A boy's text book on gas engines

by Fay Leone Faurote

Let us work the cannon the same way. Let us call the farthest point to which the bullet travels going in “H” and the farthest point to which it travels going out “K.” Now let us assume that the bullet is at “H,” and that it is just starting out in the direction of “K.” If we open the hole “I” in the side of the cannon by taking out the plug “L,” and put a hose, connected with our gas tank, in there, then the outward motion of the bullet “P” will pull the cannon full of gas, won’t it? Before the gas has a chance to escape we will put in the plug “L” again. Now we have the cylinder full of gas, but as the bullet is at the end of its stroke, and cannot go any further, we will have to push the gas together again and get the bullet into position “H.” This will be a good thing for the gas, because it will crowd the particles of it closer together, and make it explode quicker, so we will do this. Of course, in order to keep the gas in there we have had to close up the touch-hole of the cannon, but now that we are ready to fire it, we will take this plug out, and touch a match to the gas. An explosion follows, and the bullet travels from the position “H” to the position “K.” All this time the crank of the grindstone must have been turning because the bullet and the crank are fastened together, and therefore, instead of traveling through the air, the bullet has used up its energy in turning the grindstone. When you get a grindstone started it is rather hard to stop, isn’t it? And if you didn’t stop it, it would keep on turning around, wouldn’t it? If this is true, we might as well let it clean the cannon. As the hole “I” is connected with the gas tank, we cannot let it force the burnt gas out there, can we? We will therefore pull out the plug “J” in the hole “E” just as the bullet reaches the point “K” so that in coming back it will force the burnt gases and smoke out through the hole “E.” Now we are all ready to start over again; the cannon has been cleaned out, and the bullet still being fastened to the grindstone, which is turning, as a result of the explosion, would immediately begin starting out on another outward stroke. If we put in the plug “J” again and pull out the plug “L,” the bullet or piston as we might call it now, will suck in another charge of gas.

Fig. 7—Grinding a valve.

Fig. 8—A section of a Cylinder showing location of various parts—end view.

You can see that if you had two boys, one of them to pull out the plugs, and another to fire the charge you could keep the gun firing steadily, and run the grindstone. After you have done this for a while you will get tired of taking out the plugs and putting them in, and standing there with a match lit all the time, and you would wish there was some way to make the grindstone, which was running, do all this for you. This is exactly what happened to some of the old engineers, and so they set about trying to accomplish this result. They succeeded in rigging a piece of machinery that would open and close these holes automatically, and with the introduction of electricity they also devised a way whereby the charge could be ignited by an electric spark instead of a match. The plugs which cover the holes, they called valves and the plug which contained the electric wires, used for firing the gas, they called a spark plug.

Now let us see what we have learned in this chapter. We have found that it takes four strokes to explode one charge of gas

1. Suction stroke, during which the gas is sucked into the barrel of the cannon, or cylinder as it is called.

2. The compression stroke, during which the gas is compressed so that it will burn easier.

3. The explosive stroke, or working stroke, called so on account of the fact that the explosive force of the gas is used to turn the wheel.