The Locomotive Of Today

The Engine : Hackivorth’s Gear, Walschaert's Gear. 107 moves, the reversing shaft has to be raised or lowered until this ceases. This having been done, the other clead centre upon that side is tried in the same way, and the lead equalisec for both ends by moving the shaft backwards, or .forwards as found necessary. All clead centres are treated m thesame way, and the valves are then set; the process is much simpler than that required for link motions. A.mong other radial gears is Hackworth s, where t valve motion is taken from one eccentric, which is fixed upon the axle exactly opposite the crank, and has lts rod working vertically, with the end attached to a block moving m a pair of curved guides ; the amount of cut-off given to the slide valve depends upon the inclination given to these guides, m this respect the gear is similar to that last descnbed. not larø-ely used, however, on locomotives. . . In Walschaert’s motion, which is not, correctly speaking, a radial gear, as no ellipses are described by it, t e va ve as its travel controlled from two perfectly distinet movements, one that of the crosshead, the other that of an eccentric fixed upon the crank axle, these being combined by a system ot levers, so that the motion of the slide valve is the same as that derived from the stationary link. A slot link is used o enabling the motion to be reversed from fore to back gear reqUAnd’example of this motion applied to an inside cylindered engine is shown in Fig. 22, The crosshead has a prolonga- tion upon it, carried clown to a convement point for connection to a union bar, which at its other extremity, is attached to the end of a combination lever, this latter has two holes for the attachment of the valve rod and radius rod respectively, the former at the end, and the latter just below it At the tar ena of the radius rod is fixed the quadrant block which moves. m a slot link, pivotted, and allowed to oscillate about its trunnions, working in carriers projecting from the slide bar bracket To the lower extremity of the slot link the end of the eccentric rod is attached, so that when the crank axle revolves the link vibrates backwards and forwards about its fixed centre. The eccentric itself is keyed upon the axle, usually __ a right angles to the crank, though its position may be varæc to suit special requirements, and thus, as far as it ane link are concerned, the valve may have no lead, but through the combination lever the eccentric and crosshead motions are so combined that the angular advance is in effeet restored, and as a result the valve possesses a constant lead. If the eccentric is fixed as in the illustration m advance of the crank when moving forwards, the bottom of the slot lin