Identifier: stationarysteame00thur (find matches)
Title: Stationary steam engines, simple and compound; especially as adapted to electric lighting purposes
Year: 1890 (1890s)
Authors: Thurston, Robert Henry, 1839-1903
Subjects: Steam-engines
Publisher: New York, J. Wiley & sons
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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ed to driving either large or small electric lightingplants; and, if purchased of a reliable maker, may be con-fidently expected to give satisfaction. THE GREENE ENGINE. AT EARLY all drop cut-off engines are constructed,•^ ^ like those described in the preceding article,with a single eccentric, which drives both the steamand the exhaust valves. Both sets of valves must, therefore,have the same motion relatively to the piston, except so faras their motion can be modified, as in the Corliss engine, bythe method of connection of valve and eccentric. Theymust stop and start at the same instant, and their motionduring their travel must be more or less similar. But sucha system is controlled in its action by the necessary motionof the exhaust valve. That valve must be adjusted toopen and to close very nearly at the beginning andthe end of the return stroke, in order that the exhaustmay be prompt and free, and that the compression shallbe right. The movement of the gear, on the steam side,
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ELECTRIC LIGHTING PLANTS. 39 must thus be also one which shall open the valveto take steam at the commencement of the steam stroke,and, if the valve is not tripped, close the port at the endof that stroke. It is further evident, that if the valve is tobe detached by its own motion, it can only be tripped dur-ing the forward part of its movement, and that, passing thatstage, and commencing to return before the cut-off takesplace, the valve must be allowed to remain undetacheduntil the end of stroke, and steam must follow full stroke.An engine thus constructed, and so adjusted to its work asto cut-off at about half stroke, will evidently, if the work orthe steam pressure becomes variable, be likely to operatevery irregularly, at one time cutting off at a little insidehalf stroke, and then jumping to full stroke. This varia-tion of steam distribution may thus itself introduce a dis-turbing element, and the engine may give a very unsatisfac-tory performance. Such an adjustment of power of

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