o 30 rn z o o T3 C m 33 . CO 41 n| *^Jfd o O Z o 2 o O z CD T, Q O) H O O D O) ^ c O M 33 1 Z O m rn z o z m TREASURY DEPARTMENT UNITED STATES COAST GUARD HANDBOOK ON CARE AND OPERATION OF GASOLINE ENGINES PREPARED UNDER DIRECTION OF THE CAPTAIN COMMANDANT WASHINGTON GOVERNMENT PRINTING OFFICE 1917 ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 10 CENTS PER COPY LETTER OF PROMULGATION. TREASURY DEPARTMENT, UNITED STATES COAST GUARD, Washington, January IS, 1911. The following " Handbook on Care and Operation of Gasoline Engines " has been prepared by Second Lieutenant of Engineers W. M. Prall, United States Coast Guard, and is issued to officers and enlisted men of the Coast Guard for the information and guidance of all concerned. E. P. BEBTHOLF, Captain Commandant. 3 357468 HANDBOOK ON CARE AND OPERATION OF GASOLINE ENGINES. CHAPTER I. PURPOSE FOB WHICH THIS PAMPHLET IS ISSUED. No attempt has been made in the preparation of this pam- phlet to cover all the phases of design, construction, and opera- tion of gasoline engines. It is not expected that the contents will be of any material aid to the person who has had consid- erable experience in handling these engines. The sole object in view is to present the subject of gasoline engines in such a manner that persons without special education or practical training along mechanical lines can acquire a good general idea of how these engines work, how they should be cared for, and the special meanings of words and expressions when used in connection with engines of this type. In. other words, these few chapters are intended as a sort of primer for the use of enlisted men intrusted with the care and operation of gasoline engines. Manufacturers .of gasoline engines and of gasoline motor vehicles often publish information and instructions concerning their products for the guidance of their patrons. Frequently, however, these articles make use of such technical terms and expressions that a reader, who has not made a study of the sub- ject, soon becomes confused and discouraged. In some cases, too, these articles are written with the purpose of convincing the reader that the design, materials, and method of construc- tion of the particular engine described are the only ones that can be used with success. 5 6 CAR! / JTD OPERATION OF GASOLINE ENGINES. There is also available at present an abundance of literature on the subject of the gasoline engine, which, though thoroughly reliable, is written for the use of trained designers and engi- neers, but is of little value to others. This pamphlet is prepared with the hope that it will enable the reader to gain sufficient knowledge of the subject to make possible the reading of more extensive works with understand- ing, and enable him to secure the most satisfactory service from an engine of which he has charge. CHAPTER II. GASOLINE. What gasoline is. In certain parts of the world large tracts of land have been found, underlying which are immense quanti- ties of inflammable liquid commonly known as crude oil. In this country there are three principal oil regions : The Pennsylvania, which includes parts of West Virginia and Ohio ; the Texas region, which extends into Oklahoma and Kansas ; and the Cali- fornia region. To obtain the oil, wells are drilled to depths varying from an average of about 100 feet in the Pennsylvania region to 3,000 or 5,000 feet in California. Occasionally upon drilling a well the oil is forced violently to the surface of the earth, forming what is known as a " gusher," but more often the oil has to be removed from the wells by means of pumps. This natural oil is usually thick, heavy, and dark brown or green in color. But crude oil is really a mixture of several kinds of oil, differing greatly in their nature, and quite easily sepa- rated one from the other by the process known as distillation. To better understand the nature of crude oil let us consider a liquid, fresh water, for example, which is not a mixture of dif- ferent kinds of liquids. When a vessel of pure fresh water is boiled, a gas known as steam is formed, which can be carried to a cooling chamber and condensed ; that is, cooled until it again becomes liquid. No matter how much of the water from the vessel has boiled away, the condensed steam is always found to be water, the last drop condensed being exactly like the first drop, and all exactly like the water which was boiled. 7 8 CARE AND OPERATION OF GASOLINE ENGINES. When crude oil is slightly heated gases are given off which may be condensed to a liquid by cooling. This liquid is not at all like the original oil, but is quite colorless, light as compared with crude oil, and easily vaporized (changed to the form of gas) by slight heating. The crude oil, if further heated, con- tinues to give off gases which, when condensed, form a liquid much like that first obtained, but slightly heavier and not quite so easily vaporized. This process can be continued and a whole series of liquids obtained, each slightly heavier and less easily vaporized than the one before it, until the product is no longer colorless, but yellow, green, or brown. The first liquids thus obtained are not of much use commercially. They vaporize so rapidly that explosive gas is generated at ordinary temper- atures, making these oils too dangerous for ordinary use. After these, however, comes a series of oils which are of great value in modern life, known as gasoline, kerosene, and lubricating oils. Gasoline is the part of crude oil obtained after the lighter liquids referred to above have been distilled off and while the heating proceeds from about 230 F. to about 280 F. Kerosene is obtained as the distillation continues between 280 and 500. After that, lubricating oils are produced. The remainder, a thick, heavy, sticky oil, is suitable for use as fuel, and is used in some parts of the country for firing locomotives, making steam for factories and power plants, and as fuel on steam vessels. It is with gasoline that we are interested, this short descrip- tion of one process of refining crude oil being given to explain what gasoline is, where it is obtained, and how it may be pro- duced. Several methods are used commercially to separate these products, but all depend upon the difference between the boiling temperature of the various liquids. Recently attempts which promise to be successful have been made to perfect processes by which the heavier oils can be converted into more valuable lighter CARE AND OPERATION OF GASOLINE ENGINES. 9 oils. This can be done, but the commercial success of the under- taking depends upon the cost of the operations and the difference between the price obtainable for the oil before and after treat- ment. How gasoline produces power. Chemists tell us that gasoline is composed principally of carbon and hydrogen. Carbon we are familiar with in the form of charcoal and coke, which substances fire practically pure carbon. Hydrogen is a gas. It is due to processes of nature, very little understood, even by the chemists, that these two elements have been so united that they form oil. Air is a mixture of two gases, oxygen and nitrogen; these gases are not united with each other, but simply mixed together, as pepper might be mixed with salt. When gasoline vapor is mixed with air in the proper propor- tions we have what is called an explosive mixture. As long as the mixture is kept cool no action will take place, but let the least part of the mixture be sufficiently heated and a change will occur, so violent that it is termed an explosion. What happens to cause this violent action? In the first place, it may be said that the carbon and hydrogen are held together in gasoline by an attraction that is very weak. When mixed with air and heated, the carbon and hydrogen no longer stay united as gasoline, but each is strongly attracted to the oxygen. The carbon suddenly unites with part of the oxygen present and forms a gas known as carbon dioxide, and the hydrogen unites even more suddenly with the other part of the oxygen and forms water. This sudden action creates a large amount of heat, which causes the temperature of the carbon dioxide and water to rise very high, so high that the water is present only in the gaseous form of steam., Nitrogen present in the mixture does not change, though its temperature is raised by the heat of the other gases. It is well known that a gas if highly heated expands to sev- eral times its original volume, or, if it is heated when confined 10 CAEE AND OPEBATION OF GASOLINE ENGINES. in a closed vessel so that it can not expand, it creates a high pressure. It is because of these facts that gasoline can be used as a source of power in the gasoline engine, and it is evident that what is commonly regarded as the dangerous prop- erty of gasoline, the explosiveness of the gas generated there- from, is also the very property that makes it so useful. Precautions that must be taken in handling gasoline. There are two chief sources of danger from gasoline if it is not prop- erly handled the danger of fire and the danger of explosion. As gasoline evaporates rapidly in the presence of air, it forms a rich mixture of inflammable gas near the surface of the liquid. If ignited this gas burns rapidly ; the heat accelerates evapora- tion from the surface and causes the volume of flarne to increase with great rapidity. To avoid the danger of fire, gasoline should always be kept in strong, tight tanks, and whenever handled in the open air no flame or spark should be allowed in the vicinity. Gasoline itself is not explosive. It is only the mixture of gasoline vapor and air that will explode, as before described. When gasoline is handled or left exposed to the air in a confined space, such as a closed garage or boathouse, evaporation, espe- cially in warm weather, may cause the contained air to be so charged with vapor that the mixture would be exploded by a flame or spark. It is therefore always expedient to have proper ventilation in rooms where gasoline is exposed to the air or where tanks containing gasoline are stored, the frequent change of air carry- ing away vapors and preventing the accumulation of a rich mixture. It should also be borne in mind that an explosive mixture of gasoline vapor and air usually occupies the space over gasoline in a partially filled tank, which makes it extremely dangerous to have a flame near when the tank is opened for filling or for measuring the contents. CARE AND OPERATION OF GASOLINE ENGINES. 11 Water should not be used in an attempt to put out a gasoline lire, for the gasoline will float on top of the water and continue to burn, the only result being a spreading of the flames. Sand or ashes thrown on the fire to reduce the exposed surface of gasoline, or, better yet, a good fire extinguisher, the contents of which will generate a smothering blanket of inert gas, are the most effective means of subduing the fire. What determines the quality of gasoline? In engineering the quality of fuel for producing power is usually determined by the amount of heat which 1 pound of that fuel will produce when burned. But with gasoline, as used in the modern gas engine, another quality is commonly placed foremost. The ex- pressions " good gasoline " and " poor gasoline " are often heard, also " high-test " and " low-test " gasoline. By " good gasoline " and ' high-test gasoline " is meant that which vapor- izes readily, thus causing easy starting and smooth running of a motor. " Poor gasoline " and " low-test gasoline " lack this quality to a noticeable extent. It so happens that the ease with which gasoline is vaporized can be determined by comparing the weight of a given volume of the oil with an equal volume of pure water. If equal volumes of different grades of gasoline were carefully weighed, that found to be lightest would be best, as far as ease of vaporization is concerned ; the heaviest would be poorest. In practice, the grade of oil is determined by means of an instrument called a " hydrometer," graduated to an arbi- trary scale called the " Baume" scale." When the instrument is floated in a liquid the reading of the scale at the surface is a measure of the relative weight of the liquid as compared with water, the readings being higher for light liquids than for heavier ones. Gasoline that tests 66 Baume" is now commonly considered good. The lower grades test about 56 to 64. The reason for this variation in the quality of different grades of gasoline lies in the fact that gasoline, like the crude oil from which it is obtained, is really a mixture of several oili. 12 CARE AND OPERATION OF GASOLINE ENGINES. The weight of a given volume (say, a gallon) of gasoline de- pends upon the weights per gallon and the proportions of these separate oils. Since during distillation the lighter oils are first separated from the crude product, the weight per gallon of the oils becoming greater as the temperature of distillation increases, it is evident that the lower the temperature and the narrower the range of temperatures over which the distillation is allowed to proceed during the production of gasoline the lower will be the weight per gallon of the final product. If the distillation is allowed to proceed over a wide range of temperatures, the heavier oils distilled at the higher temperatures increase the weight per gallon of the final product, with a result that the gasoline is heavier and less readily vaporized. Of course in the latter case the amount of " gasoline " produced from a given quantity of crude oil is much greater than in the former. As kerosene oil is obtained from crude oil over the next higher range of temperature of distillation, oil producers have used this ready means of regulating their production of gasoline and kerosene to suit the demand. A few years ago, when the con- sumption of kerosene was enormous as compared with that of gasoline, distillation of the latter covered a narrow range of temperature, and the quality was high, as great in some cases as 84 Baume". On the other hand, as the recovery of kerosene was commenced at a comparatively low temperature, its weight per gallon was consequently low, a very undesirable quality, which made the kerosene vaporize so easily that it was some- what dangerous for domestic use. In more recent years con- sumption of gasoline, due to its use in motor vehicles, power boats, and the like, has so increased that oil producers, in order to meet the demand, have found it necessary to broaden more and more the range of temperature in the distillation of their crude oil, during which gasoline is produced, thus obtaining a greater quantity of heavier grade. One fortunate result, how- CARE AND OPERATION OF GASOLINE ENGINES. 13 ever, is the superior quality of the kerosene now produced, for, being distilled at a higher range of temperature, its dangerous qualities are greatly reduced without detracting from those that make it useful for light and heat. In fact, it may be truly said that the words " gasoline " and " kerosene " as ordinarily used to-day hardly mean more than " products from crude oil " suit- able for the uses with which these names are associated, gasoline being the lighter of the two, but their exact qualities depending upon the relative consumption, the sagacity of the oil refiners, and just how exacting the public is in its demands. CHAPTER III. DEFINITIONS OF WORDS AND TERMS USED WITH REFERENCE TO GASOLINE ENGINES. In many instances common words and phrases, when used in connection with gasoline engines, have a special meaning. This often confuses a reader and makes it advisable, before going fur- ther into the subject, to define or explain such of these words and expressions as are most often met with. It must be kept in mind that the definitions given in each case refer only to the use of the word or phrase in its connection with a gasoline power plant. For convenience, an alphabetical arrangement has been adopted : Air cooling. A system of cooling engine cylinders by means of a current of air. Alignment. A state of having the various parts of a machine in proper position that is, " in line " with relation to each other. When this proper relationship does not exist the parts are said to be " out of line " or " out of alignment.*' For exam- ple, the center line of a cylinder should lie in a plane perpen- dicular to the center line of the crank shaft in order to be " In alignment." Or, as another example, if the center of each crank shaft bearing is not in a single line drawn between the centers of the two end bearings, these bearings are " out of alignment." Alternating current. A current of electricity that flows through the circuit first in one direction, then in the opposite direction, the alternations occurring with great rapidity. CARE AND OPERATION OF GASOLINE ENGINES. 16 Automatic spark advance mechanism. A device, usually built on the principle of a centrifugal governor, which automatically changes the timing of the spark and eliminates the necessity of hand regulation. Baffle, or baffle plate. A partition or projection fitted In a chamber or passage to check, distribute, or change the direction of a current of gas or liquid. Battery. A group of cells used as a source of electricity. When all positive terminals are connected together and all nega- tive terminals are connected together, the cells are said to be connected in " parallel." When the positive terminal of a cell is connected to the negative terminal of the next cell, and so on, the cells are said to be connected in " series.'* When a com- bination of these two systems is used the cells are said to be connected in " multiple series." A primary battery is one that can not be recharged by passing a current through it, an example being a group of ordinary dry cells. A secondary or storage battery is one which can be recharged by causing a direct current from another source to flow through it in the opposite direction to that of the current generated by the battery itself. The cur- rent furnished by a battery is always a direct current. Bearing. Every part of a machine must have adequate sup- port ; moving parts must be so supported that excessive friction and wear will not be caused by their motion. Such a support is called a bearing. Thus a main shaft bearing consists of a frame, usually lined with antifriction metal, which is made to fit accurately, but not bind the shaft. A ball bearing is one so arranged that the shaft or rotating part is supported by steel balls which in turn are held in a recess in the fixed frame, called the ball race (sometimes the shaft or spindle is stationary and the frame revolves around it). Roller bearings are similar in arrangement, but here steel rollers instead of balls are used. The principle involved in the use of balls or .rollers is the same as that which makes it 16 CARE AND OPERATION OF GASOLINE ENGINES. advisable to use rollers when moving any heavy weight, the force necessary to cause rolling generally being less than that required to cause sliding. Binding post. A threaded screw or "post" with nuts and lock nuts or other fastening device for attaching wires to elec- trical apparatus. Bloc cylinders. When all cylinders are cast in one piece the engine is said to have " bloc cylinders," or the cylinders are cast " en bloc." The same expression is used whenever groups of cylinders are cast in one piece, and the total number of cylinders is made up of two or more of these groups, but in this case the number of cylinders in a " bloc " is usually stated. Break (as applied to electrical circuits). The interruption of flow of an electric current by making a gap in the metallic circuit. Under proper conditions a hot spark or " arc " is pro- duced at the point of break in the ignitor. Breather. A passage between the open air and the inside of a closed crank case on a four-cycle engine. Its purpose is to prevent either pressure or vacuum in the crank case. Brush. A device for making a good electrical contact between a stationary part and a moving part of a circuit. Examples are: The brushes of a dynamo which collect the current gen- erated in a moving armature, or the brush of a commutator which revolves and comes in contact with stationary insulated terminals, thus completing an electrical circuit at certain times. Bushing. A sleeve or collar used as a lining for a bearing, usually made of antifriction metal. Cam. An accurately shaped projection on a shaft for impart- ing the necessary motion to a valve, ignitor, or other part at the proper times. Cam shaft. The shaft that carries the cams for operating valves or ignitors. A cam shaft receives its motion from the crank shaft by means of spur gear or silent chain connection. CARE AND OPERATION OF GASOLINE ENGINES. 17 Carbon. A deposit of black scale or soot which forms on in- terior walls of the combustion chamber. It is caused both by the burning of the gas and by the burning of lubricating oil which finds access to the chamber. The rate of deposit is in- creased by the use of an overrich mixture of gas and by ex- cessive piston lubrication. The carbon deposit is often rough and sometimes peels up in flakes. The high portions or flakes become red hot when the engine is running and ignite the charges of gas before the piston has reached the end ol its com- pression stroke, causing a sharp thud termed the " carbon knock." Carburetor. A device for vaporizing gasoline (or other vola- tile liquid fuel) and mixing it with air to form an explosive mixture. Cell. A jar or case containing " electrodes " (one usually made of carbon, the other of zinc) and a solution of chemicals, which combination will generate an electric current. In other words, a unit of an electric battery. Centrifugal force. The tendency of a body revolving around an axle or shaft to fly away from the axle. It is used as the basic principle of most governors and automatic spark-advance mechanisms. Check valve. A valve which allows passage of gas or liquid through it in only one direction. Circuit. Electricity can flow as a current only when it has a loop or closed path of conducting material (usually metal) starting from the source of electricity and leading back to that source. Such a path is called a circuit. A " closed circuit " is one that is complete so that the current can flow. An " open circuit" is one having a break or gap (for example, an open switch), which prevents the flow of current. By a "short cir- cuit " is meant a connection (either accidental or intentional) 7661617 2 18 CARE AND OPERATION OF GASOLINE ENGINES. which allows the current to take a " short cut " from some part of the regular circuit back to the source. Circulating pump. When a water-cooling system is used some means must be employed to cause the water to circulate through the cooling jackets. A pump used for this purpose is called a circulating pump. Likewise, when forced-feed lubrication is used, a pump for forcing the oil through the system is called an oil-circulating pump. Closed circuit. (See Circuit.) Clutch. A coupling between two parts of a machine so ar- ranged that when it is " thrown out " one part can operate inde- pendently of the other part (in other words, they are discon- nected), when "thrown in" the parts are held together, one usually driving the other. In connection with gasoline engines, a clutch is often used to readily connect or disconnect the en- gine from its load without stopping the engine. It is always used on gasoline vehicles, for without it the engine could never be started without the vehicle starting at the same time. Coil. The induction coil used in ignition systems is usually spoken of simply as the "coil." (See "Induction coil.") Combustion. The burning of the gasoline mixture. This burning takes place with such rapidity that it is termed an ex- plosion. (See Chapter II.) Commutator. A device forming part of the primary circuit of an ignition system, which " closes " and " opens " this circuit in such a manner that sparks are caused at the proper times in each cylinder. Compression. After a charge of mixture has been introduced into the cylinder its volume is reduced and its pressure is in- creased by the movement of the piston toward the cylinder head. This action is called " compression." While the piston is moving toward the cylinder head, causing compression of the mixture, it is said to be making the " com- pression stroke." CARE AND OPERATION OF GASOLINE ENGINES. 19 When a leak from the combustion space (past a loose or poorly fitted piston, through a leaky valve or defective spark plug, or in any other way) allows such an escape of mixture that a proper compression of the mixture is not obtained, the cylinder is said to have " poor compression " or " has lost its compression." Connecting rod. The bar which connects the piston to the crank. It is fitted with a bearing at each end. Contact points. The points in vibrators or other forms of in- terrupters where the electric circuit is " made " and " broken." Ordinarily they are not actually points, but small, flat buttons made of platinum, platinum-iridium alloy, tungsten, or other material well adapted for resisting extreme heat and the de- structive action of the electric spark. Control. The levers, links, switches, etc., by which the regu- lation of the engine is accomplished is called the " control." Cooling fins or flanges. The ribs or projections used on air- cooled cylinders and radiators for the purpose of increasing the surface from which heat may radiate. Cooling jacket. The chamber, surrounding the cylinder and valve recesses of a water-cooled engine, through which the cool- ing water is circulated. Crank. The offset part of the shaft where the connecting rod is attached bj; means of a bearing. (Also the handle by which an engine is started by hand.) Crank case. The casing which incloses the space around the crank. Various other parts are also located within this inclosure. Cranking. The act of turning an engine to accomplish start- ing. Crank shaft. The main shaft of the engine which carries the cranks. Cup (grease or oil). A small vessel or recess for holding a supply of lubricant. They are usually so arranged that the supply of oil or grease is fed gradually to the surface lubricated. 20 CAKE AND OPERATION OF GASOLINE ENGINES. Current. The flow of electricity around a circuit. Cylinder. That part of the engine (usually an iron casting) in which the piston moves to and fro. Cylinder head. The cover which closes that end of the cylin- der which is farthest from the crank. Sometimes the head is part of the cylinder casting, but the present tendency is to make it a separate part, fastened to the cylinder by bolts. With a removable head cleaning of the combustion chamber and inspec- tion of the interior of the cylinder are more easily accomplished than when the head is cast on the cylinder. Cycle. In general, the word " cycle " means a series of events occurring in regular order and ending with all conditions in the same state as that which existed at the beginning, whereupon another cycle begins. With particular reference to a gasoline engine, a cycle means that series of operations which takes place in producing one power impulse. The words " two-cycle " and " four-cycle " in themselves really have no meaning. They were unfortunately coined by early inventors to signify the number of strokes the piston of their engines made in producing one explosive impulse. Thus when the piston makes two strokes for each explosion (or to complete a cycle) the engine is said to be of the " two-cycle " type ; when four strokes of the piston are required to produce one explosion, the engine is of the "four- cycle " type. From the above it is apparent that a stroke is not a cycle, as is often supposed and sometimes stated in books of instructions. To avoid the confusion caused by these terms some authorities distinguish between the two types by calling them " two-stroke " and " four-stroke " ; others call them " two-stroke cycle " and " four-stroke cycle " engines. Displacement, piston. By piston displacement is meant the difference between the volume of space within the cylinder when the piston is at tlie head end of its stroke and the CARE AND OPERATION OP GASOLINE ENGINES. 21 volume of space when the piston is at the crank end. It is equal to the cross-sectional area of the cylinder measured in square inches, multiplied by the length of the stroke measured in inches. Distributor. An automatic electrical device for directing the igniting current to the various cylinder spark plugs at the proper times. It operates in much the same manner as a commutator, but is so designed that it will handle the high tension current. Dowel or " dowel pin." A pin for the purpose of holding two or more parts of a machine in an exact position while the per- manent fastening is made by means of bolts or screws. Dowels are often so arranged as to make it impossible to assemble the parts except in their proper relative positions. One end of the pin is permanently fastened in one part of the machine, the other end fitting neatly into a hole in the other part. Drain cock. A faucet or valve fitted in the lower part of water chambers, radiators, carburetors, tanks, etc., for emptying or " draining " these chambers. Dual ignition system. Two systems of ignition, more or less independent, fitted to an engine so that either can be used for generating the sparks is called a dual system. As a general thing batteries and coil are used for starting, or in case of emer- gency, and a magneto used for regular running. When two sets of spark plugs are used, and the system so arranged that for regular running a spark is produced at both plugs of each cylin- der for every explosion, the system is said to be " double," or " two-point." A combination of these two arrangements is a " double dual ignition system." Dynamo. An electric generator geared or belted to the en- gine and used to furnish current for ignition, charging batteries, lighting, etc. Electrode. The two " elements " or plates of a battery cell are the electrodes. The positive plate or terminal that is, the 22 CAFJE AND OPERATION OF GASOLINE ENGINES. one through which the current flows from the cell is called the " anode." The one through which the current returns to the cell is called the " cathode." Electrolyte. The electrodes of a cell are immersed in a liquid called the " electrolyte." The chemical action between electrodes and electrolyte generates an electric current. En Hoc cylinders. (See "bloc cylinders.") Exhaust. The discharge or escape of burnt gases from the cylinders. Exhaust valve. The valve through which the burnt gases escape from a cylinder. Explosion. The violent combustion or burning of the mixture of gasoline vapor and air. Factor-of-safety. The numerical ratio between the strength of any part of an engine and the force which this part is required to resist. When an engine is spoken of as having " a general factor of safety of 12," it is meant that the strain necessary to break any part is at least 12 times as great as the actual strain that the particular part sustains when in operation. Fan. The air propeller used to cause rapid passage of air through the radiator or, on an air-cooled engine, around the cylinders. Firing order. In a multiple-cylinder engine, after an explo- sive impulse is delivered in one cylinder, each of the other cylin- ders delivers an impulse before the next explosion takes place in the first cylinder, and these impulses occur in regular order, determined by the angles of the cranks on the shaft. The order in which the impulses follow one another in the various cylin- ders is usually spoken of as the firing order. Float. Carburetors of the " float-feed " type have a small reservoir in which a constant level of gasoline is maintained. The cork block or metal drum which floats in this gasoline and automatically controls the inlet needle valve is called the " float." CARE AND OPERATION OF GASOLINE ENGINES. 23 Flywheel. The heavy wheel usually carried on one end of the crank shaft. By virtue of its weight, it causes steady opera- tion of the engine. Friction. The resistance which must be overcome to cause motion between two parts in contact with each other. Oil reduces this resistance by forming a liquid coat on the surfaces and preventing close contact. Gap. The space between the points of a spark plug across which the current jumps in forming the spark. The " circuit " is " open " at this gap, there being no metallic conductor for the current. It is high voltage that enables the current to over- come the resistance encountered at the gap. Gas. The mixture of gasoline vapor and air is often spoken of simply as the " gas." This word is also sometimes used as a short term for gasoline in the liquid form. Gasket. A layer of comparatively soft elastic material used between metal parts to form a tight joint. . A common form of gasket consists of a sheet of asbestos packing cut to proper shape to fit the joint and covered by a casing of very thin sheet copper or brass. Gears. Toothed wheels which, through the engagement of their teeth, transmit motion from one wheel to the other. When the motion is transmitted through several gears the com- bination is called a " train of gears " or a " gear train." " Half-time gears " are those that transmit motion to the cam shaft in such a way that this shaft will make one revolu- tion while the crank shaft makes two. When the axes about which a pair of gear wheels revolve do not lie parallel to each other the teeth have to be tapered and cut at an angle (one side of the wheel is smaller than the other). They are then called " bevel gears." The smaller of two or more gears of a set is called the " pinion." Recently, for high-class work, it has become the practice to cut half-time gears so that their teeth are at an angle instead 24 CARE AND OPERATION OP GASOLINE ENGINES. of straight. This causes the teeth to engage gradually and does away with much of the usual noise and vibration that attends the use of plain gears. When the teeth are cut in this manner the gears are said to be " helical." Sometimes bevel gears are made with helical teeth. A " worm gear " consists of a pinion with teeth so cut that they wind around the axis in the form of a screw engaged with a wheel having teeth properly shaped to " mesh " with this screw. Generator. (See Dynamo.) Governor. A device which automatically operates the throttle when the engine is running and regulates or limits the speed. Graphite. A solid form of lubricant, usually mixed with grease or oil, for reducing the friction of gears. Ground (electrical). An electrical connection in any part of a circuit to the body or base of the engine. It may be intentional or accidental. Two " grounds " often produce a " short circuit." Half-time shaft. A cam shaft which makes one revolution while the crank shaft makes two. (Cam shaft of a four-cycle engine. ) High tension or high voltage. As used in connection with gasoline-engine ignition this expression means " tension " or " voltage " sufficiently high to cause the current to jump across the gap in a spark plug. Hot-air pipe. A passage or pipe which conducts heated air to the carburetor. The heated air is usually drawn from a jacket around the exhaust pipe. Hydrometer. A graduated float used for measuring the weight of a liquid as compared to the weight of an equal volume of pure water. (See p. 11.) Ignition. The complete system which generates the sparks for exploding the charges of gas is often spoken of as the " ignition." Induced current. The electric current which flows through the secondary circuit of an induction coil. It Is produced by the action of another current flowing through the primary CARE AND OPERATION OF GASOLINE ENGINES. 25 circuit. The secondary circuit is high tension; the primary is low tension. Induction coil. The device in which a " low- voltage " current is transformed into a high-tension current. For jump-spark ignition a coil has two separate windings the " primary " or low- voltage winding being a comparatively few turns of fairly coarse insulated wire, the " secondary " or high-tension winding having many turns of fine wire. The current in the primary coil induces a high-tension cur- rent in the secondary coil, hence the name " induction coil." Inlet valve. The valve through which the charges of gas are admitted to the cylinder. Insulation. The nonconducting material used as a covering for electric wires or to separate any part of a circuit from con- tact with conducting material which is not a part of the circuit. Interruptor. A device which rapidly makes and breaks an electrical circuit. The magnetic vibrator is the most common form of interruptor. Jump spark. The common name for the spark generated by a high-tension current leaping across the gap. High-tension ignition is often called "jump-spark ignition." Key. A suitably shaped piece of metal, usually steel, fitted in a slot or recess, part in the shaft and part in the wheel, cam, sleeve, or other device carried on the shaft. Its purpose is to fasten these parts on the shaft. A sliding key or "feather" is one so fitted that the part carried on the shaft can move lengthwise but can not revolve except as the shaft revolves. Knock. The regularly repeated jar or thumping sound caused by a loose bearing, or other poorly fitted or loose working part. A " carbon knock " is one caused by preignition, due to exces- sive carbon deposit in the combustion chamber. L-head engine. An engine, the cylinder of which has inlet and exhaust valves located on one side of the combustion chamber. 26 CARE AND OPERATION OF GASOLINE ENGINES. Liner. A thin layer of suitable material (usually metal) placed between the two halves of an adjustable bearing to pre- vent too close contact between the bearing metal and the pin or shaft. Liners are sometimes called " shims." Low-tension (low voltage). With reference to gasoline- engine ignition " low tension " means, suitable, as regards voltage, for use with a " make-and-break " ignition system. Lubricant. Any substance used to coat the surface of bear- ings for the purpose of reducing friction between parts that rub one upon the other. Lubrication. The act or process of furnishing lubricant to bearing surfaces. Magneto. An electric generator especially designed for gas- engine ignition. It differs from a dynamo in that the current is intermittent, being furnished only at the time a spark is re- quired. For this reason a magneto has to be so connected to the engine that its armature will be driven at a speed proportionate to the engine speed, and so set that a current is generated at the proper instants for ignition. " Timing " a magneto means setting the armature so that the above conditions are achieved. Because of the intermittent nature of the current produced by a magneto, these machines are not suitable for lighting elec- tric lamps or charging storage batteries. A high-tension magneto is one that produces current at suffi- ciently high voltage to cause it to jump the gap of a spark plug. A low-tension magneto produces a current at comparatively low voltage. This low-tension current has to be transformed to high-tension current by use of an induction coil if the jump spark is used. Low-tension magnetos are sometimes used to furnish current for "make-and-break" ignition. Make-and-break ignition. An ignition system using a low- tension current and generating a spark by breaking the circuit CARE AND OPEEATION OF GASOLINE ENGINES. 27 within the combustion chamber at the proper time for ignition of each charge. Manifold. A pipe or passage having two or more branches leading to like ports or chambers of the several cylinders on multiple-cylinder engines. The two principal manifolds on an engine are the inlet manifold for conducting mixture from the carburetor to the cylinders, and the exhaust manifold for lead- ing the exhaust from the separate cylinders into a common exhaust pipe. Missing. When the proper impulses fail to take place regu- larly in one or more cylinders the engine is said to be " missing." To " find which cylinder is missing " means determining in which cylinder the explosions do not occur either with regu- larity or at all. A word commonly used by motorists is " hit- ting," meaning the opposite of missing. As an example: Sup- pose four cylinders of a six-cylinder engine are working prop- erly, while the other two cylinders do not deliver their power impulses regularly, then the four cylinders are said to be hitting, the two cylinders are missing. Mixture. The mixture of gasoline vapor and air as fur- nished by a carburetor is usually called simply " mixture." A " lean mixture " is one that has a comparatively large proportion of air as compared with the proportion of gasoline vapor. A mixture having a comparatively large proportion of gasoline is called a " rich mixture." Muffler. A device for silencing or reducing the noise of the exhaust. Needle valve. A valve capable of close adjustment so that a very small amount of gas or liquid can flow through. Oil groove. A channel cut in a bearing surface to aid in the distribution of lubricant. Oil sump. A reservoir usually formed in the lower part of the crank case or sub-base, from which lubricating oil is circu- lated to bearings and to which it returns for recirculation. 28 CARE AND OPERATION OF GASOLINE ENGINES. Open circuit. (See Circuit.) Piston. The cylindrical casting, together with its packing rings, which slides to and fro in the cylinder. Piston ring. A spring or ring neatly fitted in a groove around the piston body to form a tight joint between the piston body and the cylinder. Piston pin. The pin, carried in the piston body for forming the movable joint between the piston and the connecting rod. This pin is also sometimes called a wrist pin, gudgeon pin, or crosshead pin. Port. An opening for passage of gases into or out of a cylinder. Preignition. Explosion of the charge before the proper time. Primary circuit. The low-tension circuit of a jump-spark ignition system. Priming a cylinder. Introducing liquid gasoline into a cyl- inder or inlet manifold to facilitate starting. Priming cock. A pet cock with a cup-shaped nozzle, so fitted to the combustion chamber that it can be used to introduce liquid gasoline directly into this space. They are also some- times called " relief cocks " since they furnish a means of re- leasing part of the charge as it is compressed, thus reducing the force required to turn the engine in starting. Pump. A device for causing a flow of gas or liquid, usually through pipes or passages. The three types of pump most used in gasoline engines are: (a) Plunger pumps, having a piston or "plunger" working in a cylinder and check valves properly arranged to direct the flow. (&) Centrifugal pumps, having a bladed wheel, or " impeller," somewhat like a paddle wheel, which revolves in a chamber or casing. (c) Gear pumps, in which the flow is induced by the action of the teeth of gear wheels working in a casing. CARE AND OPERATION OF GASOLINE ENGINES. 29 Push rod. A rod or pin operated by a cam, which transmits the cam motion to another part of the engine. Radiator. The chamber or system of passages through which cylinder cooling water is circulated to reduce its temperature. Retarding the spark. Nearly all engines have the ignition mechanism so arranged that the time at which the spark occurs in the cylinder can be regulated while the engine is running. When the adjustment is such that the spark occurs just at the end of the compression stroke or a little thereafter it is said to be " retarded." Scores. Scratches or grooves worn in the bearing surfaces as a result of poor lubrication. The bearing surfaces of pistons and the cylinder bore are especially liable to score unless prop- erly lubricated and kept free of carbon or other gritty matter. Secondary circuit. The high tension circuit of a jump-spark ignition system, fitted with induction coil. Sediment trap. A bulb or pocket in a pipe line so located that dirt and solid matter settle in this chamber instead of being carried on through the piping. It is usually equipped with a strainer and arranged to be readily cleaned. Series connections. A method of connecting the various parts of an electrical circuit end to end, forming a single path for the current. Shaft. Any cylindrical bar, which transmits motion from one part of a machine to another part by virtue of a rotary motion about its own center line, is called a " shaft." Various devices such as cranks, eccentrics, cams, etc., when fitted to a shaft are usually included by the term " shaft." In a gasoline engine the principal shafts are the crank shaft and the cam shaft. Short circuit. (See Circuit.) Spark. The hot, brilliant glow caused by the electric current when the points of a make-and L break ignition plug are separated, or wlien a high tension current jumps the gap of a spark plug. 30 CARE AND OPERATION OF GASOLINE ENGINES. Spark advance. To obtain economical and satisfactory work- ing of an engine it is necessary to so regulate the time at which the spark is made that it occurs earlier in the cycle when the engine is running at high speed than when at slow speed. This regulation is usually accomplished by hand through a system of links and levers (the " spark advance mechanism "). This same mechanism is used for " retarding the spark." Spark plug. By " spark plug " is usually meant the ordinary " high-tension " plug, consisting of a threaded metal shell in- casing an insulated spindle. The gap is between this spindle and a pin fastened to the outer shell. The plug or plate which carries the movable latch and insulated pin for a " make-and- break " spark is sometimes called a spark plug, but more often an " ignitor plug," or simply " ignitor." Springs, valve. In four-cycle engines the valves are usually opened by cams which operate the push rods, these, in turn, pushing the valve stems and lifting the valves from their seats. The return motion, or closing of the valve, is accomplished by steel coiled springs, called " valve springs." Starter. The mechanism by which the working parts of the engine are set in motion to accomplish starting. A hand starter usually consists of a hand crank which engages, through a ratchet, with the crank shaft in such a way that the engine can be turned in the proper direction and the crank is pushed out of engagement when the engine begins to run under its own power. When the engine is started by other than manual effort, it is said to be self-starting, and the mechanism is called a self- starter. Strainer. A screen used as a trap for dirt and sediment in oil or gasoline pipes. Stroke. By the stroke of an engine is usually meant the linear distance the piston moves in one direction. This distance is equal to twice the " throw of the crank " arid is expressed in inches. The term " stroke " is also used to denote the movement CARE AND OPERATION OP GASOLINE ENGINES. 31 of the piston in one direction ; thus, in a four-cycle engine, by suction " stroke " is meant the movement of the piston during which a charge of mixture is drawn into the cylinder ; the com- pression " stroke " is that during which the charge is com- pressed ; the expansion " stroke " that during which the charge burns and power is delivered ; and the exhaust " stroke " that during which the burnt gases are discharged from the cylinder. (See "Cycle.") Sump. (See " Oil sump.") Switch. An electrical device used to open or close a circuit. Tension. Same as " Voltage." T-liead. A four-cycle engine having inlet valves on one side of the combustion chamber and exhaust valves on the other side is called a " T-head engine." Tliermo-siphon cooling. A water-cooling system so arranged that circulation is caused by the difference in the weight of equal volumes of water at different temperatures. Three-port engine. A two-cycle engine having three ports in the cylinder walls. Timer. For successful operation the igniting spark must always take place when the piston has reached a certain point in the cycle ; this point varies somewhat, according to the speed of the engine. That part of the ignition apparatus which deter- mines the time at which the spark occurs is often called the "timer." Timing. The act of so adjusting or setting a timer that proper ignition results is called " timing " the ignition. The adjustment of the cam-shaft gearing is called " timing " the cam shaft. Transformer. (See Induction coil.) Two-port engine. A two-cycle engine which has but two ports in the cylinder walls. Vacuum. A vacuum is said to exist in a chamber when the contained gases are rarefied ; that is, reduced to a pressure below that of the atmosphere. 32 CARE AND OPERATION OP GASOLINE ENGINES. Valve. A device for 'opening or closing a passage through which liquids or gases flow, or for regulating the flow of these substances through a passage. " Valve-in-head." When the valves of a four-cycle engine are fitted directly in the head of the cylinder the engine is said to be of the " valve-in-head " type. This construction is used to reduce the wall surface of the combustion chamber. Valve lifter. A tool for removing valve springs. Valve " push rods " are sometimes called valve lifters. Valve seat. The finished surface against which the disk of a valve presses to form a tight joint and close the passage. Valve stem.^-The rod on which the valve disk is carried and by which it is lifted from and drawn to its seat. Usually the valve disk and stem are integral ; that is, a single piece of metal. V arrangement of cylinders. With engines having more than six cylinders the customary practice is to install the cylinders in two sets of equal numbers, the two sets being inclined at a suitable angle in the form of a V. Two-cylinder motorcycle engines usually have cylinders arranged in this manner. Vaporizer. This word is sometimes used with the same mean- ing as the word carburetor, especially with reference to car- buretors of the simpler type. Voltage. The electrical pressure which causes a current of electricity to flow through a conductor. Water-cooling system. A system for preventing too high temperature of cylinder walls by circulating water through cham- bers surrounding these walls. Wiring. The insulated conductors or wires used to connect the various parts of an ignition system and form the various circuits is, as a whole, called the wiring. Wiring diagram. A sketch or plan showing the electrical con- nections of the apparatus which comprises the ignition system. Worm gear. (See " Gear,") CHAPTER IV. HOW A GASOLINE ENGINE WOKKS. A gasoline engine is a machine in which the power of an explosive mixture of gasoline vapor and air is used to produce rotary motion of a shaft. From this shaft the power can be transmitted to the apparatus which is to do the useful work. Without taking info account engines of unusual design and those working on the turbine principle, still in the experimental stage of development, there are in use to-day a vast number of makes of gasoline engines, some differing so much in appear- ance and details that it seems quite impossible that all operate on the same general principle. But in practically all gasoline engines now manufactured the following series of operations takes place. Gasoline from the supply tank is carried by piping to a vaporizing apparatus, usually called a carburetor. Here the gasoline is converted into vapor and mixed with a proper proportion of air, forming the explosive mixture. A charge of this mixture is compressed in the engine cylinder by motion of the piston toward the cylinder head. When the piston is at or near the end of its compression stroke the charge is ignited and burns, the resulting pressure driving the piston away from the cylinder head, and by means of a connecting rod and crank causing rotary motion of the crank shaft and flywheel. The weight of the flywheel keeps the shaft in motion until another charge is compressed and exploded, thus causing continuous operation. Two distinct types of engines have been developed, both operating as explained above, but differing in the method used for introducing fresh charges of gas into the cylinder. These 76616 17 3 33 34 CAKE AND OPERATION OF GASOLINE ENGINES. two types of engines are designated as two-cycle and four-cycle, because in the former a complete series of events (technically called a cycle) necessary to produce one power stroke takes place during two strokes of the piston, while in the latter four strokes of the piston are required for each power stroke. From a mechanical standpoint the two-cycle engine is mucn less complicated than the four-cycle. From a theoretical point of view the four-cycle is somewhat the simpler, since in this type the gases, both before and after combustion, are handled only in the cylinder space, while the two-cycle principle necessi- tates the use of another closed space, usually the crank case on the opposite side of the piston. As regards the relative merits of two and four cycle engines, each has distinct advantages for certain classes of work, as will be made evident by a careful study of the characteristics of each type. TH1 TWO-CYCLE ENGINE. A two-cycle gasoline engine is one in which an explosion takes place in the cylinder every time the shaft makes one revolution. Figure 1 represents in section a single cylinder engine of the ordinary two-cycle type. When the engine is running the fol- lowing operations take place. As the crank rotates in the direction of the arrow the piston (A) approaches the head of the cylinder (B) and compresses an explosive charge of gaso- line vapor and air. At the extreme end of the stroke the charge is ignited by means of an electric spark inside the cylin- der. The charge burns almost instantly, as described in the first chapter, generating heat, and therefore pressure, which forces the piston away from the cylinder head and delivers power to the crank shaft (C). When the piston uncovers the opening in the cylinder wall (D), called the exhaust port, the burnt gases escape to the open air, usually being led through a sound muffler and piping to a convenient place for discharge; but while the piston is moving away from the cylinder head a FIGURE 1. Two-port, two-cycle engine. 36 CAKE AND OPERATION OF GASOLINE ENGINES. mixture of vapor and air in the crank case is being slightly compressed, this compression being much less than that which takes place within the cylinder. Just before the piston reaches the crank end of its stroke a second opening in the cylinder wall (E), the inlet port, in the opposite side of the cylinder from the exhaust port, is uncov- ered. The compressed mixture in the crank case expands through the passage (F) and strikes the projection (K) on the piston, which deflects the flow toward the cylinder head, filling the cylinder space with a fresh charge of mixture and expelling more of the burnt gases from the exhaust port. The heavy flywheel keeps the crank in motion and starts the piston again toward the cylinder head. When the inlet port is cov- ered by the piston a suction effect is created in the crank case by the receding piston, which draws more gasoline mixture from the carburetor (H). The check valve (J) remains closed while the gases in the crank case are compressed, but opens readily to admit new mixture. The piston is now approaching the cylinder head, compressing the fresh charge of gas under exactly the same conditions which existed before, and this same cycle of events continues to take place during every revolution of the shaft. This type of gasoline engine is undoubtedly the simplest ever devised. A modification, called the three-port, two-cycle engine, has proved to be very successful, however, and these engines are now manufactured in large numbers. THE THBEE-POBT, TWO-CTCLE ENGINE. This engine is very much like the ordinary two-cycle type, except that a third opening (the intake port) is provided in the cylinder wall, as shown in figure 2 (G). This port, it will be noted, is always kept closed by the piston except at the time when the piston is near the head end of its stroke. Hence the crank-case space is tightly closed as the piston recedes and FlQORB 2. Three-ptrt, two-cyeU jla. 37 38 GAEE AND OPERATION OF GASOLINE ENGINES. an increasing vacuum is created in the crank case, which causes a strong suction to draw in new mixture from the car- buretor when the port is uncovered by the piston. The check valve (J) figure 1, is eliminated in this style of engine, for the piston, during the crank-case compression stroke, covers the port leading to the carburetor and prevents escape of the mix- ture through this passage. In all other respects the three-port engine operates in exactly the same manner as the ordinary two-port engine. THE FOUB-CYCLE GASOLINE ENGINE. As before stated, the difference between the two-cycle and four-cycle types lies chiefly in the method of introducing the explosive mixture into the cylinder. We have learned that in the two-cycle engine the mixture is first drawn into a chamber other than the cylinder space and is forced therefrom into the cylinder. In the four-cycle engine the charge is first drawn directly into the cylinder as the piston moves toward the crank As it is impossible to be drawing in this fresh charge and at the same time have an ignited charge within the cylinder, twc complete revolutions, or four strokes of the piston, are neces- sary for each power stroke. Figure 3 represents in section a single cylinder four-cycle engine. Suppose this engine is in operation, the direction of rotation being that shown by the arrow, the cylinder space con- tains a fresh charge of mixture and the two valves ( I ) and ( E ) are closed. The piston approaching the cylinder head com- presses the charge. A spark ignites it at the proper time and drives the piston toward the crank shaft just as in a two-cycle engine. This motion of the piston is called the power stroke. When the piston reaches the crank end of its stroke, the ex- haust valve (E) is opened by a mechanism driven by the crank shaft, allowing the gases to escape from the cylinder as the CARE AND OPERATION OF GASOLINE ENGINES. 39 FIGURE 3. Four-cycle engine. 40 CARE AND OPERATION OF GASOLINE ENGINES. piston moves toward the cylinder head, or makes what is termed the " exhaust stroke." The exhaust valve (E) closes when the piston has reached the head end of its stroke, and as the piston again starts toward the crank shaft the inlet valve (I) opens, allowing fresh mix- ture of gasoline vapor and air to be drawn from the carburetor during this, the intake stroke of the piston. The valve (I) closes at the end of the stroke, and both valves remain closed as the piston again moves toward the cylinder head, com- pressing the confined mixture. This is called the compression stroke, and brings us again to the same set of conditions as that with which we started. The continuous operation of the engine is made possible only by the tendency .of the heavy fly- wheel, when set in motion, to continue to revolve, and carry the piston through the exhaust, intake, and compression strokes. This is true also, though to a lesser degree, in the case of the two-cycle engine, but it must be remembered that throughout this description of how these engines work an engine having but one cylinder has been considered in each instance. MULTIPLE-CYLINDER ENGINES. It is evident that if two two-cycle engines had their shafts coupled together, two power strokes would be obtained during each revolution of the shafts, and if the connection was so made that the cranks were opposite each other, one engine would be furnishing a power stroke while the other engine was com- pressing a new charge of mixture. A much lighter flywheel would therefore be required for a pair of engines coupled as above than would be necessary for a single engine, the delivery of power to the shaft would be much more uniform, and vibra- tion would be much less than that of a single engine of the same power. In practice, instead of coupling two or more engines together to gain these advantages, two or more cylinders are so ar- CAKE AND OPERATION OE GASOLINE ENGINES. 41 ranged that their pistons are connected to one crank shaft, this shaft usually having as many cranks as there are cylinders, where the number of cylinders does not exceed 6. With 8 or 12 cylinders there are often but half as many cranks as cylinders, pairs of cylinders being arranged in a V shape so that their pistons operate on one crank. No matter how many cylinders an engine has, the same series of events takes place in each cylinder as those described in the case of single-cylinder engines, although a single carburetor is often used to furnish mixture to all cylinders. COOLING AND LUBRICATION. Every gasoline engine, whether of the two-cycle or four- cycle type, must have proper provisions for cooling the cylin- ders and for lubrication of all working parts. The cooling system is required because, without it, the rapid succession of explosions within the cylinders would soon heat the walls to such a high temperature that lubrication would be impossible, and the pistons would tend to stick in the cylinders. Even though it were possible to accomplish lubrication at this high temperature, the heat would soon become so great that the material of which cylinders and pistons are made would be damaged, and the charge of mixture would be ignited before the proper time, causing what is termed " preignition." The lubricating (oiling) system is necessary to prevent exces- sive friction and wear on moving parts of the machine. In some respects the lubricating system is the most important part ^f an engine. Derangement of the gasoline or ignition systems may cause great annoyance and make an engine run badly or refuse to run at all, but such troubles seldom cause real damage, whereas failure of the lubricating system is almost sure to cause very serious damage, such as burned-out bearings or scored pistons and cylinders. CHAPTER V. DESCRIPTION OF THE YARIOUS PARTS AND SYSTEMS OF A GASOLINE ENGINE. We have now learned what operations must take place when a gasoline engine is running. The various parts and systems which are essential to make possible these operations will now be described. A complete practical gasoline engine may be considered as an assembly of the following parts and systems : (a) The main engine body, made up by cylinders, crank case or cylinder supports, pistons, connecting rods, crank shaft, fly- wheels, valves and valve-operating mechanism, bearings, and bed- plate. (5) The gasoline system, including storage tank, piping, car- buretor, and passages for conducting the mixture of air and vapor to the engine. (c) The ignition system, which includes the battery, dynamo, or magneto, supplying the electric current, induction coils, vibrators, timing devices, wiring, switches, and spark plugs. (d) The cooling system, embracing water jackets, piping, pumps, radiators, fans, air conduits, etc., as the case may be. (e) The lubricating system, consisting of oil reservoirs, grease cups, pumps, regulating devices, indicators, piping, and passages. Mufflers, governors, self-starters, and various other equipment not absolutely essential to make the engine run are quite neces- sary in some cases for convenience or to adapt the engine to certain uses. 42 CARE AND OPEEATION OF GASOLINE ENGINES. 43 THE MAIN BODY OF THE ENGINE. Cylinders are ordinarily made of cast iron on account of its cheapness, the comparative ease with which this material can be cast into intricate shapes and machined to accurate dimensions, and the fact that this material has properties which make it very efficient in resisting the wearing effect of the reciprocating piston. As the cylinders constitute the largest part of an engine their form and arrangement determines the general arrangement of the complete machine. Most engines now manufactured have vertical cylinders, the head, or closed end, being uppermost. This type occupies somewhat less floor space than is required for an engine of equal power having horizontal cylinders. But as floor space in some instances is not of primary importance many stationary engines are built with horizontal cylinders. The vertical arrangement of cylinders is especially adapted for marine and automobile use, as here only a restricted amount of space is available, and the low position of the crank shaft is required to allow direct connection to a propeller shaft or drive shaft. A few years ago, when the automobile industry was in its infancy, designers seemed to attempt to hide the pro- pelling apparatus beneath the seat or body of the vehicle. En- gines having horizontal cylinders were therefore used. Experi- ence, however, showed the desirability of setting aside a" special place for the engine where it would be readily accessible for inspection, cleaning, and repair. The location which best ful- fills these conditions is at the front of the vehicle, the engine being set with shaft lengthwise, and covered only by a light sheet-metal hood. This arrangement is now universally used. Recently several automobile manufacturers have brought out" machines with engines having 8 or 12 cylinders. If all these cylinders were arranged vertically in a single row, the complete engine would be so long that the body of the car would have to be very short, or the length of the car would be too great 44 CARE AND OPERATION OF GASOLINE ENGINES. for practical use in street traffic. Automobile engines having 8 or 12 cylinders are therefore arranged with two sets of 4 or 6 cylinders, these two sets being inclined at an angle of 45 from the vertical if the number of cylinders is 8, and 30 if there are 12 cylinders, and so arranged that the pistons of the forward cylinder of each set are both connected to the forward crank of the shaft, the pistons of the next two cylinders are connected with the second crank, and so on. Eight and twelve cylinder aeroplane engines usually have the cylinders arranged in this manner, though some makers place the two sets of cylinders horizontally. An engine thus arranged is said to have " opposed " cylinders. Four and six cylinder aeroplane engines are usually of the vertical type, this engine being much like that of a four or six cylinder automobile. In the design of cylinders a vast variety of arrangements of minor parts has been devised. In some cases the cylinder and cylinder head are cast together ; in others the heads are separate and held in place by bolts. The first arrangement eliminates the joint between the cylinder and head and reduces the number of separate parts, the second makes it much easier to open the cylinder, as by simply removing the head the interior of the cylinder and combustion space is exposed for inspection and cleaning. Some two-cycle engines have a single casting for the cylinder and crank case, removable plates being fitted to the crank case for access to the working parts and for installing the crank shaft. Other engines have the cylinders bolted to the crank case. The cylinder of a two-cycle engine must be carefully de- signed and accurately made as regards the location of the ex- haust and inlet ports, because the economical operation of the engine depends largely on the time and duration of inlet and exhaust. In a similar way the design of combustion chamber and valve arrangement of four-cycle engines is of extreme importance from the standpoint of economy. Four-cycle engines CAKE AND OPERATION OF GASOLINE ENGINES. 45 having inlet valve chamber on one side and exhaust valve cham- ber on the opposite side of the combustion chamber are called T head engines because of the likness of the shape of the cylinder casting to the letter T. Where both valves are on one side of the cylinder the engine is an L head, the casting having a general shape like an inverted L. A " valve-in-head " engine has its valves fitted directly in the cylinder head. In multiple-cylinder engines each cylinder may be a separate casting, or two or more cylinders may be cast together ; that is, 11 en bloc." This point is determined by practical considerations, such as the use for which the engine is built, the number of a single size to be manufactured, cost of construction, etc. As to the relative merits of these various arrangements, al- though manufacturers of certain types devote considerable space in catalogues and pamphlets to arguments "proving" their de- sign is superior to others, the fact remains that engines of almost every conceivable design have been successful. Proper propor- tion of parts, high quality of material, and good workmanship apparently have more to do with the ultimate success or failure of an engine than type and general arrangements. CRANK CASE. The ordinary type of two-cycle engine must have a separate air-tight crank case for each cylinder, because, as we have learned, these engines utilize the crank case as a sort of pump chamber for introducing the mixture into the cylinder. With engines working on the four-cycle principle there is no abso- lute necessity for any crank-case at all, many engines, especially in the larger sizes, being constructed with the cylinders mounted on columns, leaving the crank shaft, connecting rods, etc., en- tirely exposed. This arrangement is not practicable in small engines, and the usual practice is to inclose the crank shaft and bearings in a case common to all cylinders, which prevents 6 CARE AND OPERATION OP GASOLINE ENGINES. dirt from reaching the working surfaces and facilitates lubrica- tion. The upper part of this case is usually made of cast iron and provided with webs to support the crank-shaft bearings. The lower part may be of cast iron, pressed steel, or aluminum alloy, and is often arranged to form an oil reservoir. CRANK SHAFT. Crank shafts are made of forged steel. In high-grade en- gines and those built for service requiring a minimum weight of engine per horsepower developed, steel containing a small proportion of other elements, such as vanadium and nickel, which give the metal greater strength, is used. Shafts are made by forging the rough bar (or billet) into the approximate shape required in the finished shaft, then surplus metal is re- moved by machine tools and the bearing surfaces turned to ex- act dimensions. For high-class engines, after being finished in this manner, the shaft is given a heat treatment to improve the quality of the metal, then all bearing surfaces are carefully ground to a smooth, glassy finish. The crank shaft revolves in the main bearings. In large en- gines these bearings are carried by a foundation frame or bed- plate ; in small four-cycle engines, by webs of metal cast in the crank case ; in small two-cycle engines by plates on the sides of, or between, the separate crank cases. The position of the cranks with relation to each other in multiple-cylinder engines is so fixed that equal intervals will elapse between explosions in the various cylinders, insuring as nearly as possible a constant delivery of power. CONNECTING BODS. Connecting rods are usually made of forged steel, though cast bronze is sometimes used in small engines. The shape of cross CARE AND. OPERATION OF GASOLINE ENGINES. 47 section of the rod is often made similar to an I, H, or H-, as with the same weight of metal a rod having one of these shapes has greater strength to resist bending than would be obtained in a plain round one. The crank end of the rod is enlarged to form a bearing for connection to the crank pin. This bearing ordi- narily is in halves, one half being on the solid end of the con- necting rod, the other half being a cap held in place by the connecting-rod bolts. The other end of the rod is fitted with a bearing to allow it to swing on the wrist pin, or, in some en- gines, this pin is fastened solidly in the connecting rod and works in bearings in the walls of the piston. PISTONS. Pistons are made of cast iron or, for light high-speed engines, of aluminum alloy. As it is impossible to make a piston that will fit a cylinder closely enough to prevent leakage and at the same time not be so tight as to cause excessive friction between the surface of the piston and the cylinder wall, special provision is made to prevent leakage by turning recesses in the body of the piston and accurately fitting split metal rings of such shape and dimensions that elasticity causes them to press tightly against the cylinder wall. Two-cycle engines are often spoken of as being valveless. In a certain sense this statement is true, for no special parts are necessary to regulate the admission of mixture and the discharge of burnt gases from the cylinder, these operations being entirely controlled by the piston as it reciprocates. To properly regulate these events a two-cycle engine piston has a projection, as shown in figure 1 (K), to prevent the fresh charge passing directly across the cylinder and escaping through the exhaust passage. In some three-port engines an opening is provided in the side of the piston for the admission of mixture from the, carbureter to the crank case. 48 CARE AND OPERATION OF GASOLINE ENGINES. TAT.TTS. With four-cycle engines, admission and exhaust valves before referred to (fig. 3) (I and E) are installed. These valves are almost invariably operated by cams on a shaft which is geared to the crank shaft in such a manner that it makes one revolu- tion while the crank shaft makes two. On account of this fact cam shafts are sometimes called " half-time shafts." f ,...-, .. CAW SHAFTS. The location and arrangement of cam shafts and their driving gear varies greatly in different makes of engines. With T-head, multiple-cylinder, four-cycle engines, all cylinders have exhaust valves on one side and inlet valves on the other side. These engines often have two cam shafts, one carrying the cams that operate the exhaust valves, the other for the inlet- valve cams. Some T-head engines, however, have a single cam shaft located over the cylinder heads, from which all the valves are operated by levers. When two cam shafts are used, and in L-head engines, which have but one cam shaft, a loca- tion as shown in figure 3 is usually chosen, though in some ngines outside of the crank case. In large engines the cams are separate steel forgings fastened in their proper places on a plain shaft; in the smaller engines the cams and shaft are usually one solid forging. While it is cheaper to make the cams and shaft separate, and assemble the parts to form the complete cam shaft, there is always danger with a small shaft built up in this way that the fastenings will work loose and allow the cams to slip out of position and oper- ate the valves at other than the proper time. In fact great care has to be exercised in making cam shafts, for accuracy with which the valves of a four-cycle engine open and close at the proper times Is absolutely necessary for smooth running. CARE AND OPERATION OF GASOLINE ENGINES. 49 FLYWHEELS. Flywheels are made of cast iron because this metal is heavy, cheap, and easily cast and machined. Aside from its purpose of keeping the engine in motion during intervals when power is not being delivered by the explosions, the flywheel exercises a steady- ing effect on the machine by its tendency to eliminate sudden changes in the speed of rotation of the shaft. One-cylinder stationary engines often have two flywheels of comparatively large diameter, for in this case there is no objection to the con- siderable weight, and full advantage can be taken of the steady- ing effect. With a two-cylinder engine, the flywheel may be much lighter than that required for a single-cylinder engine of the same type and power. This is true to a greater degree with engines having more than two cylinders, until with 8 or 12 cylinders the necessity for a flywheel is almost eliminated, power being delivered by one or more of the several pistons at all times. This is one of the advantages of multiple-cylinder engines, especially where a light-weight engine is required, as in ^ > 3 250 S< 3 -3 b^^ ; 3