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Q. 48.—Could the breaking of a side rod totally disable an engine with the Stephenson link motion?
A.—Yes, on certain types of engines where the eccentrics are attached to other than the main-axleand this is quite common on engines with three or more pairs of driving-wheels—if a side rod connecting the main pair of driving-wheels with the pair that mounts the eccentric axle should break, the same section of side rod on the other side of the engine should be taken down, and this would render the valve motion inoperative. With the Walschaert gear the eccentric is always on the main pair of wheels, and therefore is unaffected by any damage to side rods.
Q. 49.—In cases requiring the valve to be blocked, the valve-stem should, of course, first be disconnected, or at least disconnection made at some point between the valve and the regular source of its motion, and with the Stephenson link motion the valve-stem is the most convenient place: Is it, with the Walschaert gear?
A.-No; it is practically out of the question to disconnect the valve-stem itself on most engines having the Walschaert gear, as it usually has a crosshead working in a guide and there is no place between the crosshead and the packing gland for its separation, but the same effect is produced by disconnecting the radius rod.
Q. 50.-If disconnection of the radius rod in the Walschaert gear has the same effect as disconnecting the valve-stem of the common link motion, then the radius rod will have to come down whenever the engine is so disabled on one side that the valve must be blocked; so you will explain in detail how one should go about it.
A.—The radius rod need not be taken down in all such cases of disability, but will always have to be, at least, disconnected.
Remove the pin from the joint of radius rod and combination lever and raise the disconnected end of the radius rod just above any chance of interference with the combination lever, suspending the 'rod by strong wiring or rope of such length as to permit it to swing freely to the motion of the link, taking particular care that the suspended end of the radius rod will not strike anything else. This method should only be resorted to, however, when the engine has only a short distance to go to reach its terminal and can be run at a moderate speed, only. In answer to subsequent questions on breakdowns the following instructions for disconnecting the radius rod should be observed:
If the engine is to be run any considerable distance, or may be speeded up at times, with one side disabled, a safer and more commendable method is, first, place the reverse lever in the centre notch of the quadrant in order to get the back end of the radius rod and the link-block in the exact centre of the link; then saw a couple of pieces of wood to fit, and insert them between the bottom of the link and the link-block, and secure them in position in order to support the back end of the radius rod at the centre of the link; now disconnect the hanger between lifting arm and radius rod and take out the pin from the front end of the latter at its connection with the combination lever, wiring the radius rod up, as previously directed, or suspending it by anything that will support its weight, as there will be no motion imparted to it now. After centering the valve, and blocking it or clamping the valve-stem-or trusting that the pressure of the steam will hold it in its central position—it will not be necessary to do anything with the combination lever, as the motion imparted to its lower end will not be likely to affect the valve, even if not clamped; but,-after disconnecting the radius rod from the combination lever, always watch the first movement of the crosshead to see that the combination lever does not strike the wrist-pinthe pin by which the front end of the main rod is connected to the crosshead—as the motion of the lever is altered by the disconnection and pause of its upper end. Blocks of the proper size to hold the radius rod in the centre of the link, and with their upper ends shaped half-round, should be carried on all engines equipped with the Walschaert valve gear.* .
Q. 51.—What should be done in case of a broken radius rod?
A.—The best plan is to take down all of the pieces of the broken rod, disconnecting them from the combination lever, suspension bar, or hanger, and linkblock; but if there is very much left of the rod forward of the link, it can be blocked up in the centre of the link, disconnected from the suspension bar, and its front end wired or tied up as before mentioned, and the valve centred and secured.
Q. 52.—When the suspension bar, or hanger, is connected to an extension of the radius rod back of the link, and that back extension of the rod should get broken off, or the suspension bar or lifting arm should break, what should you do?
A.—These troubles should be treated about alike. If the engine is to run forward, place a short block in the link under the radius rod or the link-block, so that the forward section of the radius rod will be held at about the same position in the link as the one on the other side when the reverse lever is in the notch that it will be expected to work in. An average should be struck in regard to this, as the reverse lever should neither be hooked up any further, after the positions of the radius rods have been matched, nor dropped a notch lower. Of course, the broken parts should be detached, and another block placed in the link above the link-block or radius rod to prevent their slipping up.
* The construction of the Walschaert link is a little different in detail as designed by the different locomotive builders, and the shape of the blocks to be used in the link when it is desired to carry the radius rod and link-block without motion, varies enough that it would not be practicable to illustrate a pattern.
Q. 53.-An eccentric rod seldom breaks with the Walschaert gear, while it is not uncommon in the Stephenson link motion; if, however, the Walschaert eccentric rod should break, what then should be done?
A.—After removing the broken parts of a Walschaert eccentric rod throw the reverse lever to the forward corner notch in order to lower the radius rod and block to the bottom of the link; then disconnect the suspension bar from the radius rod, and the radius rod from the combination lever; raise the front end of the radius rod above interference, and, wiring through the pin hole, attach its forward end firmly and immovably to anything convenient and solid in order to keep the link from rotating, as with the eccentric rod detached there will be nothing but the radius rod to keep it steadied. Block the valve, etc., in the manner heretofore described, and proceed (see also page 185).
Q. 54.—If the valve-stem should break what course should you pursue?