tems, one of which was used on Pierce-Arrow cars, is shown at Fig. 282. It will be observed that an air pump of the four-cylinder type was attached to the gear box and driven from the counter shaft of that member. This supplied air to an air reservoir or container attached to the chassis. This container communicated with the top of an air distributor when a suitable control valve was open. An air pressure gauge is provided to enable one to ascertain the air pressure available. The top of each cylinder is provided with a check valve, through which air can flow only in one direction, i.e., from the tank to the interior of the cylinder. Under explosive pressure these check valves close. The function of

Fig. 283.-Some Important Components of Early Chalmers Air Starting

System.

the distributor is practically the same as that of an ignition timer, its purpose being to distribute the air to the cylinders of the engine only in the proper firing order. All the while that the engine is running and the car is in motion the air pump is functioning unless thrown out of action by an easily manipulated clutch control lever. When it is desired to start the car a starting valve is opened which permits the air to flow to the top of the distributor, and then through a pipe to the check valve on top of the cylinder about to explode. As the air is going through under considerable pressure it will move the piston down just as the explosion would, and start the engine rotating. The inside of the distributor rotates and directs a charge of air to the cylinder next to fire. In this way the engine is given a number of revolutions, and finally a charge of gas will be ignited and the engine start off on its cycle of operation. One of the advantages of the air starter system is that a source of air is provided for blowing up tires.

The general arrangement of the Chalmers air starter was practically the same as that depicted. Some of the components were of different construction. Instead of being driven by enclosed. gearing the air pump was operated through a silent chain from the pump shaft, as shown in the upper left hand corner, Fig. 283. In this air pump the cylinders were water jacketed in order to prevent overheating. The construction of the dash push valve is clearly shown at C. This member not only serves to admit air to the center of the distributor, but also opens the cylinder starting valves to permit the air to flow into the cylinder. The starting valve construction is clearly shown at E, this consisting of a simple fitting adapted to be screwed into the cylinders and communicating with the interior of the combustion chamber. The bell crank X was used to depress the valve stem Y, and thus provide communication between the air distributor and the combustion chamber interior. As the distributor was one of the important parts of all air-starting systems, that used on the Chalmers car when equipped with the air starter is shown at Fig. 284. By referring to the sectional view at the right of the illustration it will be apparent that its function is practically the same as that of a

primary timer or secondary distributor of a magneto, except that instead of distributing electrical energy a blast of air was directed to the cylinders in the proper firing order. The rotating distributor disc is provided with one slot which registers consecutively with the openings to which the pipes running to the various cylinders were fastened. About the only trouble with an air-starting system was faulty check valve action or leaks in the pipe line or distributor which permitted the escape of air. If no air pressure was supplied to the tank the pump was at fault. This may be easily determined on inspection; the same troubles should be looked for as described for the air pressure pump sometimes used in connection with the pressure system of fuel supply./

Fig. 284.-Showing Construction of Distributing Mechanism Employed with Air Starting System.

Pres-to-lite Primer.-Where a car is equipped with a Presto-lite gas tank it is possible to secure easy starting by hand cranking, and even to run the engine on acetylene gas in an emergency if the gasoline supply fails by using a simple priming fitting shown at Fig. 285. The outfit consists of an automatic reducing valve attached to the gas tank, a pipe line running to the dash, and a push valve so mounted that acetylene gas may be admitted into

the inlet manifold through a pipe running from the push valve to the intake member. As shown at A, a simple lever is rigged up so the push button may be operated from the front of the car. At B the push button is worked by the foot. The arrangement of the parts is clearly shown in the view at the bottom of the illustration. It is said that a properly charged gas tank will run a 25 H. P. motor from ten to twelve miles if the gasoline supply should fail. The reason the acetylene gas provides easy starting is that it is very inflammable and does not need to be vaporized as the liquid fuel does. The gas primer is of special value when used in connection with mechanical starters of various kinds. Before depressing the push button it is necessary to open the main shut-off valve incorporated with the push button assembly on the dash. This permits the gas to flow from the automatic pressure regulator to the body of the device where the push button valve provides access with the pipe running to the intake manifold. Obviously this priming system can be used only with cars equipped with a gas tank. On the modern electrically lighted and started cars the gas tank will be unnecessary, and is not apt to be used. However, the gas tank would probably be applied for lighting purposes on cars equipped with air starters, and on these models. it would be of particular advantage inasmuch as the tendency of the air current passing to the cylinders is to retard prompt vaporization of the fuel sucked in from the carburetor, the rich acetylene gas would provide a rich mixture, and would enable the engine to run for a long enough period to permit the explosion to heat up the cylinders enough so the gasoline would vaporize promptly.

Electric Starter Forms.-Electric lighting, cranking and ignition systems for motor cars are of such recent development that it is not possible to describe all systems used for this purpose. Not only do the individual systems vary in detail, but the components of the same system are often of different construction when used on cars of different makes. The standard equipment must include three component parts, namely, the generator which is driven by the engine and which produces electric current to keep the storage battery charged, and the starting motor which is in

Fig. 285.-Showing Method of Utilizing Pres-to-lite Gas Tank to Facilitate Starting the Automobile Power Plant.

mechanical connection with the engine and in electrical connection with the storage battery when it is desired to turn the engine over for starting. If the motor and generator are combined in one instrument the starting system is known as a one unit type. If the motor is one appliance and the generator another, the system is said to be a two unit system. Each of these has advantages, and both forms have demonstrated that they are thoroughly prac