UNIT V SECTION 5 THE INTERNAL-COMBUSTION ENGINE IS ONE OF THE GREATEST DEVELOPMENTS OF MODERN CIVILIZATION ' Introduction. The greatest thing civilization has had thus far is the internal combustion engine. For the first time in the history of the world mankind has had a small, mobile, inanimate power device. The greatest factor that has caused the development of all our civilizing devices has been the use of inanimate pxjwer. The internal combustion engine has absolutely changed our whole method of living. The city has developed because of its wonderful system of electrical distribution. Back of this is a great power unit. If the power unit stops, the lights go out and the motors stop. But with the internal combustion engine we carry with us the power-house. We move it wherever we please. — C. F. Kettering. The automobile is one of the commonest pieces of machinery in everyday use ; more than thirty million are in daily use upon our roads. It has become so necessary in our modern life that it has been called the "fourth necessity," giving way only to food, clothing, and shelter. The internal-combustion engine, exemplified by the ordinary automobile engine, is more efficient than the combination of a steam engine and boiler. In this case the boiler is not necessary, because the combustion of the powdered coal, fuel oil, kerosene, gasoline, natural gas, or other fuel takes place within the cylinder of the engine itself and thus eliminates the heat losses of the boiler. The internal-combustion engine is much lighter in weight than the steam engine-boiler combination in comparison with the power developed. Internal-combustion engines also possess the advantage of compactness, ease, and quickness of starting and stopping, along with ease of attachment to machines to be operated. Since internal-combustion engines are used widely by nearly everybody in the form of automobiles, tractors, airplanes, motor boats, power and light plants, graders, motorcycles, pumps, and scores of * Most of the material in this Section has been selected from the booklets, When the Wheels Revolve and Diesel, the Modern Power, through the courtesy of the General Motors Corporation. 328
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.