
 generator to overheat with the possibility of burning it out. 
 
 In addition to the resistance in series with the shunt field winding 
 there is another resistance "E" which is connected in parallel with 
 the field winding. The function of this resistance is to absorb the 
 field energy when the regulator contacts are opened and reduce 
 sparking at the contacts. 
 
222 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 193 External Wiring on Nash 
 
 Fig. 193 shows the complete wiring of the lighting system on the 
 Nash Trucks. 
 
 DELCO 
 
 The Delco Starting and Lighting System as used on the Cadillac 
 Car consists of a single unit motor-generator which furnishes the 
 current for charging the storage battery, the lights, and ignition 
 system and also runs as a motor cranking the engine. The motor- 
 generator is a four-pole machine with separate sets of field and arma- 
 ture windings necessitating two commutators being used which are 
 located at opposite ends of the armature. The motor is series 
 wound and the generator shunt wound. The motor-generator, when 
 acting as a generator, is driven at engine speeds by the fan shaft 
 which in turn is driven by a silent chain from the cam shaft at the 
 front end of the engine. To prevent the voltage of the current 
 generated from rising too high when the engine is running at high 
 speeds the third brush system of current regulation is employed 
 which has been explained. 
 
 When acting as a motor the sole function of the motor-generator 
 is to crank the engine. In starting first the operator pushes down the 
 ignition lever on the combination switch. This closes the ignition 
 circuit and the circuit between the storage battery and the generator 
 windings on the motor-generator causing the armature to revolve 
 slowly. 
 
* STARTING AND LIGHTING SYSTEMS 
 
 223 
 
 A ratchet clutch (Fig. 194) in the front end of the generator allows 
 the armature to rotate ahead of the driving shaft. The clicking 
 noise that is heard when the ignition switch is turned on comes from 
 this clutch. 
 
 GENERATOR COMMUTATOR t f NDR THIS COVER 
 
 x "MOTOR COMMUTATOR UNDER THIS COVEH 
 
 *s^ ^~~~ STA RTE R BUTTON 
 
 PlMtON CM ARK4TURE SHAFT 
 
 [^ JDLER GEARS CONTAIN IN'G 
 
 Ml - 'Hpfc ^^x^^ . OVER-RWNIN6 CLUTCH '^ HU3 
 
 ^* ^ GEAR TEETH. CUT ON FLYWHEEL 
 
 GENEPATOR 
 DRIVING 
 
 AT THIS END 
 
 WIRE TO MOTOR GENERATOR 
 
 Fig. 194 Installation of Delco on Cadillac 
 
 As the starter button is pushed down it first causes the starter 
 gears to mesh with the teeth on the flywheel. The proper meshing 
 of the gears is made easy by the slow rotation of the armature which 
 begins as soon as the ignition is turned on. As the starter button is 
 pushed further down the circuit between the storage battery and the 
 generator windings of the motor-generator is broken at "X" (Fig. 195). 
 As the movement of the starter button is completed the circuit is 
 closed between the storage battery and the motor windings on the 
 motor-generator by the motor brushes coming in contact with the 
 commutator, causing it to act as a powerful electric motor, which 
 rapidly cranks the engine. 
 
 The gear ratio between the armature shaft and the crank shaft 
 being approximately 25 to 1, the armature would be driven at an 
 excessively high rate of speed after starting the engine before the 
 operator let the starter button back, if it were not for an over-running 
 clutch^in^hejiub of the idler gears between the flywheel and the 
 
224 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 armature shaft. The electric motor cranks the engine through this 
 clutch but after the engine has started and begins to run faster than 
 the electric motor the clutch releases. 
 
 The starter button is let up as soon as the engine is running under 
 its own power. The first movement of the button breaks the circuit 
 between the electric motor and the storage battery by lifting the 
 brushes from the commutator. A further movement causes the 
 starter gears to slide out of mesh and the release of the button com- 
 pletes the circuit between the generator and the storage battery at 
 "X" which was broken when the starter button was pushed down. 
 The engine running and the circuit being closed between the storage 
 battery and the generator windings of the motor-generator the 
 generation of current begins. 
 
 MLAO llHT P^ 4f 
 
 D i 
 
 M CA* 
 
 Fig. 195 Internal Wiring of Delco 
 
 Fig. 195 is a complete wiring diagram of the starting, lighting, and 
 ignition system used on the Cadillac Car. Circuit breakers take the 
 place of fuses in the lighting circuit and no cut-out is provided. When 
 the generator voltage is less than the voltage of the battery, current 
 will flow back through the generator. The amount flowing is some- 
 what less than that flowing through it when first starting. This is 
 so little that it is practically negligable (about 5 amperes). The cir- 
 cuit between the generator and battery is broken when the ignition 
 switch is thrown off. 
 
 A Delco generator with a single set of windings is installed on 
 some Standardized B Trucks. It furnishes current for lights and 
 ignition but does not crank the engine. No cut-out is provided 
 
STARTING AND LIGHTING SYSTEMS 
 
 225 
 
 except the ignition switch which breaks the circuit between generator 
 and battery when in the "off" position. When thrown to the "on" 
 position the generator will turn slowly as a motor until the engine is 
 started causing a "clicking" noise due to the over-running clutch 
 which permits it to turn free of the engine. As in the system on the 
 Cadillac Car very .little current is used in this way. 
 
 FORD MAGNETO 
 
 This magneto may be classified as a high frequency alternating 
 current magneto. It serves merely as a source of primary current 
 
 Magneto Coil Spool 
 
 Copper Wire 
 
 End of Ribbon 1 
 Grounded Here J 
 
 To Coil 
 
 Magneto Coil Support 
 
 Magnet 
 Flywheel 
 
 Magnet Clamp 
 
 Fig. 196 Ford Magneto 
 
 for the vibrating coil type of ignition system and for supplying 
 current for lights. 
 
 The construction is as shown in Fig. 196. The sixteen armature 
 coils are stationary and are wound around cores of soft iron which 
 are supported on an iron frame. An equal number of permanent 
 magnets of the horseshoe type are secured to a non-magnetic ring 
 attached to the flywheel and revolve with it. 
 
226 MOTOR VEHICLES AND THEIR ENGINES 
 
 The north poles of two adjacent magnets are joined together and 
 likewise the next pair of south poles. When a pair of north poles 
 are in front of the core of one coil, the magnetic flux will flow in 
 through this core across the supporting frame and out through the 
 cores of the adjacent coils to the south poles of the magnets. When 
 the flywheel makes J^ of a revolution the coil cores which were 
 opposite the north poles of the magnets will be opposite the south 
 poles causing a complete reversal of magnetic flux to take place in 
 every coil core. This induces a voltage causing current to flow in 
 each of the coils. The coils are connected in series and one end is 
 grounded. The other end is connected to the insulated binding post 
 on the outside of the flywheel housing from which the current supply 
 is drawn. Hence, as the flywheel revolves an alternating current of 
 high frequency will be obtained from this magneto. This current is 
 used for exciting the primary of the ignition system as well as for 
 lighting purposes. 
 
 As there is no regulation in the system to control the voltage or 
 output, the current generated will depend directly upon the speed of 
 the engine. Therefore, the faster the engine goes the better will be 
 the results obtained from the ignition system and likewise the inten- 
 sity of the lights will increase. It will often be noticed on Ford Cars 
 that there is a considerable variation in the intensity of the lights. 
 Since the current generated is alternating a storage battery cannot 
 be connected in the line to overcome these difficulties. 
 
CHAPTER XXI 
 
 POWER TRANSMISSION 
 
 To transmit the power developed by the engine to the wheels of 
 a motor-propelled vehicle certain parts are necessary because of the 
 conditions under which a motor vehicle is operated. The application 
 of the engine power to the driving wheels through these parts is called 
 Power Transmission and their arrangement will be discussed in this 
 chapter. 
 
 The units composing the power-transmission system are prac- 
 tically the same on all modern trucks and motor cars but their ar- 
 rangement varies, depending upon the method of drive and the type 
 of units used. The following units will be found on all modern 
 machines; a clutch, a transmission or gear set, drive shafts, universal 
 joints, differentials, and axles extending to the driven members 
 (chain sprockets or wheels). 
 
 When the power is transmitted to the rear wheels only, the ar- 
 rangement of the parts will be as shown in Fig. 197. This arrangement 
 is typical of light cars of two wheel drive, except the Ford in which 
 the parts are arranged as shown in Fig. 199. In Fig. 197 the power 
 is transmitted from the engine through the clutch " A" to the trans- 
 mission "B" then through the drive shaft "C" with universal joints 
 "D" to the differential. The differential transmits the power to 
 the rear wheels. 
 
 If the engine, clutch, and transmission are not a unit power 
 plant, that is, if they are not contained in the same housing it will be 
 necessary to have an arrangement as shown in Fig. 198. The only 
 difference is that a shaft "E" and universal joints "F" (sometimes 
 called alignment joints) are between the clutch and transmission. 
 
 Because of the special type of transmission used on the Ford the 
 clutch and transmission are reversed but in all other respects it is 
 identical in its system of power transmission. 
 
 The location and arrangement of the units of power transmission 
 on a chain drive apparatus differs as shown in Fig. 200. The differen- 
 tial is now contained in the same housing as the transmission. There 
 is no drive shaft with universal joints between these parts. The 
 power is transmitted in the usual way to the transmission and then 
 direct to the differential. From the differential it is transmitted 
 by jack shafts "G" to the sprockets "H" and to the wheel sprockets 
 "I" by chain "J." 
 
 227 
 
228 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 197 
 
 Fig. 198 
 
POWER TRANSMISSION 
 
 229 
 
 Fig. 199 
 
 H 
 
 // 
 
 Fig. 200 
 
230 MOTOR VEHICLES AND THEIR ENGINES 
 
 * J 
 
 G e 
 
 r - JSI 
 
 Fig. 201 
 
 f e 
 
 G ~ ~ 6 
 
 Fig. 202 
 
 * x g 
 
POWER TRANSMISSION 231 
 
 When the truck is arranged to drive and steer with all four wheels 
 it requires a different arrangement of the Power Transmission units. 
 The power must be transmitted not only to the rear wheels but also 
 to the front wheels. The general arrangement of the parts is shown 
 in Fig. 201. In this arrangement the power is transmitted from the 
 engine to the transmission "D" through the clutch "A" and shaft 
 "B" with universal joints "C." The transmission instead of having 
 one shaft projecting to connect to the drive shaft is so arranged that 
 there is a shaft "E" having both ends " E' " and "E"" projecting and 
 offset slightly from the centre line of the truck. From the trans- 
 mission the power is transmitted to the differentials "H'" and "H" J 
 by drive shafts " F' " and " F" " employing universal joints " G." From 
 the differentials the drive is transmitted to the wheels by the axles 
 which employ universal joints at " J." 
 
 When four-wheel drive is employed with two-wheel steering the 
 arrangement of parts is shown in Fig. 202. 
 
 The power is transmitted from the engine to the transmission 
 "D" through the clutch "A," shaft "B," and universal joints "C." 
 Here the construction differs. A differential "E" is driven by a 
 chain direct from the transmission, the two forming a unit. From 
 this centre differential two shafts "E'" and "E*" project in opposite 
 directions. These shafts are connected to the differentials "H'" and 
 "H"" on the axles by the drive shafts "F'" and "F ;/ " with universals 
 "G." The power is transmitted to the wheels by the axles. The 
 front axle is equipped with universal joints " J." 
 
 In the following chapters the different units making up the power 
 transmission system will be discussed in the order in which they are 
 generally found on trucks and motor cars. The function, operation, 
 and different types will be treated fully. 
 
CHAPTER XXII 
 
 CLUTCHES 
 
 Every motor vehicle propelled by a gasoline engine requires some 
 device to disconnect the engine from the remaining part of the power 
 transmission system. The device used to accomplish this is called a 
 clutch. 
 
 A clutch has one member positively driven by the engine and the 
 other attached to the transmission shaft. When these members are 
 separated the engine will run without driving the transmission shaft 
 thus permitting the gears to be shifted easily. The surfaces of the 
 clutch members should be of such material that the driven member 
 slips on the other when pressure is first applied. As the pressure is 
 increased the driven member is gradually brought to the speed of 
 the other member the slippage entirely ceasing and the two making 
 firm contact. This drive is accomplished by the friction between 
 the two members which depends upon the materials in contact and 
 the pressure forcing them together. This force must be sufficient 
 to prevent slipping when the clutch is engaged and the surfaces 
 must be of such material as to provide sufficient friction to carry the 
 load. The clutch must be easy to operate, requiring as little exertion 
 as possible on the part of the driver. It must not take hold too 
 suddenly or it will cause a jerky operation of the car and put a 
 tremendous strain on the rest of the power transmission units. 
 Provision must be made so that the tension with which the members 
 are held in contact may be varied. It is desirable to have the driven 
 member as light as possible so that it will not continue to rotate for 
 any length of time after the clutch has been disengaged. Protection 
 from dirt and dust should be provided to protect the friction material 
 from excessive wear. For this reason practically all clutches on 
 modern motor-propelled vehicles are housed. 
 
 When a clutch is disengaged the driven member will continue to 
 spin due to its inertia. The heavier the driven member the longer 
 this spinning will continue. When shifting gears it is desirable to 
 have the speed of the transmission shaft reduced and a clutch 
 brake is often provided to reduce the speed of the driven member. 
 This is accomplished by bringing this part in contact with some 
 stationary part of the car when the clutch pedal is fully depressed. 
 Care must be exercised not to depress the foot pedal too far so that 
 
 232 
 
CLUTCHES 
 
 233 
 
 the clutch brake entirely stops the driven member. This would 
 cause the transmission shaft to be at rest, making the shifting of 
 gears difficult. 
 
 Actual constructions of clutches vary on every make of motor 
 vehicle but they may all be grouped under three general headings; 
 cone clutches (internal and external), multiple disc clutches (wet 
 and dry), and plate clutches (wet and dry). 
 
 -A- 
 
 Fig. 203 External Cone Clutch 
 
 Fig. 203 shows diagrammatically an external cone clutch in two 
 positions. A shows the clutch engaged and B shows it disengaged. 
 The driving member of the clutch is the fly wheel "F," the inner 
 surface "I" of which is conically machined at an angle of 12 to 15. 
 The driven member of the clutch is the housing "H" which is lightly 
 constructed and is supported by a bearing on an extension of the 
 crank shaft. It is conically shaped to fit perfectly with the inner 
 surface of the fly wheel. The conical surface is faced with some high 
 friction material "R" such as leather or Raybestos. These surfaces 
 "I" and "R" are forced together by the action of the spring "S." 
 This spring tension can be adjusted by nut "N." 
 
 To disengage the clutch a foot pedal operated by the driver is 
 provided. It is pivoted at " P " and the lower end is forked engaging 
 a yoke " Y " attached to the housing " H.' ' When the pedal is pushed 
 forward it moves part "H" backward so that the surfaces "I" and 
 "R" are no longer in contact. This permits the flywheel to revolve 
 
234 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fiy "WHEEL 
 
 CLUTCH 
 CONE 
 
 CLUTCH 
 FACING 
 
 CLUTCH 
 PEDAL 
 
 EXPANDER- SPRING 
 ADJUSTING NUT 
 THRUST BEARING 
 GREASE CUP 
 RELEASE RING 
 RELEASE ROD 
 
 independently of part "H;" thus the engine is disconnected from the 
 power transmission system. To disengage the clutch it is necessary 
 to compress the spring "S" which requires considerable pressure on 
 the yoke "Y." Hence the pedal is constructed with sufficient 
 leverage to require little effort on the part of the driver. 
 
 To function properly the clutch should be released gradually. 
 This permits slipping between surfaces "I" and "R" resulting in a 
 gradual application of power to "H" until the spring "S" exerts its 
 
 full pressure. This forces 
 the two friction surfaces 
 together so that they 
 turn- as one. 
 
 Fig. 204 shows the 
 cone clutch used on the 
 Buick four-cylinder auto- 
 mobile. The springs 
 holding the clutch in en- 
 gagement are arranged 
 differently from that 
 shown in Fig. 203 but 
 the operation is identical. 
 The expander springs are 
 provided to press the 
 leather facing out at sev- 
 eral points and assure 
 gradual engagement of 
 the clutch. This practise 
 is quite common where 
 leather-faced cone clut- 
 ches are used. 
 
 Fig. 205 shows dia- 
 grammatically an inter- 
 nal cone clutch in two 
 positions. A shows the 
 clutch engaged and B 
 shows it disengaged. The 
 operation of this clutch 
 It is held in engagement 
 It 
 
 CLUTCH GEAR 
 RELEASE YOLK 
 CLUTCH SLEEVE 
 
 Fig. 204 Typical Cone Clutch 
 
 is identical with that of the external type, 
 by the spring "S" and is disengaged by depressing the foot pedal, 
 differs in that the spring "S" is placed inside the driven member 
 "H." The spring forces "H" to the rear to engage the friction 
 surfaces "R" and "I." Adjusting nut "N" regulates the tension 
 on the spring as before. 
 
CLUTCHES 
 
 235 
 
 This type was originally designed to better protect the friction 
 surfaces from exposure to dust and dirt of the road. The general 
 
 Fig. 205 Internal Cone Clutch 
 
 adoption of clutch housings has eliminated this design because of the 
 difficulty in disassembling it. 
 
 Cone clutches are usually faced with leather. To secure smooth 
 action the leather must be kept soft and pliable by the frequent 
 application of Neat's Foot oil. If this is neglected the leather be- 
 comes hard and dry resulting in " grabbing" even when the foot pedal 
 is gradually released. This puts sudden strains on the power trans- 
 mission units causing the car to operate jerkily. 
 
 If oil or grease is allowed to accumulate on the surface of a leather- 
 faced cone clutch slipping will result when the clutch is engaged. 
 This can be temporarily overcome by applying Fuller's Earth but 
 the leather should be thoroughly washed with gasoline and then 
 treated with Neat's Foot oil a-t the earliest opportunity. 
 
 Fig. 206 shows diagrammatically a multiple disc clutch. Its 
 principle of operation is the same as that of the cone clutch. The 
 power from the engine is transmitted to the driven member by 
 friction. The friction surfaces are held in contact by a spring "S" 
 which is released by depressing a foot pedal. The tension on this 
 spring is adjustable by means of the nut "N." Shaft "F" from the 
 engine has plates or discs "R" keyed to it. Between these plates 
 are placed plates or discs "I" keyed to the housing "H" which is 
 
236 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 attached to shaft "T" running to the transmission. Both sets of 
 plates "R" and "I" are free to move laterally but must revolve 
 with the members to which they are keyed. When the foot pedal 
 is released the spring "S" forces these plates together and the fric- 
 
 Fig. 206 Multiple Disc Clutch 
 
 tion between them causes the assembly to revolve as a unit. As 
 the clutch engages there will be a slippage between the plates until 
 the spring tension has forced all the plates tightly in contact. 
 When disengaging the clutch the spring is compressed and the 
 housing "H" is moved to the rear. This, however, does not separate 
 the plates "I" and "R." Cork or spring inserts are often placed in 
 one set of plates to accomplish this and prevent " dragging." In 
 some clutches both sets of plates are of metal, one set usually being 
 made of bronze and the other of steel. This construction is usually 
 found where the plates run in oil. Multiple disc clutches that run 
 dry generally have one set of plates covered with some high friction 
 material such as Raybestos. 
 
 Fig. 207 shows the multiple disc clutch used on the Packard 
 Trucks. It is a dry clutch composed of two sets of steel discs. The 
 set which is keyed to the housing bolted to the fly wheel is faced 
 with special friction material. 
 
 Fig. 208 Shows the multiple disc clutch used on the F. W. D. 
 trucks. This is the Hele* Shaw clutch and the discs run in oil. There 
 are two sets of discs, one of steel which is keyed to the transmission 
 
CLUTCHES 
 
 237 
 
 Fig. 207 Packard Clutch 
 
 shaft and one of bronze which is keyed to the housing bolted to 
 the flywheel. These discs are V-grooved (Fig. 209) which increases 
 the amount of friction surface. 
 
 separate the plates when 
 the clutch is disengaged, dis- 
 engaging springs are used. 
 The operation of this clutch 
 is identical with all other 
 multiple disc clutches. 
 
 Fig. 210 shows diagram- 
 matically a plate clutch in two 
 positions. A shows the clutch 
 engaged and B shows it disen- 
 gaged. The principle of oper- 
 ation of this clutch is the same 
 
 Fig. 208 Hele Shaw Clutch 
 
 as that of the cone clutch. The power of the engine is transmitted 
 to the driven member by friction. The friction surfaces are held 
 
 Fig. 209 Discs in Hele Shaw Clutch 
 
 in contact by spring "S" which is released by depressing the foot 
 pedal. The tension on the spring "S" may be adjusted by means of 
 
238 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 the nut "N." Between the housing "H" and the machined face of 
 the fly wheel "I" is placed a plate "P" of special friction material 
 
 Fig. 210 Plate Clutch 
 
 independent of all moving parts. When the clutch is gradually en- 
 gaged slippage takes place between the surface "R" and plate "P' 
 
 B U 12131415 B PBB202 
 
 Fig. 211 Nash Clutch 
 
 and surface "I" and plate "P." This permits a more gradual appli- 
 cation -of power than if the friction material were fastened to either 
 

 CLUTCHES 
 
 239 
 
 the flywheel or housing. As the pressure of the spring increases 
 forcing the plate "P" and surfaces "I" and "R" together the 
 slippage ceases and the whole assembly turns as one unit. 
 
 Plate clutches are sometimes constructed with two plates of 
 friction material separated by a steel disc pinned to the flywheel. 
 The increased surfaces permit more slippage and therefore give a 
 smoother operating clutch. Plate clutches are built to run dry or in 
 a bath of oil depending upon the materials used. 
 
 Fig. 211 shows the dry plate clutch used on the Nash Trucks. 
 The spring "14" forces the friction surfaces "5" in contact with the 
 flywheel. The power of the engine is transmitted from the fly wheel 
 to the drive plate "2" which is keyed to shaft " 16" connected to the 
 transmission. 
 
 The White plate clutch runs in a bath of light oil (Fig. 2.12). 
 The operation of this clutch is as follows: The spring "15" forces 
 housing "14" forward and in so doing raises arm "10" to which are 
 attached the wedge-shape pieces "11." As part "16" is stationary 
 the wedge-shape part will force the friction surfaces together thus 
 permitting the flywheel to drive the friction plate "3" which is 
 bolted to the clutch shaft "7" connecting with the transmission. 
 
 42 39 41 40 
 
 Fig. 212 White Clutch 
 
 When the foot pedal is depressed the wedge-shaped part "11" 
 is lowered thus permitting the friction surfaces to separate 
 and the flywheel to turn without driving the friction plate "3." 
 
240 MOTOR VEHICLES AND THEIR ENGINES 
 
 There are three general clutch troubles; slipping, gripping, and 
 dragging. 
 
 Slipping as previously explained may result from the condition 
 of the friction surfaces. Dry clutches slip when too much oil has 
 accumulated on their surfaces. Wet clutches sometimes slip when 
 too heavy a lubricant is used as the spring tension will not be suffi- 
 cient to force the oil from between the plates. This prevents the 
 friction surfaces from coming intimately into contact. It is par- 
 ticularly true of multiple disc clutches. Slipping is usually the 
 result of insufficient spring tension since the friction between the 
 surfaces depends upon the pressure exerted by the spring. This is 
 remedied by tightening up on the clutch adjusting nut. 
 
 Gripping may be the result of the condition of the friction sur- 
 faces as has already been explained under cone clutches. However, 
 it is usually the result of too much spring tension due to the adjusting 
 nut being too tight. This nut should be loosened until the proper 
 spring tension is obtained. 
 
 Dragging results from the adjusting nut being so tight that con- 
 siderable spring tension is exerted even when the clutch pedal is 
 released. In a wet clutch, if the oil is too heavy or is left in the 
 clutch so long that it becomes "gummy," the plates will adhere and 
 dragging will result. This is particularly true of multiple disc 
 clutches. It is remedied by washing out the clutch with kerosene 
 and refilling with proper lubricant^ 
 
CHAPTER XXIII 
 
 TRANSMISSIONS 
 
 An internal combustion engine does not develop its full power at 
 low speeds, therefore, an automobile engine cannot pull much of a 
 load at low speed and gears must be interposed between the engine 
 and driving wheels. This permits the crank shaft to turn at the 
 speed necessary to produce the desired power while the wheels turn 
 at the speed the road conditions or grades require. To secure 
 flexibility of operation three and sometimes four speed ratios are 
 provided. To back the car a set of gears are arranged in the trans- 
 mission to reverse the direction of the drive transmitted to the wheels. 
 The gears, shafts, and other parts necessary for varying the forward 
 speed and obtaining a reverse are all contained in a housing or gear 
 case and the assembly is called a transmission although it would be 
 more correct to call it a gear set. 
 
 The transmission may be located in any one of three places; as 
 part of a unit with the engine and clutch, as a separate unit between 
 the clutch and rear axle, or as part of a unit with the rear axle which 
 is very rarely found on modern motor vehicles. 
 
 Before taking up transmissions proper, gears will be briefly 
 discussed. By the use of gears a mechanical advantage is obtained 
 permitting heavy loads to be lifted with the minimum amount of 
 power. 
 
 At A (Fig. 213) a weight "W" is shown supported by a rope 
 wound about a roller "R." When the crank "C" is turned the rope 
 
 Fig. 213 Mechanical Advantage of Gears 
 
 is wound upon the roller lifting the weight. The amount of force 
 required to lift the weight will depend upon the length of the crank 
 
 241 
 
242 MOTOR VEHICLES AND THEIR ENGINES 
 
 arm "C" and the diameter of the roller "R." At B (Fig. 213) is 
 shown the same weight supported by the rope wound on a roller 
 "R" of exactly the same size but which is made fast to the large 
 gear wheel "G." Meshing with "G" is a smaller gear or pinion 
 "P" to which is attached a crank "C" the same length as before. 
 When the crank is turned pinion "P" revolves causing gear "G" 
 to revolve also and lift the weight "W" by winding up the rope on 
 roller "R." The force required to lift weight "W" in this case will 
 be considerably less than before because of the gear reduction between 
 the crank "C" and roller "R." In both cases the total work done 
 is the same which is lifting the weight through a certain distance. In 
 the first case one revolution of the crank winds one turn of rope upon 
 the roller lifting the weight a corresponding amount. In the second 
 case one revolution of the crank does not turn the gear "G" one 
 revolution because the pinion "P" can turn "G" only as many 
 teeth as are on the total circumference of "P." If the gear had 
 twice as many teeth as the pinion two turns of the crank would be 
 required to revolve the roller once. Hence, two turns of the crank 
 at B would lift the weight "W" only as far as one turn did at A, 
 but only half as much force (disregarding friction) would be required. 
 It can thus be seen that the force necessary to do a given amount of 
 work can be reduced by the use of gears. The reduction depends 
 upon the number of teeth on the two gears in mesh. 
 
 By the use of gears in the transmission an automobile engine is 
 able to pull a heavy load up a steep grade. Their use also explains 
 why the speed of the machine decreases while the engine continues 
 to run as fast or even faster than before. 
 
 When two gears are meshed, one driving the other, they will 
 rotate as shown in Fig. 214. At A is shown two spur gears in mesh. 
 
 Fig. 214 Rotation of Gears 
 
 If "P" turns as indicated it will drive "G" in the opposite direction. 
 At B is shown an internal gear and pinion in mesh. If "P" turns as 
 

 TRANSMISSIONS 
 
 243 
 
 indicated it will drive "G" in the same direction. The rotation of 
 i ; combinations of more than two gears such as shown at C can be 
 traced out the same fundamentals applying. 
 
 The expression "gear ratio" or "gear reduction" means the 
 relation between the number of teeth on one gear as compared to 
 I the number on the gear which is driven by it. For example, if one 
 gear has 12 teeth and drives a gear having 42 teeth the gear ratio is 
 42 to 12 or 3H to 1. This term will be used throughout the fol- 
 lowing chapters on the power transmission system wherever gears 
 are encountered, hence, must be clearly understood. 
 
 The earliest form of transmission was a friction type in which no 
 gears were used. This gave unlimited speed ratios between the 
 engine and drive shaft and also eliminated the clutch. 
 
 Fig. 215 Friction Transmission 
 
 Fig. 215 shows two views of a friction transmission. The driven 
 wheel slides on a counter-shaft and can be shifted across the face of 
 the driving disc and engaged at different positions at varying dis- 
 tances from its center. The further the driven wheel is moved 
 toward the outer edge of the disc the greater will be its speed. For 
 example, the greatest speed will be obtained when the wheel is in 
 position G and the least at position D. To obtain reverse the wheel 
 is simply shifted to the other side of the disc to some position such 
 as C. 
 
 The drive is interrupted by moving the driving disc forward. 
 Friction is obtained between the driving disc and driven wheel, 
 usually faced with fibre, by pressure exerted on the disc by a spring 
 (not shown). In this way clutch action is obtained. 
 
 Since only a very small amount of contact surface is possible 
 with this transmission slipping results when heavy loads are pulled. 
 This wears out the friction surface rapidly. A much heavier spring 
 than that used for ordinary clutches is required since the contact 
 surfaces are smaller. The disc and wheel must be made so large for 
 
244 MOTOR VEHICLES AND THEIR ENGINES 
 
 heavy pulling that the construction becomes cumbersome making 
 its use prohibitive on all but the lightest machines. 
 
 To obtain positive transmission of power gear types of transmis- 
 sions were developed. There are three types now in common use. 
 These are the progressive, the selective, and the planetary. The 
 different gear ratios are obtained by bringing different combinations 
 of gears into action. In the selective and progressive types this is 
 accomplished by shifting gears or dogs. 
 
 The progressive type of transmission has but one set of sliding 
 gears shifted by moving a lever forward one notch for each higher 
 ratio. From the neutral position the lever is moved straight back- 
 ward for reverse. A typical three-speed progressive gear set is shown 
 in Fig. 216, the positions of the gears when in neutral, low, second, 
 high, and reverse being shown. 
 
 The power of the engine is transmitted to a short hollow shaft 
 "A" called a sleeve which carries a gear "B" that is in permanent 
 mesh with a gear "C" on the end of the countershaft. Parallel to 
 the countershaft is another shaft, one end of which is supported by 
 a bearing in the hollow sleeve. Though the sleeve supports this 
 shaft the two may revolve independently of each other. The second 
 shaft is square or of such construction that the two paired gears 
 may slide along but must revolve with it. The gears on the square 
 shaft are of different sizes and in sliding come successively into mesh 
 with gears carried on the countershaft. Because the gears "B" and 
 "C" are in mesh the countershaft revolves when the engine revolves, 
 but the speed of the square shaft depends on the combination of 
 gears in mesh between it and the countershaft. When the sliding 
 gears are in such a position that they are not in mesh with the coun- 
 tershaft gears the square shaft is independent of the countershaft 
 and may revolve or be stationary. The gears are then in the neutral 
 position. When the sliding pair is moved so that its larger gear is 
 in mesh with the smallest of the countershaft gears "D," the square 
 shaft will revolve at a slower speed than the countershaft because its 
 gear is larger than the one driving it. This is low speed position. 
 Again sliding the moving pair will separate these gears and bring the 
 next pair "E" into mesh the square shaft then moving at a higher 
 speed. It still moves slower than the countershaft because of the 
 difference in the size of the gears. Sliding the moving pair still 
 farther along the shaft will disengage the second speed gears and 
 engage the high speed in which the square shaft revolves at the speed 
 of the sleeve and crank shaft. This is effected by locking the moving 
 pair to the sleeve by means of a dog "G." This dog consists of 
 several fingers projecting from the moving pair corresponding to 
 

 TRANSMISSIONS 
 
 245 
 
 the spaces between similar fingers on the end of the sleeve. The 
 locking together of the square shaft and sleeve gives direct drive. 
 In direct drive the power of the engine is directly applied to the square 
 shaft avoiding the loss that occurs through the friction of the gear 
 teeth at other speeds. The revolution of the square shaft is trans- 
 mitted to the driving wheels, the speed of the car corresponding to the 
 
 C **~\ I . 'TJ -rrJU^=. 
 
 Fig. 216 Progressive Transmission 
 
 speed at which the square shaft is driven by the gear combinations 
 between it and the countershaft. 
 
 To obtain the reverse which enables the car to be backed without 
 reversing the engine, a third gear "JF " is introduced between the low 
 speed gears of the square shaft and countershaft. When the car is 
 
246 MOTOR VEHICLES AND THEIR ENGINES 
 
 going forward the square shaft and countershaft revolve in opposite 
 directions. When the reverse gear is introduced between them the 
 square shaft is revolved in the same direction as the countershaft 
 reversing the rotation of the driving wheels. 
 
 This type of transmission will rarely be found on modern motor 
 vehicles, the principal objection being that it is necessary to pass 
 through one or more gears in shifting from high back to neutral. 
 If this shift is made when the car is in motion stripped gears may 
 result. 
 
 A modified form of this type sometimes called a semi-progressive 
 transmission is used on motor-cycles. Fig. 217 shows the three- 
 
 Fig. 217 Indian Motor Cycle Transmission 
 
 speed gear set used on the Indian Motor-Cycle. The gears are 
 shown in the neutral position which is between the low and inter- 
 mediate gears on the countershaft. Motor-Cycles not requiring a re- 
 verse gear, intermediate is the only gear that must be passed through 
 in going into high or back to neutral. This modified type of pro- 
 gressive gear set will generally be found on modern motor-cycles. 
 
 The selective type of sliding gear transmission is so called because 
 it is possible to engage any set of gears desired in moving from the 
 neutral position without passing through any other gears. Selective 
 gear sets are constructed with either three or four speeds forward 
 and a reverse. 
 
 Fig. 218 shows a typical three-speed gear set in which the position 
 of the gears when in neutral, low, intermediate, high, and reverse 
 are shown. 
 
REVERSE IDLER GEAR L~T" 
 
 -B 
 
 NiON SHAFT C 
 
 H 1 Ti 
 NEUTRAL 
 
 --COUNTER SHAFT D 
 
 ,F 
 
 FIRST SPEED 
 OR" LOW" 
 
 SECOND SPEED '-_Jj 
 OHlNTERMEOIATE 
 
 THIRD OR 
 
 "HIGH" SPEED N 
 
 REVERSE 
 
 Fig. 218 Selective Transmission 
 
 247 
 
248 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 The revolution of the engine is transmitted to the countershaft 
 "D" through the gears "B" and "A" which are always in mesh. 
 All gears on the countershaft are permanently keyed to it. The shaft 
 "E" is supported at one end by bearing in the hollow end of the 
 shaft coming from the engine and at the other end by the bearing 
 where it passes through the transmission case for attachment to the 
 drive shaft. The gears "F" and "G" are free to slide along shaft 
 "E" but are forced to turn with it because of the keys on its surface. 
 Each of these sliding gears have collars forged on them in which 
 shifter forks engage as shown in Fig. 219. 
 
 Fig. 219 Gear Shift Mechanism 
 
 The movement of the gear shift lever "A" to the right or left 
 picks up one or the other of these forks shifting the particular gear 
 to which it is attached. When the gear shift lever is in neutral po- 
 sition the gears will be as shown in neutral (Fig. 218). If the gear 
 shift lever is moved to the position of first speed gear "G" will be 
 moved along the shaft "E" until it meshes with gear "H" on the 
 countershaft. If the gear shift lever is now moved in the opposite 
 direction gear "G" will be moved to the reverse position. In 
 changing from low to reverse, gear "G" passes through the same 
 position it occupied on the shaft "E" when in neutral. If second 
 speed is desired the gear shift lever must be moved to the opposite 
 side of the control sector (Fig. 219) and in the opposite direction to 
 that in going into first speed. This now causes the gear "F" to 
 be shifted and it is moved to the position shown for second speed. 
 If direct drive is desired the gear shift lever must be moved in the 
 opposite direction shifting gear "F" to the position shown for high 
 speed. In going from second to high the gear "F" passes through 
 the same position it occupies on the shaft "E" when in neutral. 
 
 Fig. 220 shows a typical three-speed selective sliding gear trans- 
 mission which is used on the Dodge Car. The exact location of the 
 
240 
 
250 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 reverse idler pinion is clearly shown as is also the bearing of the sliding 
 gear shaft in the hollow end of the clutch shaft. One feature of this 
 transmission is that the countershaft does not revolve when running 
 on high gear. This is because the gear on the clutch shaft is shifted 
 so it does not drive the countershaft gear when in high. 
 
 Bait Bearing 
 
 Countershaft and Gears 
 
 Bearings 
 
 Lower Half of 
 Gear Case 
 
 Main Shaft 
 
 Reverse, I stand 2nd 
 Speed Shift Member 
 
 Fig. 221 White Transmission 
 
 Fig. 221 shows the four-speed transmission used on the White 
 Motor Cars. It is identical with the three-speed transmission except 
 for the addition of another set of gears. This transmission is ar- 
 ranged so that on third speed the drive is direct, while on fourth speed 
 the drive shaft turns faster than the engine shaft. This arrangement 
 permits increased speed with light loads. The usual four-speed con- 
 struction especially for trucks has direct drive on fourth speed and 
 three lower gear ratios permitting greater flexibility of drive. Se- 
 lective sliding gear or sliding dog transmissions are almost universally 
 used on modern cars and trucks, the three-speed type being the most 
 common. 
 
 When heavy loads are pulled a considerable strain is put on the 
 gear teeth when they are being shifted sometimes causing the teeth 
 to be stripped from the gear. To eliminate this trouble on heavy 
 cars and trucks the gears are placed permanently in mesh, the drive 
 
TRANSMISSIONS 
 
 251 
 
 being obtained by engaging dogs or individual clutches. This 
 construction is especially desirable on four-wheel drive trucks. 
 
 Fig. 222 shows the selective sliding dog gear set used on the F. 
 W. D. Trucks. The gears on the countershaft and main shaft are 
 always in mesh. Shifting dogs are moved along the main shaft just 
 as the gears are shifted hi ordinary selective types of transmission. 
 
 Fig. 222 F. W . D. Transmission 
 
 One feature of this transmission is that when the high speed dog is 
 shifted forward engaging the engine shaft a yoke throws out the dog 
 on the countershaft so that it does not revolve. 
 
 Fig. 223 shows the selective transmission used on the Nash 
 Trucks. This transmission is of the sliding dog type but differs in 
 having dogs and gears integral with each other. The shifting gears 
 are provided with clutches or dogs of four jaws and are shifted on 
 both the countershaft and mainshaft. The power from the engine is 
 applied to the main shaft "4" called the "spline shaft." Upon this 
 spline shaft and driven by it are the sliding gears "10" consisting of 
 a unit of two gears whose outer ends are provided with dogs. Gear 
 "7" is free to turn on the spline shaft and gear "11" is also free to 
 turn on it but is bolted to the drive sprocket " 15." The countershaft 
 "28" called the "lay shaft" carries the sliding gears "30" and "32" 
 which are provided with dogs and free to turn on it. Gear "29" is 
 keyed to the lay shaft and in constant mesh with gear "7, " and gear 
 "34" is also keyed to the lay shaft and in constant mesh with gear 
 "11." The reverse gear shaft "48" carries the reverse gears "50" 
 which may be shifted to engage gears "10" and "11." 
 
252 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 15 
 
 TRANSMISSION ASSEMBLY 
 
 4 Splineshaft 
 
 7 Transmission third-speed drive gear 
 10 Transmission splineshaft sliding gear 
 11 Transmission drive sprocket gear 
 15 Splineshaft drive sprocket 
 28 Transmission layshaft 
 29 Transmission layshaft third- 
 speed gear 
 
 30 Transmission layshaft second-speed gear 
 
 32 Transmission layshaft first-speed gear 
 
 34 Transmission layshaft drive geaf 
 
 41 Transmission countershaft 
 
 43 Countershaft drive sprocket 
 
 48 Reverse gear shaft 
 
 50 Reverse gear 
 
 51 Silent drive chain 
 
 Fig. 223 Nash Transmission 
 
 When the gear shift lever is moved to first speed position gear 
 "32" is shifted so its dogs engage those of gear "34." The power 
 is now transmitted from the spline shaft by gear "10" to gear "32," 
 to gear "34," to gear "11," and sprocket "15," through chain "51" 
 to the transmission countershaft "41." When the gear shift lever 
 is moved to the second speed position the dogs of gears "32" and 
 "28" are disengaged and those of "30" and "29" are engaged. 
 This is accomplished because one shifting fork controls both gears. 
 The power is now transmitted from the spline shaft by gear "10" 
 to gear "30," to gear "29" and shaft "28," to gear "34," to gear 
 "11," and to the counter-shaft as before. In moving the gear shift 
 lever from second to third speed position the neutral position is 
 passed through which disengages gear "30." Gear "10" is moved 
 forward its dogs engaging those of gear " 7." The power is now trans- 
 mitted from the spline shaft to gear "10" to gear "7," to gear "29" 
 
TRANSMISSIONS 
 
 253 
 
 and shaft "28," to gear "34," to gear "11," and to the transmission 
 countershaft as before. When the gear shift lever is in fourth speed 
 position the dogs of gear "10" are disengaged from those of gear "7" 
 and engaged with those of gear "11." The power is now transmitted 
 directly from the spline shaft by the dogs of gear " 10," to gear " 11," 
 and to the transmission countershaft as before. When the gear shift 
 lever is in reverse position, gear "50" meshes with gear "10" and 
 the pinion paired with gear "50" meshes with gear "11." The 
 power is now transmitted from the spline shaft through gear "10," 
 to gear pair "50," to gear "11," and to the transmission countershaft 
 as before, rotation being in the opposite direction. 
 
 The planetary transmission differs from the progressive and 
 selective types in that the groups of gears always remain in mesh and 
 revolve around a main axis. The different sets of gears are brought 
 into action by stopping the revolution of the parts which support the 
 gears. To hold these parts from revolving brake bands are com- 
 monly used. In this way a simple operating transmission can be 
 constructed having no dogs or gears to be meshed when changing 
 speeds. 
 
 To understand the operation of the Ford Planetary Transmission 
 it is necessary to know fully the exact assembly of the parts. In 
 
 Fig. 224 Ford Transmission Disassembled 
 
 Fig. 224 the transmission parts are shown in their relative assembling 
 positions and the groups in their different stages of assembling. 
 
 The first operation is the assembling of group 2 which is as fol- 
 lows: Place the brake drum on the table with the hub in a vertical 
 position. Then place the slow-speed drum and gear over the hub 
 
254 MOTOR VEHICLES AND THEIR ENGINES 
 
 with gear uppermost. Next place the reverse drum over the slow 
 speed drum so that the reverse gear is just behind the slow speed 
 gear. Then place the driven gear in position so that the teeth will 
 be downward and key it to the brake drum housing. The triple 
 gear should now be meshed with the gears attached to each of the 
 drums so that the punch marks line up. The gears should then be 
 tied so that they cannot move. 
 
 The assembly should now be placed on the flywheel as shown in 
 group 3 so that the triple gears fit on the triple gear pin and the trans- 
 mission shaft extends beyond the inner face of the brake drum. 
 The clutch drum key should be fitted in the transmission shaft so 
 that it will hold the clutch drum rigid to it when put in place. The 
 clutch drum should next be placed on the transmission shaft and the 
 set screw fastened. The clutch plates should next be placed over 
 the clutch drum. Put a large disc on first then a small disc alter- 
 nating with large and small discs until the entire set is assembled in 
 
 Fig. 225 Assembled Transmission 
 
 position. The large discs are keyed to the brake drum and the small 
 discs are keyed to the disc drum so that they must revolve with the 
 parts to which they are keyed but can be moved backward or for- 
 ward. Next put the clutch push ring in place and attach the driving 
 plate to the brake drum so that the studs on the clutch push ring 
 press against the clutch fingers. Then place the clutch shift, clutch 
 spring, and clutch spring support in place and fasten with clutch 
 spring and support pin. The assembly is now complete (Fig. 225). 
 Fig. 226 shows the pedals and brake bands attached in their proper 
 places. 
 
Fig. 226 Control Pedals 
 
 Fig. 227 shows diagrammatically the arrangement of the parts of 
 the Ford Planetary Transmission in cross section and will be used to 
 explain its operation. 
 
 
 Fig. 22? Sectional Diagram of Ford Transmission 
 
 HIGH SPEED. When the foot clutch pedal is released it allows 
 collar " C " to force arms " A " forward. This forces the plates of the 
 clutch together so that the shaft "S" and housing "B" are driven 
 as one unit. Every time the flywheel "F" makes one revolution the 
 housing "B" also makes a complete revolution. In this manner 
 drive is obtained, the entire transmission revolving as one unit and 
 the drive is taken through the clutch. At all other speeds the clutch 
 
256 MOTOR VEHICLES AND THEIR ENGINES 
 
 is out of operation and the clutch pedal must be depressed slightly 
 to free it. 
 
 SLOW SPEED. When the clutch pedal is depressed all the way 
 it not only releases the clutch but causes a brake band to hold fast 
 the drum "L." 
 
 As the flywheel from which project the studs carrying the triple 
 gears (Fig. 227) revolves it will be necessary for the gears to revolve 
 on their own axes. Assuming gear*"l" has 20 teeth and gear "2" 
 
 A B 
 
 Fig. 228 Diagram Explaining Operation of Transmission 
 
 has 30 teeth (Fig. 228 A) the operation will be as follows: As the 
 gear attached to "L" is held stationary by the brake band, gear "2" 
 which is in mesh with it will have to roll on gear "L." When gear 
 "2 " has rolled 30 teeth to position X it will have turned one complete 
 revolution. As gear "2" turns one complete revolution gear "1" 
 must also turn one complete revolution. Assuming that it rolls on 
 gear "B" it would roll 20 teeth to a position Y, This cannot be 
 true for the triple gear pinion has to be at X, therefore, gear "1" 
 must drag gear " B " with it the distance from Y to X. When driving 
 in high, gear "B" turns at the same speed as the flywheel. Now it 
 does not turn as fast thus giving low speed. 
 
 REVERSE. In this position the clutch pedal is pressed just far 
 enough to release the clutch. The reverse foot pedal is pressed all 
 the way down. This contracts a brake on the drum "R" (Fig. 227). 
 As the flywheel revolves carrying with it the triple gears the following 
 condition will result. As the gear attached to "R" is held stationary 
 the triple gears will have to revolve on their own axes causing gear 
 "3" to roll on gear "R" (Fig. 228 B). Assuming that gear "3" has 
 
TRANSMISSIONS 257 
 
 10 teeth it will turn one revolution when it has rolled 10 teeth on 
 "R" and will be at position Z. At the same time gear " 1 " will have 
 to revolve one revolution. Assuming that it can roll at the same time 
 on gear "B" it would be at position X when it had turned one revo- 
 lution. As it cannot be there but must be at position Z since "B" 
 is free to move and "R" is not it will have to turn "B " through the 
 distance from Y to Z. This turns "B" in the reverse direction and 
 at a slower rate of speed than the engine. 
 
 It must be remembered that low and reverse speeds are de- 
 pendent upon the brakes holding the bands fixed assuming that the 
 housing "B" is free to move. This is not exactly true as the weight 
 in driving the car forms a brake on "B" thus tending to hold it 
 fixed. The brakes on the drums "R" and "L," therefore, must be in 
 very good condition for they must have a greater braking force than 
 that applied by the weight of the car and friction of the working 
 parts of the power transmission units, or else the drums will slip 
 under the brake bands and a loss of developed power to the drive 
 wheels will result. 
 
CHAPTER XXIV 
 
 DRIVES 
 
 From the transmission or gear set the power must next be de- 
 livered to the differential and thence to the wheels. It is desirable 
 to do this in the most efficient manner by reducing frictional losses 
 to a minimum, yet the method of drive employed must have sufficient 
 flexibility to allow for the movement of the frame up and down on 
 the springs. The usual method is by a shaft from the transmission 
 direct to the differential. In some cases where the differential is not 
 placed on the rear axle the final drive to the wheels is made by chains. 
 
 When a shaft drive is used universal joints are necessary to secure 
 the required flexibility. Fig. 229 shows a typical universal joint. 
 
 Fig. 229 Universal Joint 
 
 By being pivoted so its parts can turn about axes perpendicular to 
 each other one member of the joint may remain rigid while the other 
 moves through variable angles. This ability of a universal joint to 
 adjust itself to transmit power through variable angles makes it 
 applicable to shaft drives. 
 
 One or more universal joints must be incorporated in the drive 
 from the transmission to the differential. This gives the necessary 
 flexibility to compensate for the movement of the rear axle due to 
 spring action. Universal joints are always used at points where the 
 
 258 
 
DRIVES 
 
 259 
 
 drive is transmitted by shafts at variable angles. Referring to 
 chapter 22 the power transmission charts show universal joints 
 used at the following points: Between the clutch and transmission to 
 relieve any strains occasioned by twisting the frame, on drive shafts 
 as just explained, on axles whose wheels are both driven and steered 
 to permit the wheels to turn. 
 
 The drive shaft may be tubular which gives it greater strength 
 and stiffness without excessive weight. It often is enclosed in an 
 extension of the rear axle housing or it may be exposed. 
 
 Fig. 230 Enclosed Drive Shaft 
 
 Fig. 230 shows the enclosed drive shaft used on the Dodge Car. 
 A construction of this kind is advantageous since it protects the 
 moving parts and at the same time takes any possible strain on the 
 shaft other than that of driving the car. 
 
 Fig. 231 Method of Drive 
 
 Fig. 231 shows the usual arrangement of the power transmission 
 units employed on shaft drive machines. There is less loss of power 
 
260 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 due to angularity at the universal joints and less wear when the 
 units are nearly in alignment. 
 
 In addition to universal joints a sliding or telescopic joint must 
 be provided at some point between the transmission and rear axle 
 due to the slight variations in the distance between them as the 
 frame moves up and down. This joint is many times overlooked 
 and its lubrication often neglected. 
 
 The drive shaft transmits power to the housing carrying the dif- 
 ferential gears through a pair of bevel, helical, or worm gears. In 
 each case the pinion (small gear) or worm is keyed to the shaft and 
 meshes with the large driving gear or worm wheel bolted to a flange on 
 the differential housing. 
 
 Fig. 232 shows the bevel gear drive used on the Ford car. The 
 drive shaft on which is keyed the pinion, meshes with the large drive 
 
 Fig. 232 Bevel Gear Drive 
 
 gear (ring gear) bolted to the differential housing. When the shaft 
 rotates the drive gear is caused to revolve, turning the axles, and in 
 this way the drive is transmitted to the wheels. There is considerable 
 gear reduction at the rear axle, for the large bevel gear turns one re- 
 volution to every three (or more) revolutions of the pinion. Hence, 
 the drive shaft turns at several times the speed of the axles, which 
 correspondingly decreases the power required to drive the wheels. 
 This is generally called " differential reduction" and will depend upon 
 the power required. 
 
DRIVES 
 
 261 
 
 Fig. 233 shows the helical or spiral bevel driving gears. The an- 
 gular cut teeth eliminate backlash and play between the teeth insuring 
 quiet operation. In addition, 
 continuous driving action re- 
 sults, at least two teeth being 
 partly engaged at all times, 
 overcoming any tendency to 
 wear irregularly. This type of 
 gear is rapidly replacing the or- 
 dinary bevel gear, with its single 
 tooth contact. 
 
 Fig. 234 shows a typical 
 worm drive. The worm is 
 keyed to the drive shaft and 
 placed above the gear wheel 
 which is the ordinary arrange- 
 ment. Several teeth are in 
 mesh at once resulting in quiet 
 and continuous operation. The 
 gear wheel is usually made of 
 steel and the worm of bronze to 
 reduce friction to a minimum. 
 Because of the large gear re- 
 ductions obtainable with this 
 type of drive it is particularly 
 well suited for trucks where a 
 differential reduction of be- 
 tween 7 and 9 to 1 is desired. 
 
 To obtain a large differential 
 reduction on heavy trucks, 
 chains are used for the final drive. Fig. 200 shows a typical 
 arrangement of chain drive. The differential is generally housed 
 with the transmission gears and jack shafts drive chains by means 
 of sprockets on their ends. A dead axle is used and the wheels 
 carry sprockets of larger diameter than those used on the jack shafts. 
 This permits an additional reduction to that obtained at the differ- 
 ential. When a chain drive is used, universal joints are not neces- 
 sary unless used between the clutch and transmission, since the 
 chain is flexible and adjusts itself to the movement of the frame 
 up and down on the springs. A chain drive is objectionable, 
 because it is noisy and wears excessively, being exposed to the dust 
 and dirt of the road. 
 
 Fig. 233 Helical Gear Drive 
 
262 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 A chain tends to pull the rear axle forward since all the power is 
 delivered by the pull of the chains on the sprockets. To keep the 
 rear axle from being twisted out of place, and also to adjust the ten- 
 sion on the chain, radius rods are used. These are attached by flexi- 
 
 Fig. 234 Worm Gear Drive 
 
 ble couplings, usually ball joints, to the frame and axle and their 
 length is adjustable. In this way the driving strain is transmitted to 
 the frame. 
 
 On shaft-driven machines the driving strain is transmitted to the 
 frame through torque arms, radius rods, torque tubes, distance rods, 
 or the springs. The torque arm is more common on heavy cars and 
 the torque tube on lighter machines, it generally being the extension 
 of the rear axle housing covering the drive shaft. Where the Hotch- 
 kiss Drive is used (drive taken through the springs), the main spring 
 leaf is made extra heavy to take this additional strain. 
 
CHAPTER XXV 
 
 DIFFERENTIALS 
 
 m a car travels around a corner the distance traveled by the 
 outside wheels is greater than that traveled by the inside wheels. If 
 the wheels are mounted on dead axles so that they turn independently 
 of each other, like the front wheels on an ordinary passenger vehicle, 
 they will turn at different speeds to compensate for the difference in 
 travel. If the wheels are positively driven by the engine, a device is 
 necessary which will permit them to revolve at different speeds with- 
 out interfering with their driving the car. To accomplish this a 
 system of gears called the differential is provided. 
 
 Fig. 235 Differential Action Explained 
 
 The action of the simple differential is shown in Fig. 235. At 
 A two shafts "K" and "K-l" are attached to the large bevel gear 
 wheels "H" and "H-l" and meshing with them is the pinion "G" 
 attached to the shaft "F." When the shaft "F" is pulled forward 
 as shown, but not rotated about its axis, the pinion "G" will not re- 
 volve. Since it is meshed with both gear wheels "H" and "H-l" 
 they will be turned about their axes, causing the shafts "K" and 
 "K-l " to revolve equally and in the same direction that the shaft "F" 
 is being pulled. The pinion "G" merely acts as a connection or 
 clutch between the two gear wheels. If the axle "K" is held sta- 
 tionary (Fig. 235B), its gear wheel "H" cannot revolve when the 
 shaft "F" is pulled forward as before. This causes the pinion "G" 
 
 263 
 
264 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 to roll on the gear "H" revolving about its axis, while "H-l" 
 turns at a greater speed than before. This is because it is forced 
 to revolve at the speed with which shaft "F" is pulled for- 
 ward plus the speed imparted to it by the pinion "G" revolving 
 on its own axis. Shaft " K-l " still revolves in the same direction that 
 shaft "F" is being pulled. If shaft "K" is allowed to slip a 
 little (Fig. 235C) so that it revolves in the same direction as at A 
 but not nearly so much, as indicated by the arrow, the amount that 
 pinion "G" rolls on the gear "H" will be correspondingly 
 reduced. Shaft "K-l" will be driven as before by both the pull 
 on "F" and the turning of the pinion "G" on its axis. Therefore, 
 the pinion "G" will not revolve as much as it did before, since gear 
 "H" is now also turning correspondingly, reducing the amount that 
 the shaft "K-l" revolves. 
 
 This is the principle upon which all differentials are built, different 
 arrangements of gears being used to accomplish this same result. In 
 the differential, the shafts "K" and "K-l " are the axles to which the 
 wheels are attached, either one of which may revolve slower than the 
 driving speed. The revolution of the other increases a corresponding 
 amount due to the differential action of the gears. 
 
 Fig. 236 Bevel Gear Differential 
 
DIFFERENTIALS 
 
 265 
 
 Fig. 236 shows diagrammatically a simple bevel gear differential . 
 The pinion "G" is mounted on a short axle or stud "F" which is 
 carried by a differential housing "E. " This housing is driven by the 
 rear axle drive in this case, bevel gears " C " and " B " being employed. 
 When the gear wheel "C" turns in the direction shown the differential 
 housing turns with it, carrying the stud "F" and pinion "G" in just 
 the same way as when the shaft "F" was pulled over by hand. Any 
 difference in the rotation of the rear wheels is compensated for by the 
 rotation of the differential pinion "G" on the stud "F" while re- 
 volving bodily about the axis "X-Y." If the pinion "G" rotates, it 
 must roll on one of the differential gears "H" or "H-l" and the 
 amount of motion in rolling on the one gear is transmitted to the 
 other as an additional turning or driving effort. Any retarded 
 motion of one wheel results in an accelerated motion of the other. 
 The rotation of the engine is thus transmitted to the rear wheels in 
 proportion to the distance each wheel travels. 
 
 In Fig. 236 only one pinion is shown and the differential housing is 
 merely a frame bolted to the main driving gear. In actual differentials 
 several pinions are employed and the differential housing usually 
 partially encloses the differential gears. There are three general 
 types of differential gears employed on modern motor vehicles. These 
 are the bevel gear, the spur gear, and the worm gear types of differen- 
 tials. 
 
 Fig. 237 Ford Differential 
 
 Fig. 237 shows a typical bevel gear differential. Both the differen- 
 tial gears and driving gears are clearly shown. The differential 
 
266 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 housing can be seen attached to the main driving gear and carrying 
 the differential pinions. 
 
 The objection to the bevel gear differential is, that whichever 
 wheel offers the least resistance is turned the fastest causing a loss of 
 traction. If one wheel gets in the mud or loose dirt or sand, the 
 wheel on solid ground will not be driven while the other spins around 
 due to the differential action. 
 
 The bevel gear differential was the 
 first type developed, but the spur gear 
 differential will be found on many 
 modern cars. Fig. 238 shows a spur 
 gear type of differential. The axle gears 
 are spur gears instead of bevel gears 
 and the bevel pinion is replaced by two 
 spur pinions meshing with each other 
 at their inner ends. Their outer ends 
 mesh with and drive the spur gears on 
 the axles, the pinions revolving on the 
 studs carried by the differential housing 
 which is driven by rear axle driving 
 gears as before. The pinions in this 
 case revolve parallel to the axle instead 
 of at right angles to it as in the bevel 
 gear type. 
 
 Fig. 23SSpur Gear 
 Differential 
 
 If the pinions were long enough to mesh with both the axle gears 
 and not with each other, driving the differential housing would cause 
 them to roll on the axle gears all rotating on their studs in the same 
 direction the axle gears remaining stationary. By meshing them 
 with each other they cannot revolve in the same direction for when 
 two gears are in mesh they must revolve in opposite directions. This 
 prevents the pinions from rolling around on the axle gears when the 
 housing is revolved and as long as there is equal resistance on both the 
 wheels they will not revolve on their studs, but will act as a lock or 
 clutch between the two axle gears carrying them around with the 
 housing as in the bevel gear type and having the same disadvantages. 
 
 If the machine is turning a corner the greater distance traveled 
 by the outside wheel will cause the pinions to revolve on their studs 
 permitting one differential gear to turn faster than the other. This is 
 identically the same action as is obtained by the use of bevel gears. 
 
 Fig. 239 shows the worm gear differential which is used on the Nash 
 Quad Trucks. This differential is made with two pinions "C" 
 mounted in the differential housing "H" which is rotated by the 
 driving gears. The two crown wheels "A" and "A-l" are attached 
 
DIFFERENTIALS 
 
 267 
 
 to the shafts driving the wheels. Between the crown wheels "A" 
 and the pinion " C " the worm gears " B " are interposed. The worms 
 "B" are mounted with their axles at right angles to those of the 
 pinion "C." When housing "H" is revolved it will carry with it 
 
 H 
 
 Fig. 239 M. and S. Differential 
 
 the pinion " C " and worm gears " B. " If the car is traveling straight 
 ahead these gears will not revolve on their own axes and the movement 
 of "A" and " A-l " will be the same. Assuming that gear "A-l" was 
 held stationary, worm gear "B" would roll on it. The worm gear 
 "B" in turn would drive pinion "C," but this is not possible since 
 pinion "C" cannot drive the other worm gear "B" which is in mesh 
 with crown wheel "A." If the pitch is less than 45 degrees a pinion 
 cannot turn a worm gear but the worm can turn the pinion. This is 
 the principle upon which this differential is constructed As explained, 
 if one wheel is stationary and the other free, the differential action 
 would be locked and the free wheel would not spin. When turning a 
 corner the action is as follows : "A-l" or " A " being driven at a greater 
 
268 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 speed than the other permits the gear "B " which is in mesh with it to 
 roll on its surface. The one traveling faster will cause the gear " B " in 
 mesh with it to turn on its axis, this movement being adjusted by the 
 pinion gear "C." From this it is seen that a differential of this con- 
 struction is desirable. In case the car is ditched, the wheel which is 
 free will not have all the turning transmitted to it thus making it 
 possible to pull out. 
 
 Fig. 240 Differential Lock 
 
 When bevel or spur differentials are employed a differential 
 locking system is used. Fig. 240 shows diagrammatically the differ- 
 ential lock used on the F. W. D. trucks. A dog is shifted on the 
 axle shaft so that it engages or locks with the differential housing. 
 This prevents the differential pinions from turning and the whole 
 system of gears turns as a unit. In this way the two drive shafts 
 revolve equally causing both front and rear wheels to be driven. 
 
 When both the front and rear wheels are driven a differential 
 must be placed on the front axle as well as the rear. When a four- 
 wheel drive truck is steered by turning both the front and rear wheels, 
 as is done on the Nash Quad Trucks, both front and rear inside wheels 
 will travel the same distance in turning a corner as will both front and 
 rear outside wheels. This is because the rear wheels follow in the 
 tracks of the front wheels. 
 
DIFFERENTIALS 269 
 
 When only the front wheels are steered on a four-wheel drive 
 truck such as the F. W. D. the front and rear wheels do not track 
 when turning, the rear wheels cutting the corner. Therefore the 
 drive shaft driving the front wheels must turn at a greater speed 
 than that driving the rear wheels which necessitates a third differen- 
 tial being placed between them. This is usually enclosed in a housing 
 bolted to the transmission and driven by a chain from the main 
 transmission shaft. A typical construction of this kind is shown in 
 Fig. 222. 
 
CHAPTER XXVI 
 
 RUNNING GEAR 
 
 The parts of a motor vehicle not included in developing and 
 transmitting power are classified under the general heading of run- 
 ning gear. This includes such parts as frames, springs, axles, wheels, 
 brakes, steering gear, etc. 
 
 FRAMES ] 
 
 The frame is the skeleton of the motor vehicle to which all other 
 parts are directly or indirectly attached. Most frames manufac- 
 tured for trucks and cars employ pressed steel side members which 
 are of channel section. The cross members and side members are 
 riveted in order to make tight joints and reinforcing plates are used 
 to secure additional stiffness. Such parts as spring hangers are 
 riveted to the frame. The side members are built with sufficient 
 depth at the center to carry the load between the axles without 
 bending and in some cases truss rods are used on cars or heavy trucks 
 having long wheel bases. Since there is a tendency to bend the 
 frame at the center the top part of the channel members will be under 
 compression. For this reason holes must not be drilled in the top 
 part of frames since these would weaken the members at the point of 
 greatest stress, often resulting in sagging or complete buckling. 
 
 In addition to the cross members bracing the frame they often 
 support a sub-frame to which the engine and sometimes the trans- 
 mission are bolted. This gives the necessary flexibility of support 
 for these units reducing the distortion due to uneven roads to a 
 minimum. Sub-frames are not necessary when unit power plants 
 are used supported by the main frame at three points. 
 
 SPRINGS 
 
 The frame is attached to the axles by springs which reduce the 
 road shock transmitted to the axles by the wheels thus protecting 
 the units supported directly by the frame. It is necessary that the 
 springs be both strong and resilient and for this reason the built up 
 or laminated leaf spring is universally used on motor-propelled 
 vehicles. 
 
 270 
 
RUNNING GEAR 
 
 271 
 
 The action of the spring leaves may be compared to a deck of 
 cards. When held at the center and the ends bent up the cards slip 
 on each other. The outer cards slip the most since they must con- 
 form to a curve of greater circumference than the inner ones. When 
 the pressure on the ends of the deck is released the cards spring back 
 to their original position. If a solid piece of card-board of the same 
 size as the deck were used bending would cause it to buckle, since its 
 layers could not slip on each other. Therefore, the flexibility of a 
 spring depends upon the number of leaves composing it and when 
 pressure is applied at its ends the leaves slip on each other to conform 
 to the changed radius of curvature. For this reason some lubricant 
 must be placed between the spring leaves. 
 
 Fig. 241 Semi-Elliptical Spring 
 
 The semi-elliptical spring (Fig. 241) is clamped at its center "A" 
 to the axle by a spring saddle clip. One end of the spring is generally 
 bolted to the frame as at "B" while the other end is attached by 
 means of a spring shackle which allows it to move sufficiently to 
 compensate for the elongation of the spring when compressed. 
 
 Fig. 242 Three-Quarter Elliptical Spring 
 
 The three-quarter elliptical spring (Fig. 242) is clamped to the 
 axle in the usual manner at "A." One end is bolted to the frame at 
 
272 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 "C" the other being rigidly held by spring saddle clips to the frame 
 "D." A spring shackle bolt "B" holds the two members of 
 
 the spring together allowing 
 enough movement to com- 
 pensate for the elongation of 
 the main leaves when the 
 spring is compressed. 
 
 The full elliptical spring 
 (Fig. 243) is attached rigidly 
 to both the axle and frame at 
 points "A" in the usual man- 
 ner. Spring shackles are not 
 necessary since both top and 
 
 Fig. 243 Full Elliptical Spring 
 
 bottom members will elongate 
 the same amount when com- 
 pressed. This type of spring is little used on automobiles because 
 the springs cannot be used to transmit the driving effort to the 
 frame due to their method of attachment. 
 
 Fig. 244 Platform Springs 
 
 The platform spring construction (Fig. 244) is a combination of 
 three semi-elliptical springs arranged as shown and used for attaching 
 the frame to the rear axle only. The front ends of the two lower 
 springs are bolted to the frame as at "C" their rear ends being 
 attached to the third spring by the double shackles or ball and socket 
 connections "B." This spring is rigidly fastened to the frame at 
 the center of the rear cross member "E." 
 
 Fig. 245 Cantilever Spring 
 
RUNNING GEAR 
 
 273 
 
 Fig. 245 shows a cantilever type of spring. It does not differ 
 much from the semi-elliptical spring in construction being built up 
 in the same way, but made flatter and heavier. However, it is 
 attached quite differently since the front end "A" is free to move in 
 a shackle "B" bolted to the frame. A saddle "E" is clipped about 
 the spring at or near its center and is pivoted on the pin "F" attached 
 to the frame. The rear end "G" is fastened to the axle "H" by a 
 shackle allowing free movement of the spring or it may be attached 
 rigidly at this point. The action of this spring is similar to a spring- 
 board and when running over rough roads permits the axle "H" 
 to oscillate up and down. 
 
 AXLES 
 
 The springs are attached to the axles which support the weight 
 of the car. There are two types of axle construction, the dead axle 
 which remains stationary and the live axle which revolves driving 
 the wheels. 
 
 Dead axles are used for front axles on two- wheel drive machines and 
 for rear axles when the final drive is by chain and for front and rear 
 when internal gear drive to the wheels is used as on the Nash Trucks. 
 
 Spring Pad 
 
 Drag Link Ar 
 
 TOP VIEW 
 
 .Tie Bar 
 
 Wheel Hub 
 
 Steering: Arm 
 
 "If 
 
 .Steering: Knuckle 
 
 tteel Forging 1 ** 
 
 SIDE VIEW 
 
 teering Knuckle 
 
 Wheel Hub \\ Steering Arm Spring Seat 
 
 Steel Tube 
 Tie Bar 
 
 .Steering Knuckle Spring Seat 
 
 Spring Seat Axle 
 
 / ^ 5n 
 
 Fig. 246 Front Axles 
 
274 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 246 shows typical front axles. Dead axles may be tubular 
 (B) or "I beam" (A) section, the latter being a very common con- 
 struction for front axles. "I beam" axles are generally drop-forged 
 from a single piece of steel, spring seats being an integral part as 
 shown. 
 
 Live axles are always split into two parts each of which is driven 
 by one of the differential gears. A housing completely encloses axles 
 and gears protecting them from water, dust, and injury. There are 
 three types of live axles; the full floating, the three-quarter floating, 
 and the semi-floating. 
 
 Fig. 247 Full Floating Axle 
 
 Fig. 247 shows the construction of a full floating live axle. The 
 wheel "M" is supported by two bearings "B" running directly 
 upon the axle housing "A." The axle shaft "E" is fastened to the 
 wheel hub flange "N" by means of the coupling "K" through which 
 the rotary motion of the axle shaft is transmitted to the wheel. The 
 axle shaft may be removed from the housing without disturbing the 
 wheel by removing the coupling "K." 
 
 The axle shaft "E" is not supported at either end by bearings 
 and its position is maintained by the way it is attached at both ends. 
 
RUNNING GEAR 
 
 275 
 
 Thus the only strain on the axle shaft'is that of driving the wheels 
 and for this reason it is known as a full floating axle. 
 
 Fig. 248 shows a three-quarter floating construction of live axle. 
 The wheel "M" is supported by the single bearing "B" which runs 
 on the axle housing "A." The axle shaft "E" is rigidly keyed to 
 
 Fig. 248 Three-Quarter Axle 
 
 the hub "N" thus maintaining the alignment of the wheel. This 
 prevents the axle shaft from being removed without first removing 
 the wheel. As in the full floating type the axle shaft is not sup- 
 ported by bearings at either end but differs in the type of bearings 
 employed and method of attachment to the wheels. For this reason 
 it is called a three-quarter floating axle. 
 
 Fig. 249 shows a semi-floating construction of live axle. The inner 
 end of axle shaft "D" is sometimes fixed to the differential gear or 
 else prevented from moving endwise by a collar on the axle shaft. 
 The hub "K" of the wheel "M" is keyed to the outer end "H" of 
 the axle shaft as in the three-quarter floating type. The axle housing 
 "A" supports a bearing "B" which is placed inside its outer end. 
 Both the wheel and bearing "B" must be removed in order to with- 
 draw the axle shaft. This arrangement results in the axle shaft "E" 
 supporting the weight of the machine in addition to transmitting 
 rotation to the wheels. For this reason it is called a semi-floating axle. 
 
276 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 249 Semi-Floating Axle 
 
 WHEELS 
 
 Wooden automobile wheels are nearly always of the artillery 
 type, that is, the spokes at the hub are tapered so they wedge to- 
 gether in a solid mass which gives great 
 strength. These wheels are made of second 
 growth hickory and flanges are bolted to both 
 sides of the wheel hub (Fig. 250) for reinforce- 
 ment. 
 
 The great advantage of the wooden wheel is 
 that it has a certain amount of natural spring 
 which absorbs some of the road shock. Wooden 
 wheels are light but strong and can sustain 
 heavy loads. However, they often break when 
 side thrust is transmitted to them such as 
 occasioned by the machine skidding around a 
 corner. To make the wheels stronger, particu- 
 larly their resistance to side thrust, they are 
 generally dished. This is accomplished by 
 the spokes at a slight angle with the 
 
 pi 250 Artillery 
 
 Wood Wheel axle which results in the plane of the rim 
 
RUNNING GEAR 
 
 277 
 
 being outside the plane of the hub. Greater resiliency is also obtained 
 in this way since the road shocks are not transmitted radially to the 
 hub as would be the case with the ordinary construction. Wooden 
 wheels are affected by dampness and must be kept well painted. 
 
 On heavy trucks, cast steel wheels are used in which the spokes, 
 hubs, and rim are all cast in one piece their form being very similar to 
 the artillery wood wheel. These wheels are very strong but have the 
 objection of being heavier for the additional strength obtained. 
 
 Steel wheels may also be constructed without spokes, a solid disc 
 of metal joining the rim and hub. These wheels are made of both 
 cast steel and pressed steel. 
 
 In order to [obtain light 
 weight without sacrificing 
 strength, wire wheels were 
 adopted of a construction some- 
 what similar to those used on 
 bicycles (Fig. 251). The load is 
 not carried by the spokes under 
 compression as in the wooden 
 wheel, but by those under tension, 
 all the spokes between the hub 
 and the top of the rim carrying 
 the load. These wheels are very 
 flexible and absorb a great deal 
 of the road shock. Side 'thrust 
 
 Fig. 251 Wire Wheel 
 
 is taken up in this type of wheel by the staggard arrangement of 
 the spokes. 
 
 BRAKES 
 
 Brakes and their operating mechanism are very important parts 
 of a motor vehicle. They may be classified under two general head- 
 ings, the external contracting and the internal expanding. A and B 
 (Fig. 252), show typical constructions of internal 'expanding brakes. 
 C and D show typical constructions of external contracting brakes. 
 
 In the internal expanding brake, shown at A, the shoes faced with 
 friction material are hinged at a common point as shown^ their free 
 ends being attached to a lever arm by toggle linkage. When the 
 lever is moved to the left the shoes are forced outward against the 
 brake drum. Another construction is shown at B which employs a 
 cam to separate the free ends of the shoes. In actual construction, 
 springs (not shown) are used to disengage the shoes when the pressure 
 on the lever is released. 
 
278 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 252 Types of Brakes 
 
 In the external contracting type shown at C, the brake band lined 
 with friction material is attached to a double bell crank lever so that 
 when pulled to the left the band is contracted on the braked rum. 
 Another method of controlling the contraction of the brake band is 
 shown at D. In this construction, an adjustment is provided to 
 compensate for wear on the friction material. In actual construction, 
 springs are used to hold the brake band away from the drum and 
 prevent it from dragging when released. The brake drums may be 
 either attached to the wheels or to the drive shaft. 
 
 Fig. 253 shows a typical construction of shaft brake usecTon the 
 F. W. D. Trucks. When a brake is placed on the drive shaft, the 
 breaking effect is transmitted equally to the wheels through the power 
 transmission units. However, such a brake does not overcome the 
 differential action and skidding may result. 
 
 When the drums are on the wheels the same drum is used for both 
 external and internal brakes, the usual arrangement being to use the 
 contracting brake for service and the expanding brake for emergency. 
 Fig. 254 shows this arrangement. Two internal brakes are sometimes 
 used eliminating the contracting brake, because of the protection from 
 ust and water thus obtained. 
 
RUNNING GEAR 
 
 Fig. 253 Shaft Brake 
 
 Some method of equalizing the pull transmitted from the brake 
 pedal or lever to the brake drums on the wheels is necessary, since an 
 unequal braking on the wheels will cause the machine to skid. This is 
 accomplished by the use of brake equalizers. 
 
 Fig. 254 Typical Wheel Brake 
 
280 MOTOR VEHICLES AND THEIR ENGINES 
 
 Fig. 255 shows a typical arrangement of brake rods and equalizers. 
 The foot pedal controls the external contracting brakes and the emer- 
 gency lever, the internal expanding brakes. When the foot pedal is 
 depressed, rod "H" is pulled forward causing the shaft "X" to turn 
 pulling equally on the rods "L" and "K" which control the brake 
 levers "E." If one brake is worn more than another, the breaking 
 will not be equal unless compensated for by adjusting the brake shoes 
 or by using a shorter rod between "X" and "E." The latter is ac- 
 complished by screwing the yoke at " E " further up on the rod. The 
 operation of the equalizer on the emergency brakes is identical. 
 
 The troubles which are usually experienced with brakes are; un- 
 equal braking, grabbing (usually on one brake), dragging, and slipping. 
 
 Fig. 255 Brake Rods and Equalizers 
 
 To overcome unequal braking, the brake equalizers may be ad- 
 justed as just explained or the brakes adjusted at the drum. 
 
 Grabbing may be the result of the condition 'of the friction sur- 
 faces. This trouble is more apt to be experienced with external 
 brakes because of their exposed position. It can usually be over- 
 come by thoroughly cleaning and treating the friction material, the 
 treatment depending upon the kind of material used. When one 
 brake grabs it nearly always results from one equalizer rod being too 
 short or the opposite rod being too long. 
 
 Dragging brakes may result from the springs on the brakes not 
 completely disengaging the brake bands or shoes when released, but 
 
RUNNING GEAR 281 
 
 it is more often the result of improper adjustment of the brake levers. 
 In adjusting the equalizers care should be exercised not to take up the 
 loose side, when loosening on the tight side would give the proper 
 movement of the foot pedal. It is possible to shorten the equalizer 
 rods so much that the foot pedal or lever will be in its disengaged posi- 
 tion when the brakes are still engaged. The same thing results when 
 the rods "R" or "H" (Fig. 256) are shortened too much. If both 
 brakes drag equally, the rods "R" or "H" should be lengthened. 
 
 Slipping often results from grease or oil getting on the friction 
 material. It can be remedied by thoroughly washing with gasoline 
 or kerosene. Worn out brake linings will cause the brakes to slip and 
 should be relined before worn completely through. If the equalizer 
 rods or brake rods "R" or "H" are too long, slipping will result when 
 the pedal or lever is applied since sufficient tension will not be put on 
 the brake levers "D" or "P." The rods "H" and "R" should be 
 short enough so that the brakes are tightened on the drums before 
 the pedal is completely depressed or the lever pulled all the way back. 
 
 Stop screws are sometimes provided as shown at "0" and "E" 
 (Fig. 255) to limit the motion of the brake arms. When making ad- 
 justments the setting of these screws must be correspondingly changed. 
 
 STEERING GEAR 
 
 In order to change the direction of motion of a motor vehicle, the 
 position of the steering wheels must be altered. These are usually the 
 front wheels although some machines are steered by turning both the 
 front and rear wheels. In a horse-drawn vehicle the front and rear 
 axles are parallel to each other when it is moving straight ahead and 
 and the front and rear wheels are in alignment. When turning the 
 front axle is swung out of parallel with the rear axle, pivoting at a 
 point mid-way between the front wheels. This requires a movable 
 front axle with but a single point of support for the front end of the 
 vehicle and such a construction would be impracticable for a motor 
 vehicle. The great weight supported by the front axle prohibits its 
 movement and an unstable condition would exist if the front axle were 
 moved out of parallel with the rear axle. In order for the wheels to be 
 moved while the axle is held rigid, each wheel is separately pivoted at 
 either end of the axle. These pivoted ends are called the knuckles 
 and are connected by a tie rod so that both wheels move together. 
 
 For a wheel to follow a curved path without slipping it must at 
 all times be tangent to this path and perpendicular to the radius of 
 curvature. Fig. 256 shows the paths of the front and rear wheels of 
 both a horse-drawn vehicle and a motor vehicle when changing di- 
 
282 MOTOR VEHICLES AND THEIR ENGINES 
 
 rection. The front wheels of the horse-drawn vehicle remain parallel 
 at all times since they are perpendicular to a common radius. The 
 intersection of a line passing through the front axle with one passing 
 through the rear axle locates the point about which the vehicle is 
 turning. In the case of the motor vehicle, however, the front wheels 
 are not parallel when changing direction, since they are perpendicular 
 to two different radii which both intersect a line passing through the 
 rear axle at the point about which the vehicle is turning. The front 
 wheels in this case are parallel with each other only when the steering 
 knuckle spindles are in line with the stationary axle which will be 
 when the vehicle is moving straight ahead. 
 
 Fig. 256 Steering Arrangements Compared 
 
 If the steering knuckle arms projected at right angles to the axle, 
 the tie rod would cause both wheels to move through the same angle 
 and be parallel at all times. This is prevented by inclining the 
 knuckle arms toward each other so that their center lines intersect at 
 the center of the rear axle. In this way the inside wheel will be 
 turned more than the outside one when changing direction. 
 
 Fig. 257 shows a conventional arrangement of the parts composing 
 the steering apparatus. The steering wheel "K" is fixed to the post 
 "H" which is generally encased. The gear "G" is attached to the 
 post "H" and meshes with the gear "L" which is keyed to a short 
 1 shaft the other end of which is square and carries a lever or pitman 
 arm "F." The arm "F" is connected by a drag link "E" to one of 
 the arms "C" of the steering knuckle "B." The two steering 
 knuckle arms "C" are connected by the tie rod "D" transmitting 
 the turning motion to both knuckles. Each knuckle is pivoted on a 
 king bolt which holds it in place on the axle forming a bearing about 
 which it turns. The wheels are carried by the steering knuekle 
 spindles "R" forged integral with the knuckle. 
 
RUNNING GEAR 
 
 283 
 
 To make steering easier, both the plane of the wheel and the axis 
 about which the steering knuckle turns are inclined toward each 
 
 Fig. 257 Steering Apparatus 
 
 other. This is called CAMBER (Fig. 258) . If a line passing through 
 the axis of the king bolt strikes the ground at the point where the 
 wheel rests, the wheel is pivoted so as to turn about its point of con- 
 tact with the ground and consequently turns easily. However, the 
 amount of inclination is never 
 this great, usually being just 
 enough to make the spokes of 
 dished wheels vertical. Hence 
 this pivot point generally falls 
 outside the wheel's point of 
 contact with the ground . CAST- 
 ER EFFECT is obtained by 
 canting the axle so that the 
 bottom of the king bolt is ap- 
 proximately Y% of an inch ahead 
 of the top where the car is level. 
 This tends to keep the steering 
 wheels straight in the direction 
 the machine is traveling. The resistance of the road to the motion 
 of the machine tends to spread the front edges of the wheels apart. 
 For this reason the front wheels are GATHERED slightly the 
 distance between the front edges being somewhat less than that be- 
 tween their rear edges. 
 
 Fig. 258 Camber 
 
284 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 There are two types of steering gear, the reversible and the ir- 
 reversible. The former transmits road shocks back through the 
 steering gear causing the steering wheel to turn. The latter will not 
 transmit road shocks through the steering gear, the steering wheel 
 remaining steady. The type of steering apparatus will depend upon 
 whether or not the gear keyed to the steering arm can turn the gear 
 keyed to the steering post; and when worm gears of proper pitch are 
 used this is not possible, an irreversible gear resulting. A reversible 
 gear results when bevel gears are used while the nut and screw con- 
 struction may be either reversible or irreversible, depending upon the 
 pitch of the screw. 
 
 To absorb the road shock especially when the irreversible type of 
 steering gear is used, the ends of the drag link are enlarged and carry a 
 spring thrust device. Within certain limits, movements of the steer- 
 ing wheel will cause compression of these springs preventing undue 
 pressures being exerted on the steering knuckle arms or the pitman 
 arm. The tension on these springs is adj ustable and they are generally 
 packed with grease and enclosed in a leather boot. 
 
 Fig. 259 Irreversible Sleering Gear 
 
 Fig. 259 shows a typical irreversible steering gear which is em- 
 ployed on the Dodge Car. 
 
 BEARINGS 
 
 A bearing is necessary when one moving part of a machine turns 
 on another. Energy is required to overcome the friction between 
 
RUNNING GEAR 
 
 285 
 
 moving surfaces in contact and depends upon the total area and the 
 materials composing these surfaces. In the motor propelled vehicle 
 it is important that the power generated by the engine should be 
 delivered to the traction members with as little loss as possible. For 
 this reason all engine bearings and those used in the various units of 
 the power transmission system are designed to reduce the frictional 
 loss to a minimum. There are three kinds of bearings in common use; 
 plain, roller, and ball. 
 
 Plain bearings are almost universally used throughout the engine 
 though they consume considerably more energy than the other types. 
 However, they are necessary in order to obtain sufficient bearing 
 surface to carry the heavy thrust resulting from the power impulses in 
 the cylinders. The usual construction is to finish and polish the shaft 
 or pin to a mirror-like surface*, the surface against which it bears 
 being of babbit or other low friction metal. Since there is considerable 
 friction surface very good lubrication is necessary and special pro- 
 visions such as oil grooves must be made to obtain the best lubrica- 
 tion possible. Plain bearings are also found on all parts of the 
 machine where a loss of energy due to friction does not make any 
 difference, such as on brake pedals, gear shift levers, spring bolts, etc. 
 
 Roller and ball bearings are used throughout the power transmis- 
 sion system, the former being used when the load is heavy or the end 
 thrust is great and the latter where the load on the bearing is uniform 
 and not heavy. 
 
 \Coi7f. 
 
 Fig. 260 Anti-Friction Bearings 
 
 Fig. 260 shows some commercial construction of ball and roller 
 bearings. The ball bearing at A is a cup and cone design. This 
 bearing has an angular contact and is capable of taking radial and 
 light thrust loads. Such bearings are adjustable to a slight degree, 
 
286 MOTOR VEHICLES AND THEIR ENGINES 
 
 as lost motion may be eliminated by forcing the cup or cone into more 
 intimate contact with the balls. The ball bearing shown at B is of the 
 annular type and is adapted only for radial loads and very light end 
 thrust and is not adjustable. Since there is only a point contact in 
 ball bearings, friction is a minimum requiring light oil and infrequent 
 lubrication. 
 
 The roller bearing shown at C is provided with straight rollers and 
 can take only radial loads. That shown at D employs tapered race 
 members and correspondingly tapered rollers. Bearings of this type 
 will carry not only radial loads but also resist end thrust. This bear- 
 ing is adjustable for wear by moving one of the race members into 
 closer contact with the rollers. Roller bearings, having a line con- 
 tact, are stronger than ball bearings but absorb more power because 
 of the increased surfaces in con- 
 tact. Therefore heavier oil 
 and more lubrication is neces- 
 sary than with ball bearings. 
 
 Fig. 261 shows a typical 
 installation of conical roller 
 bearings on the front wheels 
 and knuckles of a modern 
 automobile. With this arrange- 
 ment both the radial and Fig. 261 Roller-Bearing Installation 
 thrust loads are carried. 
 
 Roller bearings are either solid or constructed as shown in Fig. 263. 
 These rollers are constructed by rolling strips of steel into helices and 
 are arranged in the bearing so that right and left helices alternate. 
 This type gives increased flexibility reducing the transmitted strain 
 resulting from sudden shock. In addition the arrangement of the 
 helices is such as to keep the lubricant in continuous circulation over 
 the entire bearing surface. 
 
 To space the balls or rollers in a bearing, cages or separators are 
 used and are so constructed as to present the minimum amount of 
 surface to the moving parts. These cages are usually made as light 
 as possible and of soft material, such as brass. 
 
 MUFFLERS 
 
 Mufflers are used on motor vehicles to reduce the noise of the es- 
 caping exhaust gases. This noise results from the sudden expansion 
 of the gases when the exhaust valves are opened. It is not difficult to 
 muffle the gases so that there will be but little noise, yet it is quite a 
 problem to do it without producing back pressure in the muffling 
 
RUNNING GEAR 
 
 287 
 
 Jnlct 
 
 Inlet 
 
 I 
 
 Fig. 262 Typical Mufflers 
 
288 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 device that will cause considerable loss of power. A muffler should 
 offer minimum resistance to the passage of the gas and means should 
 be provided for not only breaking the entering stream into smaller 
 streams but the capacity of the muffler should be sufficiently large to 
 
 STEEL SLEEVE 
 
 Fig. 263 Hyatt Bearings 
 
 permit the gases to expand to nearly atmospheric pressure before they 
 are discharged into the ay\ As the gas is delayed in its passage through 
 the muffler from the cylinders to the open air its temperature is 
 reduced, thus decreasing its expansion. Fig. 262 shows several com- 
 mercial designs of mufflers, all built on the same principle, but dif- 
 fering somewhat in construction. 
 
CHAPTER XXVII 
 
 TIRES AND RIMS 
 
 The wheels of motor vehicles are almost without exception pro- 
 vided with rubber tires. If the wheels were not properly tired the 
 vibration transmitted to the machinery would soon cause it to shake 
 itself to pieces. The great weight and speed of motor vehicles and 
 the delicate construction of their machinery require additional 
 protection to that afforded by the springs alone. 
 
 There are two types of tires in general use at the present time. 
 These are the solid tire and the pneumatic tire. The former consists 
 of a solid band of rubber, the resiliency or spring of the material itself 
 being depended upon to absorb the road shock. This type of tire 
 is used on trucks and other heavy motor vehicles where the speed is 
 comparatively low. On lighter cars of higher speed solid tires would 
 not be suitable since they would not absorb sufficient vibration. For 
 this reason pneumatic tires are used. With the pneumatic tire not 
 only the resiliency of the rubber but also that of the air with which it 
 is inflated absorbs road shocks which would otherwise be transmitted 
 to the machine. This is because a pneumatic tire is compressed 
 when it strikes an obstacle in the road while a solid tire is only 
 distorted. 
 
 The pneumatic tire in general use is of the double tube construc- 
 tion, being composed of two members, the inner tube and the shoe 
 or casing. The inner tube is utilized to retain the air and is made of 
 pure Para rubber approximately one-sixteenth of an inch in thickness. 
 Such a tube would not be sufficiently strong to run directly on the 
 road surface, necessitating the use of an outside casing of sufficient 
 strength and wearing qualities to protect the inner tube. The casing 
 is provided with some means of attachment to the rim so that when 
 an inner tube is placed in it and inflated the casing will be held 
 firmly in place. 
 
 Fig. 264 shows a cross-section of a pneumatic tire. The main 
 portion of the outer casing is composed of alternate layers of Sea 
 Island cotton fabric and high-grade rubber composition. This 
 composition is forced into the meshes of the cloth so that when 
 vulcanized all the layers of fabric will be intimately joined together. 
 The fabric body is the part of the casing that gives it its strength, 
 the number of layers of fabric used depending upon the size of the 
 tire. Outside of the fabric body is placed a layer of very resilient 
 
 289 
 
290 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Bead 
 
 Breaker Strips 
 
 abricBodj 
 
 Km Channel 
 
 Fig. 264 Cross-Section of Pneumatic Tire 
 
 Para rubber called the padding, which is thickest at the center of 
 the tread and tapers off on either side as shown. The purpose of the 
 padding is to give a certain amount of elasticity to the casing. On 
 top of the padding and extending slightly beyond the center of the 
 tread are placed several pieces of heavy fabric called breaker strips 
 which offer resistance to any sharp object which penetrates the tread, 
 tending to deflect it to one side, thus protecting the padding and 
 fabric body. The outside surface is called the tread and is that part 
 of the tire which is subjected to the greatest wear since it is in con- 
 tact with the road surface. It must resist the abrasive action of the 
 road and when used on driving wheels it suffers additional wear due 
 to the tractive effort producing friction between the wheels and the 
 ground. For this reason the tread must be of very tough rubber 
 composition and differs from the material used for the padding and 
 inner tube in not possessing so great a degree of elasticity. This 
 is sacrificed in favor of great strength and resistance to wear which, 
 of course, is essential. 
 
 |There are two processes of building tires used by modern tire 
 manufacturers. The first of these is known as the " moulded process " 
 
TIRES AND RIMS 291 
 
 where the tire is built up on a core and then clamped in a mould and 
 vulcanized by steam. The other is known as the " wrapped tread 
 process " where the tire is built up on a core as before and then tightly 
 wrapped with strips of canvas and vulcanized. 
 
 Another construction of pneumatic tire is the cord tire. It does 
 not differ materially in the way in which it is built up and vulcanized, 
 but instead of layers of fabric being used the fabric body is composed 
 of layers of cord, rubber composition being used as before. When 
 the tire is vulcanized the layers of cord become filled with rubber and 
 the whole mass is bound firmly together. Owing to its construction 
 the cord tire cannot be as easily repaired as the fabric tire and it 
 requires expert workmanship to repair a portion of a cord tire injured 
 by a blow-out. Tires of this construction are much more resilient 
 and give greater mileage than the stiffer fabric tire making them 
 more desirable. There is also a cord-fabric tire in which the layers 
 of cord composing the fabric body are replaced by layers of fine cord 
 woven into a fabric. These tires are almost as flexible as the original 
 cord tire but are much easier to repair. 
 
 Regular Clincher Type A Straight Side Type 
 
 Fig. 265 Types of Casings 
 
 Two types of casings are supplied differing in their method of 
 attachment to the rim. They are the clincher and the straight side 
 or Dunlop types. At A (Fig. 265) is shown a clincher casing. The 
 fabric is looped about a triangular insert of leather running along the 
 edges of the tire and forming a bead. It is this bead which grips the 
 flanges of the rim when the tire is inflated. This bead is either hard 
 or soft, depending upon whether the tire is to be used on Q. D. or 
 straight clincher rims. At B (Fig. 265) is shown a straight side cas- 
 ing. No bead is provided in this case the fabric being looped about 
 strands of piano wire running around the inner edges of the tire. 
 Since the steel wire does not stretch the tire will be held snugly 
 against the rim when inflated, the rim flanges preventing it from 
 slipping off the rim sideways. 
 
292 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 Inner tubes are made from seamless rubber tubing of uniform 
 thickness the most resilient rubber obtainable being used. The 
 tubing is cut the right length (which depends upon the diameter of 
 the wheel) and the two ends are permanently joined by vulcanizing 
 them together. Motor-cycle tubes are often made with two ends 
 separately vulcanized in order to facilitate their removal from the 
 casing. The only opening into the tube is where the valve stem is 
 inserted which is an air-tight joint. 
 
 Fig. 266 Valve 
 
 Air is introduced into the inner tube through a simple automatic 
 valve (Fig. 266). The valve proper is held against its seat by a 
 light spring and will only open when the valve stem is depressed 
 by hand or when air pressure is forced against it in inflating the 
 tire. When inflating a tire the air pressure on the inside holds the 
 valve firmly in place whenever the incoming pressure is stopped. 
 The valve must be screwed in tight enough to compress the rubber 
 packing and make it swell out against the walls of the valve tube, 
 forming an air-tight joint. The lower end of the valve tube or 
 stem is inserted in the inner tube, a tight joint being obtained by 
 screwing down a nut on the rubber tube and locking it in place, 
 the joint being vulcanized and protected by a spring clamp. 
 
 The tread of the tire may be smooth or non-skid. The smooth 
 tread has the disadvantage of poor traction and liability of skidding 
 on muddy roads which has led to the development of the so-called 
 non-skid tread. Non-skid or rough treads give better traction, wear 
 longer, and to some extent prevent skidding. 
 
TIRES AND RIMS 
 
 293 
 
 Fig. 267 shows several examples of commercial non-skid treads. 
 It is customary to equip passenger cars with non-skid treads on the 
 rear wheels and plain treads on the front wheels. 
 
 ft 
 
 Fig. 267 Some Non-Skid Treads 
 
 The best preventive against skidding is the use of chains. Tire 
 chains are made up of a series of short cross chains attached to two 
 long chains, the ends of which are snapped together on the inside and 
 outside of the wheels. Fig. 268 shows the method of applying non- 
 
 Fig. 268 How Chains Are Applied 
 
 skid chains. Chains increase the traction and reduce skidding to a 
 minimum. They should be applied both to the front and rear wheels 
 to obtain the best results and should be supplied for use with both 
 solid and pneumatic tires. Chains should be applied only when it is 
 necessary to travel over roads that are very soft and muddy and 
 should be immediately removed when hard road surfaces are again 
 
294 MOTOR VEHICLES AND THEIR ENGINES 
 
 encountered. This is because the cross chains chafe the tires, causing 
 bruising of the tread and excessive wear. 
 
 There are two types of rims for pneumatic tires, the clincher arid 
 the straight side or Dunlop. The clincher rim may be plain one- 
 piece, quick detachable, or demountable. The plain clincher rim 
 is very little used except on light cars, a typical construction being 
 shown in Fig. 264. The straight side rim may be quick detachable 
 or demountable, the quick detachable type usually being convertible 
 permitting either clincher or straight side tires to be used. 
 
 Fig. 269 Rim Forms 
 
 Fig. 269 shows a quick detachable rim with the clincher rim re- 
 versed to take both types of tires. To remove the tire from a quick 
 detachable rim it is only necessary to deflate it and press in the clincher 
 ring, disengaging the locking ring, which is lifted out allowing the 
 clincher ring to be removed. This permits one whole side of the tire 
 to be pulled off the rim giving a quick and easy access to the inner 
 tube for replacement or repair. 
 
 Numerous forms of demountable rims have been devised all of 
 which are constructed along practically the same lines. The rim 
 is held in place by a series of lugs or wedges which are bolted to the 
 felloe of the wheel. By taking off the nuts holding these in place 
 the whole rim may be slipped off the wheel and another substituted. 
 The advantage of the demountable rim is that an entire spare casing, 
 inner tube, and rim may be carried inflated and ready for use. In 
 case of tire trouble on the road, tires can be quickly changed and the 
 necessary tire repairs made at the end of the trip. 
 
 Demountable rims may be either quick detachable or of split 
 construction. The former permits the removal of the casing without 
 taking the rim off the wheel while with the latter type it is necessary 
 to remove the rim before the casing can be detached. 
 
TIRES AND RIMS 
 
 295 
 
 Locking 
 Wedge 
 
 ILocin$BoJt Felloe 
 
 Fig. 270 Demountable Rim 
 
 Fig. 270 shows a quick detachable demountable rim for clincher 
 tires. The locking wedge is held in place by lugs bolted to the felloe 
 of the wheel. When the retaining lugs are removed the rim may be 
 pulled from the wheel, the side where the valve stem goes through 
 the felloe being lifted off last. 
 
 On trucks and other heavy motor vehicles, pneumatic tires are not 
 generally used because of the large size that would be required to 
 carry the load. Since their speed as a rule is limited, solid rubber 
 tires may be employed to advantage. These are moulded from some 
 special rubber composition in one continuous ring and are usually 
 provided with some form of re-enforcement at their base where they 
 are clamped into the rim. Modern truck tires are quick detachable 
 or demountable and are usually held in place with wedges or flanges 
 
 Fig. 271 Solid Tire 
 
 of similar construction to those used on pneumatic rims. Fig. 271 
 shows a typical solid rubber tire on a demountable rim. It is re- 
 enforced by a hard rubber base and clamped into place in its rim. 
 
296 MOTOR VEHICLES AND THEIR ENGINES 
 
 When the load on the rear wheels is particularly heavy, extra wide 
 tires or dual tires are employed. Their construction does not differ 
 materially from the single tire type the same method of attachment 
 being employed but they are not so apt to slip side-ways on slippery 
 
 When inserting an inner tube in a casing, care must be taken not to 
 pinch or twist it and to pull the valve stem through the rim straight. 
 The following is the procedure when applying a casing to a demounta- 
 ble, rim. Clean out the casing and be sure it is dry. Shake some 
 powdered mica or soapstone into the casing and turn it once or twice 
 around to insure its whole interior being coated and then remove what 
 remains. Insert the inner tube and apply the casing to the rim, put- 
 ting the valve stem through the hole in the rim first. Assemble the rim 
 and inflate the tire to about twenty pounds pressure. Then bounce 
 the tire up and down turning it through two or three revolutions 
 which permits the inner tube to straighten out and assume its natural 
 position, preventing pinching or twisting of the tube or the valve 
 stem being crooked. Finish .inflating the tire to the proper pressure 
 for its particular size. 
 
 The following table gives the proper pressures to which different 
 sized tires should be inflated as recommended by leading tire manu- 
 facturers: 
 
 Diameter of Tire Air Pressure in Tire 
 
 Inches Pounds per Square Inch 
 
 2J 50 
 
 3 60 
 3J 70 
 
 4 80 
 4| 90 
 
 5 90 
 5J 95 
 
 6 100 
 
 The air pressure in a tire increases when the machine is driven 
 due to the heat set up by the friction of traction. This must be taken 
 into consideration when pumping up a tire before running. It is ad- 
 visable especially on a warm day to release some of the pressure after 
 running some distance. The pressure should first be tested and for 
 this purpose a tire pressure gauge should be provided as part of the 
 equipment of every machine having pneumatic tires. 
 
 The life of the tire depends directly upon the amount of care and 
 attention that it receives. Probably no part of the machine is less 
 looked after than the tires which are generally never given a thought 
 until tire trouble results. 
 
TIRES AND RIMS 297 
 
 When returning from a run a careful inspection of the tires should 
 be made and all cuts and holes should be immediately cleaned out 
 and vulcanized. If there is any oil or grease on the tires it should be 
 cleaned off, since oil attacks the rubber causing it to deteriorate. 
 Inflate all tires fully. The dead weight of the machine should never 
 be allowed to rest on a deflated tire. Before starting out upon a run 
 the pressure in the tires should be tested and any tires not pumped 
 up to the required pressure should be inflated. Running on tires 
 which are not properly inflated, causes them to be distorted, the 
 amount of distortion depending upon the pressure in the tire. Such 
 distortion, no matter how small, causes the layers of the fabric to be- 
 come separated from each other and from the tread surface resulting 
 in the tire soon going to pieces. If the pressure is allowed to become 
 so low that the tires spread out flat on the road, rim cutting may re- 
 sult and the inner tube will probably be ruined. 
 
 Fast driving and sudden starting or stopping of the machine is 
 very hard on tires causing the tread surface to be worn where the 
 wheels slide on the ground. When a machine turns a corner it tends 
 to slide outward and if the speed is great enough the tread surface of 
 the tires will be injured. Running in street car tracks or in deep 
 ruts chafes the sides of the tires and must not be indulged in. 
 
 It is very important to have the front and rear wheels in alignment. 
 If out of line the tire treads will wear in a very short time, a difference 
 of less than an inch causing a grinding wear on the tires especially the 
 front ones. 
 
 The same size tires must be used on both pairs of wheels in order 
 to equalize the traction. A plain tread tire should never be used on 
 one rear wheel when a non-skid tire is on the other. In addition to 
 excessive wear on the tires this also causes the differential gears to be 
 unduly worn. 
 
 Inner tubes should be kept in a cool dry place away from oil, 
 gasoline, and tools. It is best to keep them in a bag well dusted with 
 soapstone. Spare casings should not be exposed to the rays of the 
 sun. When a spare tire is carried inflated it should be encased in a 
 tire cover. 
 
 TIRE TROUBLES 
 
 Probably the most common tire trouble on the road is puncture. 
 When a tire is punctured not only the hole through the inner tube but 
 also that through the casing should be repaired. The former may be 
 patched or better still vulcanized while the opening through the casing 
 may be filled with ''tire dough " temporarily and later permanently 
 vulcanized. 
 
298 MOTOR VEHICLES AND THEIR ENGINES 
 
 Blow-out is the most serious tire trouble that will be encountered 
 and can only be repaired temporarily on the road. If an extra tire is 
 not carried, repair the injured casing by inserting a new inner tube 
 and using an inside and outside boot to strengthen the point in the 
 casing where the blow-out occurred. 
 
 Small or thin cuts are often overlooked but should be immediately 
 vulcanized when noticed. This is equally important when solid tires 
 are used. A stone bruise is caused by running over the corner of a 
 brick or other hard object which tears part of the tread surface from 
 the tire. The loose rubber should be trimmed away and the hole 
 filled up and vulcanized. 
 
 Sand blisters are caused by sand or grit from the road working 
 in through overlooked punctures or cuts in the casing and collecting 
 between the tread and fabric body. They should be opened by 
 cutting in with a sharp knife and the accumulated dirt thoroughly 
 cleaned out with gasoline. The opening should then be filled and 
 vulcanized. 
 
 For making road repairs a tire repair kit should be carried con- 
 taining cement, patches, tape, un vulcanized rubber, extra parts, etc., 
 and the necessary tools. A small gasoline torch vulcanizer is a very 
 valuable addition and all repairing of inner tubes should be done by 
 vulcanizing rather than by using patches. 
 
CHAPTER XXVIII 
 
 HOW TO DRIVE 
 
 Before starting an engine the driver should see that the gear shift 
 lever is in neutral position and that the emergency brakes are set. 
 The spark lever should be set at the proper position. If battery 
 ignition is used it is best to have the lever in full retard position, as 
 the spark will occur no matter how slow the engine is cranked. If 
 magneto ignition is used the lever should be advanced slightly as 
 a hotter spark is obtained in the advanced position than in the 
 retarded. There is less probability of a kick back when starting on 
 magneto since it is necessary to turn the engine at a fairly high speed, 
 approximately 100 R. P. M., to generate sufficient current to produce 
 a spark. 
 
 The position of the throttle hand control should be set so that the 
 throttle- will be slightly open. In case the carburetor is equipped 
 with an air-choking device this should be closed to cause a rich 
 mixture for starting. 
 
 The ignition switch should be turned on and the engine cranked 
 by pulling up quickly on the crank handle a quarter turn at a time. 
 If an electric cranking motor is provided depress the starting button 
 and advance the spark. If magneto ignition is used it is best to spin 
 the engine. Crank the engine with the left hand if possible and 
 stand in such a position that if the engine should kick back the 
 crank will not cause injury. 
 
 After the engine has started release the choke on the carburetor, 
 advance the spark, and close the throttle to a position which will 
 prevent racing. If a special dash adjustment is provided for regu- 
 lating the mixture allow this to remain in a position to cause a rich 
 mixture until the engine warms up. 
 
 TO START THE CAR 
 
 Allow the engine to warm up sufficiently to overcome missing 
 and to run smoothly. When satisfied that the engine is running 
 properly release the emergency brake. In case the car is on a grade 
 apply the foot brake to prevent the car from moving. Press the 
 clutch pedal all the way down and move the gear shift lever to first 
 speed position. The clutch should be allowed to engage gradually 
 
300 MOTOR VEHICLES AND THEIR ENGINES 
 
 and at the same time the throttle should be opened sufficiently to 
 prevent stalling, but not cause racing of the engine. If the foot 
 brake has been employed it should be released as the clutch is en- 
 gaged. After the clutch has fully engaged the throttle should be 
 opened sufficiently to accelerate the car to change to the next higher 
 speed. The throttle should be controlled by the foot accelerator 
 pedal. Once the car is in motion the driver must at all times keep 
 his eyes on the road in the direction in which the car is moving or 
 about to move when changing direction. 
 
 TO SHIFT GEARS (Increasing Speed) 
 
 Before starting a driver should practice moving the gear shift 
 lever to the different positions and getting his feet and hands ac- 
 customed to the location of the foot pedals and hand levers. Then 
 it will not be necessary to look away from the road in order to shift 
 gears or in any other way to control the operation of the car. To 
 change gears the clutch pedal should be depressed (it may not be 
 necessary to push it all the way down against the floor boards) and 
 the foot removed from the accelerator pedal at the same time. Move 
 the gear shift lever from first to neutral position, pausing if neces- 
 saryi, and then move to second speed position. Engage the clutch 
 immediate!^ and open the throttle either with hand or foot control 
 as soon as the clutch is engaged. The process of changing from 
 second to third or from third to fourth is identical. Bear in mind 
 that before each change is made the speed of the car should be 
 accelerated. Care should be taken when changing from a lower to a 
 higher speed that the car is moving at a sufficient rate of speed so 
 that an undue strain will not be put on the engine. Practice alone 
 in driving the particular apparatus will acquaint the driver with the 
 necessary speed required to change from one gear ratio to another. 
 
 TO SHIFT GEARS (Decreasing Speed) 
 
 When it is desired to change from a higher to a lower gear ratio 
 release the clutch and allow the hand or foot throttle control to re- 
 main open far enough so that the engine will speed up. Move the 
 gear shift lever to the neutral position and again engage the clutch 
 for an instant. Release the clutch immediately and quickly move 
 the gear shift lever from neutral to the next lower speed position 
 and engage the clutch immediately, opening the throttle by the hand 
 or foot control. 
 
 Another method of shifting to a lower gear ratio is to leave the 
 
HOW TO DRIVE 301 
 
 throttle open and release the clutch just enough to allow it to slip 
 and the engine to speed up. The gear shift lever should then be 
 moved through neutral directly to the next lower speed position and 
 the clutch engaged. This method does not require as much practice 
 but is objectionable since it wears or burns the clutch facing. 
 
 TO STOP THE CAR 
 
 To stop the car the throttle should be closed, the clutch released, 
 and the brakes applied, all being performed at the same time. The 
 amount of pressure applied at the brake pedal depends upon the dis- 
 tance in which the driver desires to stop the car. Before allowing 
 the clutch to engage after the car has stopped, move the gear shift 
 lever to the neutral position. If the car is to stand apply the emer- 
 gency brakes. If the engine is to be stopped speed it up by opening 
 the throttle just before turning the ignition switch to the "off" 
 position. If the weather is cold use the choke when stopping the 
 engine or set dash adjustment to give a rich mixture. This will 
 make starting easier if the engine is started within a reasonable 
 length of time. 
 
 DRIVING SUGGESTIONS 
 
 In operating a car it is always best to alternate the service and 
 emergency brakes rather than to use one continuously, to equalize 
 the wear on them. When approaching a very steep down grade it 
 is safest to move the gear shift lever to a lower speed position, closing 
 the throttle and permitting the car to drive the engine. When the 
 grade is not excessively steep the engine can be used as a brake with 
 the position of the gear shift lever remaining unchanged. This will 
 save the brakes and tend to cool the engine. The brakes should 
 never be applied suddenly enough to slide the driving wheels except 
 in cases of emergency. When a stop is to be made apply the brakes 
 soon enough so that the motion of the car will be gradually di- 
 minished and brought to a stop at the point desired. 
 
 To avoid accidents on the road all rules and regulations governing 
 the driving of motor vehicles on the road should be observed. When 
 turning corners or approaching cross roads warning should be given 
 to avoid collision with other vehicles which may be hidden from the 
 view of the driver. Before backing the machine the driver should 
 be sure the road is clear. In manipulating the car the front wheels 
 should never be turned by moving the steering wheel when the car 
 is not in motion. This puts undue strain on the steering apparatus 
 
302 MOTOR VEHICLES AND THEIR ENGINES 
 
 and will cause lost motion in the steering gear. If it becomes neces- 
 sary to turn the front wheels of a car while it is standing still, they 
 should be moved by applying force not only to the steering wheel 
 but also by pulling the front wheels around. 
 
 When a car skids the tendency is for an inexperienced driver to 
 apply the brakes and turn the front wheels in the opposite direction 
 to that in which he is skidding. This should not be done as it only 
 accentuates the skidding and the car may be ditched or skid into 
 another vehicle or the curbing. When the machine starts to skid 
 turn the steering wheels in the direction in which the car is skidding 
 and partially close the throttle but not entirely, or it will have the 
 same effect as applying the brakes. When the car straightens out 
 the power may be again applied gradually and the machine brought 
 back to the center of the road. When skidding on narrow roads it 
 is best to apply the power and steer for the center of the road. This 
 will aggravate the skid for a moment but brings the machine around 
 at an angle with the front wheels in the center of the road. The 
 momentum of the car will cause the rear wheels to climb back onto 
 the road again. 
 
CHAPTER XXIX 
 
 ENGINE TROUBLES EXPERIENCED ON THE ROAD 
 
 If the engine will not start when the driver wants to take the 
 machine from the parking space it is a very difficult matter to locate 
 the trouble and it can only be located by a systematic search. It is 
 always best to look over the ignition system first, then see if there is 
 any gasoline at the carburetor. It will often take some time to find 
 the trouble. However, if the engine once starts there is no reason for 
 difficulty in locating the trouble as there will always be an indication 
 which should point to the source of the trouble. The great difficulty 
 with inexperienced drivers is that they do not reason out the matter 
 carefully before attempting to remedy it. Also an inexpereinced man 
 usually looks for all troubles in the same place no matter what the 
 indication. Nearly all the difficulties experienced with the engine 
 arise from one of three sources; ignition, carburetion, or engine. 
 These are outlined in the following table. The method of determin- 
 ing the trouble and remedy is explained at the end of the table. The 
 trouble is located by the indication it gives the driver. 
 
 I. Engine Misses : 
 
 A. Ignition. 
 
 1. Plugs. 
 
 a. Short circuited. 
 
 b. Broken porcelain. 
 
 c. Too large a gap. 
 
 2. Cable. 
 
 a. Broken. 
 
 b. Grounded. 
 
 3. Instrument. 
 
 a. Dirty distributor. 
 
 b. Interrupter points (On Magneto). 
 
 B. Carburetor. 
 
 1. Water in the carburetor. 
 
 2. Dirt in the line. 
 
 3. No pressure or no gas. 
 
 4. Too lean a mixture. 
 
 C. Engine. 
 
 1. Cold. 
 
 2. Valves sticking. 
 
 303 
 
304 MOTOR VEHICLES AND THEIR ENGINES 
 
 II. Back Fires Through the Carburetor: 
 
 A. Ignition. 
 
 1. Wired wrong. 
 
 2. Timed wrong. 
 
 B. Carburetor. 
 
 1. Water in carburetor. 
 
 2. Dirt in the line. 
 
 3. No pressure or no gas. 
 
 4. Too lean a mixture. 
 
 C. Engine. 
 
 1. Valve sticking (Inlet), 
 
 III. Engine Knocks: 
 
 A. Ignition. 
 
 1. Too far advanced. 
 
 B. Engine. 
 
 1. Carbonized cylinders (pre-ignition) 
 
 2. Overheated engine. 
 
 3. Loose bearings. 
 
 4. Loose pistons. 
 
 IV. Engine Lacks Power : 
 
 A. Ignition. 
 
 1. Retarded spark. 
 
 B. Carburetor. 
 
 1. Too rich a mixture. 
 
 C. Engine. 
 
 1. Exhaust valve not seating. 
 
 2. Carbon in cylinder. 
 
 3. Overheated engine. 
 
 4. Lack of lubrication. 
 
 5. Governor connections sticking. 
 
 D. Brakes. 
 
 1. Dragging. 
 
 E. Clutch. 
 
 1. Slipping. 
 
 V. Engine Overheats: 
 
 A. Ignition. 
 
 1. Retarded spark. 
 
 B. Carburetor. 
 
 1. Rich mixture. 
 
ENGINE TROUBLES EXPERIENCED ON THE ROAD 305 
 
 C. Engine. 
 
 1. Cooling system. 
 
 a. Fan belt off. 
 
 b. No water. 
 
 c. No circulation. 
 
 d. Anti-freezing mixture. 
 
 2. Carbonized cylinders. 
 
 3. Lack of lubrication. 
 
 VI. Engine Stops: 
 
 A. Engine and Car Stop gradually. 
 1. Trouble with fuel. 
 
 B. Engine and Car stop suddenly. 
 1. Mechanical trouble. 
 
 C. Engine stops suddenly, car gradually. 
 1. Trouble with ignition. 
 
 VII. Engine Won't Stop: 
 
 A. Ignition. 
 
 1. Cable. 
 
 2. Switch. 
 
 B. Pre-ignition. 
 
 1. Carbon in cylinders. 
 
 2. Overheated engine. 
 
 Now consider how each of these indications may differ so that it 
 is possible to locate the exact source of trouble without first investi- 
 gating. If a car has been on the road for some time and the engine 
 misses it will either miss regularly in one or more cylinders or irregu- 
 larly in all cylinders. If the former the miss is due to ignition. The 
 cylinder in which the miss is occurring can be easily determined by 
 short circuiting each plug with a screw driver. This is done by al- 
 lowing the screw driver to touch the central electrode of the plug and 
 also the engine. When a plug is short-circuited, and it does not affect 
 the operation of the engine, it shows that there was no spark jumping 
 across the electrodes of the plug. If the cable to this plug is dis- 
 connected and held a short distance from the central electrode of the 
 plug from which it was removed, a spark will or will not jump this gap. 
 If it does jump the gap it shows that the plug is short-circuited. The 
 plug is either carbonized or the insulator is broken. If a spark does 
 not occur place the cable near the engine and if a spark occurs it 
 shows that the gap was too large at the electrodes of the plug. If no 
 spark occurs it shows that the trouble is not in the plug but at some 
 
306 . MOTOR VEHICLES AND THEIR ENGINES 
 
 point ahead of this. If the engine is firing on all but one cylinder the 
 trouble must be some place between the distributor rotor and the 
 plug. First see if the distributor is dirty and then check up the 
 cable to see if it is broken or grounded. One point to be remembered 
 is that the parts of the magneto or battery ignition system incorpora- 
 ted in the instruments will effect the operation on all cylinders and 
 there is no need of looking for the trouble there if only one cylinder 
 misses. If every other cylinder to fire misses and magneto ignition is 
 used, it is often due to the timing lever housing being jammed over to 
 one side so that the interrupter points are opened only by one cam. 
 In no case is it necessary to file the interrupter points to overcome a 
 miss for the interrupter affects the operation on every cylinder and not 
 one. 
 
 If the miss is irregular it is due to carburetor or fuel troubles. To 
 locate the trouble open the pet cock at the bottom of the carburetor 
 and if there is any water in the carburetor it will run out. This opera- 
 tion also shows whether the gasoline runs freely. If it does not there 
 may be dirt in the line or no gasoline supply. After everything else 
 has been tried to overcome the trouble adjust the carburetor to com- 
 pensate for too lean a mixture. 
 
 When an engine is first started it will often miss. This is due to the 
 engine being cold. Under no circumstance should time be wasted to 
 overcome missing until the engine is warm. If an exhaust valve 
 sticks it will cause the engine to miss as the gases will be forced out on 
 the compression stroke. This is difficult to locate as it is a regular 
 miss but usually results from an overheated engine. 
 
 If an engine back-fires when first started and does so continuously 
 it is best to check up the wiring and timing of the ignition system. 
 If the engine is running smoothly and suddenly starts to back-fire 
 through the carburetor it is possible that the magneto coupling has 
 slipped. 
 
 If there is water in the carburetor it may suddenly shut off the 
 supply of gasoline and cause so lean a mixture that back-firing results. 
 Dirt in the line or running out of gasoline would have the same 
 effect. If back-firing into the carburetor is experienced in addition 
 to missing of the engine it is probably due to too lean a mixture. 
 Back-firing also results from the inlet valve sticking or not seating 
 properly. 
 
 If the engine suddenly develops a knock while in operation it 
 may be due to the ignition being too far advanced for the condition 
 under which the car is operating and the spark lever should be 
 retarded. This will be noticed mostly when the car is under a hard 
 pull such as on hills or when going through sandy roads. If the 
 
ENGINE TROUBLES EXPERIENCED ON THE ROAD 307 
 
 engine develops a knock, after having been run for a short while, 
 which cannot be overcome by retarding the spark it may be due to 
 carbon in the cylinders or an overheated engine both of which would 
 cause pre-ignition of the charge. By pre-ignition is meant that the 
 incoming charge when under compression is ignited due to the heat 
 in the cylinder regardless of when the ignition spark takes place. 
 Loose bearings and loose pistons will cause knocks but these should 
 easily be distinguished from ignition knocks as they are present at 
 all times. 
 
 If the engine shows a lack of power it may be "that the ignition 
 system is too far retarded due to the coupling driving the magneto 
 having slipped. If too rich a mixture is used it will cause a loss of 
 power but can easily be discovered by the black smoke which is 
 given off at the exhaust pipe. Every precaution should be taken to 
 locate the trouble when an engine shows a lack of power as it may be 
 caused from the valves not seating properly, carbon in the cylinders, 
 overheated engine, lack of lubrication, or the governor connection 
 sticking. If lack of lubrication is causing the trouble it will soon 
 lead to mechanical troubles such as scoring of the cylinder walls or 
 burning out the bearings. An engine will often give an apparent 
 indication of a lack of power due to the brakes dragging or the clutch 
 slipping. 
 
 If an engine overheats it is best to check up and see whether or 
 not the car is being operated on a retarded spark or if the mixture is 
 too rich. The usual causes of the engine overheating are troubles 
 experienced with the cooling system. Fan belts often break or slip, 
 the water may have leaked out some place in the cooling system, or 
 the circulation may be stopped in some way. If anti-freezing mix- 
 tures are allowed to remain in the cooling system in warm weather 
 they will cause overheating of the engine due to their low conductivity 
 of heat. Carbon in the cylinders causes the engine to overheat and 
 is deterimental to its operation. If the engine is not lubricated 
 properly it will overheat due to the additional friction of the 
 parts. 
 
 If after the car is in operation the car and engine slow down 
 gradually the trouble is without doubt due to a lack of fuel or some 
 trouble with the fuel system or carburetor. When the car stops 
 under these conditions the engine usually back-fires into the carbure- 
 tor just before the car stops. 
 
 If the car and engine stop suddenly it is an indication of some 
 mechanical trouble such as a frozen bearing, broken connecting rod, 
 or some other part which suddenly puts a brake on the movement of 
 the car. 
 
308 MOTOR VEHICLES AND THEIR ENGINES 
 
 If the engine suddenly stops operating and the car continues to 
 coast the trouble can be traced to the ignition system. A discon- 
 nected or broken wire usually causes the trouble. 
 
 If the engine will not stop when the ignition switch is thrown to 
 the "off" position it is possible with magneto ignition that the cable 
 between the magneto and switch is disconnected. That is, the switch 
 does not connect the primary of the magneto to the ground. If the 
 engine is overheated, due to lack of proper cooling or carbon in the 
 cylinders, the engine will continue to operate due to the pre-ignition. 
 
CHAPTER XXX 
 
 LUBRICATION 
 
 Lubrication is the principal problem in the care and upkeep of the 
 motor vehicle. If proper lubrication is maintained a great part of 
 the work required to keep a motor vehicle in good condition has been 
 accomplished. 
 
 Before taking up the use of lubricants the purpose and reason for 
 their use should be understood. Whenever any two metal surfaces 
 rub against each other such as a shaft in a bearing or two gear teeth 
 meshing together there is friction no matter how highly polished the 
 
 Fig. 273 Magnified Bearing Surface 
 
 surfaces. If the surfaces were examined under a microscope they 
 would appear to be covered with minute irregularities (Fig. 273). 
 These irregularities if allowed to rub on each other would cause a 
 loss of power and considerable wear and the heat set up would cause 
 them to bind. 
 
310 MOTOR VEHICLES AND THEIR ENGINES 
 
 To prevent this condition some substance usually a layer of oil or 
 grease called a lubricant is placed between the surfaces to separate 
 them. The lubricant consists of a vast number of minutely dimen- 
 sioned balls composed of fat and tied together by a mother liquor 
 which maintains their separation. All the motion and rubbing comes 
 between these balls of fat which are not hard like metal and, therefore, 
 rub against each other with but little friction. 
 
 It is not enough to place the lubricating film between the surfaces, 
 it must be kept there. To do this it is necessary to choose a lubricant 
 that has the required properties to withstand the conditions under 
 which it has to perform its duties. For this reason lubricants are 
 rated in accordance with certain tests such as viscosity, flash point, 
 fire point, cold point, and specific gravity. 
 
 Viscosity or fluidity of the lubricant is one of the most important 
 things to be considered in its selection. If the lubricant flows too 
 easily it will run out at the end of the bearing. Nearly all oils have 
 good viscosity at ordinary temperatures but when heated they thin 
 out too much and flow too freely. When a lubricant is to be used in 
 an engine the viscosity should be measured at 100 degrees Fahrenheit, 
 200 degrees Fahrenheit, and 300 degrees Fahrenheit to have a lubri- 
 cant that is neither too heavy at low temperatures nor too thin at 
 high temperatures. 
 
 Specific Gravity of the lubricant shows its body or density. This 
 is important for it is necessary to have a lubricant that has sufficient 
 body to withstand the pressure to which it is subjected. 
 
 Flash Point of an oil is the lowest temperature at which the vapors 
 arising from it will ignite. When an oil is used in an internal combus- 
 tion engine and thus exposed to severe heat it becomes imperative to 
 use an oil of high flash point. This should not be much below 400 
 degrees Fahrenheit. 
 
 Fire Point of an oil is the lowest temperature at which the oil 
 itself ignites from the burning of its vapors. Since the fire point of 
 an oil is always higher than the flash point it is of little value if the 
 flash point is high. 
 
 Cold Point of an oil is the lowest temperature at which the oil will 
 pour. This characteristic need only be taken into consideration 
 because of its effect on free circulation of oil through exterior feed 
 pipes when pressure is not applied. It also affects the lubricating 
 qualities of the oil until it thaws out. 
 
 These specifications must be carefully considered in the selection 
 of a lubricant and the correct lubricants to use will be specified in 
 the Lubrication Tables in manufacturer's catalogues. When selecting 
 engine oils it is necessary to consider carefully the fire point, flash 
 
LUBRICATION 
 
 311 
 
 point, and viscosity. Bear in mind that an air-cooled engine re- 
 quires a heavier oil and one of a higher flash point than a water- 
 cooled engine. It is also true that m warm weather a heavier lubri- 
 cant is necessary than in cold weather. 
 
 It is well to consider the sources from which lubricants are ob- 
 tained. The light oils such as cylinder oils are almost always mineral 
 oils. The heavier oils for transmissions are usually mineral oils 
 made by adding animal or vegetable fats to thicken them. The 
 greases are usually vegetable or animal substances of a soapy nature 
 with mineral oils added to make them lubricants. Greases are 
 usually of two kinds, cup grease and gear grease. The main differ- 
 ence is that cup grease will break down into soap and oil if heated 
 while gear grease will not. 
 
 There are many methods used in lubricating an engine and only 
 those most commonly found will be discussed. The parts requiring 
 lubrication are the main crank shaft bearings, crank pin bearings, 
 wrist pin bearings, cam shaft bearings, timing gears, cams, valve 
 lifters and guides, pistons, piston rings, and cylinder walls. The 
 following systems are employed: 
 
 I 
 
 Fig. 274 Splash System 
 
 SPLASH. The oil is held in the crank case being supplied either 
 by a mechanical oiler or direct from some outside source. As the 
 engine turns over the lower ends of the connecting rods or dippers 
 on the connecting rods strike the oil and splash it in all directions. 
 This fills the cups that supply the main bearings. The crank pin 
 bearings receive their oil through holes bored into the bearings. 
 When the connecting rods dip, the oil is splashed up on the piston and 
 cylinder walls. The oil which is splashed to the inner surface of the 
 piston will drop off the lug (Fig. 274) and supply the wrist pin bearing. 
 The cam shaft bearings and lifter rod bearings depend upon the splash 
 for obtaining their lubrication. Thus all of the parts are lubricated 
 by the dipping of the connecting rods into the lubricant. 
 
312 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 It is important not to let the oil level get too low. In putting 
 oil in the crank case it is also important not to have it too high. 
 Too much oil will cause carbon to be formed in the cylinders which 
 results in fouling of the spark plugs, pre-ignition, overheating, and 
 knocking. It also causes a blue or white smoke at the exhaust which 
 should not be confused with black smoke produced by too rich a 
 mixture. 
 
 Fig. 275 Splash with Circulating Pump 
 
 SPLASH WITH CIRCULATING PUMP. This system is 
 designed to overcome the difficulty experienced with over-lubrication 
 as in the splash system. Oil is supplied from the reservoir or sump, 
 by means of a pump to splash troughs (Fig. 275) . These troughs are 
 designed to hold only sufficient oil for proper lubrication and will 
 overflow if too much oil is supplied to them. In this way the diffi- 
 culty of over lubricating is reduced to a minimum. In every other 
 respect this system is identical with the splash. 
 
 Fig. 276 Force Feed and Splash 
 
 FORCE FEED AND SPLASH. Oil is forced by pump pressure 
 direct to the main crank shaft bearings (Fig. 276). The overflow 
 falls into the splash troughs in the crank case into which the con- 
 necting rods dip and splash oil to all other parts of the engine. A 
 
LUBRICATION 
 
 313 
 
 constant oil level is maintained in the splash troughs by an overflow 
 to the sump or reservoir below, from which the oil is again circulated. 
 
 Fig. 277 Force Feed 
 
 FORCE FEED. The oil is forced by pump pressure direct to the 
 main crank shaft bearings and then through holes drilled in the crank 
 arms to the crank pin bearings (Fig. 277). As the oil overflows from 
 the crank pin bearings it is thrown by centrifugal force to the cylinder 
 walls, piston walls, the wrist pin, and all other parts. There is no 
 splash in this system as the connecting rods do not dip into oil. The 
 overflow of the oil returns to the sump or reservoir and is again 
 circulated. 
 
 Fig. 278 Full-Force Feed 
 
 FULL FORCE FEED. Oil is forced by pump pressure direct to 
 the main crank shaft bearings and through holes in the crank arms 
 to the crank pin bearings. From here it is led by pipes or hollow 
 connecting rods to the wrist pin bearings (Fig. 278). The cam shaft 
 is usually hollow and has its bearings supplied by the same pressure. 
 The piston and cylinder walls are supplied by oil thrown from the 
 lower ends of the connecting rods*. In some cases the overflow of 
 the oil from the wrist pins is used to assist in lubricating the piston 
 and cylinder walls. 
 
314 MOTOR VEHICLES AND THEIR ENGINES 
 
 As it is continually necessary to add more lubricant to the engine 
 it may be necessary to change the kind of oil used. If so, it is best to 
 drain out the old oil and clean the crank case with kerosene and then 
 refill with fresh oil. The reason for this is that oils do not always 
 mix readily. When two oils are shaken or stirred up as in an engine 
 air bubbles will form. This causes a mixture of air and oil to be 
 brought into contact with the surfaces instead of all lubricant. 
 
 Cleaning and draining of the crank case should also be done once a 
 month or about every 1,000 miles of running. It should be done also 
 at the end of the first 500 and 1,000 miles run with a new car. Drain 
 out the old oil through the plug in the bottom of the crank case and 
 refill with about a gallon of kerosene. If the engine has an electric 
 starter turn the engine over with the starter for about fifteen seconds. 
 If there is no starter the engine may be run for about the same length 
 of time. This will thoroughly clean out the circulating system and 
 the kerosene may now be drained from the crank case.' It is impor- 
 tant that all the kerosene be drained from the crank case as 
 any that is left will mix with the new oil, reducing its lubricating 
 qualities. In some engines such as the Wisconsin the splash par- 
 titions in the crank case will retain considerable kerosene and it 
 will be necessary to remove the lower half of the crank-case to drain 
 thoroughly. This removal gives a chance for the inspection of the 
 pistons, connecting rods, main bearings, etc., and advantage should be 
 taken of this opportunity. After the kerosene is thoroughly drained 
 from the crank-case the oil strainer should be cleaned and replaced 
 and the crank-case refilled to the proper level with fresh oil. Before 
 starting the engine it is wise to turn it over several times by hand to 
 fill the circulating system with fresh oil. If the oil circulating system 
 on the engine is supplied with a pressure gauge, excessive pressure or 
 no pressure at all at a car speed of fifteen to twenty-five miles an hour 
 indicates plugging of the oil circulation system and should be investi- 
 gated immediately. The same is true of the stoppage or irregular 
 action of a sight feed if one is supplied. In the case of the White 
 (Model T. E. B. 0.) this latter trouble might be due to stoppage in the 
 oil pump check valves which should be investigated immediately. 
 
 The proper level for oil in the transmission case is such that all the 
 gears on the upper shaft dip one-half an inch or so into the oil. The 
 transmission case should be drained, cleaned with kerosene, and re- 
 filled every five thousand miles or about twice a year. The level 
 should be inspected monthly. 
 
 A wet plate or multiple disc clutch should be drained and cleaned 
 with kerosene once a month or every 1,000 miles. When cleaning 
 with kerosene run the engine and disengage the clutch several times. 
 
LUBRICATION 315 
 
 Do not use too heavy an oil in the clutch as it will cause it to either 
 slip, drag, or both. 
 
 Oil or grease may be used in the differential housing. The deter- 
 mining factor in many cases is leakage of the lubricant from the 
 end of the rear axle onto the brake drums. If this is continuous 
 and cannot be stopped by the use of a new felt washer in the 
 rear axle it will be advisable to mix some heavier grease with the 
 lubricant recommended, to prevent this leakage. 
 
 A general rule may be given for the use of grease cups. Turn the 
 cup till the grease is seen to start squeezing from the bearing. There 
 are of course exceptions to the general rule such as when the grease 
 might reach parts that would be injured by it or when the cup is so 
 located that no grease can escape. However, as a general rule 
 grease cups are turned too little rather than too much. Be careful 
 to wipe off all excess grease as it collects dirt and grit which may work 
 into the bearing and cause damage. It is also better to use oil in place 
 of grease on brake equalizer slides and other exposed places as it is not 
 so liable to pick up dirt and grit. 
 
 It must be remembered in handling grease cups that the threads 
 are very fine and easily crossed. The cap must be held square with 
 the threads when starting to turn it on. If the cap turns hard the 
 threads are probably crossed. The cap should be backed off and a 
 new start made. If this is not done the threads will be stripped and 
 the cap spoiled. The same thing applies to grease guns which 
 usually have fine threads on the cap. 
 
 As already stated gasoline and kerosene are used to wash out 
 lubrication from any part and for this reason care should be taken not 
 to over prime an engine. If too much gasoline is used when priming 
 an engine it will wash the oil away from the piston and cylinder walls 
 causing a loss of compression. This makes it very hard to start the 
 engine and if started will often result in scoring the cylinders or 
 pistons. This is because the oil in circulating to these parts will often 
 require more time than it takes for the parts to heat up and expand 
 due to the additional friction. The proper method of priming an 
 engine is to fill the primary cup full and then open the cock and allow 
 only this amount to flow into the cylinder. Do not squirt it in direct 
 from the oil can. 
 
 The following lubrication "don'ts" will give some of the necessary 
 points which must be carefully considered : 
 
 Don't forget that an air cooled engine requires heavier oil than a 
 water cooled engine because of its higher operating temperature. 
 
 Don't think that oil never wears out. 
 
 Don't judge the viscosity of an oil at atmospheric temperature. 
 
316 MOTOR VEHICLES AND THEIR ENGINES 
 
 Remember that when oil passes through the bearings it has a much 
 higher temperature than the surrounding air. 
 
 Don't fill the oil reservoir above the correct level. Enough is 
 sufficient, too much causes trouble. 
 
 Don't expect lubricating oil to perform the impossible task of cor- 
 recting mechanical defects. Too much clearance between piston and 
 cylinder or bad and leaky piston rings will surely fill the cylinder with 
 carbon even when the best lubricating oil is used. 
 
 Don't use a light oil when a heavy oil is required, under the im- 
 pression that an oil must be light in order to reach the parts. 
 
 Don't use a heavy oil when a light oil is required such as on 
 ball bearings in the magneto. 
 
 Don't use grease which is not semi-fluid in transmission or dif- 
 ferentials. After the gears have cut tracks in hard grease further 
 lubrication is impossible and rapid wear will result. 
 
 Don't run the engine fast when a car is new and the bearings are 
 tight. Wait until the car has made at least 500 to 1,000 miles. 
 
 Don't fill the reservoir by pouring oil into it through a dirty or 
 sandy funnel. 
 
 Don't lose sight of the fact that the life of the car depends upon 
 the proper lubrication of the parts. 
 
 Don't forget that lubricating should be done often and at regular 
 intervals. 
 
CHAPTER XXXI 
 
 CARE AND ADJUSTMENT 
 
 To keep motor propelled vehicles in proper running condition it is 
 necessary that certain parts be inspected and adjusted at regular in- 
 tervals. Besides these adjustments certain repairs will be outlined 
 in this chapter which are likely to become necessary under running 
 conditions. Repairs which require special tools and machinery, re- 
 sulting from accident or other breakage, are not discussed in this 
 book. 
 
 TESTING COMPRESSION. To test the compression on a warm 
 engine each cylinder must be considered separately. Open the pet 
 cocks on all the cylinders except the one that is to be tested and turn the 
 engine over until the piston comes up against compression in that cyl- 
 inder. If the compression is good the crank should resist being turned 
 over and if the pull on the crank is released it should fly back as if 
 moved by a spring. Hold the crank up against compression for ten or 
 fifteen seconds and see if the gas in the cylinder leaks out relieving the 
 pressure. The length of time that the cylinder will hold compression 
 indicates the amount of leakage. Try the compression of each cyl- 
 inder in turn and see if it is the same in all. Loss of compression is 
 due to the gas leaking out of the cylinder and these leaks are of three 
 
 1. Past various joints such as cylinder head gasket, valve cap, 
 spark plug, priming cock, etc. 
 
 2. Past pistons and piston rings. 
 
 3. Past valves. 
 
 Leaks of the first class can usually be detected by the hissing 
 sound of the escaping gas around the joints and may be located by 
 running oil around these joints and watching for bubbles as the engine 
 is turned by hand or run slowly. Leaks through the cylinder head 
 gasket can be detected by the above method unless the leak is into the 
 water jacket. This may be detected by the presence of water in the 
 cylinders after the engine has been idle for some time or by listening 
 at the radiator cap for the noise of the gas gurgling into the water. 
 
 Leaks of the second class should be tested for after determining 
 that the leak is not of the first class by putting a couple of tablespoon- 
 fuls of heavy oil in the leaking cylinder and determining whether the 
 compression has been improved. If this does not improve the com- 
 
 317 
 
318 MOTOR VEHICLES AND THEIR ENGINES 
 
 pression it shows that the leak must be past the valves. Such leaks 
 may be due to improper adjustment of the valve tappets, to a valve 
 sticking, or to a valve which is warped or does not seat properly. In 
 the latter case the valve will probably have to be ground. 
 
 ADJUSTING VALVE TAPPETS. Most engines are provided 
 with adjusting nuts for regulating the clearance between the valve 
 stem and the push rod. The different instruction books and the Care 
 and Adjustment Tables in the next chapter give the proper "cold" 
 clearance for the different engines on the cars used in the service. 
 When measuring valve clearance, be sure that the valve whose clear- 
 ance is to be tested is in the closed position. If the piston of one cyl- 
 inder is placed at top dead center on compression both valves will be 
 closed and their clearance may be tested. Another good method is to 
 turn the engine over by hand until one valve is wide open and then 
 turn another full revolution. The valve will now be closed and the 
 nose of the cam on the cam shaft will be pointing directly away from 
 the tappet. After the valve is closed, select a gauge of the proper 
 thickness and slip it between the valve stem and the push rod. Ad- 
 just the adjusting nut so that the gauge will just slip freely between 
 the two and tighten the locknut. In tightening this nut, be sure that 
 the adjustment is not changed and the nut is tight. Check the clear- 
 ance after the adjustment is set. If a thickness gauge is not available 
 one can be made of several thicknesses of paper remembering that the 
 paper in this book is about 0.003 inch thick. In case the cold clear- 
 ance is not known the clearance may be checked while the engine is 
 hot. The engine should be run until thoroughly warm and the ad- 
 justment made to allow a perceptible amount of play. This should be 
 just enough to show that there is play and no more. The object of 
 this play is to allow for further heating of the engine, for a small 
 amount of wear on the valve at its seat, and to insure that the tappet 
 is not preventing the valve from seating. When valves are adjusted 
 for cold clearance it is best to use this method of checking their 
 clearance. If after checking the valve clearance the compression 
 leaks past the valves they should be ground. 
 
 VALVE GRINDING. To grind a valve first remove the valve 
 cap or drain the radiator and remove the cylinder head cover. Lift 
 the valve spring with a valve lifter tool and remove the valve spring 
 retainer, lifting out the valve. Remove the spring and turn down 
 the valve tappet adjusting screw so as not to interfere with the valve 
 stem. Clean the carbon from the valve and from around its seat. 
 If a valve is very badly pitted, if the head is warped or out of line with 
 its seat, or if shoulders appear on the face of its seat, the valve should 
 be refaced by a mechanic with the proper tools before grinding. Place 
 
CARE AND ADJUSTMENT 319 
 
 some waste or a piece of cloth in the gas passage and in the passage 
 to the cylinder to prevent the grinding compound from getting into 
 these places and place a little valve grinding compound on the face of 
 the valve. This compound comes in coarse, medium, and fine grades, 
 Unless the valve is badly pitted the medium grade should be used 
 first and the grinding finished with the fine. Be sparing of the com- 
 pound and do not plaster the rest of the valve head with it. The 
 compound should be put on in a smooth coat. Put a light spring 
 under the valve head when replacing it in its seat to lift the valve off 
 its seat when the pressure used in grinding is removed. With a screw- 
 driver or brace turn the valve about a half turn first to the right and 
 then to the left, exerting about three or four pounds downward pres- 
 sure. At frequent intervals let the valve lift off its seat and turn it to 
 a new position before reseating. Continue the oscillating motion as 
 before until a silvery band appears completely around the valve. 
 There should be no pits or breaks in this band and the grinding should 
 be continued until this is accomplished. This band need not be over 
 Vie inch to 3 / 3 2 inch wide. After the band is established a smooth 
 finish should be given the surfaces using the fine grinding compound. 
 Make sure that none of it gets into the cylinder, gas passages, or valve 
 stem guide. Valve grinding requires patience and persistence to do 
 good work. Be very careful in grinding valves not to interchange 
 them nor put the wrong valve in the wrong seat, as it will not make a 
 gas tight joint. The exhaust valves being exposed to the hot gases 
 will require grinding much more often than the inlet valves. After 
 the valves are ground they may be replaced, the spring and spring 
 retainer put in place, and the valve tappet adjusted. 
 
 CARBON REMOVAL. If carbon becomes excessive it causes 
 overheating of the engine, lack of power, pre-ignition, and a tendency 
 for explosions to continue after the ignition switch has been turned off. 
 
 The cylinders can be kept reasonably free of carbon by removing 
 the spark plugs and introducing a tablespoonful of kerosene in each 
 cylinder about once a week. The kerosene should be inserted when 
 the engine is hot and the best results will be obtained by placing it 
 in the cylinders at night in order that it may have an opportunity 
 to soften the carbon deposit before the engine is used again. 
 
 If the engine has been run for some time without cleaning out the 
 cylinders it is well to pour about a pint of kerosene through the air 
 intake of the carburetor with the engine hot and running at high 
 speed and the spark lever fully retarded. Do not choke the engine 
 with the kerosene but pour it in as fast as the engine will take it and 
 run. After this operation place a tablespoonful of kerosene in each 
 cylinder and allow the engine to stand idle for ten or twelve hours. 
 
320 MOTOR VEHICLES AND THEIR ENGINES 
 
 If an excessive amount of carbon has accumulated in the cylinders 
 kerosene will not remove it. It can then be removed in one of several 
 ways. It can be scraped out by removing the cylinder head casting 
 or valve caps, it may be loosened and blown out through the exhaust 
 by the use of a carbon removing chain in the cylinder, it may be dis- 
 solved out with a carbon remover, or it may be burned out with 
 oxygen. 
 
 If the cylinder head is removable it is an easy matter to remove 
 the carbon by scraping. Turn the engine over until the piston in the 
 cylinder to be scraped is at top dead center on compression stroke. 
 This prevents loose carbon from getting into the valve parts and 
 reduces to a minimum the amount of carbon getting in between the 
 piston and cylinder walls. All holes in the cylinder block such as 
 water jackets and stud holes should be packed with waste. 
 
 It is very difficult to remove carbon by scraping through valve 
 cap holes. Special scrapers are required for scraping the cylinder 
 head and the top of the piston. They must be worked back and 
 forth over the surface with considerable pressure until the scratching 
 sensation stops and the tool seems to glide freely over the surface. 
 Be very careful not to scratch the surface. Blow out the carbon at 
 frequent intervals with an air hose if possible or with a hand bellows 
 if compressed air is not available. Be sure to scrape the entire inner 
 surface of the combustion space and do not leave any jagged patches 
 as they will become incandescent and cause pre-ignition. Continue 
 scraping until the air does not blow out any more carbon dust. 
 The same precautions should be taken regarding keeping the valves 
 closed and dust out of the cylinders as when the cylinder head is 
 removable. 
 
 After carbon has been scraped and as much as possible blown out 
 pour about a half a glassful of kerosene into the cylinder and apply 
 the air blast. This should remove the remaining carbon. Another 
 half glassful should now be poured into the cylinder and the engine 
 turned over several times by hand. This will remove any carbon 
 which may have worked down between the piston and the cylinder. 
 The crank case should now be drained and washed with kerosene 
 and refilled with fresh oil. 
 
 When using a carbon removing chain it should be placed in posi- 
 tion on top of the piston through the exhaust valve cap opening. 
 Remove the spark plug and inject into the cylinder about two table- 
 spoonfuls of kerosene. The chain used should be joined at its ends 
 and should be made of spring steel or piano wire which is hard but 
 not brittle. The links should not exceed % inch in diameter and 
 the total length should be about twelve inches. Screw back the 
 
CARE AND ADJUSTMENT 321 
 
 valve cap leaving out the spark plug and run the engine for several 
 minutes. The carbon loosed by the chain will be blown out. 
 
 To use liquid carbon remover, remove the valve caps and turn two 
 cylinders to top dead center. This should be done when the engine 
 is warm. Put the carbon remover in these two cylinders allowing it 
 to remain for about an hour and then remove it by syphoning. 
 The combustion chamber should now be dried out as well as possible 
 with a dry cloth. Repeat the same process in the other pair of 
 cylinders. This method is not as effective as scraping or burning out 
 the carbon. 
 
 In burning out the carbon one piston is brought to top dead center 
 on compression, the spark plug and one of the valve caps removed, 
 and a small piece of burning waste dropped into the cylinder. 
 The operator then directs a jet of oxygen on the carbon at the point 
 where the waste is burning. This causes the carbon to burn rapidly 
 and to be entirely consumed. By following the burning carbon 
 around the cylinder with the jet of oxygen it will be evenly burned 
 out. Care must be taken to have the cooling system full of water 
 while the carbon is being burned to prevent overheating of the 
 cylinder casting. 
 
 When scraping can be conveniently done it is probably the best 
 method but on some engines it is difficult to accomplish without 
 dismantling. The burning out method is also good when done care- 
 fully by an experienced operator. The chain method and the use of 
 decarbonizing liquids are not so good. The latter is rather ineffective 
 when the carbon deposit is heavy. 
 
 PACKING WATER PUMP GLANDS. The water pump glands 
 should be packed with a good grade of waterproof asbestos or com- 
 pounded packing. If loose twisted asbestos rope is available untwist 
 one strand, soak it thoroughly with cylinder oil, and cover with as 
 much fine graphite as it will retain. Always coil the packing round 
 the shaft in the direction the packing nut turns when tightened so 
 it will not tend to unwind when the packing nut is screwed on. The 
 gland nuts should not be tightened any more than is necessary to 
 prevent the leakage of water. 
 
 CLEANING THE COOLING SYSTEM. The cooling system 
 should be flushed with a stream of warm water (if possible) under 
 pressure by forcing it through the system in the reverse direction to 
 which the water flows when the engine is operating. To accom- 
 plish this disconnect the radiator at the lower connection and insert 
 a hose so the water is forced in at the bottom of the radiator. This 
 should remove all loose dirt and sediment. In case there is a plug 
 in the front of the radiator it may be removed and the water forced 
 
322 MOTOR VEHICLES AND THEIR ENGINES 
 
 in at this point. In this case the lower hose connection to the radiator 
 must be plugged. 
 
 After the engine has been used some time and the cooling system 
 refilled a number of times, probably with all kinds of dirty water, a 
 deposit will form on the inside surfaces of the entire cooling system. 
 This prevents proper cooling of the cylinders and of the water in the 
 radiator. To remove this scale dissolve six pounds of washing soda 
 in five gallons of boiling water and pour this into the radiator leaving 
 it in the system while the car operates for a day. Then drain out 
 and flush the cooling system with clean water being careful to refill 
 it with clean water. In addition it is necessary to drain the radiator 
 and refill with fresh water at frequent intervals. 
 
 FUEL FEED SYSTEM. Gasoline should be strained before it 
 is put into the tank. A wire gauze or chamois strainer can be used 
 in the funnel when pouring the gasoline in the tank. In case chamois 
 is used be sure to keep the funnel in contact with the tank to prevent 
 the. generation of dangerous static electricity. 
 
 To prevent water from accumulating the sediment trap when 
 provided and the carburetor should be drained frequently. This is 
 particularly important in winter as the water may freeze and stop 
 up the gasoline line. The carburetor strainer should be removed 
 frequently and cleaned. In most carburetors this is accomplished 
 by loosening a union at the bottom of the carburetor on the feed line 
 after which the carburetor may be removed. In unscrewing the 
 union on the feed line be careful not to unscrew the whole union 
 fitting and twist the gasoline line. Also be sure not to cross the 
 threads in screwing the union back on. 
 
 The joints in the air intake manifold should be examined to see 
 that there are no leaks as they are frequently the cause of missing in 
 the engine. When the engine is running these leaks may be detected 
 by putting oil on the suspected spot which will be drawn into the 
 manifold if there is a leak. Shellacking the joints will stop this 
 trouble but when used at the joints above the governor shellac 
 should be applied very sparingly as it may flow down into the 
 governor and interfere with its action. Blotting paper without 
 shellac may be used for gaskets at these joints. 
 
 If on inspection it is found that the carburetor is flooding with 
 the truck standing on level ground the cause may be dirt under the 
 float needle valve or a leaky valve. The small cap on top of the 
 float chamber should be removed exposing the top of the needle valve 
 stem which if lifted or turned may release the dirt causing the leak. 
 If the leak is due to a leaky valve a few light taps on the top of the 
 valve stem may. cause it to seat properly. Never use grinding com- 
 
CARE AND ADJUSTMENT 323 
 
 pound on this valve as not only the valve but also the seat might 
 be ruined. Further details as to care of the carburetor and the 
 methods of making adjustments will be found in the chapters on 
 carburetors. 
 
 WIRING. All wiring of the starting, lighting, and ignition 
 systems which is exposed should be inspected regularly to see that it 
 is not chafed or rubbed so as to expose the bare wire and cause a 
 ground. The wires may also be broken inside the insulation without 
 giving any indication on the outside. This is most apt to happen 
 where the wire takes a sudden bend or vibrates excessively. Loose 
 connections should be tightened and where a wire is made fast to a 
 terminal it should be soldered. A grounded primary wire on a Ford 
 car may be detected by the constant buzzing of the vibrator on the 
 corresponding coil. The car should not be cranked in this condition 
 as it is very apt to kick back. 
 
 SPARK PLUGS. These should be examined frequently to see if 
 they are badly carbonized, porcelains broken, and if the points are 
 improperly adjusted or in good condition. In removing plugs care 
 should be taken not to allow the wrench to slip and break the porce- 
 lain of the plug being removed or of the adjacent one. This may be 
 avoided by never using a worn or incorrect sized wrench for this pur- 
 pose and by always starting with the right hand plug when removing 
 or replacing them. Plugs when removed may be cleaned with gaso- 
 line. If the plug is demountable the porcelain may be removed and 
 the carbon cleaned off with an old tooth brush and gasoline. If it 
 is impossible to remove the porcelain the plug is harder to clean and 
 the carbon may be scraped off the metal parts after being softened 
 with gasoline. A knife or other sharp tool may be used but care must 
 be taken not to scratch the glazed surface of the porcelain as this 
 will cause it to become oil soaked and the carbon will form readily 
 on its surface. 
 
 The gap between the points of the plug should be between 1 / 32 *' 
 and l /to> With battery ignition, or on the Ford, the gap may be 
 larger than with high tension magneto ignition. Most manufac- 
 turers of magnetos and ignition systems furnish with their apparatus 
 a wrench or screwdriver with a gauge attached of the proper thick- 
 ness so that it will just slip between the points of the plug when 
 properly adjusted. As a substitute gauge for battery ignition a worn 
 dime may be used but for magneto ignition the gap should be con- 
 siderably smaller. This gap should be inspected frequently as the 
 points may pit or wear away causing the gap to become too wide. 
 This will make it difficult to start the engine and may cause the plug 
 to miss fire at low speeds or when pulling hard or accelerating. 
 
324 MOTOR VEHICLES AND THEIR ENGINES 
 
 The plug should be examined carefully in case it does not fire to 
 see if a porcelain is cracked for this would cause the plug to become 
 short-circuited. The crack may be a fine line crack which is rather 
 difficult to detect. In replacing bad plugs be careful to get the proper 
 type of plug. Not only must the proper thread be used but the plug 
 should also have the proper length as previously explained. When 
 inserting a half -inch plug be careful not to screw it too tightly into a 
 hot engine for when it reaches the same temperature as the engine it 
 may be difficult to remove the plug. 
 
 DISTRIBUTOR. The distributor cover on a magneto or battery 
 system should be removed regularly to examine the brushes or con- 
 tacts. The distributor plate should be cleaned with a cloth dipped 
 in gasoline. After cleaning the distributor the rotor or brush track 
 should be given a very fine application of vaseline. If the distributor 
 has brushes be very careful not to lose or damage them in removing 
 the cover. If the car is equipped with a timer and multi-unit coil 
 the timer should be cleaned at frequent intervals with a cloth wet 
 with gasoline. 
 
 INTERRUPTERS. Another important part of the magneto or 
 ignition system is the interrupter. The interrupter lever should be 
 examined to see that it is free to move and the gap between the 
 interrupter points should be inspected. To check the adjustment 
 of these points set the interrupter lever on the center of the cam 
 which gives the maximum opening of the points. Then check the gap 
 between them with the gauge supplied for that purpose on the mag- 
 neto wrench or screw driver. If this should not be available set the 
 points from 0.015" to 0.020" apart using a post card to gauge the dis- 
 tance. This gap should be checked on each cam particularly on those 
 magnetos which have the cams on the interrupter lever housing. If 
 the cams are worn or the housing is worn or distorted the gaps will be 
 unequal. This may be corrected by shimming under the cam which 
 gives the least opening. This work as well as the filing of the breaker 
 points should be done only by experienced mechanics. If the breaker 
 points are pitted or do not make a good contact it will be necessary to 
 dress the points with a fine file until the surfaces are smooth and make 
 proper contact. The gap should be properly adjusted after the 
 points are filed. The points of a vibrator need the same attention, 
 the proper gap being about l / sz lf with the spring held all the way down. 
 
 LUBRICATION OF MAGNETO. In lubricating a magneto fol- 
 low instructions given as proper lubrication is one of the essential 
 points for satisfactory operation of a magneto or timer-distributor. 
 Too much oil is as bad as too little, since it is apt to get on the windings 
 or breaker points. 
 
CARE AND ADJUSTMENT 325 
 
 IGNITION TIMING. To time the magneto first bring number 
 one piston (the one nearest the radiator) to top dead center on com- 
 pression stroke. This may be done by opening the priming cocks on 
 the other cylinders and turning the engine until compression is felt. 
 The piston is then coming up on compression stroke and if the fly 
 wheel is exposed it may be brought to top dead center by checking the 
 marks on the flywheel. If the flywheel is not exposed an approxi- 
 mate method may be used which is close enough to check the setting 
 of the magneto and determine whether faulty timing is the cause of 
 trouble. Insert a wire or stick through the spark plug hole and turn 
 the engine until this wire stops rising. If this is carefully done the 
 position of top dead center can be located to within about five degrees. 
 If it is necessary to connect up the magneto by this method, it is best 
 to continue turning the engine after the piston reaches the top of its 
 stroke until it just starts to move downward again. This will prevent 
 timing the magneto too early which might cause the engine to kick 
 back when being cranked. However, the magneto should never be 
 set by this approximate method except in case of an emergency. 
 
 With the engine set at top dead center the magneto should be 
 turned until the distributor contact is opposite the brush to number 
 one cylinder. Then set so that the contact points are just about to 
 open with the spark retarded. The magneto should be turned in the 
 direction of rotation in making this adjustment. Some magnetos are 
 marked on the distributor plate with a line and an L or R depending 
 on the direction of rotation of the magneto. This mark is so located 
 that it comes opposite a marking pin just as the contact points open, 
 with the distributor contact opposite the lead to number one cylinder. 
 This simplifies the checking of the timing considerably when the 
 breaker box is inaccessible. After timing the magneto to the engine 
 connect the coupling between them. After the two are connected 
 check the setting to make sure nothing was displaced while tightening 
 the coupling. Observe which way the distributor rotates and con- 
 nect the leads from the distributor so that each cylinder receives the 
 spark in the proper firing order. 
 
 A timer-distributor on a battery ignition system is timed in prac- 
 tically the same manner. Bring number one piston to top dead 
 center on compression stroke as before, but continue to turn the engine 
 until the exhaust valve on the other cylinder which is on top center 
 (number 4 on a four cylinder engine or number 6 on a six cylinder 
 engine) just closes. Loosen the breaker cam adjusting screw on the 
 vertical shaft and set the breaker points so they just start to open with 
 the spark fully retarded. The rotor must also be in such a position 
 that the distributor makes contact with the segment for number one 
 
326 MOTOR VEHICLES AND THEIR ENGINES 
 
 cylinder. The breaker cam must be set carefully so that the points 
 will open and close as the slack in the distributor gears is taken up 
 first in one direction and then in the other. Tighten the adjusting 
 screw and after replacing the rotor connect the leads to the plugs as 
 in the case of the magneto. 
 
 To time the " commutator" on the Ford bring number one piston 
 to top dead center on compression stroke as before. As the cylinder 
 head must be removed to properly time the "commutator" the meth- 
 od given above for determining firing position is not applicable. The 
 simplest way to determine this position is by watching the exhaust 
 valve of number four cylinder, for as it closes piston number one will 
 be at top dead center on compression stroke. After reaching top dead 
 center continue to turn the engine until the piston has traveled y% 
 on the downward stroke. Set the " commutator" in the full retarded 
 position and place the roller so that it is just starting to make contact 
 with number one segment. Connect up the primary wires so that the 
 spark occurs in the proper cylinder. It must be remembered that the 
 firing order of the Ford is 1-2-4-3, which is different from most four- 
 cylinder engines. 
 
 CLUTCH ADJUSTMENTS. If the clutch slips before adjusting 
 the clutch spring make sure that the clutch pedal is not striking the 
 floor boards or that some other obstruction is not preventing the 
 clutch. spring from forcing the friction surfaces together. When it is 
 necessary to adjust the spring tension this is accomplished by moving 
 the adjusting nut provided for that purpose. After the adjustment 
 has been made make sure the nut is securely locked in place. 
 
 If the clutch has a clutch brake see that it is properly adjusted. 
 This brake should be so adjusted that it takes effect only at the ex- 
 treme outward position of the clutch pedal. Common clutch troubles 
 and their remedies are covered in chapter 23. 
 
 WHEEL ALIGNMENT. The method of aligning the wheels 
 depends upon whether the vehicle is steered by two or all four wheels. 
 On a two- wheel steered vehicle a simple method is as follows : Turn 
 the steering wheel until the right front wheel is in line with the right- 
 rear wheel. To determine this a piece of string may be stretched 
 along the outside of the right wheels touching both the front and rear 
 edges of both wheels lightly or they may be aligned by the eye. With 
 the wheels set in this position test the front wheels for " gather" or 
 "toeing in" by sighting along the inner edge of the left front wheel. 
 If properly adjusted an inch to an inch and a half of the rear wheel will 
 be visible which is approximately one quarter of an inch "gather " 
 If more or less of the rear wheel is visible the tie rod should be 
 adjusted. 
 
CARE AND ADJUSTMENT 327 
 
 With a four-wheel steered vehicle both sets of wheels should be 
 set to "toe in" and the simplest way is to measure the amount of 
 difference in distance between the edges of the front and rear of the 
 wheels with a stick when they are set approximately parallel with the 
 frame. 
 
 To determine the amount of "gather" by these methods it is 
 necessary for the wheels to run true. This may be determined by 
 jacking them up one at a time and spinning them. If not true a 
 wooden wheel may be turned up as follows: Hold a piece of chalk 
 against the side of the spinning wheel to indicate where the wheel is 
 distorted. Cardboard shims may now be placed between the spokes 
 and inner hup plate where necessary to make the wheel run true. 
 When demountable rims are used do not confuse the improper setting 
 of the rim bolts causing the tire to run out of true with a wheel out of 
 true. Both should be avoided as they cause undue wear on the tires. 
 
 STEERING GEAR. While the wheel is jacked up it should be 
 tested for play in the wheel bearings, steering knuckle, and also tie 
 rod or the drag link. This play should be taken up at once if pos- 
 sible. Lost motion in the steering gear should be taken up as soon 
 as it is discovered if an adjustment for this purpose is provided. In 
 some constructions the steering arm is actuated by a short shaft with 
 a square end on which the arm fits. Lost motion often occurs at 
 this point and the steering arm should be inspected and clamped 
 tightly on the shaft if any movement occurs between them. 
 
 BRAKE ADJUSTMENT. Before adjusting the brakes make 
 sure that the cause of their failure to work is not due to oil or grease 
 on the linings. If this is the case make sure that the grease or oil is 
 thoroughly removed with kerosene. It will probably be necessary 
 in case of a wheel brake to remove the wheel to do this properly and 
 to remove the brake band in case of a transmission brake. If the 
 brake band is clean and does not need replacement it is ready for 
 adjustment. In a transmission brake there are usually two places 
 for adjustment, at the brake adjusting screw to allow for wear of the 
 brake band and on the brake rods to adjust the position of the brake 
 pedal. Wheel brakes usually have another adjustment to obtain 
 equal pull from the equalizer. 
 
 In adjusting any brake be sure to observe the following points: 
 
 First, make sure that the brake lining clears the drum all around 
 by a small and approximately equal amount with the brake pedal 
 in the fully released position. This adjustment can usually be made 
 with the adjusting screws on the brake and by the brake band 
 supports. 
 
 Second, with the pedal approximately one third depressed the lin- 
 
328 MOTOR VEHICLES AND THEIR ENGINES 
 
 ing should make uniform contact throughout its entire surface with 
 the brake drum. This may be accomplished by adjusting the brake 
 rods and the brake adjusting screws making sure in case of wheel 
 brakes that all take hold at the same time. 
 
 If these adjustments are properly made the service brake should 
 lock the wheels with the car running light when the brake pedal is 
 two-thirds depressed. If the brakes grab or screech a few drops of 
 castor oil or light mineral oil may stop the trouble. 
 
 SPRINGS. In addition to spring lubrication it is important 
 that the spring clips be properly adjusted. The clips themselves 
 should be examined to see that they are not broken and that they fit 
 snugly to the leaves. The bolts should be kept tight but not so tight 
 as to cause the tops of the clips, to be bent in over the top of the spring 
 pinching it and causing either the spring or clip to break. The spring 
 saddle bolts should be inspected frequently to see that they are not 
 loose. 
 
CHAPTER XXXII 
 
 CARE AND ADJUSTMENT TABLES 
 
 A systematic method of attention at definite intervals is necessary 
 to keep motor vehicles operating satisfactorily. Lack of attention 
 does not show immediately, often resulting in certain parts being 
 neglected when unsystematic methods are used. 
 
 Lubrication, adjustment, and inspection should be done at regular 
 intervals rather than on a mileage basis. Particularly when the 
 apparatus is in continuous use, such as trucks or cars used for com- 
 mercial purposes. However, common sense must be used to prevent 
 under or over lubrication when a vehicle is used more than usual or 
 very little. In this case it is best to go back to the mileage basis. 
 It is a popular misconception, particularly among chauffeurs, that 
 lubrication is over-emphasized. To illustrate the method of making 
 systematic inspection, on the basis of daily, weekly, and monthly 
 attention, a table is worked out for the Dodge and Ford cars, as well 
 as F. W. D. and Nash trucks. 
 
 A very important point in the care of a car and one strongly 
 emphasized in the French army is the inspection of motor vehicles on 
 the road. During the first hour's running most of the troubles which 
 will occur have started to develop and an inspection for leaks and 
 loose parts as outlined in Table I made at this time may save serious 
 trouble later. A few moments spent in this manner reduces to a 
 minimum the loss of time which occurs due to break-downs and also 
 keeps down the repair expenses. This will be particularly true of 
 trucks when the apparatus is used continually. 
 
 If all garages or truck and car owners would make out a chart as 
 shown in Table 6 for each particular car, they could keep an exact 
 record of the oil and gasoline used and have a record of the systematic 
 method used to keep the car in proper running order. The only 
 addition needed to make this table complete is to consult the man- 
 ufacturers lubrication chart and list separately each part to be 
 lubricated just as is done in the table for the other cars and trucks. 
 Uses the same checking system as used for the care of the car. 
 
 329 
 
330 MOTOR VEHICLES AND THEIR ENGINES 
 
 TABLE 1 
 ROAD INSPECTION FOR TRUCKS 
 
 1 Before leaving the garage in the morning the oil level in 
 the crank case should be examined, the radiator filled with 
 soft water, and the gasoline tank examined to see if there is 
 sufficient gasoline. Run the engine until warm before starting 
 the car, meanwhile looking for gasoline, oil, or water leaks. 
 It is especially important to have the engine warm before 
 starting the car in cold weather. 
 
 2. As soon as the car is started test the steering mechanism and 
 
 brakes for proper operation, and correct any troubles. Listen 
 carefully for unusual sounds and locate their causes. 
 
 3. After running for about an hour stop the car and examine as 
 
 follows : 
 
 A. Let the engine idle and lift hood. 
 
 Inspect fan belt for tension and bearings for overheating. 
 Examine engine for compression leaks around valve caps and 
 
 plugs. 
 
 Look for air leaks around carburetor and intake manifold. 
 Feel pipe at water pump to see if pump is operating properly. 
 Examine magneto and cables for loose connections. 
 If oil pump can be tested by opening pet cocks do so. 
 
 B. Feel brake drums to see if they are hot due to dragging 
 
 brakes. 
 
 Inspect springs for loose clips and shifted or broken leaves. 
 Note any leakage of oil from differential, axles, or wheels. 
 If the wheels have grease plugs examine to see if tight. 
 Examine hub caps, universal joints, housing, and grease cup 
 
 caps to see if secure. 
 
 C. Note any oil leaks from transmission, universal joints, or 
 
 clutch and if the car has a transmission brake, examine for 
 heat due to brake band dragging. 
 
 D. Examine ground under engine for oil or water dropping 
 
 from leaks. 
 If engine has external oil pump look for oil leaks at pump 
 
 and tubing. 
 Have some one turn steering wheel and examine all steering 
 
 mechanism, particularly drag links and tie rods for loose 
 
 connections. 
 
CARE AND ADJUSTMENT TABLES 331 
 
 4. This inspection should be very carefully made if the car has just 
 
 returned from the repair shop, as defects which may not be 
 noticed in the shop will develop when the engine becomes 
 thoroughly " warmed up." 
 
 5. On returning to the garage, fill with gasoline and carry out the 
 
 daily attention prescribed herein for the particular car. 
 In cold weather drain all water from the cooling system and 
 suspend a tag marked " Drained" from the filler cap. This 
 must always be done when the system is drained. 
 
 TABLE 2 
 
 DODGE CARS 
 
 DAILY ATTENTION 
 
 A. The oil level indicator rod should be examined and enough 
 
 medium grade cylinder oil should be added to bring the top 
 of the rod to within Y^' of the waterjackets. The oil should 
 never be allowed to fall so low that the top of the rod is 
 within }/< of the lower casting. 
 
 B. Turn the following grease cups and refill when necessary with 
 
 cup grease: 
 
 1. Clutch release grease cup. 
 
 2. Engine fan shaft grease cup. 
 
 3. Steering gear tie rod grease cups. 
 
 4. Spring bolt grease cups. 
 
 5. Steering gear worm wheel shaft grease cup. 
 
 6. Steering gear drag link grease cups. 
 
 C. Turn up water pump grease cups and refill every 100 miles. 
 
 D. Examine tires and see that they are properly inflated. 
 
 WEEKLY ATTENTION 
 
 A. With cup grease, 
 
 1. Pack the steering gear drag link. 
 
 2. Remove plug and fill universal joint housing. 
 
 B. With cylinder oil (medium) fill, 
 
 1. Rear spring seat strap oil cups. 
 
 2. Brake operating shaft oilers. 
 
 3. Steering knuckle bolt oil cups. 
 
332 MOTOR VEHICLES AND THEIR ENGINES 
 
 C. Put a few drops of cylinder oil in, 
 
 1. Steering wheel oil hole. 
 
 2. Brake equalizer clevis pins. 
 
 3. All brake pull rods and yoke clevis pins. 
 
 4. Brake operating shaft oilers. 
 
 5. Hand brake lever latch rod and button. 
 
 6. Accelerator pedal shaft brackets. 
 
 7. Spark and throttle rod ball and socket joints. 
 
 8. Brake pedal. 
 
 9. Clutch pedal shaft oil holes. 
 
 D. Clean thoroughly engine, running gear, and body, carefully 
 
 wiping off all excess oil and grease. 
 
 E. Test the specific gravity in each cell of the storage battery with 
 
 a hydrometer. If the specific gravity is below 1.200 the bat- 
 tery needs attention. 
 
 After testing fill with distilled water until the liquid stands 
 y above the plates. Do not fill too full and do not add any- 
 thing but distilled water. 
 
 F. Inspect engine. 
 
 1. See that wiring connections are tight and clean. 
 
 2. Remove, clean, and adjust the spark plugs. 
 
 3. Clean the distributor plate with a dry rag and apply a very 
 
 small amount of vaseline to the distributor track (250 
 miles). 
 
 4. While engine is running inspect water pump packing and 
 
 grease cups for leaks. 
 
 5. Listen to the engine when running for loose bearings or noisy 
 
 timing gears. 
 
 6. Make sure that the oil purnp case cover is securely attached 
 
 and that there is no leak through the gasket. 
 
 7. See that the oil gage registers properly when the engine is 
 
 running. 
 
 8. Test for compression in each cylinder, by turning the engine 
 
 over by hand, and locate cause if compression is weak. 
 
 9. Inject a tablespoonful of kerosene in each cylinder through 
 
 the pet cocks while the engine is hot and let it stand over 
 night'to loosen the carbon in the cylinder. 
 
CARE AND ADJUSTMENT TABLES 333 
 
 G. Inspect cooling system. 
 
 1. Look for leaks in radiator and hose. 
 
 2. See that the fan belt rides evenly and that it has the proper 
 
 tension. 
 
 3. Drain radiator and refill with fresh water. 
 
 H. Inspect gasoline line and carburetor for leaks and clean the 
 strainer. 
 
 I. Examine brake bands to see that they are not dragging or bind- 
 ing or that oil is not leaking on them from the rear axle. Wipe 
 off the brake drums with kerosene if they are oily. 
 
 J. Test front wheels for alignment and see if rear wheels track front 
 wheels. 
 
 K. Inspect springs to see that spring clips are tight and that the 
 leaves have not shifted. 
 
 L. Examine tires for cuts, stone bruising, sand blisters, etc. Test 
 
 air pressure with tire gauge. 
 
 M. Note during week all body squeeks, rattles, etc., and remedy by 
 tightening bolts. Inspect car thoroughly for loose bolts, etc. 
 
 MONTHLY ATTENTION 
 
 A. Remove oil strainer from breather pipe and clean and drain oil 
 
 from crank case (1000 miles). 
 
 Remove blow-out plug at rear end of distributing oil tube in 
 the interior of the crank case and disconnect oil tube at the 
 pump. Blow through this pipe to clean it out. Every other 
 month remove oil strainer at bottom of crank case and clean 
 (2000 miles). Before replacing strainer wash out pan with 
 kerosene poured in through the breather tube. Turn engine 
 over rapidly by hand or starter to remove remaining kerosene. 
 Replace strainer, reconnect oil tube, and refill crank case with 
 six quarts of cylinder oil (medium). When engine is running 
 examine exposed oil pipes for leaks. 
 
 B. Make sure that the valves have the proper clearance (0.004") 
 
 and set those that have not by adjusting the valve tappet 
 adjusting screws. 
 
 C. The wiring of the starting, lighting, and ignition systems should 
 
 be inspected carefully to see that all terminal connections are 
 tight and that the insulation has not been chafed or rubbed 
 off to cause a short circuit. Put four or five drops of cylinder 
 oil (medium) in distributor bearing oil well. 
 
334 MOTOR VEHICLES AND THEIR ENGINES 
 
 D. Remove the plug in the lower end of the steering gear housing 
 
 and fill with cup grease. Also put several drops of cylinder 
 oil (medium) in the spring oiler at the top of the column. 
 
 E. Inspect level of oil in the transmission which should be kept 
 
 up to the idler gear. Every three months (2500 miles) drain 
 the transmission, wash with kerosene, and refill with five pints 
 of transmission oil. 
 
 F. Remove clutch inspection plate and examine clutch release 
 
 grease tube and clutch operation and alignment. 
 
 G. Remove upper and lower plug from differential housing and fill 
 
 with steam cylinder or transmission oil until it runs out of 
 lower plug. Drain, clean with kerosene oil, and refill with 
 oil every three months. 
 
 H. Remove wheels, clean bearings, and repack with grease every 
 two months, packing the front wheels one month and the 
 rear wheels the next. 
 I. Lubricate between the spring leaves every two months with 
 
 grease and graphite. 
 
 J. Examine the chassis for loose bolts or other loose parts, par- 
 ticularly in the following places : 
 
 1. Universal joint ring and yokes. 
 
 2. Transmission arm bolts. 
 
 3. Front motor support bolts. 
 
 4. Oil pan and transmission bolts. 
 
 TABLE 3 
 
 FORD CARS 
 
 DAILY ATTENTION 
 
 A. The crank case should be filled with cylinder oil (medium) until 
 
 it runs out of the upper pet cock. The oil must at all times 
 be kept above the level of the lower pet cock. 
 
 B. Turn the following grease cups and refill when necessary with 
 
 cup grease: 
 
 1. Fan grease cup, several turns. 
 
 2. Rear axle roller bearing grease cup, all the way down. 
 
 C. Put a few drops of cylinder oil (medium) in the following 
 
 places : 
 
 1. Commutator. 
 
 2. Front and rear spring hangers. 
 
CARE AND ADJUSTMENT TABLES 335 
 
 3. Spindle arm and spindle body bolts. 
 
 4. Ball joints on steering connecting rod. 
 D. Inspect and test, 
 
 1. Brakes and adjust if necessary. 
 
 2. Tires for proper inflation. 
 
 3. Tighten loose nuts and wiring terminals. 
 
 4. Springs for breakage. 
 
 5. Wheel alignment and all steering connections. 
 
 WEEKLY ATTENTION 
 
 A. Examine car for gasoline, water, or oil leaks. 
 
 B. Wash and polish car. 
 
 C. Clean the outside of engine and crank case thoroughly. 
 
 D. Wipe off any oil or grease on fan belt and adjust or replace same 
 
 if necessary. 
 
 E. Jack up front end of car and try for excessive lateral play in 
 
 wheels, adjusting the bearings when necessary. 
 
 F. Test alignment of front wheels and adjust if necessary. 
 
 G. Inspect steering system thoroughly. 
 H. Adjust foot pedals. 
 
 I. Equalize and adjust emergency brakes. 
 J. Tighten all loose bolts. 
 
 K. Tighten all loose connections in the ignition system. 
 L. Oil the following parts with a few drops of cylinder oil 
 (medium) : 
 
 1. Starting crank handle. 
 
 2. Ball and socket joints on spark control lever. 
 
 3. Hand brake lever pawl and lift handle. 
 
 4. Controller shaft brackets. 
 
 5. Speed lever on controller shaft. 
 
 6. Brake rod clevis pins. 
 
 7. Brake rod supports. 
 
 8. Emergency brake shoe cam shafts. 
 
 M. Turn the following grease cups and refill when necessary with 
 cup grease: 
 
 1. Steering post bracket grease cup, two turns. 
 
 2. Universal ball joint grease cup, turn down and refill twice. 
 
 3. Drive' shaft housing grease cup, front end, two turns. 
 N. Examine spark plugs, clean and adjust gaps. 
 
336 MOTOR VEHICLES AND THEIR ENGINES 
 
 0. Fill front hub caps with cup grease. 
 
 P. Examine tires for cuts and bruises and test for proper inflation. 
 
 Q. Drain carburetor and sediment bulb of dirt and water. 
 
 MONTHLY ATTENTION 
 
 A. Drain crank case, wash with kerosene, and refill with cylinder oil 
 
 (medium), (1000 miles). 
 
 B. Clean cooling system and examine and repair leaky radiator, 
 
 faulty connections, and worn out hose. 
 
 C. Clean gasoline line. 
 
 D. Remove and clean commutator case. 
 
 E. Examine commutator roller for too much play and wires for 
 
 frayed insulation. 
 
 F. Examine coil unit. 
 
 G. File pitted or uneven points and adjust same to a gap of }(& an 
 
 inch when springs are carefully depressed. 
 H. Remove and clean magneto contact plug on top of transmission 
 
 cover and see that contact points are at the end of the coil 
 
 spring when replacing the plug. 
 I. Test for poor compression, leaking cylinder head gasket, loose 
 
 bearings, and carbon in the cylinders. 
 
 J. Remove the steering case cover, pack the case with cup grease. 
 K. Inspect ball and socket joint at end of steering connecting rod 
 
 and eliminate all loose motion by removing and filing down 
 
 faces of the ball socket caps. 
 L. Jack up front axle and examine for loose spindle arm and worn 
 
 spindle body bushings. 
 M. Examine spring hanger bushing, front and rear, and replace when 
 
 necessary. 
 
 N. Remove front wheel, examine and pack bearings with grease. 
 
 Inspect stationary and adjusting cones before replacing. 
 O. Remove front radius rod ball cap and pack with grease. 
 P. Remove rear hub cap and tighten rear hub lock nuts. 
 Q. Tighten engine bolts to frame. 
 R. Grease springs with graphite and cup grease and replace the 
 
 tie bolts when necessary. 
 S. Tighten spring clip nuts which hold the front and rear spring 
 
 to cross members of the frame. 
 
CARE AND ADJUSTMENT TABLES 337 
 
 T. Tighten spring retainer clips. 
 U. Reline transmission bands if necessary. 
 V. Equalize and adjust emergency brake. 
 
 W. Remove plug in rear axle and fill differential housing one-third 
 full of non-fluid transmission lubricant (1000 miles). 
 
 TABLE 4 
 
 F. W. D. TRUCKS 
 DAILY ATTENTION 
 
 A. The crank case should be filled with cylinder oil (medium) 
 
 until the oil just runs from the upper pet cock on the crank 
 case with engine stopped and car level. Care must be taken 
 not to put more oil than is just necessary to bring it to this 
 level. Do not depend on the oil gauge to tell you the oil level. 
 Make sure the pet cocks on the crank case are not plugged. 
 
 B. A few drops of cylinder oil (medium) should be placed on each 
 
 of the following places : 
 
 1. Outer starting crank bearing. 
 
 2. Inner starting crank bearing. 
 
 3. Rocker pin bearing on fan belt bracket. 
 
 4. Radiator support bearings. 
 
 5. The dogs on the gear shift lever and gear shift lever shaft 
 
 and bearings. 
 
 6. All pins on gear shift rods and clutch and brake rods. 
 
 7. Clutch pedal and brake pedal bearings. 
 
 8. Foot brake bell crank bearings and on pins in foot brake 
 
 mechanism. 
 
 9. Emergency brake equalizer pins and slides. 
 
 10. Pins on emergency brake mechanism. 
 
 11. Spark and throttle control joints and bearings. 
 
 12. Plunger on horn. 
 
 13. Shaft inside upper torque rod spring. After lubricating 
 
 wipe off excess oil. 
 
 C. Turn the following grease cups and when necessary fill with 
 
 cup grease. 
 
 1. Fan pulley bearing, several turns. 
 
 2. Fan belt drive shaft, several turns. 
 
 3. Front spring bolts, one turn. 
 
 4. Steering knuckle, four turns. 
 
338 MOTOR VEHICLES AND THEIR ENGINES 
 
 5. Steering arms, one turn. 
 
 6. Clutch shifter shaft and shifter, several turns. 
 
 7. Water pump, two turns. 
 
 8. Torque rod and arms, one turn. 
 
 9. Gear shifter and jackshaft, one turn. 
 10. Rear springs bolts, one turn. 
 
 D. Turn down grease cups on upper propeller shaft universal joints 
 two turns every other day. 
 
 F. Clean, trim, and fill all lamps and acetylene generator. 
 
 G. Wipe off magneto and wiring. 
 
 WEEKLY ATTENTION 
 
 A. Clean truck thoroughly. 
 
 B. Thoroughly clean engine and engine compartment. 
 
 C. Remove spark plugs, clean and adjust gaps, and replace; inspect 
 
 and clean wiring, and clean distributor plate with gasoline. 
 
 D. Run the engine, watching for water and oil leaks, unusual 
 
 sounds and loose parts; examine for air leaks around inlet 
 manifold and carburetor. 
 
 E. When engine is hot, stop and test compression by turning over 
 
 by hand. 
 
 F. While the engine is hot inject a tablespoonful of kerosene in each 
 
 cylinder through the petcocks and let stand overnight to 
 loosen the carbon. 
 
 G. Turn clutch so that one filling plug is on top. Remove plug and 
 
 turn engine J/ revolution until next plug is on top. Remove 
 this plug and add a mixture of cylinder oil (medium) and 
 kerosene till it runs out of the lower open plug. Replace the 
 plugs. The proportions of oil and kerosene vary from two 
 parts kerosene to one of oil in cold weather to one part kero- 
 sene to two of oil in hot weather. Inspect clutch pedal to 
 see that it does not strike floor board when the clutch is 
 engaged. Adjust clutch brake if necessary. 
 
 H. Pack lower propeller shaft universal joints with grease. 
 
 I. Tighten bolts on alignment joint. 
 
 J. Tighten spring clip nuts and inspect springs for shifted or 
 broken spring leaves. 
 
 K. Inspect wheels for alignment, play, and tighten grease plugs. 
 Inspect tires for cuts and see that rim bolts are tight. 
 
CARE AND ADJUSTMENT TABLES 339 
 
 L. Inspect brake bands and see that they are free from oil and do 
 
 not drag on the drums. 
 
 M. Take up all play on torsion rod springs. 
 N. Drain radiator and refill with fresh water. See that fan belt 
 
 is free from grease and has proper tension. 
 O. Pack ball joints on drag link with grease. 
 
 BI-WEEKLY ATTENTION 
 
 A. On the Eiseman Type G 4 Edition II, Magneto, 20 drops of light 
 
 oil (3 in 1) should be distributed as follows (500 miles): 
 
 1. Oil hole on breaker box, 1 drop. 
 
 2. Small hole at driving end, 5 drops. 
 
 3. Large hole at driving end, 14 drops. 
 
 B. Inspect transmission and subtransmission. Level in transmis- 
 
 sion should be just above top of countershaft. If below add 
 transmission oil to bring it to the required level. Drain 
 the subtransmission which should contain six quarts of trans- 
 mission oil. Add enough to the oil drained out to make up 
 the six quarts and replace. Every three months the trans- 
 mission and subtransmission should be drained, washed with 
 kerosene, and refilled. 
 
 C. Fill the foot brake drum with grease through the plug in 
 
 the cap on the rear of the drum. Remove cap and clean 
 bearings every three months 
 
 D. Check valve clearance adjusting if necessary (intake .004," 
 
 exhaust .006"). 
 
 MONTHLY ATTENTION 
 
 A. Examine interrupter points on magneto, smoothing and ad- 
 
 justing if necessary. Examine control connections and check 
 timing of magneto. 
 
 B. Drain carburetor, gasoline tank, and piping to remove dirt and 
 
 water. 
 
 C. Drain crank case, flush with kerosene, remove lower half of 
 
 crank case, clean, and refill with six quarts of cylinder oil 
 medium). While crank case is off inspect bearings for loose- 
 ness (1000 miles). 
 
 D. Put four ounces of cylinder oil (medium) in governor. 
 
 E. Repack alignment joint with grease. 
 
340 MOTOR VEHICLES AND THEIR ENGINES 
 
 F. Fill front and rear axle housing with grease through plug 
 
 holes. Every three months, drain housing wash with kerosene, 
 and refill with grease. 
 
 G. Fill wheel bearings with grease through plug in hub. 
 
 H. Lift spring retained cover on top of steering column and inject 
 
 ^ pint of transmission oil. 
 
 I. Every two months grease the spring leaves with grease and 
 graphite. 
 
 TABLE 5 
 
 NASH QUAD TRUCKS 
 DAILY ATTENTION 
 
 A. The crank case should be filled with cylinder oil (medium) until 
 
 the indicator rod on the left side of the engine reads 2)4 gal- 
 
 B. Turn the following grease cups and when necessary refill with 
 
 cup grease: 
 
 1. Steering knuckle grease cups. 
 
 2. Water pump grease cups. 
 
 3. Clutch grease cups. 
 
 C. Put a few drops of cylinder oil (medium) in the following 
 
 parts : 
 
 1. Spring shackle oil holes. 
 
 2. Tie rod clevis pins. 
 
 3. Clutch, brake, and gear shift mechanism oil holes. 
 
 4. Motor support oil holes. 
 
 5. Starting crank bearing and dog. 
 
 D. Every second day fill propeller shaft universal joints with cup 
 
 grease. 
 
 E. Wipe off magneto, spark plugs, and wiring. 
 
 WEEKLY ATTENTION 
 
 A. Clean truck thoroughly. 
 
 B. Clean engine and running gear thoroughly. 
 
 C. Remove spark plugs, clean and adjust gaps, and replace. Inspect 
 
 and clean wiring and clean distributor plate with gasoline. 
 
 D. Run the engine watching for oil and water leaks, unusual sounds, 
 
 and loose parts. Examine for air leaks around inlet manifold 
 and carburetor. 
 
CARE AND ADJUSTMENT TABLES 341 
 
 E. When engine is hot stop and test for compression by turning 
 
 over by hand. 
 
 F. While hot, inject a tablespoonful of kerosene in each cylinder 
 
 through the pet cock and allow to stand over night to loosen 
 carbon. 
 
 G. Pack the following parts with grease : 
 
 1. Fan pulley hub. 
 
 2. Drag link boots. 
 
 3. Steering column housing. 
 
 4. Axle universal joints. 
 
 H. Turn the steering tube grease cups and refill when necessary 
 with cup grease. 
 
 I. Oil the following parts with cylinder oil (medium) : 
 
 1. Shifter box and lever. 
 
 2. Hand brake shaft. 
 
 3. Brake rocker shafts and all joints on brake connections. 
 
 4. Transmission support. 
 
 5. Steering knuckle brake cam studs. 
 
 6. Governor drive gears. 
 
 7. Governor (fill chamber weekly and drain monthly). 
 
 J. Tighten spring clip nuts and inspect springs for shifted or 
 broken leaves. 
 
 K. Inspect wheels for alignment and play. Inspect tires for cuts 
 and see that rim bolts are tight 
 
 L. Inspect brake bands and see that they are free from oil and do 
 not drag on the drums. If oily wash with kerosene. 
 
 M. Drain and refill radiator with fresh water. 
 
 BI-WEEKLY ATTENTION 
 
 A. On. the Eiseman Type G 4 Edition II magneto, 20 drops of oil 
 
 should be distributed as follows (500 miles) : 
 
 1. Oil hole on breaker box, 1 drop. 
 
 2. Small hole on driving end, 5 drops. 
 
 3. Large hole on driving end, 14 drops. 
 
 B. Inspect transmission and add enough transmission oil to fill 
 
 case half full or to the level of the overflow plug. 
 
 C. Fill differential housing with transmission lubricant. If this is 
 
 too heavy in winter add some cylinder oil till of the right 
 consistency. 
 
342 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 
 MONTHLY ATTENTION 
 
 A. Examine interrupter points on magneto, smoothing and ad- 
 
 justing if necessary. Examine control connections and check 
 timing of magneto. 
 
 B. Check valve clearance and adjust if necessary (0.006" on inlet 
 
 valves, 0.008" on exhaust). 
 
 C. Drain carburetor, gasoline tank, and piping to remove dirt and 
 
 water. 
 
 D. Drain crank case, flush with kerosene, and refill with cylinder oil. 
 
 E. Fill wheel bearings with grease through inner plug in wheel 
 
 housing. 
 
 F. Lubricate internal gears in wheels through outer plugs in wheel 
 
 housings with transmission lubricant. Do not put in too 
 much as it may leak out on the brake drums. 
 
 G. Every two months grease the spring leaves with grease and 
 
 graphite. 
 
 TABLE 6 
 
 SAMPLE TABLE OF CARE AND ADJUSTMENT 
 FOR GARAGES 
 
 DAILY 
 
 
 8 
 
 9 
 
 10 
 
 11 
 
 12 
 
 13 
 
 1. Gasoline supply 
 
 8 gal 
 
 7 eal 
 
 
 
 
 
 2. Oil level crank case 
 
 1 pt 
 
 x 
 
 
 
 
 
 3. Fill up with water 
 
 x 
 
 x 
 
 
 
 
 
 4. Inspect tires for proper inflation 
 5. Springs for breakage 
 
 X 
 
 x 
 
 X 
 
 x 
 
 
 
 
 
 6. Lubricate as specified by man- 
 ufacturers 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
CARE AND ADJUSTMENT TABLES 
 WEEKLY 
 
 343 
 
 MAY 
 
 8 
 
 15 
 
 22 
 
 1. Clean apparatus thoroughly X X 
 
 2. Thoroughly clean engine and engine compart- 
 
 ment X X 
 
 3. Remove spark plugs, clean and adjust gap, and 
 
 replace X X 
 
 4. Inspect and clean wiring X X 
 
 5. Clean distributor plate with gasoline X X 
 
 6. With engine running check for. 
 
 (a) Water leaks .' X X 
 
 (b) Oil leaks X X 
 
 (c) Unusual sounds X X 
 
 (d) Loose parts X X 
 
 (e) Gasoline line leaks X X 
 
 (f) Air leaks around carburetor and intake. X X 
 
 r i G i G 
 
 7. While engine is hot, test compression by turn- I 2 G 2 G 
 
 ing over by hand . . . 1 3 G 3 F 
 
 I 4 F 4 W 
 
 8. While the engine is still hot inject a tablespoon- 
 
 ful of kerosene in each cylinder and let stand 
 
 over night to loosen up carbon X X 
 
 9. Drain radiator and refill with soft water X X 
 
 10. See that fan belt is free from grease and has 
 
 proper tension X X 
 
 11. Inspect wheels for wheel alignment and play. . X X 
 
 12. Inspect steering apparatus X X 
 
 13. Inspect tires for cuts and see if rim bolts are 
 
 tight X X 
 
 14. Inspect brake bands to see if they are free from 
 
 oil and do not drag on drums; see if they 
 
 brake equally X X 
 
 15. Tighten spring clips and inspect springs for 
 
 cracked, broken, or shifted spring leaves .... X X 
 
 16. If car has storage battery, test specific gravity 
 
 in each cell. If the reading is below 1.200 
 the battery needs attention. After testing 
 fill with distilled water till the liquid stands 
 H inch above plates X X 
 
 17. Lubrication as specified by manufacturers 
 
344 
 
 MOTOR VEHICLES AND THEIR ENGINES 
 MONTHLY 
 
 May 
 
 June 
 
 July 
 
 Aug. 
 
 1. Check valve clearance and adjust X 
 
 2. Examine interrupter points on ignition system. X 
 
 3. Examine control connections. X 
 
 4. Check timing of ignition X 
 
 5. Check all wiring for loose connection and 
 
 chaffed wires X 
 
 6. Drain carburetor, gasoline tank, and piping 
 
 to remove dirt and water X 
 
 7. Clean cooling system X 
 
 8. Test for play in wheel bearings X 
 
 9. Test for play in differential X 
 
 10. Test for play in steering apparatus X 
 
 11. Drain crank case, clean with kerosene, and 
 
 refill with new oil 6 qts 
 
 12. Lubricate as specified by manufacturers 
 
INDEX 
 
INDEX 
 
 Page 
 
 Accelerating Well 68 
 
 Air Cooling 35 
 
 Air Cooled Engine 35 
 
 Air Pressure in Tires 296 
 
 Alcohol as Fuel 62 
 
 Alcohol Use in Radiator 46 
 
 Alignment of Wheels 326 
 
 Ampere, Definition of . . 129 
 
 Anti-freezing Mixtures 46 
 
 Armature 
 
 Generator 210 
 
 Magneto 172 
 
 Atwater-Kent Ignition System ... 168 
 
 Automatic Spark Advance 161 
 
 Auxiliary Air 67 
 
 Auxiliary Air Valve 67 
 
 Axles 
 
 Dead 273 
 
 Live 273 
 
 Axles, Rear 
 
 Full Floating 274 
 
 Semi-Floating 275 
 
 Three-quarter Floating 275 
 
 B 
 
 Backfiring in Carburetors 304, 306 
 
 Ball Bearings 235 
 
 Bar Magnets 117 
 
 Batteries 
 
 Dry 135 
 
 Simple 135 
 
 Storage 138 
 
 Battery Connections 
 
 Parallel 137 
 
 Series 136 
 
 Series-Parallel 137 
 
 Battery Ignition Systems 
 
 Atwater-Kent. 168 
 
 Delco 165 
 
 Four-unit Coil (Ford) 159 
 
 Northeast 161 
 
 Reason for 151 
 
 Remy 168 
 
 Simple 156 
 
 Bearings 
 
 Ball 285 
 
 Plain 285 
 
 Roller 285 
 
 Bendix Drive 219 
 
 Benzol as Fuel 61 
 
 Berling Magnetos 191 
 
 Bevel Gear Drive 260 
 
 Bever Gear Differential. . . 265 
 
 Page 
 
 Bijur Lighting System 219 
 
 Blow-out, Tire 297 
 
 Bosch Magneto 182, 203 
 
 Brake Adjustments 280, 327 
 
 Brake Drums 279 
 
 Brake Equalizers 280 
 
 Brake Rods 280 
 
 Brakes 
 
 External 279 
 
 Internal 277 
 
 Shaft 279 
 
 Wheel 279 
 
 Brake Troubles 280 
 
 Buick Clutch. . . 234 
 
 CadUlac- 
 
 Carburetor. . . , 83 
 
 Cooling System 40 
 
 Firing Order 30 
 
 Pump 39 
 
 Thermostat 39 
 
 Calcium Chloride, Use in Radiator 47 
 
 Camber 283 
 
 Cannon and Engine compared ... 8 
 
 Carbon Monixide 67 
 
 Carbon Removal 319 
 
 Carburetor 
 
 Adjustment Precautions 67 
 
 Definition of 63 
 
 Simple 64 
 
 Carburetors 
 
 Cadillac 83 
 
 Holley 114 
 
 Hudson 91 
 
 Kingston Model E 75 
 
 Kingston Model Y 114 
 
 Marvel 86 
 
 Packard 76 
 
 Peerless 78 
 
 Pierce Arrow 79 
 
 Rayfield 104 
 
 Schebler Model A Special 106 
 
 Schebler Model E 72 
 
 Schebler Model H 73 
 
 Stewart 89 
 
 Stromberg Model G 81 
 
 Stromberg Model M 93 
 
 White 109 
 
 Zenith 99 
 
 Carburetion, Principles of 63 
 
 Care and Adjustment Tables 
 
 Dodge 331 
 
 Ford 334 
 
 F. W. D. . . 337 
 
 347 
 
348 
 
 INDEX 
 
 Page 
 
 Care of Gasoline 54 
 
 Casings, Tire 291 
 
 Caster Effect 283 
 
 Cells (see Batteries). 
 
 Centrifugal Pump 44 
 
 Chain Drive 258 
 
 Charging Storage Batteries 143 
 
 Chemical Reaction in Storage Bat- 
 tery 140 
 
 Chokes 69 
 
 Circuit Breaker 218 
 
 Clincher Tires 291 
 
 Clutch Adjustment 326 
 
 ClutchBrake 232 
 
 Clutch, Object of 232 
 
 Clutch Requirements 232 
 
 Clutch Troubles 240 
 
 Coils- 
 Induction 151 
 
 Vibrating 149 
 
 Cold Test for Oils 310 
 
 Combustion of Fuel 1 
 
 Combustion of Gasoline 
 
 Lower Limit 63 
 
 Upper Limit 63 
 
 Commutator 209 
 
 Compound Wound Machines 212 
 
 Compression Leaks 317 
 
 Condensers for Cooling Systems. . 41 
 
 Condensers for Ignition 150 
 
 Conductors 131 
 
 Cone Clutch 233 
 
 Cooling Losses 5 
 
 Pooling Systems 34 
 
 Cooling System, Cleaning 321 
 
 Cord Tires 289 
 
 Counter Balancing of Parts 21 
 
 Counter Balance Weights 22 
 
 Crank Case, Cleaning 314 
 
 Crude Oil as Fuel. 55 
 
 Crude Oil, Composition of 55 
 
 Cup Grease 311 
 
 Cut Out, Magnetic 214 
 
 Cycle of an Engine 8 
 
 Delco Ignition System 165 
 
 Delco Starting and Lighting System 222 
 
 Diesel Engine 1 
 
 Differential Lock 268 
 
 Differential, Object of 263 
 
 Differential, Operation of 263 
 
 Differential Reduction 260 
 
 Direct Current Machines 207 
 
 Distance Rods 262 
 
 Distilled Water, Use 143 
 
 Distillation of Crude Oil 56 
 
 Distributors 154, 324 
 
 Distributor, Speed of 155 
 
 Dixie Magneto . 197 
 
 Page 
 
 Dodge- 
 Care and Adjustment Table. . 331 
 
 Drive Shaft 259 
 
 Firing Order 25 
 
 Fuel Feed System 50 
 
 Ignition Syst m 161 
 
 Steering Apparatus 284 
 
 Timing... 18 
 
 Transmission 248 
 
 Drag Link 282 
 
 Draining Radiator 46 
 
 Drive, How to 299 
 
 Drive Shafts 259 
 
 Dry Cell, Composition of 136 
 
 Dual Ignition 201 
 
 Dunlop Tires 291 
 
 E 
 
 Efficiency- 
 Mechanical . 
 Thermal. . 
 
 6 
 
 7 
 
 Eight Cylinder Engine 28 
 
 Eisemann Magneto 188 
 
 Electrical Circuits 132 
 
 Electrical Lag 152 
 
 Electrical Resistance 131 
 
 Electrical Symbols 134 
 
 Electricity 128 
 
 Electrolyte 138 
 
 Electro-Magnetic Induction 146 
 
 Engine Balance 21 
 
 Engine Horse Power 6 
 
 Engine Knock 304, 306 
 
 Engine Lacks Power 304, 307 
 
 Engine Misses 303, 305 
 
 Engine Nomenclature 2 
 
 Engine Overheats 304, 307 
 
 Engine Timing, Average 19 
 
 Engine Troubles 303 
 
 Engine Won't Stop 305, 308 
 
 Expansion Due to Heat 1 
 
 Fans 45 
 
 Faraday's Law 175 
 
 Field Windings 210 
 
 Fire Point for Oils 310 
 
 Firing Orders 
 
 Cadillac 30 
 
 Dodge 25 
 
 Ford 25 
 
 Four-wheeled Tractor 25 
 
 F. W. D 25 
 
 Holt 25 
 
 Nash 25 
 
 Packard 25 
 
 Packard 12 30 
 
 Standardized B 25 
 
 White.. ... 25 
 
INDEX 
 
 349 
 
 Page 
 Firing Orders, Possible 
 
 Four Cylinder 25 
 
 Six Cylinder 28 
 
 Flash Point of Oils 310 
 
 Flexible Couplings 178 
 
 Float Chambers 64, 70 
 
 Flooding Carburetor 69 
 
 Fly-wheel, Reason for. ; 30 
 
 Force Cooling System 37 
 
 Ford- 
 Bevel Gear Drive 260 
 
 Care and Adjustment Table. . . 334 
 
 Commutator Timing 326 
 
 Cooling System 37 
 
 Differential 265 
 
 Firing Order 25 
 
 Ignition Wiring 169 
 
 Magneto 225 
 
 Transmission 253 
 
 Four Cycle Engine 13 
 
 Four Cycle Engine Operation .... 10 
 
 Four Cylinder Engine 25 
 
 Four Unit Coil Ignition System . . 159 
 Four-wheel Tractor Firing Order. . 25 
 
 Frames 270 
 
 Freezing of Storage Batteries 144 
 
 Friction Transmission 243 
 
 Front Axles 273 
 
 Fuel Feed Systems 48, 322 
 
 Fuel Oil 56 
 
 Fuels 55 
 
 F. W. D. 
 
 Care and Adjustment Table . . 337 
 
 Firing Order 25 
 
 Timing 18 
 
 Transmission. . .251 
 
 Gas Engine 1 
 
 Gasoline as Fuel 58 
 
 Gasoline Fire, How Extinguished. 54 
 
 Gather 283 
 
 Gear Grease 316 
 
 Gear Ratio 243 
 
 Gear Reduction 243 
 
 Gear Rotation 242 
 
 Gear Shift Mechanism 248 
 
 Generator Armature 210 
 
 Generator, Charging Rate 214 
 
 Generator, Principle of 208 
 
 Generator Regulation 215 
 
 Glycerine, Use in Radiator 47 
 
 Governors ; 71 
 
 Gravity Fuel Feed System 48 
 
 Grids, Storage Battery 138 
 
 Heat Energy Diagram 5 
 
 Hete-Shaw Clutch.. . 236 
 
 Page 
 
 Helical Gear Drive 261 
 
 High Tension Magnetos 178, 196 
 
 Holly Carburetor 114 
 
 Holt 
 
 FiringOrder 25 
 
 Radiator 44 
 
 Timing 18 
 
 Horse Power 
 
 Brake 6 
 
 Formulae 6 
 
 Indicated 7 
 
 Hotchkiss Drive 262 
 
 How to Drive 299 
 
 Hudson Carburetor 91 
 
 Hydrometer 141 
 
 I 
 
 Ignition Timing 21, 325 
 
 Impulse Starter 177 
 
 Indian Motorcycle Transmission. 246 
 
 Induction, Laws of 147 
 
 Induction Coil, Vibrating 158 
 
 Inertia, Gasoline 68 
 
 Inner Tubes 292 
 
 Insulators 131 
 
 Interrupter, Gap at Points of. ... 154 
 
 K 
 
 Kerosene as Fuel 61 
 
 Kerosene in Cooling System 47 
 
 King Pin 282 
 
 Kingston Carburetors 75, 114 
 
 Knocks, Engine 304, 306 
 
 K. W. Magneto 196 
 
 Laws of Induction 147 
 
 Laws of Magnets 122 
 
 Lean Mixture 64 
 
 Leese-Neville System 218 
 
 Loadstone 117 
 
 Low Tension Magnetos. . . 178, 196, 201 
 Lubricants 
 
 Specifications of 310 
 
 Cold Point 310 
 
 Fire Point 310 
 
 Flash Point 310 
 
 Specific Gravity 310 
 
 Viscosity 310 
 
 Lubricating Systems 
 
 Force Feed 313 
 
 Force Feed with Splash 312 
 
 Full Force Feed 313 
 
 Splash 311 
 
 Splash with Circulating Pump. 312 
 
350 
 
 INDEX 
 
 Page 
 
 Lubrication, Object of 309 
 
 Lubrication of Clutch 314 
 
 Lubrication of Engine 3 
 
 Lubrication of Joints 314 
 
 Lubrication of Magneto 324 
 
 Lubrication Troubles 314 
 
 M 
 
 Magnetic Induction 122 
 
 Magnetic Field, Resultant 120 
 
 Magnetic Fields 
 
 About Bar Magnet 118 
 
 About Current Carrying Con- 
 ductor 124 
 
 About an Electro-Magnet 126 
 
 About a Helix 125 
 
 About Horse Shoe Magnet. ... 119 
 
 About a Loop of Wire 125 
 
 About Solenoid 125 
 
 Magnetic Leakage 117 
 
 Magnetic Substance 117 
 
 Magnetic Whirls 124 
 
 Magnetism, Definition of 117 
 
 Magneto and Battery Systems 
 
 Bosch Dual 203 
 
 Remy Dual 201 
 
 Vibrating Duplex 205 
 
 Magneto Lubrication 324 
 
 Magneto, Principle of Operation 
 
 Armature Type 172 
 
 Rotor Type 193 
 
 Magneto, Typical Construction ... 179 
 Magnetos 
 
 BerlingB21 192 
 
 BerlingF41 191 
 
 Bosch Du4 182 
 
 Bosch LT4 186 
 
 Bosch ZEV 186 
 
 Bosch ZR4 185 
 
 Dixie 197 
 
 Eisemann 188 
 
 Ford 225 
 
 K-W 196 
 
 Remy 193,201 
 
 Magnets 
 
 Effect of Heat 123 
 
 Effect of Vibration 123 
 
 Electro 126 
 
 Permanent 117 
 
 M. and S. Differentials 267 
 
 Marking of Fly Wheel 19 
 
 Marking of Timing Gear 19 
 
 Marvel Carburetor 86 
 
 Master Vibrator 160 
 
 Mechanical Advantage of Gears. . 241 
 
 Mechanical Balance 21 
 
 Method of Drive 259 
 
 Mixture, Lean, Perfect or Rich ... 64 
 
 Molecular Theory 122 
 
 Motor, Electric 212 
 
 Motor-cycle Magnetos 179 
 
 Motor-generator 
 
 Effect of Speed on 214 
 
 Rotation 213 
 
 Motor, Principle of 212 
 
 Motor Rule 213 
 
 Mufflers 286 
 
 Multiple Disc Clutch 240 
 
 Multi-cylinder Engine, Advantages 30 
 Mutual Induction 148 
 
 N 
 Nash 
 
 Care and Adjustment Table. . 340 
 
 Clutch 239 
 
 Firing Order 25 
 
 Transmission 251 
 
 Needle Valves 66 
 
 Negative Plates, Composition of. . 138 
 
 Non-Megnetic Substances 117 
 
 Non-saturated Coil (also see 
 
 Timers) 154 
 
 Northeast Ignition System 161 
 
 Northeast Starting and Lighting 
 
 System 215 
 
 Offset Cylinders 
 
 Ohm, Definition of 
 
 Ohm's Law 
 
 Oil (see Lubricants). 
 
 One Cylinder Engine 
 
 Over-heated Engine, Effect of. 
 
 20 
 129 
 130 
 
 21 
 34 
 
 Packard 
 
 Carburetor 76 
 
 Clutch 236 
 
 Cooling System 41 
 
 Firing Order 25,30 
 
 Packing Water Pump Glands 321 
 
 Peerless Carburetor 78 
 
 Permeability 119 
 
 Pet Cocks 69 
 
 Pierce- Arrow Carburetor 79 
 
 Pitman Arm 282 
 
 Plain Bearings 285 
 
 Planitary Transmission 253 
 
 Plate Clutch 237 
 
 Plates for Storage Battery 138 
 
 Pneumatic Tires 289 
 
 Pocketed Spark Plugs 158 
 
 .Polarity 117 
 
 Positive Plates, Composition 138 
 
 Power Balance 21 
 
 Power Overlap 33 
 
 Power Transmission Units 227 
 
 Pressure Fuel Feed System 49 
 
 Pressure, for Tires 296 
 
INDEX 
 
 351 
 
 Page 
 
 Pressure Gauge 49 
 
 Pressure Pump, Gasoline 49 
 
 Primary Air 65 
 
 Priming 69,315 
 
 Progressive Gear Transmission . . . 244- 
 Puddle Type Carburetor 114 
 
 Pumps 
 
 Centrifugal 44 
 
 Gear. . 43 
 
 Quick Detachable Tires 294 
 
 Radiators 
 
 Cellular 45 
 
 Honey-comb 44 
 
 Tubular 44 
 
 Radius Rods 262 
 
 Rate of Flame Propagation 64 
 
 Rayfield Carburetor 104 
 
 Rear Axles 274 
 
 Remy Ignition System 168 
 
 Remy Magneto 193, 201 
 
 Residual Magnetism 210 
 
 Reversing Switch, Ignition 163 
 
 Rich Mixtures 64 
 
 Right-hand Rule for Magnetism. . 126 
 Right-hand Rule for Induction. . . 147 
 
 Rims 289 
 
 Road Inspection 330 
 
 Rock of the Piston 17 
 
 Roller Bearings 285 
 
 Running Gear 270 
 
 Safety Spark Gap 185 
 
 Saturated Coil 154 
 
 Schebler Carburetors 91, 106 
 
 Secondary Air 67 
 
 Selective Gear Transmission 246 
 
 Self-Induction 148 
 
 Series Wound Machine 211 
 
 Shaft Drive 258 
 
 Shunt Wound Machine 211 
 
 Six Cylinder Engine 26 
 
 Skidding 302 
 
 Spark Plugs 156 
 
 Spark Plug Gap 157 
 
 Spark Plug Location 157 
 
 Spark Plug Threads 157 
 
 Spark Plug Troubles 323 
 
 Specific Gravity, Storage Battery. 141 
 
 Spray Nozzle 64 
 
 Spring Clips 273 
 
 Spring Saddle Clips 271, 328 
 
 Spring Shackles 271 
 
 Page 
 
 Springs 
 
 Cantilever 272 
 
 Full Elliptic 272 
 
 Platform 272 
 
 Three-quarters Elliptic 272 
 
 Semi-Elliptic 272 
 
 Springs, Care of 328 
 
 Spur Gear Differential 266 
 
 Standardized B 
 
 Firing Order 25 
 
 Starting and Lighting Systems 
 
 Bijur 220 
 
 Detco 222 
 
 Ford 225 
 
 Leese-Neville 218 
 
 Northeast 215 
 
 Steering Apparatus 282 
 
 Steering Gear 
 
 Irreversible 284 
 
 Reversible 284 
 
 Steering Gear Adjustment 327 
 
 Steering, How Accomplished 281 
 
 Steering Knuckle 282 
 
 Stewart Carburetor 89 
 
 Stewart Vacuum System 51 
 
 Storage Battery Charging Board . . 145 
 Storage Batteries 
 
 Care of 143 
 
 Charging 143 
 
 To Put in Operation 142 
 
 Strokes of a Four-cycle Engine 
 
 Compression 10 
 
 Exhaust 10 
 
 Suction 10 
 
 Power 10 
 
 Stromberg Carburetors 81, 93 
 
 Sub-frame 270 
 
 Suction, effect of 65 
 
 Temperature for Cooling Water . . 34 
 
 Thawing Out Engine. 47 
 
 Thermo-Syphon Cooling System . . 35 
 Thermostatic Controlled Cooling 
 
 System 39 
 
 Thermostat 39 
 
 Third Differential 269 
 
 Threads, Spark Plug 157 
 
 Three-point Suspension 270 
 
 Three-cylinder Engine 26 
 
 Throttle 65 
 
 Thrust Bearing 286 
 
 Tie Rod 282 
 
 Timer Control 154 
 
 Timer-Distributor 155 
 
 Timers 152 
 
 Timer Speed 153 
 
 Tire Casing 289 
 
 Tire Chains 293 
 
 Tire Construction. . . 289 
 
352 
 
 INDEX 
 
 Tires- 
 Pneumatic 289 
 
 Solid 293 
 
 Tires, Care and Attention 296 
 
 Tires, Troubles and Repairs. . . 297 
 
 Toe in on Wheels 326 
 
 Torque Arms 262 
 
 Torque Tubes 262 
 
 Transmission 
 
 Object of 241 
 
 Types 244 
 
 Twelve Cylinder Engine 30 
 
 Two-cycle Engine 
 
 Advantages 13 
 
 Disadvantages 13 
 
 Two Port 11 
 
 Three Port 12 
 
 Two-cylinder Engine 
 
 Vertical 180. . 23 
 
 Vertical 360 23 
 
 Unisparker 168 
 
 Universal Joints 258 
 
 Vacuum Fuel Feed System 51 
 
 Valve Clearance 318 
 
 Valve Grinding 318 
 
 Valve Tappet Adjustment 318 
 
 Page 
 Valve Timing 
 
 Exhaust 16 
 
 Inlet 14 
 
 Valves, Inner Tubes 292 
 
 Vaporization of Liquids 69 
 
 Venturi Tube 65 
 
 Vibrators 149 
 
 Viscosity of Oils 310 
 
 Volt, Definition of 129 
 
 Voltage 
 
 Of Dry Cells 136 
 
 Of Storage Cells 138 
 
 W 
 
 Water Analogy for Current Flow 1 28 , 1 32 
 
 Wheel Alignment 326 
 
 Wheels- 
 Steel 277 
 
 Wire 277 
 
 Wood 276 
 
 White- 
 Carburetor 109 
 
 Clutch 239 
 
 Firing Order 25 
 
 Timing 18 
 
 Transmission 250 
 
 Wiring Inspection 323 
 
 Worm Drive 261 
 
 Worm Gear Differential . . . 266 
 
 Zenith Carburetor. . 99 
 
UNIVERSITY OF CALIFORNIA LIBRARY 
 BERKELEY 
 
 Return to desk from which borrowed. 
 This book is DUE on the last date stamped below. 
 
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 : EB L 2 1990 
 AB i-Ld 07 1990 
 
 
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 ERSITY OF CALIFORNIA LIBRARY OF THE UNIVERSITY 0<F CALIFORNIA 
 
 
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