BROKEN TUMBLING-SHAFT.
This accident is very serious; but it need not disable the engine, although it will lessen the engineer’s power to manage it freely. To get the engine going, calculate the position the links must stand in to pull the train, and cut pieces of wood to fit between the block and the top and bottom of the links, so that the latter may be kept in the required position. For forward motion, there will be short pieces in the top, and long pieces in the bottom. When back motion is needed, reverse the pieces of wood. A common plan is to use one piece of wood, working the engine in full gear.
The same treatment will keep an engine going when the tumbling-shaft arms, the reach-rod, the link-hanger, or the saddle-pin breaks. The failure of a link-hanger or saddle-pin will only necessitate the blocking of one side.
BROKEN VALVE-STEM, OR VALVE-YOKE.
For a valve-stem broken, the eccentric-strap or link need not be interfered with. If the break is outside the steam-chest, take down the valve-stem rod, and set the valve on the middle of the seat; take down the main rod, and secure the piston as previously directed. With a valve-stem broken inside the chest, or a valve-yoke broken, a little additional work is necessary. The steam-chest cover must now come up, and the valve be secured in its proper place by pieces of wood, or any other material that will keep it from moving; and the stuffing-box must be closed, to prevent escape of steam through the space vacated by the valve-stem.
WHEN A ROCKER-SHAFT OR LOWER ROCKER-ARM BREAKS.
A broken rocker-shaft, or the fracture of the lower arm, entails the taking down of both eccentrics and the link, besides the main rod, and the securing of the valves and piston. The breaking of an upper rocker-arm is equivalent to a broken valve-stem, and requires the same treatment.
MISCELLANEOUS ACCIDENTS TO VALVE-MOTION.
Accidents to the valve-seat, such as the breaking of a bridge, can be fixed for running the engine home on one side, by covering the ports, and stripping that side of the engine, just as had to be done for a broken valve-yoke. If a serious break in a bridge occurs, it is indicated by a tremendous blow through the exhaust port, out by the stack. A mishap of much less consequence than a broken bridge is a “cocked” valve, and the small mishap is very liable to be mistaken for the greater one. Where the yoke is tight fitted, or out of true with the line of the stem, some engines have a trick of raising the valve away from the seat, and holding it there. This generally happens going into a station; and, when steam is applied in starting out, an empty roar sounds through the stack. Moving the valve with the reverse-lever by quick jerks will generally reseat a cocked valve, but sometimes it gets stuck so fast that it has to be hammered out of the yoke.
When a locomotive shows the symptoms which indicate a broken valve, a broken bridge, or a cocked valve, the engineer should exhaust every means of testing the matter from the outside before he begins an interior inspection by raising the steam-chest cover. If jerking the valve with the reverse-lever, or moving the engine a little, will not stop the blow, he should disconnect the valve-stem, and shake the valve by that means.