TJ 
 
 T 
 
 3 
 
 UC-NRLF 
 
LIBRARY 
 
 UNIVERSITY -OF CALIFORNIA. 
 
 Class 
 
GASOLOGY 
 
 Price Fifty Cents 
 
GASOLOGY 
 
 BEING A REPRINT FROM THE 
 
 GAS ENGINE COURSE OF 
 
 GAS REVIEW 
 
 PUBLISHED BY 
 
 GAS REVIE w 
 
 I! 
 
 MADISON, WISCONSIN 
 
\ 
 
 Copyright, 1910 
 
 By 
 We American Ghresherman 
 
FOREWORD 
 
 This little volume is a compilation of the first twenty- 
 seven lessons of the "Gas Engine Course" which has been 
 published as a serial in Gas Review. 
 
 When Gas Review first started three years ago it was 
 deemed advisable to offer a complete course in gas and gas- 
 oline engineering. One requirement of these lessons was 
 that they were to be written in plain, simple language that 
 anyone could understand. We have followed that idea all 
 the way through and the lessons won the approval of our 
 readers from the start. 
 
 There were many calls for back copies of Gas Review 
 from those who subscribed late and who wanted to own a 
 complete copy of the lessons and we concluded to publish 
 them in book form since we were unable to supply back 
 copies of the magazine. 
 
 The lessons do not cover the whole subject for the reason 
 that they are not yet completed. However, as far as they 
 have gone they cover the subject quite completely and it is 
 believed will give the reader much valuable information in 
 regard to the best modern practice. 
 
 We have drawn freely from many sources in preparing 
 the lessons and make no claims for originality in anything 
 except the phraseology and general arrangement of the sub- 
 ject matter. In these particulars we believe we have suc- 
 ceeded in producing a book that has the great merit of 
 clearness and simplicity. It is a book primarily for the 
 beginner and the actual user. 
 
CONTENTS 
 
 CHAPTEE I. GAS ENGINE PRINCIPLES. 
 
 Explanation of the events in a four-cycle engine; comparison of gas en- 
 gine and steam engine; transformation of heat into useful work; heat units; 
 chemistry of combustion; proportions of the fuel mixture; timing of igni- 
 tion; simple methods of cooling the cylinder; laws governing pressure, vol- 
 ume and temperature of a gas. 
 
 CHAPTER II. IGNITION. 
 
 Methods of ignition; description of the hot tube system; ignition by com- 
 pressing the charge; systems of electric ignition; electrical terms defined; 
 kinds of batteries; action of simple primary cell; polarization; Edison Le 
 Lande cell; arrangement of cells; construction and chemical action of dry 
 cells. 
 
 CHAPTEE III. MAGNETISM AND COILS. 
 
 Magnetos; magnetism and magnetic lines of force; electro-magnetic in- 
 duction; the kick coil; jump spark coil with vibrator; induction; condensers. 
 
 CHAPTEE IV. DYNAMO ELECTRIC GENERATORS. 
 
 How an electric current is generated; description of simple generator; 
 the action of a magneto; high tension and low tension magnetos; magneto 
 troubles; testing and repairing a magneto. 
 
 CHAPTEE V. STORAGE BATTERIES. 
 
 The elements and the electrolyte; explanation of chemical reactions; 
 charging a storage battery; charging from a lighting circuit; the rating of 
 storage batteries; laying up a battery. 
 
 CHAPTEE VI. WIRING AN ENGINE. 
 
 Cells connected in series, in multiple, in series multiple; simple make and 
 break ignition; description of timer; wiring single cylinder engine using 
 battery and jump spark; same with two batteries; wiring two-cylinder ver- 
 tical engine jump spark using two batteries; same for two-cylinder op- 
 posed engine one coil dry cells and storage battery; wiring for four- 
 cylinder engine using battery; same with one coil and distributer; wiring 
 multi- cylinder engine with magneto; same with magneto and battery. 
 
 CHAPTEE VII. ENGINE BALANCE. 
 
 Methods of balancing a single cylinder engine; effect of fly wheels; ar- 
 rangement of cranks in multi-cylinder engines; the order of firing; effect 
 of rotating and of reciprocating parts. 
 
 CHAPTEE VIII. CARBURETORS. 
 
 Carburetion defined; proportion of air to gasoline required; principles of 
 carburetion; effect of faulty mixtures; action of the spray carburetor; dif- 
 ferent forms of spray carburetors ; types of carburetors ; action of float feed 
 carburetors; automatic carburetors; examples of modern carburetors. 
 
 CHAPTEE IX. HORSE POWER FORMULAS. 
 
 How work is measured; horse power; formulas for figuring horse power; 
 gas engine efficiency. 
 
CHAPTER I 
 
 GAS ENGINE PRINCIPLES 
 
 LESSON I. 
 
 In presenting this series of lessons on the gas engine, the aim will 
 be to explain as clearly as possible the principles of action of each 
 type considered, the various mechanisms by which the engine is en- 
 abled to perform its operations, together with directions in regard to 
 the care and proper method of handling gas engines. 
 
 Very little attention will be given to the principles of designing 
 and the computations necessary for the proportioning of the various 
 parts. Neither will 
 much attention be 
 given to the mathe- 
 matical theory of the 
 gas engine beyond 
 what can be worked 
 out by the simpler 
 rules of arithmetic. 
 The aim of these 
 lessons is to help 
 
 those who are running gas engines, rather those who are designing 
 them. To this end the lessons will be rather elementary in character. 
 
 The term gas engine is commonly applied to any engine in which 
 the fuel is first turned into a gaseous state and then burned in the en- 
 gine cylinder. Gasoline engines, kerosene engines, crude oil engines 
 and alcohol engines are all called gas engines, as well as those that run 
 on either city gas or producer -gas. A better appellation for such 
 engines and one that is now frequently applied is "internal combus- 
 tion engines." 
 
 The general principles governing both the construction and the 
 operation of a gas engine are nearly the same as in a steam engine. 
 The object in both is to obtain useful work from heat, that is, to 
 transform heat energy into work. In the steam engine fuel is burned 
 in a furnace under a boiler which contains water. The water is 
 heated to the boiling point and steam is formed. This steam is piped 
 to the cylinder of an engine and is there made to push a piston back 
 and forth and rotate a shaft which is connected therewith by suitable 
 connectors. In the steam engine, therefore, there are three distinct 
 
 218577 
 
GASOLOGY. 
 
 parts, the furnace, the toiler and the engine the two latter may be 
 close together, or: at a considerable distance from each other and con- 
 nected by means of a steam pipe. In any event, the source of heat and 
 the moving piston are at a considerable distance apart, with the boiler 
 intervening. 
 
 In the case of the gas engine the transformation of heat into work 
 is accomplished in a simpler and more nearly direct manner. The 
 fuel, together with the necessary air for combustion, is introduced di- 
 rectly into the engine cylinder where it is burned. The gases or smoke 
 resulting from this burning of the fuel are raised to a very high tem- 
 perature, estimated at from two thousand to three thousand degrees 
 Fahrenheit. This high temperature causes the pressure of the gases to 
 rise and provides the motive force for moving the piston. 
 
 In both the steam engine and the gas engine heat is the motive 
 force. In both, heat is applied to a gaseous substance in order to raise 
 its pressure and do work. In the former the gas is steam, in the lat- 
 ter it is smoke resulting from the combustion of the charge of fuel 
 introduced into the cylinder. The similarity in the principles of op- 
 eration of the two types of engines has thus been pointed out, and it is 
 quite evident that of the two the gas engine is the simpler. It ought 
 also to be more efficient, that is, it ought to transform a larger amount 
 of heat energy of the fuel into work than the steam engine because of 
 its simplicity, and, as a matter of fact, it does. The average steam 
 engine can only turn from five to ten per cent of the heat energy of 
 the fuel into work, while an ordinary gas engine utilizes from twelve to 
 twenty-five per cent. Despite the difference in efficiency, however, the 
 
 steam engine possesses 
 certain advantages in 
 operation that make it 
 a more desirable form 
 of motor for many 
 kinds of work than the 
 gas engine, while for 
 certain other purposes 
 the gas engine is with- 
 out a rival. 
 
 $ Ccmpnititf if 
 \ the clacft 
 
 
 ! 
 
 
 
 
 
 \ \. 5* 
 
 FIG. 2. 
 
 Before going further into the matter of efficiencies or advantages 
 of the different types of heat engines, we will first discuss the ele- 
 mentary mechanism of a gas engine. 
 
 Every gas engine, no matter whether it uses alcohol, gasoline, kero- 
 sene or some other gaseous or liquid fuel, must have certain parts, no 
 matter how different engines may vary in other details. These parts 
 are shown diagramatically in the four accompanying sketches Figs, 
 
GAS ENGINE PRINCIPLES. 
 
 1, 2, 3 and 4, with all the parts named. The type of engine illustrat- 
 ed is called the four-stroke cycle engine or sometimes-, simply the 
 four cycle engine, since four separate strokes of the piston are nec- 
 essary to complete its cycle of operation. There is another type of 
 engine which completes its entire cycle in two strokes, or one revo- 
 lution of the crank shaft, called a two-stroke cycle engine. 
 
 Referring to Fig. 1, it will be noticed that the length of the cylin- 
 der is considerably greater than the length of the stroke and of the 
 piston combined. When the piston is at the left end of the cylinder 
 there is still left 
 a considerable space 
 between the piston 
 and the cylinder 
 head. This space is 
 sometimes called the 
 clearance, sometimes 
 the compression 
 chamber and some- 
 times the explosion 
 
 FIG. 3. 
 
 chamber, since it performs all three of these functions. Both the 
 inlet valve and the exhaust valve are located in this chamber and both 
 open inward. When the piston moves toward the right from its 
 extreme inner position, a charge of fuel and air, which has been 
 first mixed in the proper proportions, is drawn in through the inlet 
 valve, while at the same time the exhaust valve is held shut. 
 
 On the return stroke of the piston, shown in Fig. 2, both valves re- 
 main closed and the charge is forced back and compressed in the com- 
 pression chamber. The amount of compression varies according to the 
 size of the chamber in the various makes of engines and according 
 to the fuel used, but may be taken roughly as being from fifty to one 
 hundred and fifty pounds per square inch. Just before reaching 
 
 the inner dead cen- 
 ter, the charge is ig- 
 nited, combustion or 
 explosion takes place, 
 and the piston 
 starts toward the 
 right again, as 
 shown in Fig. 3. 
 
 T-, During this stroke 
 
 -C IG. 4. i ,1 n 
 
 both valves remain 
 
 closed until almost at the end of the stroke, when the exhaust valve 
 is forced open and the spent charge is allowed to escape. During 
 the fourth stroke, see Fig. 4, the exhaust valve remains open and the 
 
8 GASOLOGY. 
 
 burnt gases are forced out of the cylinder by the retreating piston. Just 
 previous to the end of this stroke the exhaust valve snaps shut and 
 on the fifth stroke a new charge is drawn in, thus beginning a new 
 cycle of operations, and subsequently the whole series of operations 
 is repeated indefinitely and automatically as long as the mechanism 
 is in running order. 
 
 While the above parts are essential to every gas engine, it will be 
 understood, of course, 'that an engine so constructed would not run. 
 There are other parts and details necessary to a complete working en- 
 gine, all of which will be taken up and described in subsequent les- 
 sons. 
 
 * 
 
 LESSON II. 
 
 The gas engine, like the steam engine, is a heat motor. It trans- 
 forms heat into mechanical energy. Consequently, to be in any meas- 
 ure complete, a study of the gas engine must include a study of the 
 laws of heat. 
 
 Heat is not a substance but a condition. It has been defined as a 
 form of energy. When a body is hot all of its particles or molecules 
 are in a rapid state of vibration; the hotter it is the more rapid the 
 vibration. As it cools, the particles move less and less rapidly and 
 through shorter distances, thus causing the body to contract. There 
 is a difference between temperature and quantity of heat. Tempera- 
 ture merely measures the intensity of heat and not the amount. For 
 example, if a small rod of iron be heated red hot and then be plunged 
 into a barrel of water, it will lose its heat to the water without raising 
 have absorbed all the heat of the iron down to its own temperature, 
 the temperature of the water a perceptible amount. Yet the water will 
 
 In order to measure quantity of heat, a unit of measurement has 
 been adopted by engineers, called the British Thermal Unit generally 
 written in engineering work simply B. t. u. A B. t. u. may be defined 
 as the amount of heat necessary to raise one pound of water from 
 sixty-two to sixty-three degrees F. The heating of two pounds of 
 water through the same range of temperature requires two heat units 
 and so on. Water is taken as the measuring substance because it ab- 
 sorbs more heat for a certain weight than almost anything else. 
 
 There is, as foreshadowed in the first part of this lesson, a definite 
 relation between heat and work. Careful experiments have proven 
 that a heat unit is equal in mechanical energy to 778 foot pounds. 
 That is, the amount of heat necessary to heat one pound of water one 
 degree is equivalent to raising a weight of 778 pounds one foot high, 
 or, what is the same thing, raising one pound 778 feet high. 
 
GAS ENGINE PRINCIPLES. 9 
 
 The reader may inquire at this point what the above conception of 
 heat has to do with a gas engine. The answer is easily given. A 
 pound of fuel contains a certain number of B. t. u. and since it is the 
 duty of the engine to transform them into work, it follows that if we 
 want to find out just how efficient an engine is we must measure the 
 number of heat units supplied in the form of fuel and then determine 
 how many of these heat units have been turned into useful work at 
 the band wheel. To illustrate, every pound of gasoline contains from 
 18,000 to 20,000 B. t. u. If on testing an engine we found that for 
 every pound of gasoline used we obtained the value of 4,500 to 5,000 
 B. t. u. in useful work, then the actual heat efficiency of the engine 
 would be twenty-five per cent. That is, one-quarter of the heat 
 producing power of the gasoline was turned into useful work and 
 three-quarters was lost. That which is lost is carried away, in 
 part by the jacket water, in part by the exhaust gases, while 
 the remainder is lost in overcoming the friction of the engine 
 and through radiation. A complete test of an engine takes account of 
 all these losses and if the engineer who makes the tests understands the 
 laws of heat, he can determine very closely just how much is lost in 
 each of the different ways above mentioned. A complete discussion 
 of the laws of heat will be reserved for a future lesson when directions 
 will be given for making a complete test. 
 
 We will now proceed to discuss some of the effects of heat. The 
 general effect of heating a body is to cause it to expand. If a gas, 
 such as air, is heated it expands, or if it is imprisoned so that it can- 
 not expand, it exerts a pressure on the walls of the containing vessel 
 in proportion to its absolute temperature. The absolute temperature, 
 by the way, is measured from absolute zero, that is, a point 461 de- 
 grees below zero on the Fahrenheit scale and is the point at which all 
 molecular motion ceases. Above that temperature all the bodies are 
 supposed to contain some heat and their particles are in a state of 
 motion. The expansion or rise in pressure of a gas when heated is 
 the principle that is taken advantage of in a gas engine. 
 
 As explained in lesson I, a charge is drawn into the cylinder and 
 there compressed. At the moment when the piston is passing center 
 the charge is ignited and burned, the temperature of the resulting gas 
 is raised to between 2,000 and 3,000 F., and since this gas is imprisoned 
 behind the piston in a small space it exerts a tremendous pressure upon 
 the piston at the beginning of the stroke. The amount of the pressure 
 varies under different conditions of adjustment of the engine and 
 upon the amount of fuel and air admitted to the cylinder and the 
 proportion in which the two are mixed. In ordinary gas engines the 
 pressure often amounts to 350 or 400 pounds per square inch, thus 
 
10 GASOLOGY. 
 
 giving a total pressure on an eight-inch piston of somewhere near 
 20,000 pounds. This pressure, it must be borne in mind, is not in the 
 nature of a blow such as would be struck with a heavy hammer, but to 
 the sudden energy imparted to the gases by the liberation of the heat 
 energy of the fuel they contain when first admitted to the cylinder. 
 As the piston advances on its power stroke the gases expand and this 
 pressure falls rapidly until at the end of the stroke when the ex- 
 haust valve opens, the pressure is comparatively small. On account 
 of the very high initial pressure, however, the average pressure for the 
 whole stroke is quite high, as it must be considering the fact that 
 there is only one power stroke in every four strokes of the piston. 
 
 Since the motive power of the engine is heat and this heat is gen- 
 erated by the combustion of fuel in the engine cylinder, it follows, nat- 
 urally, that a knowledge of the principles of combustion is essential 
 to a proper understanding of the working of a gas engine. The lack 
 of understanding of this important subject is responsible for a con- 
 siderable amount of the difficulty in handling these engines. 
 
 Combustion or burning is a chemical process and may, for our pur- 
 poses, be defined as .a combination with oxygen. The oxygen is sup- 
 plied by the air, which consists of two gases, oxygen and nitrogen, 
 mixed in the proportion of 786 parts of nitrogen and 214 parts of oxy- 
 gen, by volume. When fuel burns, the oxygen of the air unites with 
 the carbon and hydrogen in the fuel, forming a new chemical com- 
 pound. This compound is in the form of a gas and is the resulting 
 smoke of combustion. The liquid fuels, such as gasoline, kerosene 
 and alcohol, are composed of carbon and hydrogen in varying propor- 
 tions, depending upon the fuel used. When they are introduced into 
 an engine cylinder they are mixed with the proper amount of air in a 
 chamber called a carburetor, from which they pass directly to the 
 engine cylinder. When the charge of air and fuel passes into the 
 cylinder the fuel is either in the form of a gas or vapor or else in a 
 very finely divided mist or fog. 
 
 Ignition is started by passing a flame through some portion of the 
 charge, as in the case of the electric spark or by means of a heated 
 body. The gas at this place is heated to the ignition point and the 
 resulting flame rapidly propagates itself throughout the mass. 
 
 A certain amount of carbon requires a definite quantity of oxygen 
 for complete combustion and the same is true of the hydrogen. 
 Consequently the fuel and air must be mixed in exactly the right pro- 
 portions to give the best results. If too much fuel is supplied for the 
 amount of air, the mixture will be too rich in fuel and ignition may 
 not take place at all, and if it does the heat generated will not be as 
 great as though the correct proportion were used. Consequently the 
 
GAS ENGINE PRINCIPLES. 11 
 
 engine will not develop its maximum power. On the other . hand, 
 if there is not enough fuel for the amount of air admitted, the mix- 
 ture will be lean and ignition may fail or the explosion may be 
 weak. 
 
 In the greater number of small engines using liquid fuel, the sup- 
 ply of air cannot be varied and so the correct mixture is obtained by 
 setting the oil valve to admit the right amount of fuel. The correct 
 amount of fuel is determined by the character of the exhaust gases. 
 As much fuel should be admitted as possible without showing a dense 
 smoke at the exhaust. 
 
 LESSON III. 
 
 It was shown in the last lesson that there must be the correct pro- 
 portion of fuel and air in order to obtain a mixture that will ignite 
 readily and burn to the best advantage. Such a mixture burns almost 
 instantaneously and is said to be explosive. 
 
 Gun powder, dynamite and other such explosives differ from the 
 explosive mixture in a gas engine in this particular. They do not 
 require air to supply the necessary oxygen for their complete com- 
 bustion because they contain a chemical within themselves which sup- 
 plies the necessary oxygen in copious quantities. All fire arms are 
 gas engines, nevertheless, because it is the gas formed by the burn- 
 ing of the powder which hurls the missile from the barrel. This gas 
 which is formed almost instantly is highly heated by the process of 
 burning and exerts an enormous pressure in the gun barrel just as the 
 burning of the charge in a gas engine cylinder causes pressure on the 
 piston and drives it forward. 
 
 Before any substance, either solid or liquid, can be burned it must 
 be heated to such a temperature that the carbon and hydrogen which 
 it contains are distilled from the surface in a gaseous form. The 
 temperature at which any substance will ignite is called the ignition 
 point, and this temperature is that at which the given substance be- 
 gins to give off a gas. A lump of coal does not burn as a solid but as 
 a gas. Likewise, kerosene, gasoline and alcohol and other liquids 
 used in gas engines must also be turned into a gas before they will 
 become readily explosive. Gasoline at ordinary temperatures forms 
 a gas and it is therefore easy to start an engine with this fuel except 
 in very cold weather. When the weather is severe heat must be ap- 
 plied at some point in order to start, either to the engine cylinder by 
 filling the jacket with hot water, to the air by heating the air pipe or 
 mixer with a torch or a piece of hot iron, or by heating the gasoline. 
 The latter method is somewhat dangerous and is not recommended. 
 Kerosene and alcohol both form a gas at higher temperatures than 
 
1 2 GASOLOGY. 
 
 gasoline and consequently it is more difficult to start an engine with 
 either of these fuels. After getting the cylinder warmed up by us- 
 ing gasoline to start with, however, kerosene or alcohol can then be 
 used with good success because the heat within the cylinder walls is 
 then sufficient to transform the fine mist or spray of the charge into a 
 gaseous form. While the ordinary gasoline engine may not run as 
 economically on either of these fuels as on gasoline, still it can be 
 made to work quite satisfactorily. 
 
 In order that a gas shall begin to combine with oxygen, that is, 
 to burn, it must be set fire to, it must be ignited. There are numer- 
 ous ways in which this may be accomplished, but the ordinary meth- 
 od is by means of an electric spark. The gas in immediate contact 
 with the spark is heated to a high temperature and a flame is started 
 which travels through the mass with great rapidity, provided that the 
 mixture of gas and air is in the right proportions and thoroughly 
 mixed. If the mixture is not correctly proportioned the flame will 
 travel slowly and combustion may not be complete. That is, some 
 of the gas may not be consumed when the piston reaches the end of its 
 stroke. With the ordinary gas engine these conditions may not ob- 
 tain either if too much fuel is admitted or if there is not enough. 
 In the first case a dense smoke will appear at the exhaust, in the 
 second, one or more charges may mis-fire and be forced into the 
 muffler, then when a charge is fired the hot gases coming in contact 
 with those remaining in the muffler will cause an explosion at that 
 point. In either the first case or the second the force of the ex- 
 plosion in the cylinder is weak and the engine is not developing the 
 power it should develop. 
 
 In the ordinary gasoline engine the size of the air pipe is fixed and 
 can not be changed and consequently the only way to alter the mixture 
 is by adjusting the fuel valve. 
 
 The timing of the ignition is an important point in the opera- 
 tion of gas engines. In all cases ignition should occur just before 
 the piston reaches dead center on the compression stroke. The exact 
 point depends upon the character of the gas and the speed of the en- 
 gine. Ignition should always occur early enough so that the gas 
 will be all burned by the time the piston starts on the power stroke. 
 It is a well known fact that a gas highly compressed, or in the act 
 of being compressed, burns more rapidly than when it is not com- 
 pressed or when it is expanding. In the case of a gas being com- 
 pressed the flame cap and the gas are moving toward each other, while 
 if the gas is expanding the flame cap must follow a substance that is 
 rapidly retreating before it. Consequently, if ignition occurs just 
 when the piston is at the end of its compression stroke, or after it 
 
GAS ENGINE PRINCIPLES. 13 
 
 has started on its power stroke, ignition must necessarily be much 
 slower and it may even happen that combustion will not be com- 
 pleted when the end of the stroke is reached. It must be borne in mind 
 also that the act of complete combustion is not instantaneous but, on 
 the contrary, takes an appreciable length of time. This makes it nec- 
 essary to ignite the charge before the piston reaches the end of its 
 compression stroke. In slow speed engines running at say two hundred 
 revolutions per minute, ignition should occur when the crank is from 
 five to ten degrees below center. Engines having a higher speed must 
 be ignited still earlier, until on very high speed engines, those running 
 at speeds above one thousand revolutions per minute, ignition must 
 occur just after the crank passes half stroke or nearly forty-five de- 
 grees before the crank reaches center. With rich fuel mixtures com- 
 bustion is more rapid than with lean mixtures -and consequently igni- 
 tion does not need to occur quite so early. 
 
 There is another factor that must be taken into account in the 
 timing of the ignition to get the best results, and that is the tempera- 
 ture of the gas when ignition occurs. If the gas is hot, almost at burn- 
 ing temperature, it burns much more rapidly than when at a lower 
 temperature. In an engine that is working hard, that is, one that 
 misses very few explosions, it may happen that the igniter will be 
 set to give the best results to start with, but after the engine has 
 worked for a considerable length of time the cylinder will become 
 heated so much that each new charge becomes heated almost to the 
 burning point and when the spark is formed combustion will be almost 
 instantaneous, making it necessary to retard the spark somewhat in 
 order to obtain the best results. A heavily loaded engine which works 
 all right for a time and then begins to pound in the cylinder can very 
 likely be cured by retarding the spark. 
 
 To sum up, then, if ignition occurs either too early or too late the 
 engine will not work to the best advantage and for the amount of 
 fuel consumed it will not yield the maximum amount of power. 
 
 LESSON IV. 
 
 In preceding lessons considerable space was devoted to the proper 
 mixtures of fuel and air necessary to obtain the best results. In this 
 connection here is an interesting little experiment anyone can try 
 with the ordinary four-stroke cycle engine. Start the engine in the 
 usual way and after it gets to running nicely close the fuel valve a 
 little at a time quite slowly until explosions begin to occur in the 
 muffler. Now throttle the air supply by holding a piece of cardboard 
 or a piece of board on the end of the air pipe, thus reducing the air 
 supply, and note the effect. 
 
14 
 
 GASOLOGY. 
 
GAS ENGINE PRINCIPLES. 15 
 
 The explosions will cease in the muffler and the engine will work 
 nicely because the supply of air has been cut down to make the cor- 
 rect mixture with the fuel admitted. By working carefully the fuel 
 valve and air pipe may both be almost closed and yet the explosions 
 will occur regularly and be all right, but will not have much force 
 because only a small amount of fuel is taken into the cylinder at 
 each charge. 
 
 If, when the amount of fuel is cut down so low, the air pipe were 
 left with the full opening, the mixture would be so lean that it would 
 not ignite at all and the engine would stop. When an engine runs 
 on a weak or small charge as just explained it will -of course not de- 
 velop much power. This little experiment not only illustrates the 
 effects of fuel and air mixtures, but illustrates also a means for gov- 
 erning a gas engine which is made use of in many engines, as will be 
 more fully explained in a subsequent lesson. 
 
 The cylinder of a gas engine is made of a close grained cast iron 
 and when well designed the walls are of practically uniform thick- 
 ness throughout. This is necessary on account of the intense heat, 
 which would cause unequal expansion and dangerous strains if the 
 metal varied much in thickness. The cylinder is bored as smooth as 
 possible and in the best constructions it is ground to a perfectly 
 smooth finish. Some manufacturers claim that they grind the cyl- 
 inders slightly tapering, making them two or three thousandths of an 
 inch smaller at the head end than at the crank end. Then when the 
 engine is in operation the greater heat at the head end causes greater 
 expansion and the cylinder sides become exactly parallel. Such re- 
 finements in construction are practiced only on the higher priced ma- 
 chines, such as automobile engines and the like. Ordinary gasoline 
 engine cylinders are merely bored out as true as possible on a boring 
 machine. 
 
 It has been proven by experiments that there should be no pockets 
 or chambers on the side of the combustion chamber in which a part 
 of the charge may accumulate. It appears that where such is the 
 case that the gases so trapped explode a little later than the main 
 charge and are liable to set up waves of pressure in time or synchro- 
 nism with the waves of the main explosion. These two waves of 
 force occurring at the same time and meeting are apt to have the 
 effect of a blow on the inside of the cylinder, causing an abnormally 
 high pressure for an instant which strains the entire engine without in 
 any way increasing its power. 
 
 The truth of this assertion has been proven by taking indicator 
 cards from an engine having no such pockets, then screwing a short 
 piece. of pipe capped on the outer end into the combustion chamber, 
 
16 GASOLOGY. 
 
 and taking indicator cards again, the extremely high pressures 
 were clearly shown on the cards. This fact would seem to indicate 
 that the inlet and exhaust valves should both open directly into the 
 clearance space of the cylinder, or if they open into a chamber on 
 the side of the clearance space, ignition should take place in the valve 
 chamber. 
 
 Surrounding the cylinder^and separated from it by a short space, 
 the exact amount depending upon the size of the cylinder, there is 
 an outside casing or jacket. This casing is usually made of cast iron, 
 although in some instances it is made of copper. When made of cast 
 iron it may be entirely separate from the cylinder or it may be cast 
 with the cylinder and attached thereto at intervals in the process of 
 casting. The space between the cylinder, and this outer casing con- 
 tains the cooling liquid, which may be either water or oil. Water be- 
 ing cheap and easy to obtain, is more commonly used than oil. 
 
 Since the temperature of combustion in a gas engine cylinder 
 ranges between two thousand and three thousand degrees, and since 
 cast iron melts at a temperature of about two thousand three hun- 
 dred degrees it is evident that some means must be provided to carry 
 away the excess heat. This is accomplished generally by means of 
 circulating water or oil around the cylinder. Sometimes, however, 
 in small sized engines ribs or spines of metal are cast on the outside 
 of the cylinder, thus providing a large radiating surface which con- 
 ducts the heat away from the cylinder to the air. Such engines are 
 known as air cooled engines. This method works very satisfactorily 
 with engines up to about 10-horse power, but in sizes above this the 
 heat can not radiate rapidly enough to keep the cylinder cool. 
 
 Where either water cooling or oil cooling is resorted to there are 
 two methods of circulating the liquid around the cylinder, either the 
 gravity method or the pump method. 
 
 In the first case advantage is taken of the difference in weight 
 between equal volumes of cold water and hot water, or of cold oil and 
 hot oil if oil is the liquid used. For example, at a temperature of 
 39 degrees Fahrenheit a cubic foot of water weighs sixty-two and 
 one-half pounds, while at 212 degrees Fahrenheit a cubic foot weighs 
 only fifty-nine and one-half pounds. The hotter the water the less 
 a certain volume of it weighs. If we have, then, a gas engine cyl- 
 inder connected to a tank as shown in Fig. 5, the water in the engine 
 jacket will become heated, its weight will be less than an equal vol- 
 ume in the tank and consequently the heavier water from the tank 
 will flow in by gravity through pipe B and push the lighter water out. 
 
 Care must be taken to see that an air vent is placed in the highest 
 point of pipe A, otherwise a bubble of air or steam roay form at that 
 
GAS ENGINE PRINCIPLES. 17 
 
 point and prevent circulation. A case of this kind recently came un- 
 der the writer's notice. The vent pipe was not placed in the highest 
 part of the pipe and the cylinder became hot enough to burn the 
 paint. The water should be from four to six inches higher in the 
 tank than the end of pipe A to insure circulation. If the water falls 
 below the pipe there will be no circulation. 
 
 In the second method a pump is used to force the water from the 
 tank through the cylinder. A small rotary pump driven by the engine 
 shaft is generally used. This method insures better circulation. In 
 many cases the water is delivered from the discharge pipe in the 
 form of spray, which falls thence into the main reservoir. By this 
 method radiation of the heat from the water is much more rapid and 
 a smaller quantity of water is required. It is generally conceded that 
 the temperature of the jacket discharge water should be just below the 
 boiling point or in the neighborhood of 180 degrees in order to obtain 
 the best efficiency from the engine. If the jacket water is very much 
 colder the gases in the cylinder lose their heat and consequently their 
 expansive power too rapidly and the engine lacks power. 
 
 Oil boils at a higher temperature than water and it is not uncom- 
 mon in engines cooled with oil to run with the oil in the jacket much 
 hotter than 212 degrees. If the engine is well made this is an advan- 
 tage rather than a disadvantage because the gases do not lose their 
 heat to the jacket so rapidly and a larger quantity of their heat is 
 available to do work on the piston. The limit of heat in the jacket is 
 reached when lubrication of the piston becomes difficult and it has 
 a tendency, on account of the heat, to expand and stick in the cyl- 
 inder. 
 
 LESSON V. 
 
 Another method of cooling which has been proposed, and which 
 is used in an auxiliary way to some extent, is to introduce water di- 
 rectly into the engine cylinder. This may be accomplished in one of 
 two ways ; either by introducing it in the form of a fine mist or spray 
 during the aspirating stroke, or else by means of a pump during the 
 power stroke. 
 
 If introduced during the aspirating stroke, the compression of the 
 mixture will turn the water into steam which will become further heat- 
 ed after ignition. On account of the high specific heat of water, it 
 requires a large quantity of heat to vaporize it or to raise its tempera- 
 ture after it is vaporized. Since this heat must be absorbed from the 
 heat of combustion of the charge it follows, necessarily, that the tem- 
 perature of the mixture in the cylinder will be materially reduced. 
 If very much water is introduced it may absorb so much of the heat 
 
18 GASOLOGY. 
 
 generated during compression that the gases will not be hot enough 
 to ignite readily. Especially will this be true if the charge is some- 
 what lean. This accounts for the fact that a leak of water from the 
 jacket to the cylinder makes it difficult to start the engine. 
 
 Cooling, in the method just described, cannot be carried out com- 
 pletely. Some writers declare that it is never conducive to good econ- 
 omy in any case because it reduces the temperatures and pressures in 
 the cylinder. The results of tests seem to prove, however, that under 
 certain circumstances it may be advantageous to use. In kerosene 
 engines and in many alcohol engines provision is made to use a water 
 spray, and the result of such use is always a smoother running engine. 
 A heavily loaded kerosene engine will pound heavily after it has run 
 for some time unless a large amount of jacket water or else a spray 
 of water is used. It seems advantageous in some types of engines, 
 both from an economical and mechanical viewpoint, to use a small 
 amount of water in the cylinder in addition to the regulation method 
 of cooling by means of jacket water. 
 
 Water cooling is also practiced in some cases as respects the 
 products of combustion, by introducing it into the exhaust pipe. The 
 effect is to absorb heat from the gases and allow them to escape at a 
 lower pressure, thus acting to some extent as a muffler. This practice 
 does not, of course, affect the heat in the cylinder itself. 
 
 In very large engines the piston must be cooled as well as the cylin- 
 der because the heat in the central part of a large" disc of iron, which 
 exposes relatively a small surface to the cool cylinder walls, can not 
 part with its heat rapidly enough to keep the central part at a safe 
 working temperature. Cooling, in such cases, is accomplished by 
 circulating water under pressure within the hollow part of the piston, 
 using either flexible connections or telescoping pipes to convey the 
 water. 
 
 It is also necessary to cool the exhaust valve by a water jacket 
 owing to the high degree of heat of the exhaust gases. The admis- 
 sion valve does not need cooling especially, because it is sufficiently 
 cooled by the fresh charge of cold gas and air, although it is cus- 
 tomary to bring the water jacket as close around both valves as can 
 be done conveniently. 
 
 The volume of the compression space is an important consideration 
 in gas engine design and a knowledge of the part it performs is equal- 
 ly of value to the man who operates an engine. In steam engine prac- 
 tice it is a well recognized fact that the clearance space should be 
 small in order to insure the best economy. What is true in this re- 
 spect in the steam engine is equally true in the gas engine. The 
 highest economy demands small compression volume. There is a 
 
GAS ENGINE PRINCIPLES. 19 
 
 practical limit beyond which high compression can not be carried, 
 and this limit is different for every different kind of fuel used. 
 
 In a previous lesson the statement was made that there is an exact 
 relation between heat and work. If work is done upon a gas by com- 
 pressing it, it becomes heated and, if the gas afterwards expands 
 and does work upon the piston its temperature falls. When the 
 charge in a gas engine is compressed its temperature rises in propor- 
 tion to the amount it is compressed. If compression is carried too 
 high, its temperature may reach the point at which it will ignite. The 
 vapor of gasoline ignites at comparatively low temperatures, and it has 
 been found by experience that if it is compressed much above eighty- 
 five pounds per square inch pre-ignition will take place. Alcohol 
 vapor, on the other hand, is less volatile and needs a higher tempera- 
 ture in order to burn, consequently it will stand a higher compression, 
 and with higher compression it yields greater power for a given quan- 
 tity of alcohol consumed. For this reason alcohol engines, designed 
 primarily to use alcohol, have a smaller clearance volume than do 
 gasoline engines. Engines designed to work under varying condi- 
 tions and different fuels are usually given a clearance volume equal 
 to from twenty to twenty-five per cent of the volume displaced by the 
 piston. There are certain well-known laws which govern the pres- 
 sure, volume and temperature of gases, which will presently be brief- 
 ly alluded to. It should be understood, in passing, that the three 
 quantities, pressure, volume and temperature, are inter-dependent, 
 that is, when one changes, the other two also change, unless some 
 means are taken to maintain one of them constant. The principal 
 law connected with pressure and volume is known as "Boyle's Law." 
 It may be stated thus: The pressure of a gas varies inversely as 
 the volume, if the temperature is kept constant, or the volume varies 
 inversely as the pressure with the temperature constant. Stated in 
 plainer words, it means that if a given volume of gas is compressed 
 to one-half its volume, the pressure will be doubled. For example, if 
 a cylinder full of air or any other gas at the pressure of the atmos- 
 phere be compressed to half a cylinder full, the pressure will be 
 doubled, provided some means is provided to keep the temperature of 
 the gas from rising. In other words, if air at 14.7 pounds pressure 
 is reduced to half that volume its pressure will be 29.4 pounds ab- 
 solute pressure or 14.7 pounds, as shown on a steam gauge. 
 
 The law relating to temperature and pressure states that the pressure 
 varies directly as the absolute temperature, provided the volume is 
 kept constant, or the volume varies directly as the absolute tempera- 
 ture, provided the pressure is kept constant. This means that if a cyl- 
 inder full of gas be heated the pressure will rise in direct proportion to 
 
20 GASOLOGY. 
 
 the absolute temperature. Consequently, if we simply took the cyl- 
 inder full of gas and heated it, or if it was an imnammable gas, if we 
 burned it, the increase in heat would cause the pressure to increase in 
 exact proportion to the increase in temperature. 
 
 It is upon these two laws that all theoretical calculations in re- 
 gard to gas engines are worked out. Furthermore, it is upon just such 
 considerations as these that the size of the clearance space is calculated 
 in order to give any compression pressure which we may desire. 
 
 An example of heating due to compression is often witnessed in the 
 case of starting a gas engine in cold weather. It may be too cold to 
 start the first few times the engine is turned over, but if it is turned 
 rapidly a few times the cylinder may be sufficiently warmed by the 
 compression of the gas to cause the gasoline to vaporize. 
 
CHAPTER II 
 
 IGNITION, PRIMARY BATTERIES 
 
 LESSON VI. 
 
 There are three methods in common use for igniting the charge 
 in gas engines. They are by means of a hot tube or torch, by compres- 
 sion, and by electricity. The hot tube is one of the oldest methods, but 
 has fallen largely into disuse except as an emergency device. It 
 finds its widest application, at the present time, as an auxiliary de- 
 vice to be used in case something goes wrong with the electric igniter. 
 Igniting by compression is used only on a few types of engines, such 
 as the Hornsby-Akroyd, Diesel, and a few others. Electric ignition in 
 one form or another is the method almost universally adopted. It is 
 the easiest to handle, the most reliable and certain in action, and 
 provides for the closest regulation of the time of ignition, which, by 
 the way, is a very important item in the economical operation of a 
 gas engine. 
 
 Let us first consider the hot tube system of ignition. This can be 
 best explained with reference to the accompanying diagram, Fig. 6. 
 A small tube, T , closed at the outer end, is screwed into the com- 
 pression chamber of 
 the engine. Just 
 below this tube there 
 is a gas jet in the 
 form of a Bunsen 
 burner which is sup- 
 plied with gasoline 
 by a pipe which 
 leads from a reser- 
 voir on the top of 
 the engine. Sur- 
 rounding both the 
 burner and the tube 
 there is a cast iron 
 box with a chimney 
 on the top. This box 
 prevents air currents from striking the flame and at the same time 
 directs the flame upon the tube at the desired point. The chimney 
 is lined with asbestos to prevent radiation of the heat generated by 
 the flame. 
 
 FIG. 6. 
 
22 GASOLOGY. 
 
 In operation, the action of the hot tube is as follows : A few min- 
 utes before starting the engine the burner is lighted and the tube is 
 brought up to a red heat, then when the charge is compressed a part 
 of the inflammable gas enters the tube and when it reaches the red 
 portion it becomes ignited. On the exhaust stroke there will be 
 some burnt gases still left in the tube when the new charge enters 
 the cylinder. When this charge is compressed, the burnt gases re- 
 maining in the tube from the previous charge must be compressed 
 until the new charge meets the hot portion of the tube before ig- 
 nition can again take place. Consequently, if the burner heats the 
 tube near where it enters the cylinder, ignition must occur earlier 
 than if the hot portion is further out toward the end of the tube. 
 In some engines the position of the burner is made adjustable in order 
 to vary the time of ignition, in others the burner is fixed in position at 
 a point where it has been found by experience to give the best re- 
 sults. 
 
 The life of an ordinary iron tube is very short, being only a few 
 days at most. Nickel, steel or porcelain tubes last much longer, 
 but are more expensive. The uncertainty as to timing of ignition, the 
 bother of starting and the delay caused by the burning out of the 
 tubes makes this form of ignition anything but efficient. 
 
 Prof. Hutton in his book, "The Gas Engine," has the following to 
 say about hot tube ignition: 
 
 The time of ignition with the hot tube will depend upon: 
 
 1. The length of the tube. 
 
 2. The size or volume of the passage leading to the tube. 
 
 3. The amount or degree of compression of the mixture by the 
 piston. 
 
 4. The temperature of the tube; the hotter the tube, the earlier 
 the ignition; the cooler the tube, the later. 
 
 5. The fact whether it was hottest near the open or the closed 
 end; if heated near the open end, the earlier the ignition. 
 
 6. The temperature of the mixing and igniting chambers. 
 
 7. The temperature of the jacket- water outlet. 
 
 8. The speed of the engine. 
 
 9. The quality or proportions of the air and fuel admitted. 
 
 10. The pressure of the intake or suction stroke. 
 
 11. The governing action and the system of governing. 
 
 12. Leakage; at piston, at exhaust, past valves. 
 
 13. The state of the surfaces of the tube, outside and in. 
 
 14. The location of the tube with respect to receiving and acting 
 on new or fresh mixtures or mixtures containing burnt gases. 
 
, PRIMARY BATTERIES. 
 
 Ignition by Compression. In the Diesel engine a charge of air 
 is drawn into the cylinder on the aspirating or charging stroke 
 but no fuel. This air is compressed to a very high pressure, usually 
 above five hundred pounds per square inch. When air is compressed 
 so strongly the work done upon it is transformed into heat and its 
 temperature rises very high. If now, when the piston reaches the 
 end of its stroke, a jet of oil is pumped in, this oil will be ignited 
 by the hot air and no other form of igniter will be needed. A gov- 
 ernor attached to the pump regulates the time during the power 
 stroke that the oil jet is admitted, which generally does not exceed 
 one-tenth of the stroke. 
 
 Fig. 7 shows the method of igniting the charge in the Hornsby- 
 Akroyd oil engine. The chamber at the left of the cylinder is not 
 water jacketed. It is first heated by an auxiliary burner to a red 
 heat. Then when 
 the piston makes its 
 first outward stroke 
 air is drawn into the 
 cylinder and a thin 
 jet of kerosene is 
 forced into the hot 
 chamber and is in- 
 stantly vaporized. 
 On the compression 
 stroke the air is 
 forced back through 
 the narrow neck into 
 the vaporizing chamber where it mixes with the fuel. Ignition is 
 caused by the heating effects of compression, friction, and the heat of 
 the vaporizer. At first thought it might be supposed that when the 
 oil first enters the vaporizer it would be ignited, but this can not 
 occur because it has no air to combine with. The air that is entering 
 the cylinder during the charging stroke is moving toward the rear 
 of the cylinder, away from the fuel. On the compression stroke this 
 air is forced into the chamber with the fuel and when the compression 
 stroke is nearly completed the air has mixed with the vaporized fuel 
 sufficiently to cause an explosive mixture and ignition takes place. A 
 governor controls the stroke of the pump and allows the correct 
 amount of oil to be delivered to maintain the speed of the engine. 
 There are no means for changing the time of ignition. This engine 
 is adapted for using kerosene or heavier oils. 
 
 Electric ignition, as before stated, is used by nearly all makers 
 of gas engines at the present time. There are many different systems 
 in use, some of which differ from each other in essential particulars 
 
24 
 
 and some only in minor details. A complete knowledge of electrical 
 ignition must necessarily include a considerable knowledge of elec- 
 tricity and much more than can be presented in this series of lessons. 
 However, in order to make the subject as plain as possible it will first 
 be necessary to consider some of the fundamental principles of elec- 
 tricity and that we will now proceed to do. 
 
 To begin with, electricity is one form of energy, just as heat or 
 motion is a form of energy. Electricity must always be generated 
 by some outside source of power and a given amount of power is 
 always consumed in generating a certain amount of electricity. We 
 know some things electricity can do; we know some of the laws govern- 
 ing its action, and we know something about how to handle it ; but we 
 do not know just exactly what electricity is. This need not trouble 
 us, however, because we, as gas engineers, are concerned with the 
 practical application of electricity rather than with its theory. 
 
 Electricity may be generated with a machine as in a dynamo, or 
 chemically, as in a cell; the character and properties of the current 
 delivered are the same in either case. 
 
 The unit for measuring the intensity of an electric current is called 
 a volt. It is the measure of electrical pressure or electro-motive force 
 just as pounds on a steam gauge represent steam pressure, or water 
 pressure if the gauge is attached to a water pipe. The unit for meas- 
 uring the amount of current is called an ampere. This may be rep- 
 resented by gallons in the case of water. The flow of electricity can 
 be represented very easily by comparing it with the flow of water. 
 For example, we may have a low voltage and a large current and con- 
 sequently a large amount of electricity delivered. In the same way we 
 may have a small pressure and a large stream of water and in a given 
 time a large volume of water will be delivered. Or we may have high 
 voltage and small amperage and a large amount of electricity de- 
 livered just as a high pressure of water and a small sized stream will 
 deliver a large volume of water. 
 
 Voltage applies only to the pressure of electricity and amperes to 
 the size of the current. We may have a very high voltage and small 
 current or low voltage and large current. These terms will be used 
 again and again in these lessons and the student should try to re- 
 member just what they mean. 
 
 LESSON VII. 
 
 Batteries are of two principal kinds, primary batteries and sec- 
 ondary batteries. A primary battery generates electrical current by 
 means of chemical action. A secondary battery must first be 
 
IGNITION, PRIMARY BATTERIES 
 
 25 
 
 charged by means of some outside source of current. This current 
 sets up chemical action within the cells of the battery which changes 
 the chemical nature of some of the elements in such a way that when 
 the battery is connected up to do work, these elements revert to their 
 original form and electrical current is generated. Ordinary batteries, 
 either of the wet cell or the dry cell variety, such as are used gen- 
 erally for the electrical ignition of gas engines, are familiar ex- 
 amples of primary batteries. Storage batteries are examples of sec- 
 ondary batteries. 
 
 Primary batteries are made up of a number of simple voltaic or 
 galvanic cells which are connected together by means of wires. In 
 order to understand the working of a battery, we must first study 
 the construction of a cell and the action which takes place between its 
 parts. Figure 8 is an illustration of a very simple form of cell. It 
 consists of a jar nearly filled with weak suphuric acid, called the 
 electrolyte, in which there is 
 suspended a plate of copper 
 and a plate of zinc. These 
 are marked C and Z, respec- 
 tively, in the figure. The 
 zinc plate is the positive 
 element in any cell and the 
 other plate the negative ele- 
 ment. Curiously enough, 
 however, the binding post at- 
 tached to the zinc element is 
 known as the negative pole 
 and the other as the posi- 
 tive pole of the cell. If the 
 two poles be connected by 
 means of wires an electrical 
 current will flow, in the di- 
 rection shown by the arrows, 
 from the copper plate 
 through the connectors to the 
 zinc plate. In some types of 
 cells there is very little local 
 
 FIG. 8. 
 
 action unless the cell is working on a closed circuit, bu>t in this type 
 of cell the zinc is attacked by the electrolyte whether- it is on open 
 or closed circuit, although the action is not so strong when the cir- 
 cuit is open as it is when it is closed. When the two wires a and b 
 are touched together, chemical action it set up strongly 
 
26 GASOLOGY. 
 
 cell. A part of the acid of the electrolyte is constantly decompos- 
 ing and uniting with the zinc, forming a new substance, zinc sul- 
 phate, and at the same time an electric current is generated by this 
 chemical action. 
 
 The amount of current which is generated is proportional to the 
 amount of zinc consumed or changed into zinc sulphate. There is 
 a similarity between an electrical cell and a furnace. In the latter, 
 coal is burned and heat is generated; in the former, zinc is con- 
 sumed and electricity is generated. The amount of heat that is 
 generated depends upon the amount of fuel burned, and, in like 
 manner, the amount of electricity that is generated depends upon the 
 quantity of zinc consumed. Both the generation of heat and of 
 electricity are examples of chemical activity. 
 
 Polarization. When the sulphur and oxygen of the electrolyte 
 unite with the zinc, forming zinc sulphate, hydrogen gas is set free, 
 which appears as small bubbles on the copper plate, unless there is 
 some other substance at that point for the hydrogen to unite with. 
 The formation of the bubbles of hydrogen gas represents lost energy 
 unless they can combine with some other substance, in which event 
 the energy used in their formation is given back and adds to the 
 electro motive force of the cell. Their presence on the copper plate 
 adds to the internal resistance of the cell very greatly and reduces 
 the amount of current which the voltage of the cell can send through 
 any external circuit. The formation of bubbles of hydrogen gas on 
 the copper plate is called polarization and the removal of them by any 
 means is called depolarization. All cells in commercial use are 
 designed to prevent polarization as far as possible, and generally 
 by chemical means. In this way, not only is the internal resistance 
 of the cell prevented from increasing, but the electro-motive force 
 of the cell is actually increased. 
 
 The Edison- Lalande cell is an example of one of the best and most 
 popular cells used for gas engine ignition. S,ince it is a very effi- 
 cient type of cell, and is arranged to prevent polarization, it will 
 repay a little study. The electrolyte is either a solution of potassium 
 hydrate (caustic potash) or sodium hydrate (caustic soda), and 
 water. Zinc forms one of the elements and the other is formed by 
 mixing together cupric oxide and magnesium chloride and forcing 
 the mixture into a suitably prepared plate under pressure. This 
 plate is then heated and the mass becomes thoroughly bound together. 
 This composition plate is suspended by means of copper channel 
 strips, in the electrolyte, between two plates of zinc. The terminals 
 of the elements pass up through a cover plate which insulates them 
 
IG>*/TION, PRIMARY BATTERIES. 27 
 
 from each other. So long as there is no metallic connection between 
 the two terminals, that is, between the zinc plate and the composition 
 plate, there is practically no action in the cell. In other words, the 
 zinc is not attacked unless the circuit is closed. In this respect 
 it differs from the first cell described. 
 
 The internal action of this cell is as follows: When the external 
 circuit is closed, some of the solution of potassium hydrate in con- 
 tact with the zinc plates decomposes and part of it unites with the 
 zinc, forming a new chemical substance, while the hydrogen goes 
 over to the cupric oxide plate and there unites with the oxygen 
 of the plate, thus forming water and setting free metallic copper. 
 The cupric oxide is the depolarizer since the oxygen it contains is 
 always ready and at hand to combine with the bubbles of hydrogen 
 gas. This cell, when in use, will give an electro-motive force of 
 about .7 volt. 'When freshly charged it will give a slightly higher 
 voltage. The internal resistance is very low and it gives a good 
 strong current. Since the caustic potash will absorb carbon dioxide 
 gas from the air and thus lose its virtue as an electrolyte, it is nec- 
 essary to cover the liquid in the cell with a heavy mineral oil. 
 
 These cells do not need any attention until they are exhausted, 
 that is, until either the zinc is consumed, the composition plate is 
 red all through (which can be told by digging into it with a pen 
 knife), or the electrolyte is too weak. It is not much trouble to re- 
 charge them. If the elements are all right, that is, not complete- 
 ly worn out, all that is necessary to do is to pour out the old electrolyte 
 and make a new one by using caustic potash and water. Care must 
 be taken that the top of the copper oxide plate is at least an inch 
 below the top of the liquid, otherwise the cell will be almost sure 
 to fail. 
 
 Arrangement of Cells. The usual way to arrange a number of 
 cells, to form a battery for ignition purposes, is what is called a se- 
 ries, that is, the zinc from one cell is connected to the carbon of 
 the next one and so on. One cell is arranged directly behind the 
 other in this arrangement and the current is compelled to pass 
 through all of the cells. 
 
 Another method of arranging cells in a battery is to connect all 
 of the zincs together and all of the carbons together. This amounts 
 to the same thing as making one large cell having a zinc as large 
 as the sum of all the zincs and a carbon plate whose area is equal 
 to the sum of all the carbons. This method of connecting is called 
 connecting in parallel. For some kinds of work the series method of 
 connecting is preferable, while for other kinds of work better re- 
 
28 GASOLOGY. 
 
 suits are obtained when the cells are arranged in parallel. A dis- 
 cussion of this phase of the question will be left for some subse- 
 quent lesson. 
 
 LESSON VIII. 
 
 Dry cells are made up in practically the same way as wet cells and 
 with the same active materials. The elements are zinc and carbon. 
 The outer portion or can is made of zinc and surrounds a rod of car- 
 bon which does not quite reach the bottom of the can. The electrolyte 
 consists generally of a solution of sal-ammoniac and water mixed 
 with zinc chloride. This occupies the space next to the zinc and is 
 held in position by some absorbent material, like blotting paper, 
 which is completely saturated by the solution. The space between 
 the electrolyte and the carbon rod is filled with some substance such 
 as powdered carbon and manganese dioxide which acts as a depolar- 
 izer. The details of construction and the ingredients which are used 
 are not the same in all dry cells, but the description just given will 
 give the reader a good general idea of how they are constructed. The 
 tops of dry cells are covered with hard pitch, which prevents the 
 evaporation of the electrolyte, while the outside of the can is insu- 
 lated with paper. 
 
 The chemical action that takes place in a dry cell is the same 
 as that which occurs in a wet cell, having the same elements and the 
 same electrolyte, but owing to the fact that this action takes place 
 in a paste instead of in a liquid it is not nearly so rapid. A good 
 dry cell when new will show on dead short circuit that is right 
 across the terminal about one and one-half volts, sometimes a 
 little more, and a current strength of from twenty to thirty am- 
 peres. When a dry cell battery has been in use for a number of 
 hours both the voltage and amperage will decrease the battery get 
 weaker; but if it is allowed to stand idle for some time it will re- 
 cover its normal strength. Sometimes when a dry battery is nearly 
 run down it has sufficient strength to give a spark that will ignite 
 every charge for a few minutes and then it will gradually die down 
 and the engine will stop. It often happens that only one or two 
 cells of a battery are worn out, while the others are still in good 
 condition. If these poor cells are taken out and new ones substi- 
 tuted the battery will be in good condition again. It will pay any 
 one who uses dry batteries to have an ammeter and test the cells, 
 each one separately, whenever he suspects that they are not right. A 
 good enough ammeter can be purchased for three or four dollars 
 and directions for using come with the instrument. Any cell that 
 
IGNITION, PRIMARY BATTERIES 29 
 
 shows less than six amperes is worthless and should be thrown away. 
 It is a good plan to test new cells at the time of purchasing. The 
 writer only last winter got hold of a new battery that, presumably at 
 least, had never been used and yet it was worthless. It was probably 
 old and the electrolyte had slowly evaporated. It is said that a cell 
 will not last much over three years even if not used at all, due to 
 slow evaporation of the moisture that it contains. Such a cell could 
 be made good again by introducing some new electrolyte through a 
 hole in the top or sides. Ordinarily, however, when a dry cell gives 
 out it can not be revived and the only thing to do is to throw it away 
 and get a new one. 
 
 For ordinary ignition purposes a battery made up of from four to 
 six cells is sufficient. A larger number of cells will give a hotter 
 name, but the action is so intense that it will injure the contact 
 points of the igniter, causing them to wear rapidly and become pitted. 
 Large sized cells are more economical than the smaller sizes even 
 if they do cost more than twice as much, but they will last consid- 
 erably more than twice as long. Of course, if they are accidentally 
 short circuited they will be ruined just as quickly and the loss is 
 greater. It does not take very long for a dry battery to become 
 ruined by short circuiting either ; ten or fifteen minutes will ruin any 
 battery absolutely. 
 
 Care should be taken in connecting up any battery, either of wet 
 or dry cells, to see that a good grade of insulated wire is used, pref- 
 erably rubber covered wire, and that the ends of the wire that are 
 attached to the binding posts of the cells are scraped clean and 
 bright. A film of copper oxide sometimes gathers on copper wire that 
 offers a great deal of resistance to the passage of a current of elec- 
 tricity and consequently it is necessary to scrape the surfaces that 
 form contact perfectly clean. Electricians in putting up elec- 
 trical wiring usually solder the joints together to insure good con- 
 tact and to make certain that no oxide can form between the parts 
 in contact and prevent the free flow of the current. The nuts on 
 the binding posts should be screwed down tightly. A loose con- 
 nection will soon become oxidized and prevent electricity from flow- 
 ing. In fact, a loose connection either in the battery or on the en- 
 gine is very frequently the cause of an engine's refusing to run. 
 
 Batteries should be kept in a clean, dry place and the battery 
 box should be kept covered to prevent any pieces of metal or tools 
 from accidentally finding their way into the box and short circuiting 
 some of the cells. 
 
30 GASOLOGY. 
 
 Wet cells can be recharged by putting in a new solution and new 
 elements. If the elements are carbon and zinc, the zinc is all that 
 needs renewing. The carbon does not wear out. The zinc plate is 
 all right, even if quite thin, until it begins to fall apart. When 
 new zincs are needed it pays to make a new solution. In the case 
 of the Edison-Lalande cell, both the zinc and copper oxide plate will 
 become worn out and both, together with the solution, will need re- 
 newing. Directions are usually sent out with the batteries for re- 
 charging and if these are followed faithfully there will be no trouble. 
 The chemicals used in recharging cells are inexpensive and the cost 
 of renewal is not very great. The largest cost is for zincs and cop- 
 per oxide plates. 
 
 All zincs used in electrical cells are amalgamated. This is done 
 by first cleaning the zinc plate thoroughly and then rubbing a little 
 mercury over it. The mercury unites with the zinc and protects it 
 from local electrical action, and not only makes the cell give greater 
 current, but prevents the zinc from wearing away so rapidly. Com- 
 mercial zinc is always impure. It contains particles of iron and 
 other impurities, which would cause electrical action on the neighbor- 
 ing particles of zinc. This is prevented by the coating of mercury 
 and so causes the zinc to last longer and also give better service. 
 Curiously enough, as the zinc is gradually taken into solution by the 
 electrolyte and the plate becomes thinner, the mercury is not affected 
 but retains its place on the surface of the plate to the very last. 
 
CHAPTER III 
 
 MAGNETISM AND COILS 
 
 LESSON IX. 
 
 On the shores of Lake Superior and in various other parts of the 
 world", there is found a peculiar ore which will attract iron. The 
 ore was first found by the ancients in the city of Magnesia in Asia 
 Minor and they called its property of attracting iron magnetism. 
 The ore is an iron ore somewhat similar to the scale that falls from 
 red hot iron on a blacksmith's anvil and is called magnetite. Pieces 
 of this ore, when suspended, will always point toward the north. 
 It was in early times used in navigation for a compass, and was 
 hence called a leading stone or lodestone. It was subsequently dis- 
 covered that if a piece of hardened steel be rubbed on a piece of lode- 
 stone it also be- 
 came magnetic, and 
 thus the compass 
 needle was discov- 
 ered. The former 
 is a natural magnet, 
 the latter artificial. 
 
 Artificial magnets 
 when of hard steel 
 retain their mag- 
 netism a long time 
 and are called per- 
 manent magnets. If 
 of soft iron or soft 
 steel, they lose their 
 magnetism quickly, 
 almost instantly, in 
 
 FIG. 9. 
 
 fact. The ordinary 
 
 form of permanent 
 
 magnet is a horseshoe shape, having a soft bar or keeper called an 
 
 armature across the ends to prevent loss of magnetism. 
 
 Lines of Force. If a straight bar of hard steel which has first 
 been magnetized be placed in iron filings, the filings will adhere in 
 tufts to each end, but not in the middle of the bar. The two ends 
 
32 GASOLOGY. 
 
 of the bar are called the poles, one the north pole, the other the 
 south pole. The north pole of a bar magnet will attract the south pole 
 of a compass needle and repel the north pole. Unlike poles of mag- 
 nets attract each other and like poles repel. Since the earth is a great 
 magnet whose poles very nearly coincide with the geographical poles, 
 they attract the magnetic needle. If iron filings be placed on a smooth 
 piece of paper that is held above the poles of a magnet, and the 
 paper is shaken to agitate the filings, they will arrange themselves 
 as shown in Fig. 9; and if the paper is held over only one pole the 
 filings will arrange themselves in radial lines. The lines along 
 which the filings arrange themselves are called lines of magnetic 
 force. The actual lines of force are, of course, invisible, but their 
 direction and existence are shown by the filings. The direction of 
 these lines is assumed to be from the north pole to the south pole 
 through the air or surrounding medium. 
 
 If a piece of wire be wound into a long spiral and a current of 
 electricity be sent through it, it will have all of the properties of 
 a magnet, with a north pole and a south pole and a neutral region 
 between. If suspended, it will assume a north and south direction. 
 If the coil be made of insulated wire and wound around a soft iron 
 rod, the latter will become what is called an electromagnet, with all 
 the properties of a bar magnet. When the current of electricity is 
 shut off, however, it quickly loses its magnetism, all except a very 
 small amount called residual magnetism. 
 
 Electro Magnetic Induction. This can be shown experimentally 
 by constructing two coils of wire wound over paper or wooden tubes, 
 using insulated wire. One tube should be small enough to slip 
 easily inside of the other after the winding is done. The ends of the 
 larger coil should be wound several times around a compass and then 
 fastened together. The two ends of wire of the smaller coil should 
 be attached to the binding posts of a galvanic cell. If, now, the 
 small coil be inserted in the larger one, the compass needle will be 
 deflected and the same thing will happen if it is withdrawn. This 
 shows that a current of electricity flows through the larger coil, oth- 
 erwise the compass needle would not be disturbed. Since this lat- 
 ter coil is not connected to the cell ^the source of current it follows 
 that the current which deflects the needle must be induced current. 
 If the inner coil remains stationary the needle is not affected, but 
 if it is moved then deflection occurs. The reason for this induced 
 current may be explained as follows : When a current flows through 
 the smaller coil, a magnetic field with lines of magnetic force trav- 
 eling from one end of the coil to the other through the air is 
 
MAGNETISM AND COILS. 33 
 
 set up, and completely surrounds the coil. When this coil is drop- 
 ped inside of the large coil these lines of force are cut by the coils 
 of wire in the larger coil, and a current of electricity is generated 
 therein. When no relative motion occurs between the coils no 
 current is set up in the outer coil. In order for a current to be 
 generated, therefore, lines of magnetic force must "be cut by. a mov- 
 ing conductor. This is the principle upon which all dynamo elec- 
 trical machines work, and it will be made use of later in these 
 lessons in explaining the operation of magnetos and dynamos used 
 for ignition purposes. 
 
 Spark Coils. An ordinary spark coil used for make and break 
 ignition consists of a single coil of insulated wire wound on a spool, 
 in the center of which there is a core of soft iron wires. This core is 
 insulated from and is not connected electrically with the coil. When 
 a current of electricity from say a battery flows through the coil, 
 the core of soft iron becomes magnetic and it is surrounded by lines 
 of magnetic force. The passage of a current of electricity through 
 this magnetic field sets up a counter electro-motive force that op- 
 poses the flow of current and consequently the current does not in- 
 stantly come up to its full value, but builds up rather slowly. When 
 the current is broken, as when the igniter trips, the lines of force 
 decrease slowly and this induces an electro-motive force which tends 
 to keep the current flowing in the coil. This self induction, as it is 
 called, between the loops of the coil, tends to maintain the current 
 after it is broken and the result is a bright spark at the igniter 
 points. The coil acts as a sort of reservoir for the accumulation of 
 a certain amount of electricity to be used when the circuit is 
 broken. 
 
 A coil of this kind must always be connected in series with the 
 cells of a battery for the ordinary or hammer break ignition, in order 
 to give a spark of sufficient volume and intensity to ignite the 
 charge. There is nothing about a simple coil of this kind to wear 
 out and if taken care of it should last indefinitely. If water gets in 
 between the turns of wire, a short circuit may take place, or the in- 
 sulation may be burned through by a heavy current at some time, or 
 possibly a wire may become broken inside of the coil, although this is 
 a rare occurrence. All the care a coil requires is to be kept in a dry 
 place. If it is made with the proper kind of wire, thoroughly well 
 insulated and kept dry, it will continue to give good service in- 
 definitely. 
 
 In the next lesson we will discuss the jump spark coil and then 
 take up magnetos and dynamos. The subjects of magnetism and in- 
 
34 
 
 GASOLOGY. 
 
 duction presented in this lesson will be found necessary to a clear 
 understanding of the next lesson. 
 
 LESSON X 
 
 There are two principal methods of electric ignition in common 
 use, one known as the hammer break method, the other as the jump 
 spark. In the former two rods pass through the cylinder walls to 
 the interior of the cylinder, into the clearance space. One rod is 
 carefully insulated. This is called the stationary electrode. The 
 other rod is not insulated and is movable. At the right instant 
 in the stroke some moving part on the outside of the engine, driven 
 from the main shaft, rotates the movable electrode until the two ig- 
 niter points inside the cylinder come into contact. This completes 
 
 the electric circuit. 
 Electricity flows 
 from the source of 
 current through the 
 insulated electrode, 
 then through the 
 movable electrode to 
 the points of the 
 the engine frame 
 and back through 
 the other lead wire 
 to its source. In 
 this connection it 
 may be well to note 
 that there must be a 
 complete unbroken 
 circuit for electrici- 
 ty to travel along or 
 it won't travel. At 
 the right instant a 
 tripping mechanism 
 of some sort throws 
 electrodes apart and 
 a spark is formed inside of the cylinder and the charge is ignited. 
 In the case of the jump spark there are no moving parts inside 
 of the cylinder. The current which ignites the charge does not 
 have a complete metallic circuit to travel in, but is obliged to jump 
 across a short air gap inside of the cylinder. When electricity has 
 to bridge a gap in this way it forms an arc or spark and it is this 
 
 ft-is metal plate loose, on shaft. 
 ~b-is spring con-tact piece 
 c-r,ielai contact fiece 
 a -insulating cei/af -fast- ro shaft. 
 
 ElG. 10. 
 
MAGNETISM AND COILS. 35 
 
 that ignites the charge. The current used in the hammer break 
 system could not jump a gap because it has not pressure enough, or 
 voltage enough, to use a more exact term. The same battery would 
 do in either case, but a different spark coil is necessary. This leads 
 us to a consideration of the jump spark coil, or induction coil, as it 
 is often called. 
 
 The induction coil, known also as the Ruhmkorff coil, is quite dif- 
 ferent from the simple spark coil described in the last lesson. It con- 
 sists essentially of a core of very soft, thoroughly annealed, iron 
 wires, bound together and covered with a good insulator of some 
 sort, which forms the core. Outside of this there is a coil con- 
 sisting of a few turns of rather coarse, well insulated copper wire of 
 about 14 gauge. This wire is connected with the battery, or source 
 of current, and is called the primary circuit. Outside of this again, 
 and thoroughly insulated from it, there is another coil of much finer 
 wire, about 28 gauge, called the secondary coil. This coil is made 
 up with a great many turns of wire and makes the circuit which ig- 
 nites the charge. The general arrangement and details of this piece 
 of apparatus are shown in Fig. 10, to which constant reference must 
 be made to complete the description. 
 
 At the left end of the coil there is shown a hammer, H, mounted 
 on a flat spring, forming what is called the vibrator. When at rest 
 the spring holds the hammer against the screw, W. When the 
 switch at G is closed, current from the battery can flow through 
 wire P, up through D, to screw W, then down through the vibrator 
 spring, thence through wire F, to the primary coil, and back to the 
 battery through wire M S the engine and wire P to the battery, 
 thus completing the circuit. In practice it should be noted that 
 the primary circuit is closed by the engine at the right instant. 
 When the primary circuit is closed a current flows around the pri- 
 mary coil and the core becomes an electro magnet. It immediately 
 attracts the hammer H and the circuit is broken. The core now 
 loses its magnetism and the vibrator spring throws the hammer back 
 and the circuit is again completed. As long as the circuit remains 
 closed the hammer vibrates back and forth very rapidly, in fact, hun- 
 dreds of times per second, each time opening and closing the 
 primary circuit. The result of this is to induce a current in the 
 secondary coil of very much higher voltage, which has power enough 
 to jump across the gap in the spark plug at K to the engine frame 
 and thence back to the secondary coil. 
 
 It must be remembered at this point that there is absolutely no 
 connection electrically between the primary coil and the secondary. 
 
36 GASOLOGY. 
 
 The question then arises, how is a current formed in the sec- 
 ondary coil? Kef erring to lesson IX, this statement will be found: 
 "In order for a current to be generated, therefore, lines of magnetic 
 force must be cut by a moving conductor." This was made to apply 
 to current generated by mechanical means, not chemically, as in a 
 battery. Now, it might have been stated at the same time that mo- 
 tion is only relative. For instance, suppose we wish to get away 
 from a certain object; there are two ways to do it. Either we may 
 move ourselves away or we may have the object removed. So far as 
 we and the object are concerned, the final result, that of mere 
 separation, will be as well accomplished in one way as in the other. 
 Motion, therefore, between two objects is relative. Consequently, 
 we can just as well generate current by moving the magnetic field 
 as by letting it stand still and moving the conductor. Now that 
 is just what actually happens in an induction coil. We showed in 
 the last lesson that if a current of electricity were sent through a 
 coil a magnetic field was instantly set up around the coil. If this 
 current be broken the magnetic field disappears. If now the magnetic 
 field be made to change rapidly from zero to a maximum in intensity, 
 as it does due to the vibrating current in the primary coil, the re- 
 sult is a moving magnetic field and a stationary conductor. Thus, 
 we accomplish the same result as we would obtain with a stationary 
 magnetic field and a moving conductor. Consequently, a current will 
 be induced in the secondary coil, and this current will have a much 
 higher voltage than the voltage in the primary coil. The reason for 
 this increase in voltage is due to the difference between the two coils. 
 If the secondary coil was made up with the same sized wire and the 
 same length of wire as the primary, the voltage would be practically 
 the same, but since it is made up of very much finer wire the volt- 
 age or pressure is increased, but the amperage or amount of 
 current is decreased. The reason for this may be explained in a 
 rough way by considering water flowing through a pipe. If all the 
 water that flows through a large pipe be made to pass through a 
 much smaller pipe, the velocity in the smaller pipe must be very 
 much greater, while the size of the stream or amount of current is 
 proportionately decreased. 
 
 The condenser shown in the diagram is placed inside of the box 
 containing the coil and consists of a number of sheets of tin foil 
 piled one on top of the other and insulated from each other. The 
 ends of every alternate sheet are connected at K and the other sheets 
 are connected with wire L. The object of this device is to demag- 
 netize the core instantly between each vibration of the hammer, 
 
MAGNETISM AND COILS. 37 
 
 to prevent an intense spark between the hammer and contact screw 
 W, to increase the rapidity and extent of the changes or vibrations 
 in the primary current, and by changing the magnetism of the core 
 quickly to augment the current in the secondary coil. The manner 
 in which all this is accomplished may be explained thus: When 
 the hammer is in position, shown in the diagram, the condenser is 
 practically inactive, but when the contact with W is broken a spark 
 has a tendency to jump across, but instead, current flows from D 
 through K to the condenser and charges it. The latter, however, 
 immediately reacts just as a spring reacts when struck a sharp 
 blow and sends a small current backward through K D G P, the 
 battery, engine wires S and M, thus opposing the direction of the 
 current in the primary coil and destroying it and demagnetizing the 
 core. 
 
 One of the secondary wires S is attached to the spark plug and 
 the other to some part of the engine frame. The outer casing of the 
 spark plug is connected electrically to the cylinder, while the wire that 
 passes through the plug is insulated from the cylinder, but is sep- 
 arated from the metal rim at R by only about 1-32 of an inch. 
 When current flows in the secondary coil it leaps across this small 
 air gap and forms the spark. As long as the vibrator is working 
 a stream of sparks flows across this air gap. 
 
 In some types of spark coils the vibrator instead of making a 
 large number of oscillations makes only one, and only one spark is 
 formed inside the cylinder. This, of course, is much easier on the 
 battery as it takes only a fraction as much current. 
 
CHAPTER IV 
 DYNAMO ELECTRIC GENERATORS 
 
 LESSON XI 
 
 The sources of electrical current for gas engine ignition are dry 
 cell batteries, wet cell batteries, storage batteries, dynamos and 
 magnetos. We have already discussed the first two. In this les- 
 son we will turn our attention to dynamos and magnetos, reserving 
 storage batteries for a subsequent lesson. 
 
 Batteries generate electrical energy by chemical action. Dyna- 
 mos and magnetos generate electrical energy by mechanical means. 
 
 In the case of bat- 
 teries a definite 
 quantity of certain 
 chemicals is con- 
 sumed in generating 
 a given amount of 
 electricity. While 
 in the case of a dy- 
 namo or a magneto 
 a definite amount of 
 work must be ex- 
 pended to produce 
 a given amount of 
 electricity. Batter- 
 ies transform chem- 
 ical energy into 
 electrical energy, 
 while dynamos and 
 magnetos transform mechanical energy into electrical energy. The 
 equivalent electrical energy that is generated in either case will be 
 less than either the chemical energy or the mechanical energy that 
 produces it. In other words, there is always some loss in the 
 transformation process, even under the most favorable conditions. 
 When a coil of wire is moved across a magnetic field in such a 
 way as to cut the lines of force at right angles, an electric current 
 is set up in the coil. This is the fundamental principle of opera- 
 tion of both dynamos and magnetos. 
 
DYNAMO-ELECTRIC GENERATORS. 
 
 Figure 12 is a diagram which illustrates the method by which this 
 principle is applied in a practical way. P P are the pole pieces; C is 
 the armature, which is keyed to a shaft D and which rotates be- 
 tween the pole pieces. The core of the armature is made up of a 
 large number of thin iron punchings (see Fig. 14) having slots on the 
 circumference to carry the coils of wire. The completed armature is 
 shown in Fig. 13. The loops of wire are wound lengthwise around the 
 armature and the ends are soldered to copper segments, S. One end 
 of the loop of wire 
 is soldered to a 
 segment on one side 
 of the cylinder and 
 the other end to a 
 segment on the oth- 
 er side. These cop- 
 
 per segments are 
 insulated from each 
 
 other with strips of mica, and from the shaft by a mica sleeve. All 
 of these copper strips taken together are called the comnmtator. 
 F F are the field pieces. They are soft iron columns around which 
 there is wound a continuous coil of insulated copper wire. One end 
 of this coil is connected to one of the brushes h, the other is con- 
 nected to the outside circuit and through that to the other brush. 
 The brushes collect the current from the armature, pass it through 
 the field coils, and the external circuit and back again to the other 
 
 brush, thus completing the cir- 
 cuit through the armature coil that 
 the two brushes happen to be in 
 contact with at the given instant. 
 The above description applies to 
 what is known as a direct current 
 series wound dynamo. 
 
 The little arrows pointing to- 
 ward the center of the armature 
 represent the lines of magnetic 
 force which are supposed to be 
 constantly passing between the 
 pole faces PP. We will call the 
 left pole the positive or north pole 
 N, and the other the south pole 8. 
 If the armature is rotated, a coil 
 such as a 1} cuts all the lines of force and a current of electricity 
 will be induced in it. While the conductor is passing the neutral 
 
40 GASOLOGY. 
 
 region, at the gap between the pole faces, no current will be gen- 
 erated. Current is generated only when lines of force are cut, 
 and will be greatest at the points m and n. When the coil passes 
 the north pole, revolving in the direction shown by the large ar- 
 row, the current is flowing toward the segment under the top brush, 
 but when it cuts the lines of force opposite the south pole the di- 
 rection of current is reversed. By placing the brushes just at the 
 point where the current reverses in direction a continuous current, 
 flowing always in the same direction, will be produced in the ex- 
 ternal circuit. This, then, is the purpose of the commutator; 
 namely, to produce a direct current, one that does not change its 
 direction in the external circuit. When a current flows through the 
 field coils around F f the fields and pole pieces become strong electro- 
 magnets, thus increasing the magnetic induction, or number of 
 lines of force, and consequently a stronger current is generated 
 in the armature coils. The larger the current flowing through the 
 field coils', therefore, the greater will be the strength of the mag- 
 netic field until what is known as the saturation point is reached, 
 or the point at which no more lines of force are possible. The faster 
 a dynamo is run the greater the current that will be generated. In 
 order to protect the dynamos used in gas engine ignition from too 
 heavy currents they are provided with a governor that will not 
 allow them to run much faster than about 1,400 revolutions per 
 minute. At this speed they will generate about eight or ten amperes 
 with a voltage of about ten. Since it is hardly possible to make 
 them run fast enough by turning the fly wheel by hand, a dry cell 
 battery is required for starting. When the engine comes up to 
 speed this may be switched off and the dynamo switched on to the 
 ignition circuit. Some of these dynamos must be run in connection 
 with a spark coil for make and break ignition and some generate 
 a current strong enough not to require any coil. For jump spark ig- 
 nition the coil is necessary, except with some forms of magnetos. 
 These little direct current dynamos are made very compact and 
 some of them are entirely enclosed from the dust by a metal casing. 
 They do not require very much attention except an occasional turn- 
 ing of the brushes with a file and polishing of the commutator with 
 a bit of fine sand paper. Emery paper must not be used for this 
 purpose. The commutator must not be oiled. All the lubrication 
 that is needed is a little on the armature shaft bearings. For ig- 
 nition purposes on stationary gas engines they are quite satisfactory. 
 Where they are used on road engines, difficulty may arise through 
 some of the wire connections becoming loose. This must be guarded 
 against by frequent inspection. 
 
DYNAMO-ELECTRIC GENERATORS. 
 
 41 
 
 LESSON XII. 
 
 MAGNETOS. 
 
 The fields of a magneto are made of permanent mag- 
 nets. Those of a dynamo, such as we described in the last lesson, 
 are electro-magnets. This, then, is the essential difference between 
 these two types of generators. The dynamo is provided with a field 
 winding, that is, a 
 coil of wire which 
 surrounds the field 
 pieces and either all 
 or a part of the cur- 
 rent generated flows 
 through this wind- 
 ing. This is what 
 generates the mag- 
 netic field between 
 the pole pieces. In the magneto there is no winding around the 
 field pieces. These,- instead of being made of soft iron, are made 
 of hardened steel and permanently magnetized. The armature is also 
 made differently. It consists of an H-shaped piece of soft iron around 
 which a single continuous coil of wire is wound parallel with the 
 axis. Figure 15 shows the simplest style of magneto armature, and 
 
 Fig. 16 shows an end view of the com- 
 plete machine assembled. 
 
 The armature fits very closely be- 
 tween the pole pieces, having a clearance 
 of only about one one-hundredth of an 
 inch. The pole pieces P are made of 
 soft iron and the lines of force pass 
 from the positive pole to the negative 
 through the soft iron H of the armature. 
 The manner in which the current is 
 generated will now be described. 
 
 When the armature is in the position 
 shown in Fig. 16, the lines of force pass 
 from one pole piece to the other through 
 the soft iron neck of the armature, 
 since that is the only path they can 
 travel. The brass plate at the bottom 
 is not a conductor of magnetism and 
 no lines of magnetism can pass from one pole to the other through 
 
42 
 
 GASOLOGY. 
 
 it. The armature acts just like the keeper or flat piece of iron that 
 is laid across the ends of a horse-shoe magnet. When the armature 
 is not in position the lines of force will pass through the air along 
 the lines of least resistance, through a-a or ~b-~b. But the greater 
 number will pass between the points fc-Z> since these are the nearest 
 
 together. When the armature is in the 
 position shown in Fig. 16, all of them 
 will pass through the neck of the arma- 
 ture, as before stated. 
 
 When the armature is turned to the 
 position shown in Fig. 17, the lines of 
 force are distorted, as shown, but still 
 flow through the neck N. But when the 
 armature is turned still farther so that 
 N stands vertical, as in Fig. 18, the lines 
 of force no longer flow through N f but 
 take two paths, one across a-a, the other 
 ~b-~b, since these are the paths of least 
 resistance. 
 
 When the lines of force are flowing 
 through the neck N, as in Fig. 16, the 
 soft iron core is strongly magnetized; 
 but when the armature revolves to the 
 position of Fig. 18, N is demagnetized. In this way the magnetism 
 of the armature varies from a maximum, when the neck N is hori- 
 zontal, to almost nothing when it is ver- 
 tical. As the armature revolves, there- 
 fore, there are rapid changes in the mag- 
 netic field through which the armature 
 coil is passing. We have, then, a va- 
 riable magnetic field, just as we have in 
 an induction coil, and the result is 
 that a current of electricity is induced in 
 the armature coil. Since the greatest 
 change in magnetism occurs when the 
 neck N is vertical, it follows that the 
 strongest current will be induced each 
 time N stands in a vertical position, and 
 the weakest when N is horizontal. Twice 
 in each revolution of the armature the 
 current will be a maximum, and twice it 
 will be a minimum. 
 
DYNAMO-ELECTRIC GENERATORS. 43 
 
 Since the current is variable, it follows that ignition must be made 
 to occur when armature stands with its neck in a vertical position. 
 This is the only position in which current is strong enough to pro- 
 duce a sufficiently strong spark. 
 
 It is perfectly clear in view of the above explanation that the 
 magneto must be in exact step with the engine in order to ignite the 
 charge at the right time. It must, therefore, be driven by the crank 
 shaft of the engine by some positive means. If it were driven by a 
 friction pulley or by a belt in the manner that the dynamo described 
 in the last lesson was driven, it would soon be out of time with the 
 crank shaft on account of slippage between the friction surfaces. 
 The only way to drive the armature of a magneto, where it makes a 
 complete revolution, is by means of toothed gearing. 
 
 A consideration of the principles of action of a magneto will show 
 the reader that it is not necessary for the armature to make a com- 
 plete revolution. If it is made to turn from a vertical position to a 
 horizontal position and then is whirled swiftly back to the vertical, 
 say by means of strong springs, a sufficient current will be set up 
 to ignite the charge. Some magnetos are built on this principle 
 and a push rod operated by a cam on the crank shaft or on an aux- 
 iliary shaft, if it is a four-cycle engine, will oscillate the armature of 
 the magneto at the right time. 
 
 There are two types of magnetos, one known as the low tension 
 type and the other as the high tension. The one just described is a 
 low tension magneto used for make and break ignition. A mag- 
 neto of this type is wound to deliver current at from 100 to 150 
 volts. 
 
 High tension magnetos, strictly speaking, are provided with two 
 windings, one of a few turns of coarse wire and the other of a 
 large number of turns of fine wire. Magnetos of this type generate 
 current at a high voltage, ranging from 10,000 to 20,000. Such 
 high tension magnetos are used only for jump spark ignition. Low 
 tension magnetos, in conjunction with a spark coil, are used more 
 frequently than the high tension magnetos for jump spark ig- 
 nition. 
 
 In the simple magneto just described, one end of the coil wire is 
 grounded on the metal of the armature and the other end is at- 
 tached to a metal rod passing through the armature shaft. This rod 
 is insulated from the shaft by a hard rubber bushing. There is, 
 therefore, only one terminal, and if this is connected to the insu- 
 lated electrode, the current can pass back to the armature of the 
 
44 GASOLOGY. 
 
 magneto through the engine frame when the igniter points are in 
 contact, since the magneto itself is connected directly to the metal 
 frame work of the engine. 
 
 LESSON XIII. 
 
 The general principles of magneto ignition were outlined in the 
 last lesson. A little study will show the reader that a magneto of 
 the kind therein illustrated is a very simple machine. There are 
 comparatively few parts, there is only one winding, that on the 
 armature, and there are few wire connections to work loose. In 
 fact, there are only two connections, one to the armature shaft and 
 the other to a ring or bushing which is insulated from the shaft. 
 The current is taken off by means of a brush or metal contact point 
 from this bushing. 
 
 On account of the simplicity of magnetos, and their general re- 
 liability in case of rough, hard service, they are used quite exten- 
 sively on automobiles. Two types are in general use, one the low 
 tension magneto which works through a make and break igniter, 
 or in conjunction with a spark coil for jump spark ignition. The 
 other type of magneto is known as a high tension magneto. In this 
 machine the armature is provided with two windings, one consisting 
 of a few turns of coarse wire, the other of many turns of fine 
 wire. This secondary winding is identical with the secondary wind- 
 ing on an induction coil, and like it, is insulated from the primary 
 winding. Magnetos of this type are expensive and are used only on 
 automobiles. 
 
 The higher the speed at which a magneto is run, the higher will 
 be the voltage and the hotter the spark. At slow speeds the spark 
 will be quite thin and weak, while at high speed it will be almost 
 a flame. This is particularly desirable because at high speeds igni- 
 tion and combustion must be rapid in order to be completed at the 
 instant the piston passes its dead center position. When a battery 
 is used, the spark must be advanced greatly at high speeds. While 
 it is true that the spark of the magneto must also be advanced, it 
 need not be advanced so much as a battery spark on account of its 
 greater intensity. 
 
 Magneto Troubles. Like all other mechanical devices, the magneto 
 is liable at times to give trouble. If ignition fails the first thing to 
 do is to test the magneto and see if it gives a current. An easy 
 way to do this, though some may find it a trifle severe, is to dis- 
 connect the magneto from the ignition system, then connect a piece 
 
DYNAMO-ELECTRIC GENERATORS. 45 
 
 of wire to its terminal and hold the free end with the bare fingers 
 of one hand while the other hand, also bare, is in contact with some 
 bright metallic part of the engine. Now have an assistant turn the 
 magneto quickly by turning the fly wheel of the engine. If the mag- 
 neto is in good shape a shock will be felt. By holding the free end of 
 the wire against a toothed wheel while some one turns the fly wheel 
 around quickly, a spark will be formed as the contact is broken be- 
 tween the teeth at some point in the stroke, if the magneto is 
 working right. This method of testing is just as satisfactory as the 
 first method and a little less severe on the operator. If no current is 
 being generated, it shows that something is wrong with the magneto. 
 Perhaps some oil or dirt has accummulated under the brush or spring 
 that leads the current from the armature. Or, it may be that the 
 armature wire is broken. This does not often occur and if it does, 
 the break will be found where it connects to the insulated rod passing 
 through the shaft. A drop of solder will repair the mischief at this 
 point. 
 
 Care should be taken in making any repairs on a magneto where 
 the magneto has to be taken apart. A little carelessness or ignorance 
 may easily spoil a valuable machine. The armature acts the same 
 as a keeper on a toy horseshoe magnet. It provides an easy path for 
 the lines of magnetic force. If this is taken away, the lines of 
 force pass through the air and since they meet considerable resist- 
 ance some are lost and the magneto becomes permanently weakened. 
 On the other hand, if the armature is always in place, a magnet will 
 retain its magnetism indefinitely unless abused in some other way, 
 such as being heated to a high temperature. The armature of a 
 magneto also acts as a path for the lines of magnetic force. If it is 
 removed either the space between the pole pieces must be filled with 
 a piece of soft iron or a heavy piece of soft iron must be laid across 
 the pole pieces under the arch of the magneto to provide a path for 
 the lines of force. Unless a man is well informed about magnetos he 
 had better not take them apart or try to make extensive repairs. 
 In cases where the difficulty is not easy to detect, or where consider- 
 able repairing must be done, it is better for the ordinary unskilled 
 individual to turn the job over to a good electrician. 
 
 If, after the test of the magneto, it has been found to be in good 
 condition, the trouble will be found in some of the connections, 
 probably in the spark plug. The most prevalent cause of trouble at 
 this point is due to the fouling of the igniter points. A deposit of 
 carbon, or of oil, often forms on the points which will prevent the 
 passage of a spark. Poor lubricating oil, which has a flashing point 
 
46 GASOLOGY. 
 
 somewhat too low, causes trouble since some of it will be consumed 
 while a part will merely char and form a deposit of carbon. Too 
 much lubricating oil, even of good quality, will produce as bad re- 
 sults. A plug with oil dripping from the points will not give a 
 spark. When a plug is found to be in this condition, or covered with 
 a deposit of soot or carbon, it should be washed with gasoline. The 
 gasoline dissolves the carbon and loosens it so that it can readily be 
 wiped off. The distance between the points of a spark plug should 
 not exceed one thirty-second of an inch, and, in general, should be 
 only about one-half this amount. It frequently happens that the 
 points become bent so that they either touch or else are too far apart. 
 An inspection of the plug, of course, will show if either one of these 
 things causes the trouble, and the remedy is evident. A crack in 
 the insulation of the plug often causes trouble. Moisture is apt to 
 gather in the crack, thus making an easy path for the passage of 
 the current to the engine frame instead of arching or sparking 
 across the gap and producing a spark as it should. The obvious 
 remedy, of course, is to put in a new plug. One of the best ways to 
 test a plug is to put in a new one and try it. If it works all right, 
 and the old one does not, it shows the old one is not in good con- 
 dition. When jump spark ignition is used, the man in charge 
 should see to it that there are one or two new plugs on hand in 
 case of trouble with the one in use. 
 
 Where a magneto is used for hammer break ignition, as it fre- 
 quently is, it may fail to act if the igniter points are in poor con- 
 dition. A deposit of soot on the points will cause failure; also if 
 the movable electrode sticks in contact with the stationary electrode, 
 or if the insulation of the stationary electrode is broken down. A 
 short circuit, due to any cause, such, for example, as the wearing of 
 the insulation from the wire that leads to the stationary electrode 
 at the point where it crosses the engine frame, will cause failure of 
 ignition. 
 
 Sometimes an engine fitted with a magneto will run well at low 
 speed and never miss a charge, but when the speed is increased it 
 will begin to miss. The reason for this is generally a break in the 
 insulation of the stationary electrode, which is not serious enough 
 to cause a leak of current when the voltage is low, as it is when 
 the magneto runs slowly, but which allows the current to pass 
 through the break to the engine frame when the voltage is high. 
 The obvious remedy in this case, of course, is to either repair the 
 insulation or get a new igniter block. When several cylinders are 
 fired from the same magneto, it may happen that only one of the 
 
DYNAMO-ELECTRIC' GENERATORS. 47 
 
 igniter blocks is out of order, in which case all the cylinders will 
 fire at slow speed, and this one will miss when the speed is high. 
 The manner of testing to determine which one is at fault is to dis- 
 connect the ignition system from all cylinders and try to run at high 
 speed first with one cylinder and then with another until the faulty 
 igniter is located. 
 
CHAPTER V 
 STORAGE BATTERIES 
 
 LESSON XIV. 
 
 It has already been pointed out in these lessons that the sources 
 of current for electrical ignition may be classed under two heads; 
 chemical and mechanical. Chemical generators are again sub- 
 divided into two classes; primary batteries, made up with either 
 wet cells or dry cells, and secondary batteries, called storage bat- 
 teries or accummulators. Mechanical generators may be either 
 dynamos or magnetos. 
 
 Glancing back over previous lessons in which primary cells have 
 been described, we will find that a primary cell consists of two 
 elements submerged in a liquid or paste called the electrolyte. The 
 elements are usually carbon and zinc, but very often they are copper 
 oxide and zinc. Either dry cells or wet cells may be made up with 
 either of these pairs of elements. 
 
 The electrolyte for the first named elements is generally a solu- 
 tion of sal-ammoniac and water. For the last named elements 
 caustic soda and water are used. 
 
 In all primary cells that we have considered, electricity is generated 
 by the destruction of the zinc element and the quantity of current 
 generated in a given time is proportional to the amount of zinc 
 consumed. 
 
 When zinc is acted upon by the electrolyte, bubbles of hydrogen 
 gas form on the other element. The formation of these bubbles 
 is called polarization and the effect is to weaken the voltage and 
 current output of the cell. In all well constructed cells some means 
 are used to prevent polarization. In dry cells manganese dioxide is 
 placed in contact with the carbon element to prevent polarization, 
 but it is only partially successful. It is in consequence of polari- 
 zation that dry batteries become weaker with continuous use. If 
 they are allowed to rest for a time the bubbles of hydrogen unite 
 with the oxygen of the manganese dioxide, the cell is depolarized and 
 it is quite fresh and strong again. 
 
 It is quite evident in view of the tendency of the dry cell to polar- 
 ize that it is not adapted to continuous service or for ignition pur- 
 poses for a high speed four cylinder engine such as is used in many 
 automobiles. 
 
STORAGE BATTERIES. 49 
 
 In the Edison cell polarization is largely prevented by putting a 
 depolarizing agent such as manganese dioxide in the copper oxide 
 plate. Since the chemical action in a liquid is more rapid than in 
 a paste it follows that the liquid cell is better adapted to continuous 
 service, or nearly continuous service, than is the dry cell, because 
 depolarization takes place more rapidly. 
 
 Briefly, we have considered the action of primary cells and are now 
 ready to look into the construction and operation of secondary cells. 
 
 The storage cell consists of two elements, as in the case of a pri- 
 mary cell, dipped into an electrolyte. Unlike the primary cell it 
 can not give off electrical energy in its original state when the cir- 
 cuit is closed. The storage cell must first be charged with electrical 
 energy from some source of current like a dynamo before it in turn 
 can be used as a source of current. The charging of a storage 
 battery sets up chemical action in the elements and in the electrolyte 
 which causes changes in the -material of which they are formed. 
 The electrical energy of the charging current is thus changed into 
 chemical energy which in turn works certain changes in the elec- 
 trolyte and in the elements. If now the newly charged storage 
 battery be put on a closed circuit, that is, connected up to deliver 
 current, chemical action will again take place, but in a reverse direc- 
 tion. The electrolyte and elements will be changed back to their orig- 
 inal condition and nearly as much electricity will be delivered from 
 the battery as was put into it in the first place. The current produced 
 by the battery will flow in the opposite direction to the charging 
 current. 
 
 A storage battery may be charged and discharged a great many 
 times, and if properly cared for will last for a number of years. 
 In this respect it differs from primary batteries which can not be 
 recharged ordinarily, but must be renewed when run down. 
 
 There are several substances that can be used for the electrodes 
 and electrolytes of a storage battery, but practically all that are now 
 on the market use some compound of lead for the former and sul- 
 phuric acid and water for the latter. One electrode is composed of 
 sponge lead and the other of lead peroxide. The former is the 
 negative plate, the latter the positive plate since it is from this plate 
 the current flows out. 
 
 Since lead is the only cheap metal that will withstand sulphuric 
 acid, it is used to form the support for the electrodes. The surface 
 of the cast lead plates is filled with grooves and a paste of lead oxides 
 is forced in under pressure and then treated to form either sponge 
 lead or lead peroxide as the occasion demands. 
 
50 GASOLOGY. 
 
 A number of the plates after being prepared in the way above 
 described are placed side by side in a glass jar, or, if the battery 
 is to be used for automobile ignition, the containing vessel may be 
 made of hard rubber, or of wood lined with rubber or sheet lead. The 
 electrodes are carefully insulated from each other and from the 
 bottom of the containing vessel to prevent any possibility of short 
 circuiting either by contact with each other or by dipping into the 
 sediment which may form in the bottom of the vessel. The top of 
 the vessel, if it be an automobile cell, is covered with a hard rubber 
 cover which is sealed in place with hard pitch. A small vent hole 
 in the cover allows the gas to escape, but is too small to allow much 
 of the electrolyte to spill even if the cell is turned bottom side up. 
 The two terminals come up through the cover and a suitable opening 
 is provided through which the electrolyte may be introduced. This 
 opening is stopped with a rubber cork. 
 
 Each side of each positive plate should face a negative plate, thus 
 making it necessary, generally, to have one more of the latter than 
 of the former. Automobile ignition batteries consist, generally, 
 of two cells. When this form of current generator is used it is 
 customary to have two batteries connected to the engine through 
 a double point switch so that either one may be connected in as the 
 operator desires. Since a storage battery does not recover by standing 
 idle, like a primary battery, one battery should be used until the 
 engine begins to miss, when it should be cut out and the other bat- 
 tery put in service. 
 
 The chemical reactions in a storage battery are not yet thoroughly 
 understood, but it is generally agreed that when the cell is being 
 charged, lead peroxide is formed on the positive plate and metallic 
 lead on the negative plate. During discharge, lead sulphate is 
 formed on both plates. Lead sulphate is a white substance and has 
 no electrical conductivity. If the cell is allowed to discharge too 
 much, an excessive amount of this substance is formed and the cell 
 can not be easily recharged again. Care must be taken not to al- 
 low the voltage of a dry cell to run down too low or it may be ruined. 
 When the voltage of a cell falls to 1.8 volts on discharge, it is time 
 to put it out of commission until it can be recharged. 
 
 Another reason why the voltage must not be allowed to rtm down 
 below 1.8 is that the formation of lead sulphate causes an increase 
 of volume which causes the plates to buckle and the paste to crack 
 and fall out of the grooves in the plate. 
 
 Charging a Storage Battery. Direct current must be used to 
 charge a storage battery. Alternating current can not be used ex- 
 
STORAGE BATTERIES. 51 
 
 cept in connection with a rectifier which changes the alternating 
 current to direct. The voltage of the charging current used for 
 charging a single cell must not exceed 2.5 volts. A two cell battery 
 would require a current strength -of 5 volts. The positive wire of 
 the charging line must be connected with the positive pole of the 
 battery. If the charging current is passed the wrong way into the 
 cell, the cell will be ruined. The positive and negative terminals 
 can be determined by means of a voltmeter. If this is not at hand, 
 draw off some of the electrolyte and place in a glass vessel. Con- 
 nect two strips of lead to the terminals of the battery and insert 
 them in the liquid, taking care they do not touch. The strip that 
 turns brown is connected to the positive terminal. 
 
 In charging a battery remove the vent plug from each cell to allow 
 the gas which forms to escape. This gas is hydrogen gas and is 
 highly inflammable and care must be taken not to bring a naked 
 flame near the cells while being charged. The completion of the 
 charge will be indicated by the boiling or gasing of the electrolyte, 
 and the charging current should be shut off about twenty minutes 
 after this begins. At this time the voltage of each cell will be about 
 2.5 volts. A slight overcharge will not hurt a cell, but if charging 
 is carried too far lead sulphate will form and the cell may be in- 
 jured or even ruined. 
 
 LESSON XV. 
 
 The electrolyte is made up with sulphuric acid and water, using 
 one part of chemically pure acid to three or four parts of 
 distilled water or clean rain water. The acid should be add- 
 ed to the water slowly, at the same time stirring the mixture 
 vigorously. The addition of sulphuric. acid to water generates heat 
 and care must be taken not to pour water into the acid, because heat 
 would be generated so rapidly that steam would be formed and both 
 water and acid would be thrown violently out of the vessel, burning 
 whatever it came in contact with. 
 
 In order to mix the water and acid in exactly the right proportions 
 an instrument called a hydrometer is used. This consists of a glass 
 tube weighted with mercury at the lower end, and having graduations 
 marked on the stem. This instrument indicates the weight or density 
 of a liquid as compared with pure water. It is used by allowing it 
 to float in the liquid to be tested. If floated in rain water at a tem- 
 perature of 4 C, it will sink, to a point marked 1.000 on the 
 stem. If' floated in a liquid heavier than water it will not sink 
 so far and the mark on the stem will be greater than unity. 
 
52 GASOLOGY. 
 
 In making up the electrolyte for storage batteries the acid should 
 be added until the density shows 1.200. If the density of the elec- 
 
 . , -T. trolyte drawn from 
 
 W/res I a cell tests less than 
 
 1.200 acid should be 
 added, if more, then 
 add water. An elec- 
 trolyte of higher 
 density will make 
 
 L*ws666 667 the cel1 more active < 
 
 I a ~,.L*r but it wm cauge the 
 
 | l liB/.Hy cel1 to Deteriorate 
 
 _-|IIH--- more ra pidly. The 
 
 -p IQ -^g electrolyte should be 
 
 tested frequently. 
 
 A storage battery may be tested by testing each cell separately 
 with a voltmeter. An ammeter is of no use in testing storage bat- 
 tery cells, although it is the correct instrument to use for testing 
 either dry or wet primary cells. When the voltage of the storage 
 battery cells drops to 1.8 volts per cell it is time to recharge. 
 
 The electrolyte should cover the plates to a depth of about one- 
 fourth inch. If some of the electrolyte is spilled add some of the 
 fresh solution, which may be kept at hand in a bottle for this pur- 
 pose. If some of the liquid is lost through evaporation add rain 
 water or distilled water. 
 
 The Rating of Storage Batteries. The capacity of a storage bat- 
 tery is rated in ampere hours. For example, a ten ampere hour 
 battery is capable of delivering a current of ten amperes for one hour, 
 or one ampere for ten hours. The rate of discharge is thus seen to be 
 variable, depending upon the work the battery is called upon to do. 
 A storage battery is able to supply a heavy current for a short time 
 or a smaller current for a longer time. 
 
 In considering storage batteries for electric lighting, it is cus- 
 tomary to multiply the ampere hour capacity by two to find the 
 number of 16-candle power lamps that the battery is able to carry 
 for one hour. Each carbon filament 16-candle power lamp requires 
 about one-half an ampere of current, so that one ampere per hour is 
 sufficient for two lamps. A ten ampere hour battery, therefore, will 
 run twenty lamps one hour or four lamps for five hours. 
 
 Charging from a Lighting Circuit. A convenient means of charg- 
 ing storage batteries is found in the ordinary incandescent lighting 
 circuits. If the current is alternating, a rectifier must be used which 
 
STORAGE BATTERIES. 5q 
 
 will change it to direct current, for only direct current can be used 
 in charging the battery. Where direct current at 110 or 220 volts is 
 available, lamps may be used for resistance if a suitable rheostat is 
 not at hand. 
 
 Figure 19 shows the method of wiring where lamps are used. 
 
 A bank of lamps I, connected in parallel, is connected in series with 
 the battery. A double pole switch s, connects the battery with the 
 service wires and an ammeter is placed in the line at a. This in- 
 strument is not absolutely essential, but it is well to have it in order 
 to be certain of the strength of the charging current. The 
 number of lamps used will depend upon how much current they 
 require and the charging rate of the battery. This latter quantity 
 may be determined by dividing the ampere hour capacity of the bat- 
 tery by eight. For example, if the battery is rated at forty ampere 
 hours, it will take a five ampere current to charge it. If the line pres- 
 sure is from 110 to 120 volts, then five 32-candle power lamps, each 
 requiring a current of one ampere must be used. If 16-candle power 
 lamps at one-half ampere each are used, it will require ten lamps. 
 Fewer lamps can be used, but it will require a longer time to charge 
 the battery. 
 
 Laying up a Battery. If a battery is not to be used for some time 
 it may be kept in condition by giving it a small freshening charge 
 occasionally, say once in two weeks. This charge should be given 
 at a very slow rate. Where the battery must lie idle for an extended 
 period, as it frequently does in many summer or winter resorts, it 
 should be put in dry storage. To do this proceed as follows : First 
 charge the battery at normal rate until it is completely charged, then 
 syphon out the electrolyte and place in clean bottles for use when 
 the battery is to be recharged. As each cell is emptied, refill it 
 immediately with pure cold water. After all the cells have been 
 treated in this manner, connect up the battery and discharge it until 
 the voltage falls to one volt per cell. When this point has been 
 reached the water should be drawn off. If the battery gets hot dur- 
 ing discharge add cold water to take up the excess heat. After being 
 emptied of water the battery may stand for an indefinite period with- 
 out suffering any injury. 
 
Statio 
 
 CHAPTER VI 
 WIRING AN ENGINE 
 
 LESSON XVI. 
 
 This is a subject that gives probably as much trouble as 
 any other feature of gas engine operation, and it is proposed in this 
 and succeeding lessons to present a few wiring diagrams with the 
 purpose in view of acquainting our readers with the principles, at 
 least, of this subject 
 
 All wire used should be preferably rubber insulated. Cotton insu- 
 lated wire is not 
 nearly as satisfac- 
 tory, first, because 
 the insulation soon 
 becomes worn in 
 service; and second, 
 because the cotton 
 absorbs more or less 
 moisture. Wire of 
 proper size should FIG. 20. 
 
 be used since very small wire presents too much resistance to the 
 flow of current, especially if the external circuit be long. 
 
 All joints should be scraped clean and all binding, nuts and screws 
 should be set up tightly with a pair of pliers. Wherever there is a 
 
 loose connection 
 there will form an 
 oxide of copper, 
 which is a good in- 
 sulator, and even if 
 current does pass 
 through it will be 
 weaker on account 
 
 Cttrn 
 
 corjnecteB j 
 FIG. 21. 
 
 of the resistance at 
 that point. All wires should be supported and not be allowed to hang 
 or flop. A loose wire is apt to rub against some metal part of the 
 engine and cause a short circuit at that part, thus stopping the engine 
 and perhaps ruining the battery. 
 
 The simplest style of wiring is for a single cylinder engine fitted 
 with make and break igniter. This is illustrated in figure 20. The 
 
WIRING AN ENGINE. 55 
 
 battery consisting of four cells is connected in series, that is, one 
 cell behind the other with the carbon of one cell joined to the zinc 
 of the next, and so on. When the cam, which revolves at half the 
 engine shaft speed, forces the movable electrode into contact with 
 the stationary electrode, the circuit is completed and current flows 
 from one electrode to the other. When the cam passes the movable 
 electrode the current is broken and a spark is formed at the break. 
 No more current can be used until the electrodes are again in contact. 
 Where from four to six cells are used in one battery they are 
 always connected in series since this arrangement gives the greatest 
 voltage. For other kinds of work other styles of connection are 
 sometimes adopted, as shown in figures 21 and 22. The former rep- 
 resents what is called connecting cells in multiple and the latter 
 multiple series. The voltage and amperage differ in the different 
 styles of connec- 
 tions. For example: 
 If N represents the 
 number of cells; V, 
 the voltage of one 
 cell; and A, the am- 
 will be N times V; 
 perage of one cell, 
 then the voltage of 
 
 -, . . _// t.tni ./ f \^ S&T'/ti'S 
 
 a battery in series ._ 
 
 if connected in mul- 
 tiple, V; and in multiple series S times V, where S represents the 
 number of series units. The amperage will be for series connection 
 A, for multiple N times A, and for multiple series S times A. To 
 illustrate: If the amperage of each cell shown is 20 and its voltage 
 1, then in figure 20 the battery will show four volts and twenty am- 
 peres. In figure 21 there will be one volt and one hundred amperes, 
 while figure 22 will record two volts and forty amperes. In other 
 words, we will obtain the largest flow of current from figure 21 and 
 the least current, but greatest voltage from figure 20. 
 
 Series connection adds all the voltages together, while multiple 
 connection adds the amperage of each cell. It has the effect of form- 
 ing a single cell whose carbons are the sum of all the carbons and 
 its zinc the sum of all the zincs in the individual cells. In this 
 discussion no account has been taken of resistances of either the 
 internal or external circuits. 
 
 The Timer. Where there are two or more cylinders to be ignited 
 from a single battery or other source of current, it is necessary to 
 
56 
 
 GASOLOGY. 
 
 provide what is called a timer or commutator, which will connect 
 the battery first to one cylinder and then to another in the proper 
 order of their ignition. Such a device is nothing more than a re- 
 volving switch actuated by the engine itself from gearing attached 
 to the crank shaft. A crude form of timer illustrating the principle 
 of all timers appears in figure 23. It consists of a fibre ring, usually 
 enclosed in a metal case having a cam shaft passing up through its 
 center. This shaft carries a block with an arm on the end of which 
 
 is a contact wheel. 
 The wheel is pressed 
 outward by a com- 
 pression spring. As 
 the shaft revolves, 
 it carries the con- 
 tact wheel around 
 and makes contact 
 with . the various 
 binding posts 
 through the metal 
 segments whose in- 
 ner faces are flush 
 with the fibre ring. 
 
 Shaft 
 
 Con*c* 
 
 Time* for -*-cy7/Wer Engine. 
 FIG. 23. 
 
 Whenever the con- 
 tact wheel touches one of these metal contact pieces, current can 
 flow through the contact wheel, the arm that carries it and the cam 
 shaft to the engine frame from which it can pass back through the 
 grounded connection to its source. 
 
 In this connection it may be well to state that a ground connection 
 means a connection to the engine frame, but not necessarily to the 
 earth. The timer housing is provided with a lever connection where- 
 by it may be rotated several degrees and thus change the time of 
 contact with reference to the engine shaft while the engine is run- 
 ning. Timers are made with one, two, three, four, or more binding 
 posts for engines having a like number of cylinders. 
 
 In all problems of wiring there is one fundamental fact that must 
 be borne in mind continually, and that is, each circuit must ~be com- 
 plete in order to get a current through. Here is where a lot of people 
 have trouble. They do not make certain that each circuit is complete 
 before taking up the next. If they did they would have less difficulty 
 in laying their wires. This is not as simple as it might seem when 
 one has several separate sources of current with multiple switches and 
 perhaps jump spark ignition. 
 
WIRING AN ENGINE. 
 
 57 
 
 Since jump spark ignition presents some difficulty to many people 
 we have prepared a diagram, figure 24, to illustrate one of the funda- 
 mental features of 
 this form of igni- 
 tion. The point we 
 wanted to illustrate 
 is the one just men- 
 tioned, that is, that 
 the various circuits 
 must be complete. 
 In this diagram 
 there are two cir- 
 cuits, the primary 
 marked P, and the 
 secondary marked 
 S. There are only 
 three wires to the 
 engine from the 
 coil, and this is 
 what causes trouble. 
 
 There are two 
 distinct circuits in 
 the coil the prim- 
 ary from the bat- 
 tery, consisting of 
 coarse wire, and 
 outside of this and 
 
 T/rrrer _ 
 
 FIG. 24. 
 
 insulated from it a fine coil of wire called the secondary. When the 
 
 current flows 
 through the primary, 
 an induced current 
 flows through the 
 secondary and 
 jumps the gap in 
 the spark plug. By 
 referring to the dia- 
 gram it will be seen 
 that the timer closes 
 the primary circuit, 
 using the engine as 
 a par t O f the circuit. 
 
 25. 
 
 When this occurs the secondary current flows through the spark plug, 
 
58 
 
 GASOLOGY. 
 
 jumps to the engine frame and goes back to the coil through the 
 common ground wire and thus completes the circuit. It would be 
 possible and perhaps less confusing to use two ground wires, one for 
 the primary and the other for the secondary thus making four 
 binding posts on the coil box. 
 
 LESSON XVII. 
 
 Figure 26 illustrates the method of connecting jump spark ignition 
 to a two-cylinder engine whose cranks are set 180 degrees apart. Two 
 batteries are used and two coils. Either battery may be switched in 
 by means of a two point switch on the coil box. The secondary cir- 
 cuit is completed 
 through the engine 
 frame, the vertical 
 shaft of the timer, 
 and the primary 
 connection back to 
 the spark coil where 
 '<?> connection is made 
 to the secondary 
 * winding after the 
 manner shown in 
 figure 24 in the pre- 
 ceding lesson. 
 
 In figure 27 a 
 
 TH/O cxt//yz?>?.$ - 
 
 FIG. 26. 
 
 method is shown for connecting both dry batteries and storage bat- 
 teries so that either may be used as desired. The same ground wire 
 is used for both the dry and storage batteries as are also the same 
 coil and timer. The two point switch is placed on the side of the 
 coil box. 
 
 It is customary on the best cars at the present time to use a 
 separate coil for each cylinder. This makes it easier to locate trouble, 
 when it occurs, with the ignition. The connections on the different 
 coils can be changed and if the trouble still continues it shows that 
 the difficulty is not in the coils, but if the trouble remains at the 
 same coil when connected to a different cylinder, the trouble will be 
 generally found in the coil. 
 
 Figure 28 shows a four-cylinder engine connected up with four 
 coils, the current being supplied by a battery. In wiring a multi- 
 cylinder engine each circuit should be completed and tested before 
 
WIRING AN ENGINE. 
 
 59 
 
 another one is started. In this way all danger of confusing the 
 circuits is obviated. The primary wire should first be laid from its 
 coil unit to the ap- 
 propriate timer con- 
 tact. When the 
 switch is closed the . xPnmaru 
 vibrator of the coil 
 will buzz when the 
 timer contact piece 
 makes connection 
 with the segment to 
 which the wire is at- 
 tached. A buzzing 
 of the vibrator when 
 the switch is open 
 indicates a short cir- 
 cuit somewhere. The 
 secondary wire 
 should now be put 
 down before at- 
 tempting the next 
 primary circuit. 
 This should be test- 
 
 FIG. 27. 
 
 ed by noting if a spark appears at the spark plug, which latter may 
 be unscrewed and placed with its shell in contact with the engine 
 
 frame so that the 
 spark may be ob- 
 served. When the 
 spark lever is fully 
 f retarded the spark 
 should appear when 
 the piston reaches 
 the dead center on 
 its compression 
 stroke. 
 
 The timer contacts 
 for a four - cylinder 
 engine must be ar- 
 
 ' 
 
 ranged with reference to the firing order of the different cylinders, 
 which in turn is established by the order of opening of the exhaust 
 valves. Suppose this order is 1, 2, 4, 3, as in figure 28. After the first 
 cylinder is connected up in the manner just described, the next' one 
 to be wired is number two, and the primary wire should be connected 
 
60 
 
 GASOLOGY. 
 
 to the next timer contact in the direction of rotation of the timer. 
 The primary of coil number four should be attached to the next bind- 
 ing post of the timer and the corresponding secondary run to 
 cylinder number four. The remaining coil, timer contact, and 
 cylinder should now be connected up, thus completing the wiring. 
 The direction of rotation of the timer is indicated by the arrow. 
 
 Where only a single coil is used on a multiple cylinder engine it is 
 necessary to use a timer and a secondary distributor. A diagram rep- 
 resenting this style of connection appears in figure 29. For con- 
 venience in showing the connections the primary timer and the dis- 
 tributor are separated, although this is not customary in practice. 
 Usually both are connected together, one side being for the dis- 
 tributor and the other side for the timer. Only one source of cur- 
 rent is shown in the 
 drawing, but there 
 *tor is nothing to pre- 
 vent wiring in such 
 a way as to be able 
 to use two or more 
 sources of current. 
 This style of igni- 
 tion is not used as 
 much as it has been 
 in former years. 
 The advantages of 
 the multiple coil 
 system indicate 
 some of the disad- 
 
 FIG. 29. 
 
 vantages of this type. It has, however, some positive advantages, 
 such as reducing the number of connections, and making only one 
 coil to adjust. 
 
 In our next lesson we will show different methods of 'wiring en- 
 gines for magneto ignition. 
 
 LESSON XVIII. 
 
 There are two principal methods by which ignition in a gas engine 
 cylinder may be accomplished, using a magneto. The first is with 
 a low tension magneto adapted to the make and break system of igni- 
 tion, and the second with a high tension magneto adapted to the 
 jump spark system. There are many modifications of the latter 
 system, some of which will be discussed in succeeding lessons. In 
 
WIRING AN ENGINE. 
 
 61 
 
 this lesson we will consider first the low tension system using make 
 and break ignition. In this type of ignition the igniter is just 
 the same as for battery ignition. There is one stationary electrode 
 and one movable. The movable electrode is brought into contact 
 with the stationary or insulated electrode at the proper time in the 
 stroke by the action of a cam acting on a tappet. The current from 
 the magneto flows from the magneto through the contact points, 
 thence to the engine frame and then to the magneto, completing the 
 circuit. 
 
 FIG 30. 
 
 At the right time in the stroke the two contact points are quickly 
 separated and an arc is formed in consequence, thus igniting the 
 charge. This action is in nowise different from what obtains when 
 a battery is used except that it is not necessary to use a spark coil, as 
 the voltage and strength of current of the magneto are sufficient with- 
 out any intensification with a coil. The method of wiring is therefore 
 very simple. All that is needed is a wire from the magneto ground- 
 ed on the engine frame by having its base attached thereto so that 
 the circuit is complete when the two contact points are together. 
 
 When several cylinders are fired with the same magneto it is cus- 
 tomary to use what is called a bus bar, that is, a common wire from 
 the magneto, to which all the individual wires are attached. 
 
 When it is desired to stop the engine the magneto is short cir- 
 cuited on itself by means of a switch between the bus bar and the 
 
62 
 
 GASOLOGY. 
 
 engine frame. This causes the current to go back through the en- 
 gine frame to the magneto. It would be possible to stop the engine 
 by simply opening the switch leading to the various cylinders and 
 not causing the current to go back to the magneto, but this might 
 result in injury to the magneto, since the current which it would 
 continue to generate would have no outlet and might break through 
 the insulation of its own windings, causing permanent injury. 
 
 It must be remembered in considering magneto ignition that the 
 armature of the magneto must occupy a certain position with refer- 
 
 neto 
 
 FIG. 31. 
 
 ence to the field magnets at the instant ignition occurs (see figure 30), 
 as the current generated by the magneto when in any other position is 
 very feeble. For a magneto whose armature rotates, it is necessary, 
 therefore, that it revolve at a certain speed, relative to that of the 
 crank shaft, so that it will occupy the position shown in the figure 
 when ignition occurs. It is furthermore necessary that the time of 
 ignition be fixed absolutely with reference to the speed of the en- 
 gine and this makes some sort of positive drive necessary. The 
 usual method of obtaining this is by means of a gear on the crank 
 shaft driving one having the requisite number of teeth on the arma- 
 ture shaft. A belt or friction drive is not suitable because of slip- 
 page and the consequent getting out of time of the magneto. 
 
 The correct time for ignition to occur is during the compression 
 stroke, shortly before the piston reaches dead center. On most 
 
WIRING AN ENGINE. 
 
 63 
 
 automobiles,- and, in fact, other engines as well, the piston is given 
 a lead of about one-half an inch, that is, ignition occurs when the 
 piston is from one-half to three-quarters of an inch from the end 
 of the stroke. The correct timing of the ignition, therefore, con- 
 sists in causing it to occur at this point. This may be accomplished 
 by measuring down from the top of the cylinder to the piston and 
 then adjusting the gears so as to bring the armature into the po- 
 sition shown in figure 30 at that time. 
 
 Two-Point 
 
 tv/t-h Co/ 7. 
 
 FIG. 32. 
 
 Figure 31 is a diagrammatic sketch showing the method of wir- 
 ing switches, etc., for a low tension magneto. With the above de- 
 scription no other explanation should be needed to make the system 
 perfectly plain. 
 
 Figure 32 shows how an engine may be connected up with a low 
 tension magneto using a dry battery and coil to start with. After 
 the engine comes up to speed the two point switch may be thrown 
 over, cutting out the battery and cutting in the magneto. This is 
 the common method of connecting a system of this kind, as it is 
 necessary to bring the magneto of this type up to a higher speed 
 than can conveniently be done by hand cranking, in order for it to 
 generate sufficient current for ignition. 
 
VO.OFCYL. 
 
 CHAPTER VII 
 
 ENGINE BALANCE 
 
 LESSON XIX. 
 
 One of the difficulties encountered in designing and constructing 
 all reciprocating engines, whether they be driven by steam or gas 
 
 power, is to secure steady, even motion 
 1 and prevent, so far as possible, excessive 
 
 . || vibration. 
 
 The reason for vibration in all such 
 
 . I J engines arises from the fact that all re- 
 
 -* L ciprocating parts, such as the piston and 
 
 connecting rod, are obliged to come to 
 ri rest twice during every revolution, and 
 
 ' twice be brought up to maximum speed. 
 
 In addition to this we also encounter the 
 condition of a very variable driving force 
 acting at intervals only, in the case of 
 the gas engine. This complicates the 
 problem considerably and has required 
 the exercise of the very best engineering 
 skill to overcome. Even with all the thought and study and skill 
 with which this problem has been approached it is not completely 
 solved and never can be, owing to the 
 variable and intermittent nature of the 
 forces involved. However, much prog- 
 ress has been made in the past few years, 
 thanks to the severe demands made by 
 the automobile trade, and at the present 
 time engines are built in which vibra- 
 tion has been reduced to a point which 
 is not particularly objectionable. Some 
 of the means through which this has 
 been accomplished will be explained in 
 this lesson. 
 
 Engines having only one cylinder 
 may be balanced to some extent by the 
 judicious use of counter weights placed 
 either directly opposite to the crank, 
 or else placed opposite to the crank in 
 the fly wheels. 
 
 FIG. 33. 
 
 2 
 
 -on 
 
 FIG. 34. 
 
ENGINE BALANCE. 
 
 65 
 
 C71ANKS 0* SAME <S/B 
 
 \WO.OF 
 , CYL'iS 
 
 OTtJJET? OF STROKES 
 
 1 
 
 P 
 
 & 
 
 3 
 
 c 
 
 z 
 
 s 
 
 c 
 
 ;p 
 
 & 
 
 The effect of these counter weights is to set up an oppositely 
 acting force which attains its maximum value at the instant the 
 piston and connecting rod come to rest. Thus one force acting in 
 one direction is made to offset another 
 and presumably equal force acting in 
 the opposite direction. The result is a 
 nullification of both forces and conse- 
 quent lack of vibration of the engine 
 frame. To this condition is added the 
 steadying effect of very heavy fly wheels, 
 which serve to absorb energy during the 
 power stroke and deliver it to the crank 
 shaft during the idle strokes of the en- 
 gine. A perfect or, in fact, a near ap- 
 proach to perfect absorption of vibration 
 by this means would require the engine 
 to run at constant speed, since a change 
 in speed changes the intensity of the 
 centrifugal forces set up by the revolv- 
 ing weights in a different ratio from FIG. 35. 
 the way in which the forces due to the reciprocating forces change. 
 Consequently, an engine of this type can be balanced correctly for 
 
 only one speed, and will vibrate more 
 and more as the speed varies from the 
 standard. 
 
 The difficulty inherent in the single 
 cylinder engine has led to the general 
 adoption of engines having two or more 
 cylinders. In multiple cylinder engines, 
 as they are called, the pistons and re- 
 ciprocating parts can be so arranged 
 that they move in opposite directions, 
 and, if care is taken to make these parts 
 of equal weight, they will counterbalance 
 each other at any speed and thus reduce 
 vibration to a very small amount. 
 
 This is the plan adopted in all double 
 opposed engines of the horizontal type, 
 and is found to be quite satisfactory for 
 all low powered engines. The pistons 
 
 FIG. 36. 
 
 are placed horizontally on each side of the crank shaft, with their 
 open ends opposite each other. The cranks are placed 180 degrees 
 
66 
 
 GASOLOGY. 
 
 i Z 3 4- 
 
 RRRFR 
 
 apart, or, in other words, on exactly opposite sides of the crank shaft. 
 Thus both pistons reach the head ends of their respective cylinders 
 at the same instant, but travel in opposite directions to do so. Thus 
 the shock occasioned by bringing one piston to rest is offset by the 
 other. 
 
 The order of the different events of the strokes is tabulated in 
 Fig. 34. In this table P represents the power stroke; E exhaust; S 
 suction and C compression. An outward stroke must be either a 
 power stroke or a suction stroke, and an inward stroke either exhaust 
 or compression. It will be observed that with this arrangement of 
 cylinders a power stroke can be made to occur during each revo- 
 lution, if the valves and cams are set right. The upper set of 
 events opposite 2 in the figure shows the correct arrangement, while 
 
 the lower set of events shows a faulty 
 arrangement, since it brings both power 
 strokes in the same revolution. 
 
 Two-cylinder engines are often placed 
 side by side, as indicated in Figs. 35 and 
 36. Two arrangements of the cranks are 
 possible with this construction. They 
 may be placed opposite, or 180 degrees 
 apart, or on the same side of the shaft, 
 in which case they are said to be 360 
 degrees apart. The order of strokes for 
 both cases is clearly indicated in the 
 figures. In Fig. 35, there is a power 
 stroke once in each revolution. The 
 table shows an idle stroke in each cylin- 
 der between the power strokes, but in 
 Fig. 36 both power strokes occur in a 
 single revolution, while the other revo- 
 lution is idle during both strokes in the 
 two cylinders. 
 
 In the arrangement shown in Fig. 35, the reciprocating forces are 
 not balanced, while in Fig. 36 they are. However, of the two, the 
 former is preferable, since. it gives a steadier motion to the crank 
 shaft and counter weights may be used to offset the unbalanced 
 forces due to the reciprocating parts. 
 
 Of the three arrangements of the two cylinders, the horizontal 
 double opposed possesses greater advantages and is the preferable 
 one to use. 
 
 UJ 
 
 HO. OF CYLS 
 
 onotn of sr/ro*.s 
 
 1 
 
 IP 
 
 E 
 
 xS 
 
 C 
 
 2 
 
 & 
 
 ^ 
 
 C 
 
 ^ 
 
 3 
 
 C 
 
 P, 
 
 & / 
 
 
 
 4- 
 
 3 
 
 C 
 
 y 
 
 Z 
 
 FIG. 37. 
 
ENGINE BALANCE. 67 
 
 In Fig. 37 there is shown a sketch of a four-cylinder vertical 
 engine such as is generally used. The two end cranks point in one 
 direction and the two middle ones in the opposite direction, being 
 thus arranged in pairs 180 degrees apart. The table shows the order 
 of the strokes in each cylinder. An inspection of the figure will 
 show that the order of firing is 1, 3, 4, 2. Nearly all engines of this 
 type are timed to fire in this way. 
 
 A further discussion of the four-cylinder engine will be taken up 
 in the next lesson. 
 
 LESSON XX. 
 
 Some of the difficulties of securing a perfectly balanced engine 
 were pointed out in the last lesson and will be considered at greater 
 length in the present lesson. 
 
 There are two classes of forces that produce vibration; those due 
 to reciprocating masses and those due to rotating masses. The 
 former may be perfectly balanced by similar masses acting in the 
 opposite direction at exactly the same instant and in the same line 
 of action. For example, the forces set up by the piston and other 
 reciprocating parts of one cylinder of. a double opposed engine may 
 be exactly balanced by similar parts of the other engine, provided 
 both cylinders are exactly opposite; that is, if the same center line 
 passes through both cylinders. If this condition does not exist 
 there will be what is called a force couple acting which will tend to 
 rotate the cylinder in a horizontal plane if they are placed horizon- 
 tally. 
 
 The only way to have the cylinders exactly opposite is to make 
 the connecting rods with interlocking ends, both acting on the same 
 crank pin. This, however, is rarely done in the case of gas engines, 
 since the construction of the double opposed engine is such that the 
 distance between cranks is only about one-half the length of the 
 crank pin and the lever arm of the couple is thus quite short. 
 Where vertical two-cylinder engines are used this lever arm is much 
 longer, being about one and one-half times the length of the crank 
 pin, owing to the double cylinder walls and double water jacket be- 
 tween cylinders. 
 
 A four-cylinder engine having the two outer cylinders arranged as 
 a pair and opposed to the two inner ones, is perfectly balanced so 
 far as the reciprocating forces only are concerned. One pair of 
 pistons moves in one direction and the other pair moves in the op- 
 posite direction. If care is taken to make all the pistons and con- 
 necting rods of equal weight, very good results may be obtained. In 
 
68 GASOLOGY. 
 
 the best automobile factories great care is taken in this particular, 
 it being the practice to reduce all reciprocating parts of the various 
 cylinders to the same weight within a fraction of an ounce. This 
 practice results in the minimum of vibration and is necessary for 
 high speed automobile engines and boat engines. 
 
 There are, however, some unbalanced forces even if the weights 
 of reciprocating parts are exactly the same. These arise from the 
 rotation of the crank and the oscillation of the free end of the con- 
 necting rod. These forces cause some vibration, but they can not be 
 perfectly balanced unless use is made of other rotating parts of 
 equal weight and similarly placed, revolving in an opposite direc- 
 tion. This remedy would lead to a complication of parts and the 
 benefits to be derived being small, at best, it is not generally thought 
 wise to make use of it. 
 
 In four-cylinder engines, it was shown in the last lesson, the 
 order of firing of the cylinders might be 1, 2, 4, 3; or 1, 3, 4, 2. The 
 first engines built were all arranged to fire in the order first given, but 
 a little consideration will show that the latter order will give better 
 results, since the force .of the explosion is distributed over the en- 
 gine to better advantage. This is the order that is being generally 
 adopted at the present time. 
 
 Three-cylinder engines are arranged with the cranks set 120 de- 
 grees apart instead of 180 degrees, as is the case with double op- 
 -T. 1 posed or four-cylin- 
 
 C- Z*M/7/l -* i mi 
 
 der engines. Ihis 
 arrangement results 
 in excellent balance 
 of the reciprocating 
 parts and in excel- 
 lent turning effort at 
 *t the crank shaft. 
 
 The stresses due 
 
 Crtf^-f^l^v^ ^4Sf to the explosion of 
 
 the charge are very 
 evenly distributed 
 
 5^ since there are two 
 
 -p IG gg power strokes dur- 
 
 ing two revolutions 
 
 of the crank. While the crank is making two complete turns, or 
 720 degrees of rotation, power is applied through three half revo- 
 lutions, or a total of 540 degrees. The longest period, with this ar- 
 rangement, between the end of one power stroke and the begin- 
 
ENGINE BALANCE. 69 
 
 ning of the next, is while the crank is passing through an angle of 
 60 degrees. This fact is clearly brought out in the accompanying 
 drawing, Fig. 38. Six-cylinder engines have crank shafts of sim- 
 ilar construction to three-cylinder engines, with the cranks arranged 
 in pairs. This arrangement gives six power strokes in two revolutions 
 and provides the best torque and best balance obtainable without us- 
 ing an excessive number of cylinders. In fact, very little additional 
 benefit would be obtained by using as high as twelve cylinders; 
 while the complication of parts and difficulty in keeping in repair 
 would be enormously increased. 
 
 It would, therefore, appear from the foregoing discussion that 
 for small runabouts and light powered machines, especially those of 
 the high-wheeled type, the double opposed motor has many ad- 
 vantages. It is cheap, easy to take care of, is not complicated, and 
 has fairly good torque and good balance. The four-cylinder verti- 
 cal engine is better than the double-opposed, but is more complicated, 
 costs more, and is particularly adapted to high grade cars, especially 
 touring cars and cars of large power. The six-cylinder motor rep- 
 resents about the highest grade of present day gas engine construc- 
 tion, but it is expensive, complicated and difficult for the ordinary, 
 unskilled individual to manage. It is adapted, therefore, to the 
 expensive, high grade cars, managed by skilled attendants. It prob- 
 ably will never be used to any extent, if at all, for farm engine pur- 
 poses. The one, two and four-cylinder engines are used extensively 
 for farm work at the present time; the one-cylinder motor for all 
 light work, such as sawing, grinding, pumping, etc. ; the two-cylinder 
 and four-cylinder motors for automobiles and farm tractors. There 
 are also some quite successful farm tractors of the one-cylinder 
 type. 
 
 All single cylinder engines depend upon a heavy fly wheel to 
 preserve steady motion and to a certain extent prevent vibration. 
 In general, it may be said that the heavier the fly wheel the less the 
 speed of the engine will vary. Consequently, gas engines used to 
 run electric dynamos must be fitted with very heavy fly wheels 
 or the speed of the engine will vary enough to make the lights 
 flicker badly. An engine designed for pumping and light farm work 
 will in general vary too much in speed to be used to run a dynamo. 
 If, however, it be fitted with an extra heavy fly wheel it will usually 
 prove quite satisfactory. 
 
CHAPTER VIII 
 CARBURETORS 
 
 LESSON XXL 
 
 Neither pure liquid gasoline nor pure gasoline vapor will burn 
 in a closed vessel. An engine charged with gasoline vapor only would 
 not run. In order to make gasoline vapor inflammable it must be 
 mixed with the right amount of air in order to obtain sufficient 
 oxygen for combustion. 
 
 The mixing of the air and gasoline vapor is called carburet ion. 
 That is, the air is carburetted or charged with the carbonaceous 
 fuel. The apparatus or device in which this act is accomplished 
 is called a carburetor or sometimes a mixer. The former name is 
 now used almost exclusively and is the name that will be adhered to 
 in these lessons. 
 
 In searching the literature of gas engines very little data was 
 found pertaining to mixtures of air and gasoline and apparently 
 there is little exact information available. It is known that a proper 
 mixture will explode readily and do its work with the accompaniment 
 of very little smoke at the exhaust or the clogging of the valves with 
 a deposit of tar. If the mixture is not right both of these things may 
 occur and trouble will be experienced in running the engine. 
 
 Experience indicates that only very slight variations are per- 
 missible in the mixture in order even to make the engine work at all. 
 If the maximum fuel efficiency is desired the variations in the mix- 
 ture must be very slight indeed. Stoddard is authority for the state- 
 ment that one volume of gasoline to 8,400 volumes of air at at- 
 mospheric pressure, is a good mixture; and that one volume of gas- 
 oline to 10,000 volumes of air ceases to be explosive. If less than 
 8,400 volumes of air are used per volume of gasoline, some of the 
 gasoline will emerge unburned at the exhaust. Consequently, it 
 would appear that the mixture even under ordinary working condi- 
 tions must vary only slightly in composition in order to obtain satis- 
 factory results. The quality of the fuel may also have some effect 
 upon the character of the mixture. 
 
 Gasoline as it appears on the market varies somewhat in composi- 
 tion. The gasoline sold generally at the present time will show a 
 test for specific gravity of from sixty-eight to seventy degrees Baume, 
 although some is found testing even lower than this. The boiling 
 
CARBURETORS. 7 1 
 
 point of gasoline is also a variable quantity, ranging from one 
 hundred five degrees Fahrenheit to one hundred thirty-five degrees. 
 The lighter and more volatile oils show a higher specific gravity and 
 lower boiling point To illustrate this matter of the gravity test I 
 might mention the fact that kerosene tests about forty-eight degrees, 
 Baume, while the gasoline best adapted to gas machine work tests 
 eighty-eight degrees. These figures represent the relative weights 
 of a unit volume of the liquid in comparison with pure water, all 
 at sixty degrees temperature. 
 
 In most, if not all, of the states the quality of both the gasoline 
 and kerosene is regulated by state law and all oils offered in the mar- 
 ket are inspected by the state oil inspector or his deputies. The high 
 gravity test gasolines are more volatile than the low test, that is, 
 they will vaporize more readily and at a lower temperature. Con- 
 sequently, for a high speed engine like an automobile engine the 
 high test oils give somewhat better results. They are, however, ex- 
 pensive, owing to the fact that only a comparatively small quantity 
 can be obtained from a given amount of crude petroleum. Pe- 
 troleum is a very complex substance chemically consisting of a large 
 number of oils of different densities. These are separated from the 
 crude petroleum by the process of distillation. This process con- 
 sists of heating the crude oil to a certain temperature for a given 
 length of time until all that will be vaporized at that temperature has 
 been driven off. The resulting vapors are condensed in suitable con- 
 densors, purified, and placed on the market as gasoline, naphtha, 
 kerosene, lubricating oils, etc. After each group or class of oils 
 has been separated, the temperature is raised and the next class is 
 vaporized. Each one of these classes is also a complex structure 
 since the range of temperature used in the separation of each class 
 causes several oils of different densities to be vaporized. This be- 
 comes evident at once to any one who has had much experience in 
 running gasoline engines. Stale gasoline is simply gasoline that has 
 lost its more volatile constituents by standing for a long time ex- 
 posed to the air. It resembles kerosene in its characteristics 
 and does not vaporize and carburete readily and consequently 
 it is difficult to get an engine started unless new gasoline is placed 
 in the tank, that is, if the engine has stood idle for a considerable 
 period. 
 
 The vaporizing of gasoline, kerosene or alcohol is accomplished 
 with heat, just as steam is formed in the boiling of water. Since 
 the boiling point of the three first named liquids is much lower than 
 that of water, they, of course, do not require as much heat as an 
 
72 GASOLOGY. 
 
 equal quantity of water. Nevertheless, a considerable quantity of 
 heat is required and nearly all high speed engines are equipped with 
 carburetors that are provided with an auxiliary air intake which 
 draws hot air from around the cylinders of the engine. In cold 
 weather this is essential because there is not heat enough in the 
 air to vaporize the fuel. 
 
 A considerable amount of trouble is often experienced in cold 
 weather by the freezing of the carburetor. An engine will run for 
 a time and then stop. In a few minutes it can be started again and 
 will run for a considerable time before the carburetor becomes clog- 
 ged with ice a second time. The freezing of the carburetor is caused 
 by the moisture from the air congealing on its cold surfaces. Air 
 always contains a certain amount of moisture and even if the out- 
 side air is nowhere near the freezing point, freezing of the car- 
 buretor may occur with a high speed engine. The rapid absorption 
 of heat by the gasoline vapor on its way through the carburetor 
 may lower its temperature away below the freezing point. We have 
 here, on a small scale, the same principle exemplified as in the am- 
 monia refrigerating machine. In this the liquid ammonia is vap- 
 orized with the rapid absorption of heat from the surrounding sur- 
 faces and their consequent lowering of temperature. 
 
 
 
 LESSON XXII. 
 
 CARBURETORS. 
 
 The proper mixing of the fuel takes place in the carburetor, 
 This is, as indicated in the last lesson, a rather delicate 
 process. The variation in the quality of the mixture must be 
 very slight if anything like good results are to be obtained in the 
 engine. A correct proportion of air and gasoline produces a gas 
 whose combustion is rapid ; an excess of air makes a slow burning 
 mixture, while an excess of gasoline causes not only slow burning 
 but incomplete burning of the charge. All the difficulties of back 
 firing, popping in the muffler, smoky exhaust, etc., are mostly due 
 to faulty carburetion. Back firing is generally caused by a lean 
 mixture, which is so slow burning that it is not completely consumed 
 at the end of the power stroke, but keeps on burning in the com- 
 pression space until the inlet valve opens on the suction stroke. 
 Then the flame flashes back through the carburetor and causes the 
 phenomenon known as back firing. This may become exceedingly 
 dangerous if there is a leak of gasoline around the tank or at any 
 of the points in the gasoline piping. Many automobiles have taken 
 fire and not a few have been completely burned through just this 
 
CARBURETORS. 
 
 Cause. A slow burning charge, due to an over-rich mixture, some- 
 times acts in a similar way, but it always causes a smoky exhaust 
 with sooting of the spark plugs and the inside of the cylinder; all 
 of which causes much loss of time and annoyance to the owner of 
 the engine. 
 
 If the same kind of fuel is to be used always and the speed of the 
 engine can be kept constant it is not difficult to construct a carbu- 
 retor which will give a practically constant mixture, or at least, one 
 whose variations are si slight 1 
 as to be negligible; but when, 
 engine speed, fuel, temperature 
 of the air, and everything is 
 variable, it makes the problem 
 of designing a carburetor which 
 will successfully meet all these 
 conditions exceedingly difficult. 
 There are some very good car- 
 buretors 011 the market, and 
 some that give excellent results, 
 but there is still much to be 
 desired, much that has not yet 
 been accomplished -perhaps is 
 impossible of accomplishment 
 in the design of carburetors. 
 Any of the so-called automatic 
 carburetors will work almost 
 perfectly for any given speed 
 when adjusted to that speed. 
 They will, also, on account of 
 their automatic principle, give 
 fair results at quite widely 
 varying speeds, but there is no 
 
 carburetor made that will, without having to be adjusted, give 
 equally good results at all speeds. 
 
 In order to make some of the above statements clear we will pro- 
 ceed in this and succeeding lessons to describe various types and 
 styles of carburetors. 
 
 One of the simplest carburetors in mechanical construction is 
 the spray carburetor, illustrated in Figs. 39 and 40. It consists 
 of a conical nozzle A whose opening may be regulated by the needle 
 valve B. The level of gasoline in the reservoir C is maintained 
 about a half inch below the level of the needle valve by means of 
 a pump which pumps the gasoline from the main supply tank. 
 
74 
 
 GASOLOGY. 
 
 The gasoline nozzle projects into the tipper end of the air intake 
 pipe a short distance, but enough so that all the air passing to the 
 cylinder will be charged with the vapor of gasoline. 
 
 When the engine piston moves outward on its suction stroke, it 
 causes a partial vacuum in the cylinder. Atmospheric pressure causes 
 air to rush up through the air pipe D and overcome the tension of 
 
 the inlet valve spring and en- 
 ter the cylinder. All the air 
 which enters the cylinder 
 must pass through the pipe 
 D and since it is small com- 
 pared with the bore of the 
 cylinder, the velocity of the 
 air must be quite high. In- 
 deed, it is this very air velo- 
 city that it depended upon 
 to lift the gasoline from res- 
 ervoir C to the nozzle A, 
 where it shoots out into the 
 moving column of air in a 
 fine mist or spray. The higher 
 the velocity of the current of 
 air past the nozzle the greater 
 will be the pumping effect 
 and the larger will be the 
 amount of gasoline pumped. 
 This, then, is the reason why, 
 with a carburetor of this kind, 
 a damper, or air throttle, is 
 placed in the air . pipe D. 
 This damper must always be closed when the engine is started by 
 hand in order to reduce the size of the air pipe enough to make 
 the velocity of the air sufficient to pump gasoline through the supply 
 nozzle. The reason for this increase in velocity, due to throttling, 
 will become at once apparent when one considers that the cylinder 
 must be completely filled with air at practically atmospheric pressure 
 on each suction stroke. If the piston moves slowly and the air pipe 
 is large the air will move slowly through the pipe, but if, on the 
 contrary, the size of the air pipe is greatly reduced by an air throttle 
 or damper, the velocity of air must be greatly increased in order to 
 fill the cylinder. If the air throttle were left closed after the engine 
 came up to speed, the increased pumping effect would be so great 
 
 FIG. 40. 
 
CARBURETORS. 75 
 
 that the charge would be too rich, even though the cylinder were filled 
 at practically atmospheric pressure. 
 
 Again, let us suppose that the needle valve of a carburetor similar 
 to the one illustrated were adjusted for a speed of say 400 revolu- 
 tions per minute and the engine was running satisfactorily at that 
 speed. If we should increase the speed of the engine to 800 or 900 
 revolutions we would find the mixture too rich because of the 
 greater pumping effect and it would be necessary to partly close the 
 fuel valve in order to get the same mixture as before. 
 
 In stationary engine practice there is little or no trouble with the 
 carburetor on account of variations in engine speed because the gov- 
 ernor may be depended upon to keep the speed of the engine constant, 
 but in the case of automobiles, motor boat engines, and engines of 
 a similar class, it is necessary to fit them with a carburetor which 
 will automatically take care of the variations in speed. 
 
 LESSON XXIII. 
 
 In the last lesson attention was called to the pumping 
 effect at the nozzle of the carburetor, caused by the high velocity 
 of the air rushing into the cylinder. This, however, is only one of 
 the forces impelling the gasoline. The other is atmospheric pres- 
 sure. When the piston moves outward on its suction stroke a partial 
 vacuum is created behind the piston, the admission valve opens 
 under the influence of the weight of the atmosphere, and air rushes 
 into the cylinder. The pressure in the cylinder during the charg- 
 ing stroke is at all times less than that of the atmosphere and con- 
 sequently there is some rarification, or reduction in pressure of 
 the air below that of the atmosphere, around the end of the gaso- 
 line nozzle, while full atmospheric pressure exists on the top of 
 the fuel in the reservoir. This difference in the pressure head, due 
 to the rarification or reduction of pressure in the cylinder, plus the 
 velocity head, or the reduction of pressure at the nozzle, caused by 
 the velocity of the air, are the two forces which serve to project the 
 fuel out of the nozzle. The intensity of these two forces depends 
 upon a number of conditions, as will presently be shown. 
 
 These forces at best are. small and a very slight change in condi- 
 tions is apt to affect the results materially. For example, a slight 
 change in the height of the fuel in the reservoir will reduce the 
 pressure head, while any change in the velocity of the air current 
 passing through the carburetor, due to change in the piston speed, 
 will affect the velocity head and consequently the amount of fuel 
 used. These are perhaps the two principal factors governing the 
 
76 
 
 GASOLOGY. 
 
 operation of spray carburetors of whatever class. Other factors, 
 such as the density of air, the amount of moisture it contains and its 
 temperature, all 
 have an influence 
 on carburetor per- 
 formance and serve 
 as evidence of the 
 truth of the state- 
 ment in the last les- 
 son, that it is very 
 difficult, if not im- 
 possible, to make a 
 carburetor self ad- 
 justing to all con- 
 ditions of load, en- 1 
 gine speed and' 
 weather. 
 
 In the carburetor 
 shown in the last 
 lesson the height of 
 fuel is kept practic- 
 ally constant by be- 
 ing pumped into a 
 reservoir which is 
 fitted with an over- 
 flow pipe into which 
 it discharges on 
 reaching a certain 
 level. This matter 
 of a uniform level 
 from which the gas- -p IQ ^ 
 
 oline flows, is, as 
 
 was said before, very important, because if the level is kept constant 
 the pressure head will be constant. 
 
 In looking into the history of carburetors we find three different 
 types; the surface carburetor, bubbling or filtering carburetor, and 
 the spray carburetor or vaporizer, a simple form of which we have 
 just discussed. The surface carburetor was arranged so that the air 
 on its way to the engine passed across the surface of the fuel and 
 became saturated with the fuel vapor. The objection to this form 
 of carburetor lay in the fact that only the lighter portions of the 
 fuel became volatilized, the heavier portion never being used at all. 
 
CARBURETORS. 
 
 77 
 
 In the bubbling type, the air was caused to bubble up through the 
 fuel. Here the same objection was encountered as in the surface 
 carburetor; the Volatile portion only of the fuel was used, while 
 the heavier portion remained behind. The spray carburetor or atom- 
 izer has the advantage of utilizing all of the fuel by projecting the 
 whole mass into the air where it is either entirely vaporized or 
 broken up into a 
 fine mist and car- 
 ried directly to the 
 cylinder. Practically 
 all gasoJine carbu- 
 retors at the present 
 time belong to the 
 last named class. 
 There are, however, 
 many modifications 
 in design with a 
 view of adapting 
 them to different 
 conditions or to 
 making them auto- 
 matic, which we will 
 proceed to discuss 
 in this and subse- 
 quent lessons. 
 
 Figure 41 is an 
 example of a very 
 simple form of mix- 
 ing valve or carbu- 
 retor. It consists of 
 a straight brass cast- 
 ing provided with a 
 valve which is held -pio 42 
 
 in position by a 
 
 light helical spring whose tension is such that it readily opens by 
 suction when the piston starts on its charging stroke. Gasoline is 
 fed in through the needle valve, either under pressure or by gravity. 
 The amount delivered to the engine is regulated in the usual way 
 with the milled head needle valve. If this is opened a certain 
 amount, gasoline will flow in as far as the valve seat, where it is 
 stopped by the main valve. Then, when air rushes through the 
 carburetor on its way to the engine, it opens the main valve and 
 picks up a certain amount of gasoline. This carburetor valve is 
 particularly well adapted to a gravity feed, 
 
 IV\A I N AIR 
 PORTS 
 
78 GASOLOGY. 
 
 Another style of mixing valve of somewhat similar nature is shown 
 in Fig. 42 in which a ball valve is used instead of a cone seated 
 valve.' Gasoline is fed in below the ball. When air passes up 
 through the main air ports the ball revolves, and a fine spray of 
 gasoline comes up around it. The lift of the ball can be regulated 
 by means of a cam attached to the cross shaft just above it. A milled 
 head thumb nut, shown on the left, makes the proper adjustment. 
 Auxiliary air ports are provided above the ball valve to obtain the 
 proper explosive mixture by admitting an additional amount of air 
 into the charge, while a throttle valve is provided to control the 
 quantity. 
 
 LESSON XXIV. 
 
 FLOAT FEED CARBURETORS. 
 
 All of the carburetors used on automobiles, most of those 
 used on marine engines, and many that are used on station- 
 ary engines are of the float feed automatic type. They are 
 spray carburetors or vaporizers, in so far as projecting the mass of 
 gasoline directly into the ingoing current of air is concerned, and 
 they obey all the laws for carburetors of this class laid down in the 
 preceding lessons, but they differ from the simple carburetors which 
 were described, in these particulars. They maintain a fairly uniform 
 pressure head of gasoline by not permitting it to rise above a certain 
 height in the reservoir, and they undertake to regulate the quality 
 of the mixture at all speeds of the engine and under a wide range 
 of varying conditions by maintaining the same, or practically the 
 same degree of vacuum around the point of the spray nozzle. The 
 means by which these two things are accomplished can best be ex- 
 plained in connection with Fig. 43, which represents the main 
 essentials of a float feed carburetor. 
 
 Gasoline is delivered to the float chamber by gravity from a tank 
 placed a little above the cylinder of the engine. The float consists 
 of a thin copper vessel closed on all sides with all joints carefully 
 soldered to prevent any liquid from reaching its interior. 
 
 Sometimes instead of using a metal float, a cork float is used. If 
 cork is used it must be well shellaced to prevent it from becoming 
 saturated with gasoline and losing its buoyancy. When so treated, 
 however, it is very serviceable and will remain in good condition 
 a long time. The metal float is a very good float as long as it re- 
 mains tight. It may be good for years and it may develop a leak 
 in a few weeks. A very small leak is much more troublesome, being 
 
CARBURETORS. 
 
 79 
 
 harder to find than a large one. In every case the function of the 
 float is to operate a valve which admits gasoline into the float cham- 
 ber. This may be accomplished in one of several ways. In Fig. 43, 
 the valve stem passes easily through the float. A grooved collar is 
 secured near its upper end which affords a means of connection for a 
 couple of weighted levers pivoted at P. When the gasoline falls in 
 
 GASOLINE, 
 
 FIG. 43. Elements of a Float Feed Carburetor. 
 
 the float chamber the float also falls, allowing the weights on the ends 
 of the levers to drop and lift the valve V, thus admitting more gaso- 
 line. When the float rises it pushes up on the weights and forces 
 the valve to its seat. 
 
 Two other methods of arranging the float and valve appear in Figs. 
 44 and 45. The arrangement of the float and its valve is so obvious 
 in Fig. 44 that no detailed explanation seems necessary. 
 
 In the case of Fig. 45, we have a cork float arranged in the form 
 of a horse shoe, surrounding the central air tube or mixing chamber. 
 
 In many carburetors there is some device to provide for raising 
 or lowering the level of the liquid in the float chamber by raising or 
 lowering the float. 
 
80 
 
 GASOLOGY. 
 
 In Fig. 43 the grooved collar may be shifted, in Fig. 44 the float 
 itself can be set at the required height by shifting the nuts on the 
 threaded valve stem, but in Fig. 45 there is no way provided to 
 change the position of the float. 
 
 When the piston moves from the head end of the cylinder, the 
 pressure of the gas behind it drops somewhat below atmospheric pres- 
 sure. When it moves far enough so that the difference in pressure 
 
 between the atmosphere and the 
 gas inside of the cylinder is great- 
 er than the tension of the inlet 
 valve spring, then the latter will 
 open and the charge will begin to 
 enter the cylinder. The pressure 
 in the inlet pipe, right close to 
 the cylinder, is practically the 
 same as in the cylinder and gradu- 
 ally increases to practically atmos- 
 pheric pressure at the entrance. 
 
 If the piston could be made to 
 move to the crank end of the cyl- 
 inder instantly, the reduction in 
 gas pressure would occur instantly, 
 and the amount of reduction in 
 the inlet pipe or carburetor would 
 SLbe much greater than it ever is in 
 practice. This would cause a very 
 
 FIG. 44. ValvIIttached to Float. rapi ? sl ' f air P."?* * e g , as . olin 
 
 nozzle and this with the help ot 
 
 atmospheric pressure on top of the gasoline in the reservoir would 
 cause a more than usual flow of gasoline for the given quantity of 
 air. In other words the mixture would be very rich. This, of course, 
 is the limiting condition in that direction, but, it is easy to see that 
 as we approach this condition in actual practice, by means of high 
 speed we must find some way to bring the mixture back to its proper 
 working composition. This is accomplished by means of what is 
 called an automatic air valve as shown in Fig. 43, which is held to 
 its seat by means of a light spring. This spring is given a certain 
 amount of tension and holds the valve shut until the pressure 
 above the spray nozzle falls to a point where the tension of the 
 spring is not sufficient to hold the valve shut. When this point 
 is reached, air rushes through the auxiliary air port and to a certain 
 extent at least corrects the quality of the mixture, first by dilut- 
 ing it with fresh air, and second by preventing too great a reduc- 
 tion of pressure in the mixing chamber. 
 
CARBURETORS. 
 
 81 
 
 That certain defects exist in this method of controlling the quality, 
 is freely admitted by every one who is at all acquainted with the 
 working of carburetors. There is no exactitude in the process of 
 mixing the air and 
 the gasoline. The 
 mixture is first 
 made over-rich and 
 then it is diluted a 
 certain amount. At 
 slow speeds the aux- 
 iliary valve does not 
 open, consequently, 
 from that point up 
 to the point where 
 it does work, the 
 mixture is incorrect 
 not very much 
 wrong, of course 
 but yet not quite 
 right. Then at still 
 higher speeds the 
 mixture is made so 
 very rich that 
 enough air can not 
 pass through the 
 auxiliary air 'port. 
 To be sure, the , 
 carburetor can be FlG ' 45 ' One style f Automatlc Carburetor, 
 adjusted for this higher speed all right enough, but the point I 
 .wish to make is that it is only automatic within a certain range, 
 and through only a small portion of that is it able to qualify with 
 any great degree of exactness. 
 
 The density of the air, its humidity and its temperature, all of 
 these things have an important bearing on the operation of the car- 
 buretor and all taken together, make it difficult to construct one 
 that is able to adjust itself to all conditions, automatically, and pro- 
 duce a uniform mixture. 
 
 LESSON XXV. 
 
 If you will refer to lesson XXIII, you will find in Fig. 43 that the 
 gasoline reservoir is placed at one side of the spray chamber, while in 
 Fig. 44 surrounds that chamber. 
 
82 
 
 GASOLOGY. 
 
 In some of the preceding lessons it was pointed out that it was 
 very essential to maintain a constant level of gasoline in the float 
 chamber, and especially that this level should remain constant with 
 reference to the spray nozzle. In carburetors of the type shown in 
 Fig. 43, difficulty is experienced in this respect whenever one wheel 
 of the car runs in the ditch along the side of the road, or when the 
 car moves along the side of a hill, because there is a distance of two 
 
 inches or more between the float 
 chamber and the spray nozzle. 
 The carburetor shown in Fig. 
 45 is the result of an effort to 
 overcome this difficulty by mak- 
 ing the float surround the spray 
 nozzle. In this construction the 
 latter occupies the center of 
 the reservoir, a position where 
 the level of the liquid remains 
 most nearly constant, and where 
 the rocking of a boat or the tilt- 
 ing of an automobile will affect 
 the level of gasoline at the 
 nozzle very little. 
 
 The automatic principle men- 
 tioned in the last lesson is car- 
 ried out in a different manner 
 FIG. 46. i n different carburetors; for 
 
 example, in Fig. 45, the air at 
 
 slow engine speed has low velocity and cannot overcome the tension 
 of the spring holding the auxiliary valve to its seat. 
 
 Under these conditions enough air can enter through the open 
 space below the auxiliary valve. When the speed of the engine in- 
 creases and the vacuum in the spray chamber becomes greater, the 
 rush of air through the air intake opens the auxiliary valve and al- 
 lows the entrance of a larger volume of air. The effect of the high 
 vacuum in the spray chamber, together with the rapid inrush of air 
 is sufficient to produce a mixture that would be too rich to be ex- 
 plosive, hence the necessity of reducing the richness by the admixture 
 of fresh air, either in the manner above specified or in some other 
 manner. 
 
 There has been placed on the market quite recently, a carburetor in 
 which the air passes through different sized openings normally closed 
 by ball valves. The larger balls, exposing the greater area in propor- 
 
CARBURETORS. 
 
 83 
 
 air valve 
 
 tion to their mass, will lift first, and, as the speed of the engine in- 
 creases, thus causing a higher vacuum, the other smaller balls open 
 and more air is admitted. Here, as in Eig. 45, the air all passes 
 through the spray chamber. A sectional view, showing principles of 
 the above described carburetor, appears in Fig. 46. 
 
 Fig. 47 represents another style of automatic carburetor, in which 
 the auxiliary air supply is admitted at some distance beyond the 
 spray nozzle. In order to facilitate and insure proper mixing, the 
 auxiliary air is admitted at right angles to the main current. This 
 sets up eddy currents, and the whole mass is supposed to become 
 thoroughly mixed. 
 
 There are two other 
 features in this car- 
 buretor that deserve 
 more than passing 
 notice. The first is 
 the shape of the 
 chamber around the 
 spray nozzle. The 
 air which enters 
 around the cup be- ^ 
 low passes through ^ 
 a chamber shaped 
 in such a way that & 
 the greatest velocity ' 
 of the air will be 
 just beyond the end 
 of the gasoline noz- 
 zle. This construc- 
 tion tends also to 
 cause all of the air 
 
 to be saturated with the spray of gasoline, which spreads out in can- 
 opy form from the top of the nozzle. 
 
 The other feature to which we referred is the annular hot water 
 chamber surrounding the spray chamber. This is arranged to be 
 connected to the cylinder jacket and keeps the carburetor hot in 
 cold weather. This aids in vaporizing the fuel and makes the use 
 of the ordinary sixty-eight degrees gasoline effective on high speed 
 cars in moderately cold weather. As stated in a previous lesson, the 
 vaporization of any liquid necessitates using a considerable quantity 
 of heat which must be abstracted either from the incoming air or 
 else from some other source. When the out-of-doors temperature is 
 
 Air intake. 
 
 FIG. 47. 
 
84 
 
 GASOLOGY. 
 
 well below freezing there is very little heat in the air with which 
 to effect vaporization, and some other source is imperative, especially 
 for high speed engines. 
 
 In the case of most carburetors the piping is so arranged that the 
 air can be taken from around the hot cylinders in cold weather, or by 
 means of a by-pass valve the hot air supply can be cut off and cold air 
 substituted, thus making the carburetor suitable for either summer 
 or winter use. 
 
 FIG. 48. 
 
 It is true that a large weight of mixture will be taken into the 
 cylinder when the air is quite cool, but even with air that is heated 
 to above one hundred degrees, there is no question but that the vapor- 
 ization of the gasoline cools it down close to the freezing point. 
 
 When such low temperatures are encountered, there doubtless is 
 considerable gasoline taken into the cylinder in the shape of minute 
 globules. These must be vaporized inside of the cylinder and there is 
 no certainty that there is sufficient air to effect their complete com- 
 bustion. It is much better, therefore, where a carburetor is used at 
 all, to have the vaporization completed therein and to supply the 
 
CARBURETORS. 85 
 
 engine cylinder with a dry gas. A carburetor meeting these speci- 
 fications will prove most economical in the use of gasoline. 
 
 In one of the earlier lessons of these series we pointed out that 
 practically all of the carburetors in use at the present time are 
 spray carburetors, and that the earlier forms of surface and bubbling 
 carburetors had been displaced and the reason therefor pointed out. 
 There are, however, a few carburetors now on the market, which have 
 come into some prominence quite recently, in which advantage is 
 taken of the principles of the surface carburetor. While these prin- 
 ciples are made use of, they are modified in such a way as to obviate 
 the inherent difficulties of the older type of machine. 
 
 The carburetor illustrated in Fig. 48 is an example of one of these 
 carburetors. At slow engine speeds it is a surface carburetor. Air 
 enters through the primary air ports at A in the right hand figure, 
 and becomes enriched by passing over the puddle of gasoline at B. 
 When the throttle is opened and the engine comes up to speed, the 
 auxiliary air valve is opened, air rushes through the auxiliary air 
 intake and causes a pumping effect at the nozzle which lifts the level 
 of gasoline in the spray nozzle, causing numerous fine jets of the 
 liquid to be projected into the rapidly moving column of air. 
 The higher the engine speed, the higher the gasoline rises. This 
 puts more jets in operation, with the result that a larger quantity of 
 gasoline is used, but the proportion is supposed to be adjusted cor- 
 rectly to the quantity 'of air flowing through the intake pipe. A 
 float maintains the gasoline at any desired level, while a milled head 
 screw in the center adjusts the gasoline for high engine speeds, 
 while the automatic air valve takes care of slower speeds. 
 
 There is another carburetor on the market in which the same prin- 
 ciple is applied in another way. This is a carburetor used quite ex- 
 tensively for marine engines where it is said to give good service. A 
 float valve maintains a constant level of gasoline, but instead of using 
 a nozzle to supply gasoline to the air, a very narrow annular opening 
 in the bottom of the hole, said to be only one five thousandths of an 
 inch wide, is made use of. When the engine is standing idle, gasoline 
 accumulates in a puddle in the bottom of the bowl. When the engine 
 starts, the air passing through the intake pipe with considerable ve- 
 locity impinges upon the gasoline with considerable force, as it must 
 do in order to change its direction completely and pass through the 
 supply pipe to the engine. 
 
 This operation produces a rich mixture which is necessary for 
 starting or running at slow speeds. When the engine comes up to 
 
86 GASOLOGY. 
 
 speed, the puddle is all evaporated and a fine jet or curtain of gaso- 
 line is projected into the air. 
 
 Economizers. In connection with any discussion of carburetors 
 the story is not all told until economizers are considered. These are 
 devices whose office it is to prevent excessive fluctuations in the 
 pumping effect at the spray nozzle under wide variations of speed. 
 This is accomplished by partially equalizing the pressures at the 
 three points; just above the spray nozzle, between the throttle and 
 the engine, and the space above the fuel in the gasoline reservoir. 
 The economizer is screwed into the cap of the gasoline reservoir and 
 two pipes are led out, one to a point below the throttle and the 
 other to a point above. Any sudden movement of the throttle, there- 
 fore, will not affect to any great extent the quantity of gasoline de- 
 livered at the spray nozzle, because a partial vacuum exists above 
 the gasoline,' which prevents a flood of gasoline being delivered. 
 
CHAPTER IX 
 HORSE POWER FORMULAS 
 
 LESSON XXVI. 
 
 Horse power and work and what an engine can pull are three things 
 that are hard to explain in simple language which non-technical peo- 
 ple can understand, but we are going to try it. Every mail brings 
 us requests for information about how to estimate the horse power of 
 an engine, and in every case all we can do is to make the estimate 
 without going into explanations. That is why we are taking this 
 opportunity to present a lesson on the subject. We can go into the 
 subject much more fully and show some of the reasons why we make 
 certain computations. 
 
 Almost everyone knows that a horse power is equivalent to doing 
 thirty-three thousand foot pounds of work in one minute, but there 
 are many people who apparently fail to take account of the factor 
 time. Furthermore, everyone may not know the meaning of the 
 term foot pounds. Consequently, we will start our discussion with 
 the statement that a foot pound is equal to overcoming a resistance 
 of one pound through a distance of one foot. Work is merely the 
 overcoming of resistance through distance, therefore the foot pound 
 is the measure of the amount of work done, since it takes into ac- 
 count the amount of resistance as well as the distance. A horse 
 power not only takes into account the work done in foot pounds, but 
 the time it takes in which to accomplish the work. A horse power, 
 therefore, is a measure of the rate at which work is done. In fact, 
 whenever we talk about power in any form, we are taking into ac- 
 count the factor time or the rate at which work can be done. That, 
 then, is the significance of the term horse power, a measure of the 
 rate of doing work. The man or the machine that can do work 
 the fastest has the most power. The amount of work ultimately ac- 
 complished is no measure of the power applied unless the factor 
 time is taken into account. A machine that can do twice as much 
 work in the same time must have twice as much power. 
 
 Let us now consider more in detail the meaning of the term work. 
 According to the definition just given, it consists of two factors, 
 force and distance. Force is expressed in pounds, distance in feet, 
 and work in foot pounds. We could, if we wanted, express force in 
 
88 GASOLOGY. 
 
 tons and distance in miles and the work would be expressed in ton 
 miles, but for our purpose in the discussion of horse power we will 
 confine ourselves to pounds and feet. In order to find out how much 
 work is accomplished in any given operation all that is necessary to 
 do is to multiply force by the distance through which this force 
 is exerted; for example, suppose it takes a force of two hundred 
 pounds to move a wagon on a level road, and that the distance moved 
 is twenty-four feet; how much work will be done? The result is 
 obtained by multiplying the two factors together; thus: 200x24= 
 4,800 foot pounds of work. , Again, suppose a man weighing one 
 hundred and sixty pounds climbs a ladder twelve feet high; how 
 much work does he do? Here again we multiply the force by the 
 distance through which it acts and find that the man accomplishes 
 1,920 foot pounds of work. These examples should suffice to explain 
 the meaning of the term work. 
 
 Now, let us turn our attention to power for a moment and try to 
 obtain a clear conception of what it signifies by taking some con- 
 crete examples. Take for example the case of the man going up the 
 ladder. If he went up in one minute he would, as before, do 1,920 
 foot pounds of work, no more and no less. If he went up in one-half 
 minute he would still do the same amount of work, but it would 
 require twice as much power in the second case as in the first because 
 the time is only half as much. Power, therefore, depends upon 
 speed. This can be further illustrated in this way; suppose a man 
 has a ton of wheat put up in one hundred pound sacks which he must 
 place upon a table three feet high. The amount of work to be done 
 is six thousand foot pounds. If he lifts all of them up in one min- 
 ute, it will require the expenditure of a certain amount of power. 
 If he lifts them all up in one-half minute it will require twice as 
 much power, but no more work is done in one case than in the other. 
 It will require a stronger man, however, to do the work more rapidly, 
 or, even if a weaker man can accomplish the same work he will feel 
 the effects of the strain much more. 
 
 A horse power has already been defined as 33,000 foot pounds of 
 work in one minute. Any engine that can accomplish this amount 
 of work in one minute is doing one horse power of work. If the 
 same work can be done in one-tenth of a minute it will require a 
 10-horse power engine to do the work. Time, then, is the all impor- 
 tant consideration in all matters concerning power. 
 
 This same factor, time,, enters into all considerations of the trac- 
 tive force or pulling power of an engine. The question oftens comes 
 up : How much will an engine pull on the road ? This depends upon 
 
HORSE POWER FORMULAS. 89 
 
 a number of variable factors, such as the horse power of the engine, 
 the condition of the road bed, the power lost in transmission, the 
 weight of the machine, the grip the wheels have on the road, and the 
 speed of the engine. This latter factor is the one that proves to be 
 a stumbling block for a great many people. Many people do not 
 realize that the hauling capacity of an engine decreases in exact 
 proportion to its speed. That is why in going up a steep hill it is nec- 
 essary to run an automobile on low gear. It does not have anymore 
 power when so run, but the work of lifting itself up the hill is done 
 in a longer time, and consequently less power is required. Likewise 
 a traction engine can haul a larger load if the road speed is slower. 
 Other things being equal, an engine ought to be able to pull five 
 times as much at one mile an hour as it can at five miles an hour. 
 In either case, "the same number of foot pounds of work will be done, 
 as we can easily prove. Suppose the engine is capable of pulling 
 one ton at five miles an hour; the work done is five ton miles. At 
 one mile per hour, the engine should be able to haul five tons and 
 here again work done is five ton miles per hour, just as in the former 
 case. Slow speeds on an engine enable it to haul a heavier load and 
 fast speeds a lighter load, but in either case the same number of foot 
 pounds or ton miles of work will be accomplished. 
 
 Now let us consider some of the formulas for horse power. The 
 first one to attract our attention is the old steam engine formula for 
 indicated horse power with which every one is familiar, and which 
 reads as follows : 
 
 1. 2XPXLXAXN 
 
 =H. P. 
 
 33,000 
 
 In which P represents the average force acting on the piston in 
 pounds; L, is the length of the stroke in feet; A, is the area of the 
 piston, and N is the number of revolutions of the engine per minute. 
 The factor 2 is used to change revolutions into strokes when a double 
 acting engine is used. If the engine were single acting, that is, had 
 force applied only on one side of the piston, this factor would not 
 enter. In this formula PxLxA represents the work done in foot 
 pounds during one stroke of the piston. This multiplied by 2xN 
 gives us the work done in foot pounds in one minute. If this product 
 is then divided by 33,000 we will evidently obtain the number of horse 
 power the engine is capable of developing. This is a strictly mathe- 
 matical unit, and is invariable. By its use we can calculate the 
 power of any reciprocating engine, whether it be a gas engine or a 
 
90 
 
 steam, engine, provided we can find the value of the factor P. This 
 is not always easy, however. We can, it is true, use an indicator and 
 estimate the average pressure from the diagram it traces, but even 
 this is not always reliable, especially in the case of a gas engine. 
 When the power is obtained in this way we have a measure of the 
 power developed in the cylinder of the engine, but not the power 
 which the engine will develop at the band wheel. That will always be 
 somewhat less, on account of the internal friction of the engine. The 
 only way to obtain the power the engine is able to develop to do ac- 
 tual work is by means of a brake. 
 
 Now let us see what we can find out about calculating gas engine 
 horse power. The formula for the indicated horse power of a gas 
 engine is 
 
 PXLXAXE 
 
 =H. P. 
 
 33,000 
 
 The formula is almost the same as for the steam engine, except in- 
 stead of engine strokes we use E, which represents explosions in the 
 cylinder. Just as in steam engine practice, the value of P must be 
 determined by the use of an indicator. 
 
 After you have taken your indicator cards, measured them and 
 made all the proper allowances, and have made an estimate of the 
 mean effective pressure, you are at liberty to use the formula and 
 find out how much work is done on the piston. If you want to find 
 out how much work the engine will actually do at the fly wheel, you 
 must take seventy-five or eighty per cent of the above result, because 
 anywhere from twenty to twenty-five per cent of the work done on 
 the piston is required to overcome the friction of the engine itself, 
 even if it is a good gas engine ; and if it isn't, there is no way of tell- 
 ing except after you have found the indicated power, to put on a 
 brake and take the brake horse power. The difference between the 
 brake power and the indicated power will be the amount of work 
 consumed in friction. This is never less than fifteen per cent of 
 the total power developed in the cylinder and often as high as thirty 
 per cent. 
 
 There is another way of getting at the mean effective pressure 
 by the use of what is known as Grover's formula. It reads thus : 
 
 2. 2C .01C 2 =M. E. P. 
 
 In this formula C represents the compression pressure in pounds 
 above the atmosphere. After you have found this value you are at 
 
HORSE POWER FORMULAS. 91 
 
 liberty to use it in formula 2 in place of P. After you have done 
 the necessary figuring, you are in a position to make a fairly close 
 estimate of the power of the engine. Of course, this formula is 
 not exact, and it is criticised a good deal, and with good reason, but 
 it has some merit even if not very scientific. 
 
 All of this leads up to another class of formulas known as em- 
 pirical formulas, that is, formulas that give results that are pretty 
 close, but which do not admit of any scientific explanation, or rather 
 not a very rigid one at any rate. 
 
 These formulas are divided into two classes, those applicable to 
 four-cycle engines and those applicable to two-cycle. We will con- 
 sider the four-cycle formulas first. In all of these formulas the 
 symbols, have the same value and are as follows : 
 
 D equals the diameter of the cylinder in inches; L, the stroke 
 of piston in inches; E, the revolutions of the crank shaft per min- 
 ute; N, the number of cylinders. Using these symbols, Roberts offers 
 the following formula for gasoline engines: 
 
 ,3. 
 
 H. P. 
 
 18,000 
 
 The Royal Automobile Club uses this formula: 
 4. (D+L) 2 XN 
 
 :H. P. 
 
 9.92 
 
 The American Licensed Automobile Manufacturers have adopted 
 a slightly different formula, which reads as follows, and is based on 
 a piston speed of 1,000 feet per minute. 
 
 5. 
 
 =H. P. 
 
 2.5 
 
 The American Power Boat Association formula for motors of less 
 than six inches stroke is like the last one just given except that the 
 length of stroke is taken into account. 
 
 6. 
 
 =H. P. 
 
 15.2 
 
 The last two formulas are for motors used in boats rated as auto- 
 mobile boats. For all other marine motors two-thirds of the above 
 
92 GASOLOGY. 
 
 results are to be taken. Now let us apply these formulas to an engine 
 with a four-inch bore and five-inch stroke, running at 1,200 revolu- 
 tions per minute. 
 
 Applying formula 3 we have 
 
 4X4X5X1200 
 
 =5 1/3 H. P. 
 
 18,000 
 
 By formula 4 we have 9X9 
 
 =8.2 
 
 9.92 
 
 By formula 5 we have 4X4 
 
 -=6.4 
 
 2.5 
 By formula 6 we have 4X5 
 
 15.2 
 
 =5.2 
 
 An inspection of the above results does not show very close agree- 
 ment. As a matter of fact, they are principally valuable in determin- 
 ing handicaps in a race and for purposes of comparison rather than 
 to give results that have a definite meaning. 
 
 Two-cycle formulas. 
 
 7. Roberts'. D^X^X^XN 
 
 =H. P. 
 13,600 
 
 8. A.P.B. A. D 2 XN 
 
 =H. P. for engine having six inch 
 2.1008 
 stroke or greater. 
 
 9. A.P.B.A. 
 
 12.987 
 
 The above A. P. B. A. formulas are for racing boat motors. All 
 other marine motors use the same formula and take two-thirds of the 
 results above obtained. 
 
 Applying these, formulas to the same size of motor as in the four- 
 cycle class, we obtain* the results herewith shown. 
 
 By formula 7, 7.11 H. P.; by formula 9, 6.15. These two formu- 
 las do not appear to yield much closer results than the four-cycle 
 
HORSE POWER FORMULAS. 93 
 
 formulas just discussed. As a matter of fact, Roberts' two formu- 
 las are probably as close as we can come to expressing the actual 
 horse power of a gasoline engine by means of a formula. They do 
 not amount to much more than a fair estimate and are so under- 
 stood by all engineers who have to do with problems of this kind. 
 
 LESSON XXVII. 
 
 The indicated horse power of an internal combustion engine is a 
 measure of the actual horse power developed in the engine cylinder. 
 It is, in other words, the power that is expended upon the piston and 
 is always considerably greater than what can be obtained from the 
 engine in useful work at the fly wheel. When the fuel and its proper 
 proportion of air is introduced into the engine cylinder and burned 
 it produces a very high temperature of the gas behind the piston. 
 In accordance, therefore, with the laws of heat this gas, which is at 
 the given instant enclosed in a small space, exerts tremendous pres- 
 sure upon the walls of the cylinder and upon the head of the piston. 
 In the case of ordinary gasoline engines this pressure, at the moment 
 the piston is started forward on its power stroke, may amount to 
 from 250 to 300 pounds per square inch. 
 
 The exact amount of the initial pressure is dependent upon a 
 number of things, among which may be mentioned the degree of 
 compression of the charge, the temperature of the gas at the moment 
 of ignition, the degree of completeness of the combustion before 
 the piston starts forward on its power stroke, and the quality of the 
 mixture. 
 
 If the gas is first compressed to 60 or 70 pounds and the fuel is 
 capable of raising the pressure 200 pounds, the total initial pressure 
 will be the sum of the two. Consequently, the higher the compression 
 pressure with any given fuel, the higher will be the initial pressure; 
 and, within certain limits, the greater the power of the engine. It 
 has been stated in nearly every book treating of the gas engine that 
 its efficiency depends very largely upon the degree of compression. 
 It can be proved theoretically that the higher the degree of compres- 
 sion in the case of any engine working on the Otto cycle, the greater 
 the efficiency. This means that with the expenditure of a given 
 quantity of fuel the greatest amount of work can be obtained when 
 the compression is carried to the highest point possible. This is 
 true, regardless of the kind of ;fuel used. Practically, the kind of 
 fuel exerts a marked influence because of the fact that compression 
 cannot be carried as high with some kinds of fuel as with others. 
 For example, gasoline vapor is highly inflammable and will ignite 
 
94 GASOLOGY. 
 
 at lower temperature than some other gas, such as blast furnace 
 gas or producer gas. 
 
 In ordinary medium speed gasoline engines a compression pres- 
 sure of 70 pounds is about as much as can be obtained without caus- 
 ing pre-ignition. If the engine is of the slow speed type, compression 
 pressures as high as 80 or 85 pounds are often carried out success- 
 fully, while with the high speed automobile engines a compression 
 of 60 pounds is customary. It requires, therefore, no stretch of the 
 imagination to realize that an engine suitable for one kind of fuel 
 may not be suitable for another. Furthermore, an engine that will 
 produce a given amount of power with one kind of fuel may be very 
 inefficient and lack a great deal of coming up to its power specifica- 
 tions when another kind of fuel is substituted. This can be explained 
 easily when we take into consideration the heat values of some of the 
 different fuels. 
 
 Gasoline vapor has a heat value of about 650 heat units per 
 cubic foot; producer gas from 90 to 125; city gas, 750 to 900; and 
 natural gas from 1,000 to 1,100. An engine, therefore, which uses a 
 gas of high heat value, such as natural gas, will yield considerably 
 more in horse power than the same engine using producer gas, for 
 the simple reason that the gas containing the larger number of heat 
 units contains the greater amount of energy which may be set free 
 for the doing of useful work. 
 
 The degree of completeness of combustion before the piston starts 
 forward on its power stroke has much to do with the initial pres- 
 sure. To be most effective, the fuel should all be consumed before 
 the piston has advanced an appreciable amount on its power stroke. 
 When this condition obtains, the initial pressure will be the maximum 
 for the given charge of fuel, and the piston will be driven forward 
 by the expansion of the gas solely and not by the addition of more 
 pressure due to what is known as after-burning. It can also be shown 
 theoretically and it has been proven practically that the best results 
 are obtained when the fuel is all burnt at the beginning of the stroke 
 and the expansion is adiabatic. That is, when no heat is either sup- 
 plied or taken away during the stroke. It naturally follows from the 
 construction of the engine and its method of operation that a true 
 adiabatic expansion cannot be obtained. There will be some transfer 
 of heat from the gas to the cylinder walls at the beginning of the 
 stroke and toward the end of the stroke there may be a flow of heat 
 in the opposite direction, all of which has a tendency to reduce the 
 thermal efficiency of the engine. 
 
 The quality of the mixture is another matter of importance in 
 
: : : : : 
 
 HORSE POWER Kekit'tfiAs.V . V :* 95 
 
 connection with the efficiency anS.p^f..oJ;&*.^i{TtiXe.Y. If the 
 mixture is rich in fuel gases, that is, if it contains a large quantity 
 of heat units it cannot be compressed as high as a leaner mixture, 
 and consequently its efficiency will be reduced. Almost any gas, 
 no matter how lean, if compressed high enough, can be ignited, and, 
 in view of the statement that efficiency depends upon the degree of 
 compression, it would thus appear that lean mixtures yield the higher 
 efficiencies. This appears to be true theoretically and has been worked 
 out and verified practically. 
 
 We made the statement that the power which might be obtained 
 at the fly wheel is always less than that expended upon the piston. 
 This is true in the case of the steam engine, but more particularly 
 true of the gas engine. The difference between the power supplied 
 to the engine and that which may be obtained from it, is used up 
 in internal friction. In the case of the steam engine, there is the 
 friction of all the working parts which may amount to anywhere 
 from five to twenty per cent of the power supplied. In the case of 
 the gas engine the friction is considerably higher, due to the fact 
 that for every four strokes of the engine there is only one power 
 stroke. There must be supplied by the fuel a certain extra amount 
 of power to overcome the friction of the three idle strokes, thus 
 making the difference between the indicated and brake power much 
 larger than in the case of the steam engine. The very highest 
 efficiency obtained from gas engines shows a loss of at least fifteen 
 per cent in friction, while losses of twenty and twenty-five per cent 
 are common and represent current practice. 
 
 The mechanical efficiency of an engine is represented by the ratio 
 between the brake horse power and indicated horse power; for ex-. 
 ample, if an engine indicates 5-horse power and it shows 4-horse 
 power by brake test at the fly wheel, its mechanical efficiency is four- 
 fifths or eighty per cent. 
 
 The thermal or heat efficiency, however, is a different thing and rep- 
 resents the proportion of the heat energy which is transformed into 
 mechanical energy. This is always low and for ordinary medium sized 
 gas engines is in the neighborhood of fifteen per cent. In a few cases 
 thermal efficiencies as high as twenty-five per cent have been obtained 
 for gasoline engines, while the very highest efficiencies have amounted 
 to about thirty per cent. Where the thermal efficiency is twenty- 
 five per cent it means that the heat value of one hundred pounds of 
 fuel is utilized or expended in the engine to obtain the useful effect 
 of only twenty-five pounds. There is, then, a loss of three-fourths of 
 the heat energy supplied to our best gasoline engines in transforming 
 the fuel into useful energy. 
 
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