104

MODERN STEAM PRACTICE.

on a pin and suspending-rod, having a fixed centre at end on whichthe arm oscillates; this arrangement is complicated, as a movable

Fig. 54.—Locomotive Link-motion.w, Weigh-shaft.

rod must be interposed between the link and the valve-rod, with thenecessary lifting lever and rod to raise or lower it as required to suitthe forward and backward motion of the engine (Fig. 54).

Again, some link-motions differ entirely from the foregoing, thelink oscillating on centres, on the guide-bar for the valve-rod, sup-

Fig. 55.—Locomotive Link.

ported close to the link, while the eccentric rods are connected tothe sliding-block; this arrangement admits of the boiler being placedlower down, as the link requires less head room; the link-block isof increased length to insure steadiness; and as the reversing leverSupports only the eccentric rods and link-block, the slide-valves aremore easily handled, although all can be so arranged with counter-weights to ease the labour in reversing (Fig. 55).

The great value of the link-motion not only consists in ena-bling us to control the movements of the engine, but it is like-wise admirably adapted for cutting off the steam at any portionof the piston’s stroke, thus working expansively without the aidof an additional valve and mechanism, and also simplifying the