. Farm machinery and farm motors. EccenrriG FIG. 249 haust. Fig. 249 shows the valve when at its end of thestroke, showing that the exhaust port is completelyopened, but that the inlet is not necessarily so. Fig. 250represents the position of the valve when the piston isat the opposite end of the stroke. It will be noticed that. or CranK FIG. 250 the lead in this case is the same as that in Fig. 248. Thisshould be true in all engines. A lead of 1/32 inch is about proper for most much lead in a valve allows steam to enter the cylin-der so soon that the piston has to complete its str
. Farm machinery and farm motors. EccenrriG FIG. 249 haust. Fig. 249 shows the valve when at its end of thestroke, showing that the exhaust port is completelyopened, but that the inlet is not necessarily so. Fig. 250represents the position of the valve when the piston isat the opposite end of the stroke. It will be noticed that. or CranK FIG. 250 the lead in this case is the same as that in Fig. 248. Thisshould be true in all engines. A lead of 1/32 inch is about proper for most much lead in a valve allows steam to enter the cylin-der so soon that the piston has to complete its strokeagainst boiler pressure, hence a loss of energy. Also 372 FARM MOTORS where there is too much lead the exhaust port is likely toopen so soon that the steam is released before it expandsas much as possible. Again, if it has not sufficient leadthere will be no cushioning efifect, and in addition suffi-cient steam will not have entered the cylinder by the||time the piston starts on the return stroke to produce themaximum pressure. 516. Eccentric.—The eccentric is a mechanism often!used where it is impossible to use a crank. The eccentricof a steam engine consists of a disk or sheave fastened tothe crank shaft in such a manner that it is eccentric orjout of center with the center of the shaft. Around thissheave is the e
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