. American engineer . lo (In with the <l(.sif;iiing and set-ting cif the Stevenson link niotinn are familiar with the extremesensitiveness of the valve events to any change in any of theparts composing the gear, from tlie connecting rod to the loca-tion of the lifting shaft. .\ cliange in the length or point of sus-pension of any element will have its efTect on the motion of thevalve, and this effect, being usually a bad one, calls for a modi-fication of some or all of the other |)arts. To work this out onthe drawing board is a slow process, and the usual method ofsecuring a fair equalizati
. American engineer . lo (In with the <l(.sif;iiing and set-ting cif the Stevenson link niotinn are familiar with the extremesensitiveness of the valve events to any change in any of theparts composing the gear, from tlie connecting rod to the loca-tion of the lifting shaft. .\ cliange in the length or point of sus-pension of any element will have its efTect on the motion of thevalve, and this effect, being usually a bad one, calls for a modi-fication of some or all of the other |)arts. To work this out onthe drawing board is a slow process, and the usual method ofsecuring a fair equalization of cut-off is to lay out the valve gearon the drawing board to general proportions and arrangementbest .suited to the design of the engine and then correct in-equalities by erecting it on the locomotive and securing theequalization of the cut-ofif and the valve events by using an ad-justable link saddle, whereby the offset of the saddle pin can beset in that position to secure the best movement of the valve. -H l-E. Diagram of Stephenson Valve Gear with Open Rods. 1 lie regular saddle is then made, with the pin offset to corre-spond to that obtained, and is applied to the link. In short, theerrors of design are corrected by the offset of the saddle pin. As there was no formula by which this offset could lie calcu-lated for any given arrangement and proportion of the W. Young, in charge of tlie valve designing for the .iericanLocomotive Company, umlertook to solve the problem and obtain,if possible, a formula li,\ which tlie saddle pin offset lonhl liecalculated. For this purpose he used the valve gear model at Schenectady,and set up, as a base gear, one having the following dimensions,as shown in the accom])anying illustration : Length of connecting rod ^ (, / ) 96 in. Stroke of piston =; diameter of crank =(/)).... 24 Radius of link — (C) 4H Distance between points of attachment of eccen-tric rods to link = ( D ) 12 Distance from point of support of link hanger t
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectrailroa, bookyear1912
