Man's physical universe



other machines, it is important that everyone understands the principles

of their operation.

The Automobile Is a Combination of Simple Machines.

The parts and method of operation of the gasoline engine are quite

simple in their elementary form. Let us start with the cylinder. It is

merely a tube closed at one end, about the same size and proportions

as a tall coffee can. A piece of pipe with one end closed would also

make a cylinder. Many engines

used in early automobiles actually

had cylinders made from

cast-iron pipe.

Inside this cylinder a closely

fitting piston slides up and

down. This combination gives

Fig. 110. Fig. 111.

us a pump similar to the familiar

tire pump. Each time the piston moves up and down, air is

pumped. An automobile engine pumps from twenty-five to fifty

gallons of air mixed with from 0.4 to one pint of gasoline for each

mile it travels. The figures depend upon the size of the engine.

This up-and-down movement must be converted into rotary movement

to propel the car. The crankshaft and connecting rod of the

engine do this. A crankshaft is familiar in the form of the crank for

a kitchen meat grinder, emery wheel, or foot pedal of a bicycle. The

hand crank is the crankshaft; your arm or leg, as the case may be, is

the connecting rod. x^t the maximum speed of the car the crankshaft

may be revolving over 4500 times a minute. Each time the crankshaft

Fig. 112. Fig. 113. Fig. 114.

When we

makes one revolution, the car moves ahead about half a yard.

build engines with more than one cylinder, the crankshaft has a number

of cranks.

On the end of the crankshaft, a heavy wheel called a flywheel is

mounted. If we turn the emery wheel by hand very rapidly and then

let go, the wheel will continue to revolve. This is similar to the flywheel.

It keeps the engine turning between power impulses.

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