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Show Gas Engine Works With Simplicity MOST users of the internal combustion engine en-gine have a good Idea of how It works. Among those who have not are doubtless a good many who arc repelled from a study of it by the idea that It Is extremely complex. It is not. The Scientific American gives a very clear and simple explanation of the working of the "four cycle" engine generally used in automobiles, from which the following description is condensed The power furnished by such an engine comes from expansion by explosion of a mixture of air and gas. If. however, tbtp mixture be under merely normal pressure, the expansion is but slight. It is therefore necessary to compress the mixture before firing, to a pressure several times greater than that of the air. I 71 I I I 1 I h 1 I " c S3 'Sa The figures show cylinder and explosion of com-bUBtlon com-bUBtlon chamber to the left, with the piston which operates the crank shaft and also the two valves In the combustion chamber which are operated by the cam shaft. The -valve on the left Is the Intake valve, where the explosive mixture of gas and air is admitted, and the other ahe ts tho exhaust -valve, through which, after the explosion, the dead products of combustion are released. The cam shaft Is so geared to the crank shaft (by machinery not showing) as to make the valves operate at Just the proper moments. On top of the combustion chamber is seen the spark plug. L shows tho piston at the top of the cylinder with the combustion chamber entirely closed and the explosive mixture under pressure, as indicated by the converging arrows. II. shows the firing of the spark, which Ignites the mixture. Its expansion starts the cylinder downward, as indicated by tho arrow. The di verging arrows in the combustion chamber Indicate In-dicate that the pressure is outward in all dlrec lions, but the valves are closed and only the piston can move, III shows the piston nearly all the way down and, the exhaust vi lve being slightly opened, the pressure still left in the spent and exploded mixture is sending it out. IV. shows the exhaust valve wider open and the spent products of combustion, in other words, the burnt mixture, still going out. V. shows the exhaust valve entirely open and tho piston, which Is now rising through the momentum imparted to the crank shafts is pushing out the remainder of the burnt mixture The momentum which moves the shart Is due either to a flywheel o : upon It or to other cylinders attached to it or to both of these agencies. VI. shows the piston about to begin the down stroke with the chamber closed. VII. shows the opening of the intake valve to admit tho explosive mixture, which Is being sucke-" in by the downward movement of the piston. VIII. and IX. show the continuation of this op eratlon with the piston in IX. at Its lowest point. X shows the chamber closed and the piston, still moved by the momentum of the crank shaft, beginning to rise and compress the mixture. XI shows the continuation of this operation. XII. shows tho piston at the top of its stroke with tho new unexploded mixture ready for the spark, as In I That, so far as the principle is concerned, is all there is to it, for each of the four or more rvlinders that may constitute the engine. The Scientific American's article also contains some interesting in-teresting explanations of the economy and percentage per-centage of effectiveness of the machine. The description de-scription is for what is called the "four cycle" en gine, that Is. one in which there are four distinct operations, the four strokes or the piston (two up and two down), for each explosion. In tho "two cvcle" engine the burnt mixture Is allowed to escape by Its own pressure a little before be-fore the piston reaches its lowe-st point. Then the valve or port is closed and the completion of the downward stroke sucks in the new mixture through another port, which is opened at just the proper time When the piston rises (the ports l.eing closed) it compresses this fresh mixture, and when at. the top of the stroke the spark causes it to Ignite and expand. Thus there is an explosion at the end of two strokes (one down and one up) of the piston. This may look like a wastful way to use the mixture and It actually is. yet the difference is so slight that the 'two cycle" engine Ls still very popular because of Its simplicity and numerous other advantages. It Is most used In a. single cylinder engine for small boats. f : 0 r W. JSnJL cC. Z2Pj ZC IT j3 M.Jj ' IFtodi Sucnuflc Auiclvau 1 |