. The steam-engine and other heat-motors. ngine it is the atmospheric pressure. Compressing the steam toboiler pressure is in effect avoiding the complication of consider-ing clearance. Note further that the pressure during admissionis the boiler pressure and hence the efficiency of the pipe line isincluded n the diagram factor. If the line loss is very great thesteam pressure at the throttle may be used, but that fact shouldbe specially noted. Hence in choosing a diagram factor or infinding it practically for a definite case, it is essential that theseelements be properly applied. CHAPTER IV.
. The steam-engine and other heat-motors. ngine it is the atmospheric pressure. Compressing the steam toboiler pressure is in effect avoiding the complication of consider-ing clearance. Note further that the pressure during admissionis the boiler pressure and hence the efficiency of the pipe line isincluded n the diagram factor. If the line loss is very great thesteam pressure at the throttle may be used, but that fact shouldbe specially noted. Hence in choosing a diagram factor or infinding it practically for a definite case, it is essential that theseelements be properly applied. CHAPTER IV. ZEUXER AND BILGRAM VALVE-DIAGRAMS AND DESIGNOF PLAIN SLIDE-VALVES. The Throw of Cranks and Eccentrics (Figs. 53 and 54;.—?The throw or radius of a crank is the distance from the centerof the crank-pin to the center of its shaft or the distance R inFig. 53. As it is evident from the definition that the lengthof the crank-pin radius does not affect the crank throw, a modi-fied form of the crank may be obtained by increasing the radius. Fig. 53. Fig. 54. of the crank-pin till its periphery extends beyond the shaft asin Fig. 54. This form of crank is called an eccentric. Its throw or eccentricity is the distance from the center ofthe shaft to the center of the eccentric or the distance SP inFig. 54. The eccentricity or throw of an eccentric is improperly calledthe radius of the eccentric. The radius of the eccentric circle asshown above does not affect the properties of the eccentric asan eccentric. The travel of a valve in one direction is twice the throwof its eccentric (unless modified by lever-arms), viz., 2SP—AB. 85 86 THE STEAM-ENGINE AND OTHER HEAT-MOTORS. Piston Travel with a Finite Connecting-rod (Fig. 55).Let R=OD = crank throw; L=Dd = connecting-rod length;ab = travel of cross-head;then with centers a and d, draw the arcs CAC and Dg, using thelength of the connecting-rod as a radius to the same scale thatA0= crank throw. It is evident that ad = CD = Ag = the travelo
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