[Illustration: FIG. 1.]
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 of itself. Its fly-wheel 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 fly-wheel 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 fly-wheel 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.
~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.
[Illustration: FIG. 2.]
[Illustration: FIG. 3.]
[Illustration: FIG. 4.]
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.
[Illustration: THE BEGINNING OF AN AUTOMOBILE