. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . cess. Itsradius will be equal to the eccentricity Qand the distance of its center 0 from thestraight line 6 b, will be the desired out-side lap e. In order to find the linear lead, drawa line from O making an angle with k 0equal to the preadmission angle 7-Through the point f where this line ofangular admission cuts the circle, draw theline c c parallel to b b. The distanceof these two lines apart is equal to thelinear lead. Furthermore, the angle f O 7)i is equalto the angular advance S of t
. Railway and locomotive engineering : a practical journal of railway motive power and rolling stock . cess. Itsradius will be equal to the eccentricity Qand the distance of its center 0 from thestraight line 6 b, will be the desired out-side lap e. In order to find the linear lead, drawa line from O making an angle with k 0equal to the preadmission angle 7-Through the point f where this line ofangular admission cuts the circle, draw theline c c parallel to b b. The distanceof these two lines apart is equal to thelinear lead. Furthermore, the angle f O 7)i is equalto the angular advance S of the eccentric. In order to obtain a clear illustration of the accuracy of the dimensions thus found,it is only necessary to apply them to theZeuner valve diagram as shown in Fig. accuracy of the results so obtainedis evident from the following points. Let-ting the outer circle represent the totalthrow of the crank, the eccentric circlewhose diameter is Q passes through thecenter of the diagram and cuts the hori-zontal axis outside the circle drawn witha radius equal to the outside lap c, by a. FIG. 6. distance equal to the linear lead, at thepoint e + e, and closes the port at thepoint C with the lap corresponding to theadmission angle e. Further the preadmis-sion angle 7 and the angular advance 5will be found to correspond to the anglesas found by the method described. If, in the Zeuner diagram, we have, inaddition to the outside lap e, and the re-quired travel of the valve, q, the widthof the steam ports, a, in the cylinder aswell, it will be readily understood that,for any desired amount of port opening(I K is less than a as shown in Fig. 7.\when only a portion of the port will beopened. On the other hand when a K =a, as in Fig. 7B, the port will only beopen, to its full width, for an instant atthe point B, when it will immediatelystart to close again; finally, when o Kis greater than a, as shown in 7C, the portis wide open through that portion of thethrow of the crank,
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