Bulletin . liisexpansion stroke the exhaust \al\e is open, and the gasesbegin to rush out. The piston then returns, expelling therest of the burnt gases or nearl\- all of them through yalxe which is open : ot course some burnt gases must be left behind, as much as can till the explosionchamber. This is the succession of processes occupyingfour strokes, given the name four-cycle engine. In structural detail some of the mechanism is shown inFigure i for one of these four-cycle engines. Here itappears that the piston has webs under its head to strengthenit. It has rings around part o
Bulletin . liisexpansion stroke the exhaust \al\e is open, and the gasesbegin to rush out. The piston then returns, expelling therest of the burnt gases or nearl\- all of them through yalxe which is open : ot course some burnt gases must be left behind, as much as can till the explosionchamber. This is the succession of processes occupyingfour strokes, given the name four-cycle engine. In structural detail some of the mechanism is shown inFigure i for one of these four-cycle engines. Here itappears that the piston has webs under its head to strengthenit. It has rings around part of it, so formed as to preventthe high pressure gases leaking out. There is water allaround the cylinder and around the valve chambers. Thevalves are shown with springs to close them and to keepthem closed all the time that some other piece of mechanismis not holding them open, and between the valves is shownthe igniter at F, which is nothing more than a device formaking an electric spark at the proper Fig I RE 2. A small \ertical engine is sliDwn in Figure 2 in which tlietwo valves are one above the other, the upper one beingfor inlet, and the lower one for exhaust, both providedwith springs to keep them closed, but the bottom one hav-ing in line with its stem a push rod against which a cammay act, the cam being only a lump on the small auxiliaryhalf speed shaft. When the cam does strike the push rodit will rise and the valve will open. Both valves mightbe so operated, and in most large engines are operated bysuch cams, but in some small engines, such as this, tosimplify the engine the inlet valve has no cam to operate it. It is just held to its seat by a light spring. When thepressure in the cylinder due to the suction stroke ot thepiston, becomes less than atmosphere or less than inthe mixture chamber that difference in pressure on thetwo sides of the valve forces the valve open against thespring. At the end of the suction stroke the differencein pressure is relieved;
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Keywords: ., bookcentury1, massachusettsinstituteoftechnology, verticalengine
