. Farm machinery and farm motors. p one, since the valve cannotmove quickly enough to cut off steam instantaneously, but commencesto cut ofT at C, and complete cut-off takes place at C. This fall inpressure after the valve commences to cut off and before it com-pletely cuts off is known as wire drawing. Often the exhaust valvedoes not open soon enough for the pressure to fall to the backpressure line before the piston starts in the return stroke; hence theline DE of Fig. 264 is more like the line DE of Fig. 265. 530. Attaching indicator to engine.—Where indicator diagramsare to be taken from e
. Farm machinery and farm motors. p one, since the valve cannotmove quickly enough to cut off steam instantaneously, but commencesto cut ofT at C, and complete cut-off takes place at C. This fall inpressure after the valve commences to cut off and before it com-pletely cuts off is known as wire drawing. Often the exhaust valvedoes not open soon enough for the pressure to fall to the backpressure line before the piston starts in the return stroke; hence theline DE of Fig. 264 is more like the line DE of Fig. 265. 530. Attaching indicator to engine.—Where indicator diagramsare to be taken from engines of 100 or more it is betterto have two indicators, one for each end of the cylinder; but forengines of a capacity such as are used on the farm or in cream-eries one indicator connected to both ends of the cylinder by meansof a three-way cock is fully as accurate as two. If there are noholes for attaching the indicator when the engine comes from thefactory, drill into each clearance space A A (Fig. 266) of the cylin-. FIG. 266—ATTACHING AN INDICATOR TO AN ENGINE der a hole of sufficient size to thread for ^-inch or /-inch pipe, andby means of pipe fittings connect up to the three-way cock B. Theconnection on the indicator will screw into the cock at C. Since 384 FARM MOTORS the throw of the indicator drum is only aliout ^Vz inches and thestroke of the piston is 8 to 20 inches, the length of stroke of thepiston has to be reduced to that of the indicator. There are severalmechanisms for this purpose, some of which come with the indi-cator (Fig. 267). If a reducing motion has to be devised, probablythat shown in Fig. 268 is the most simple.
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