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necessary to disconnect the valve stem nor to clamp the valve; the valve will get the eccentric movement, but the port opening will be reduced and be closed in any cut-off shorter than about 50%.
Q. 5.-Suppose the combination lever breaks very close up to the bell crank, how should one arrange?
A.-In that case remove the union link and the broken piece of the combination lever, secure the valve over the ports as has been described, disconnect the valve rod and tie up the loose parts to keep them from doing damage. Proceed under power of the other side of the engine.
Q. 6.—If the valve rod should break, what should be done?
A.-Block the valve by tightening the set-screw on the valve-stem crosshead as already understood, and either disconnect the broken valve rod from the combination lever, or tie it up in such a manner that it can swing to the motion of the combination lever without striking anything, and go on with the engine working on one side.
Q. 7.—If the vertical arms of the bell crank should get broken, what would be the best thing to do?
A.—The valve rod should be disconnected from the combination lever, and as the latter is carried by the vertical arms of the bell crank, the union link and combination lever must be taken down; the valve should
be centred and secured in the prescribed way, and you can then proceed-on one side.
Q. 8.-In these cases of failure of certain parts of the gear such as the eccentric rod or unión link, etc., what are the advantages in being able to still secure the short movement of the valve and a limited port opening when the piston is at the beginning of its stroke?
A.—On the big up-to-date engines it is impractical to try to remove the main rod in cases of breakdowns, and when it is left up and the valve is blocked at the centre of its travel, the piston will meet with high resistance toward the finish of either stroke, on account of the air compression ahead of the piston and a partial vacuum behind it; this added to the braking power at applications of the air brake may cause the drivers to slide and flatten. The port opening provided as referred to, gives relief from this effect; further, it permits oil from the lubricator to reach the cylinder and prevent the walls from becoming dry and being cut by the piston—a condition that must be particularly guarded against when the main rod is left up, in cases of breakdowns.
ACCESSIBILITY of Walschaert gear, 131, 132
Advantages in securing the short travel of the valve on
disabled side of engine, 236
be done, 233
Union link or crosshead arm failure, what to do, 234
Original style with outside admission, 224
With inside admission, 228
main rod be left in place? 182, 183
to 174 inclusive
Breakage of lower section of combination lever, or its link to the
tion of Walschaert and Stephenson gears, 170, 171
Case of broken or detached piston—what to do, 182
proportions of: for outside admission valves, 195
133 to 138 inclusive
valve motion? In cases of break-down requiring valve block-
De Glenn compound engine with Walschaert gear, 67 to 69
Designing and erecting the Walschaert valve gear, 95-126
outside admission valves, 62 to 64 inclusive
in the Stephenson gear? 164
on the centre? 160, 161
action with Walschaert gear? Position of valve with crosshead
tred, the cause and remedy, 166