Engineering Wonders of the World
Volume I

216 ENGINEERING WONDERS OF THE WORLD. The Internal Combustion Engine. Early Gas Engines. air into the Fig. 2. — DIAGRAM TO SHOW THE FOUR STROKES THAT THE PISTON OF A GAS ENGINE MAKES DURING ONE “ OTTO ” CYCLE. about ten per cent, in the best engines—the rest being wasted in the hot gases which escape up the chimney, passing off in the exhaust steam, and escaping through the metal of the pipes and cylinder. By careful “ jacketing ” the last loss may be minimized, while the prin- ciple of allowing the steam to expand in a series of cylinders of increasing bore also economizes heat. But in spite of all pre- caution and invention, the steam engine re- mains inefficient as regards the ratio of its output of energy to the fuel consumed. The gas or internal combustion engine has many features in common with the steam engine, the distinguishing difference being that the former makes the cylinder do the work of boiler and fur- nace in addition to that of extracting the power from an expanding gas. The chemical union of carbon and oxygen occurs inside the cylinder of a gas engine, and is so sudden that it has the nature of an explosion. There is no clear evidence as to who first thought of using the explosive force of gas to drive a piston. The very early gas engines of thirty-five years ago were crude affairs. Their action was as follows :—The piston, dragged forward by the momentum of the fly-wheel, sucked gas and cylinder. When it had travelled part of this stroke, the mixture was ignited by being momentarily exposed, by the opening of a port, to a flame outside the cylinder. The expansion of the burning charge produced pressure, and drove the piston to the end of its stroke. During the return stroke the burnt gases were expelled by the piston. This method gave one power stroke for every revolution of the fly-wheel; but the action was irregular, and the results obtained were poor. Yet this type of engine proved a cheap motor where small power only was required, chiefly because it saved the wages that the user of a steam engine had to pay a stoker. A critical period in the history of the gas engine was reached when a French engineer, M. Beau de Rochas, rediscovered the fact that, if gas and air be compressed before ignition, the pressure of the burning mixture is greater, and consequently the work done by a given quantity of gas is much increased. He made no practical use of his “ find,” but a German named Otto did. Hence it is that the Rochas “ cycle,” or series of happenings, Beau de Rochas.