Part 42

~WHAT CAUSES THE EXPLOSION IN A GAS ENGINE~

Fig. 3 shows the explosion. The cylinder has been filled with compressed gas, and the piston has again started on its downward travel. The spark plug, set in the top of the cylinder, makes a spark every time an electrical current passes through it. A switch on the engine permits the current to pass to the spark plug only when the engine is at this position in its action. (Fig. 3.) The consequent explosion drives the piston downward with great force, turning the fly-wheel, which by its weight continues the rotary motion after the downward impulse of the piston has been expended.

Fig. 4 shows the fly-wheel, still turning, forcing the piston up and thus expelling the burned gases from the cylinder through the exhaust valve, held open for this purpose. From this position the engine goes again to that of Fig. 1, and through 2, 3, and 4, continuously, exploding every second revolution, and giving a regular rotary motion to the fly-wheel.

The illustrations show a one-cylinder motor, but these engines can be built with two or more cylinders, arranged to explode at different times, thus giving very smooth action to the fly-wheel and main shaft.

Aeroplanes, almost all automobiles, various pumps and other machinery are driven by gasoline engines. The rotary motion can readily be transmitted by chains or gears to the propellor of an aeroplane or motor boat, or the wheels of an automobile. It is only in the past few years that the gasoline engine has reached its present high state of perfection.

CRANKCASE SHOWING BEARINGS.

The heart of the automobile is the engine. It is built around the crankcase, which is its foundation or base.]

The crankshaft serves the same purpose in an automobile as the pedals do on a bicycle.

The fly-wheel on the end helps it to keep turning at an even speed.]

The piston and the rod that connect it to the crankshaft are just like the feet and limbs of any one riding a bicycle.

Cylinders showing piston in place and connected to crankshaft.]

Cylinder added to crankcase.

The cylinders are next bolted down to the crankcase, the pistons and crankshaft having been connected, as shown in Fig. 3. A cover is placed over the gears to keep them clean.]

After the gasoline has been exploded a valve opens and allows the burned gases to escape through another pipe, called the exhaust manifold.]

Oil pump and filler added to motor.]

The electric generator makes electricity to be used for starting the engine and lighting the car.]

The water pump keeps water flowing around the cylinders to prevent them from getting too hot. This water comes back to the pump through the radiator at the front of the car. Wind blows through the radiator and cools off the water. The tire pump on up-to-date cars is run by the engine. It does not pump except when the gears, which are shown in the picture, are pulled together.]

The transmission is added.

The transmission makes it possible to reverse the car. It also enables the driver to go into high-speed gear when on level roads and low-speed gear for starting and for pulling hills.]

The frame on which the car is built.]

Large springs are placed at the front and rear of the frame. They make the car ride smoothly.]

Showing addition of full-floating rear axle.]

Wheels are next added to chassis.]

The water which keeps the engine from getting too hot is pumped around the cylinders and then through the radiator. The wind blows through the little openings in the radiator, and cools off the water. Then the water is pumped around the cylinders again.]

The finished car.]

The first American-built automobile, now in Smithsonian Institute, Washington, D. C., where this photograph was taken. The rude carriage that was a curiosity twenty years ago and less--the vehicle that vied with the two-headed calf and the wild man of Borneo at the county fairs--was the beginning of the greatest transportation aid since the birth of civilization. Because of it our standards of living have become higher. It has broadened the horizon of all of us.

Built by Elwood Haynes, in Kokomo, Indiana, 1893-1894. Equipped with one-horse-power engine. Successful trial trip made at speed of six or seven miles an hour, July 4, 1894. Gift of Elwood Haynes, 1910. 262,135.]

LEFT SIDE VIEW