. American engineer and railroad journal . se ellipses represent the two extremes of service conditions,full gear and 25 per cent, travel, and are the same in forward 24 AMERICAN ENGINEER AND RAILROAD JOURNAL. January, 1911. and backward motions. It should therefore follow that withthe two extreme positions in harmony the intermediate positionswill show corresponding harmonization. Heretofore when the valve actuating mechanism has been con-nected to the eccentric arm at a point intermediate with the endsthereof by a pivot traveling in an elliptical path, the forward endof the eccentric arm has
. American engineer and railroad journal . se ellipses represent the two extremes of service conditions,full gear and 25 per cent, travel, and are the same in forward 24 AMERICAN ENGINEER AND RAILROAD JOURNAL. January, 1911. and backward motions. It should therefore follow that withthe two extreme positions in harmony the intermediate positionswill show corresponding harmonization. Heretofore when the valve actuating mechanism has been con-nected to the eccentric arm at a point intermediate with the endsthereof by a pivot traveling in an elliptical path, the forward endof the eccentric arm has always traveled in a fixed arc or accu- ing parts also tends to reduce tlie effect of wear, and at the sametime this feature adds to the ease with which the locomotive iscontrolled from the cab. In the case of a gear which necessitates the use of a link,errors due to lost motion are often not corrected for long pe-riods owing to the difficulty of making some of the adjustments,while in the case of a gear without wearing parts, other than. MOTION DIAGRAM OF PILLIOD LOCOMOTIVE VALVE GEAR. rate path, and the ellipse described by the intermediate pivot con-nected with the valve actuating mechanism has always been ir-regular, being greater at the top than on the bottom, and caus-ing unequal valve travel and unequal distribution ofsteam. This error was produced by connecting the forward end of theradius link to a reverse of the Marshall type, and has been cor-rected by the employment of the front rocker arm. An equaltravel of the valve is thus secured during each stroke, producinguniform admission and release at each end of the cylinder, andcut-off at equi-distant points. Owing to the employment of thenew imparting motion device, the action of the valve is undis- pins, a correction is so easily made by the adjustment of tapers,or by the insertion of new parts, that the general performance ofthe engine should be more or less distinctly benefited in theaverage. Telephones
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