Man's physical universe


THE INTERNAL-COMBUSTION ENGINE 329 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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