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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w familiar to every engineeraccustomed to the management of electric lighting ma-chinery, that engines having regulators of the class to whichthat under consideration belongs are capable of giving agood regulation, even when directly connected to the dy-namo, is sufficient proof that such a system of regulationmay be able to do perfectly satisfactory work. The fric-tional resistance of the system, while in motion, is not amatter of importance; as in any system in movement, andsubject to jar, the friction is practically eliminated andevery part assumes the position that it would take in a sim-ilar system free from friction. The action of the resistancecf the valve, so far as it is transmitted to the regulator,probably acts to hold the regulator fast during the periodof its action, leaving it free to move into any new position,corresponding to the speed of the engine at the instant,without hindrance during the remainder of the time. All of these fast-running engines will be seen to have
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ELECTRIC LIGHTING PLANTS. 81 shorter strokes of piston than is customary with the earliertypes. One reason which has guided their designers to thisproportion is that the loss by internal condensation becomesless as the steam is given less time to discharge its heat, andhence high-speed of rotation and short strokes are adopted.The best proportion of stroke to diameter of piston, thenumber of revolutions in the unit of time being fixed, is easilyascertained by a very simple investigation. It is found tobe two to one. This is about the proportion generallyadopted in these engines. Many engines are, however, givena ratio of i 1-2 to i. The shorter stroke has the great ad-ditional advantage, the speed of piston being the same, ofgiving a less costly engine to build. The proportion issometimes dictated partly by the character of the work tobe done; thus, in driving the dynamo directly, the velocityof rotation must be very great and a short stroke becomesadvisable—the shorter as the speed

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