11801 52nd Dr. N.E, Marysville, Washington 98271-6225 sent us this excerpt from the 1915 edition of The Book of Wonders.
As you know, gasoline is a very inflammable fluid, and will explode if placed too close to fire.
This explosive quality is the basic principle of the gasoline engine. By admitting a small quantity of gasoline vapor into an enclosed cylinder, and exploding it by means of an electric spark, repeating this operation continuously, the engine is given a regular rotary motion.
Look at Fig. 1. Starting from the gasoline tank, the fluid is fed into the carburetor, which is a sort of atomizer. Here the gasoline is mixed with air, and broken up into a very fine spray, in which condition it will explode readily.
The engine will not start itself. Its flywheel must first be turned by hand, or by some other outside force, until the first explosion takes place. After this its action is automatic.
As shown in Fig. 1, the flywheel is being turned, and is drawing the piston down the cylinder, which in turn sucks gasoline vapor, (shown by little arrows) through the 'intake valve.' This 'intake valve,' and the 'exhaust valve' on the opposite side of the cylinder, are opened and closed at the proper time through the action of the gears shown in the illustration.
Passing to Fig. 2, the flywheel in turning has drawn the piston to its lowest point, and is now shown forcing it up the cylinder. This compresses the gasoline vapor in the cylinder to a density at which its explosion produces the greatest amount of power. The intake and exhaust valves are both closed.
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 flywheel, which by its weight continues the rotary motion after the downward impulse of the piston has been expended.
Fig. 4 shows the flywheel, 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 flywheel.
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 flywheel and main shaft.
Aero planes, 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 propeller of an aero plane 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.