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A.-Disconnect the radius rod in the recommended manner and centre the valve, blocking or clamping the valve in this case if it were possible, and leave the combination lever in place, providing that as the lower end swings forth and back it does not strike the projection of the pin that connects the main rod to the crosshead, for its motion will be somewhat changed since there is no action of the slide at its upper end; this slide—from which the valve-stem has been disconnected by breakage-may be placed at any position on the slide bar that will provide a safer swing to the combination lever, and should be blocked in that position so that the motion of the lower end of the combination lever could not induce a movement of its upper end that would result in the valve being pushed off centre.
Q: 55.-If the long (lower) section of the combination lever or its connecting link to the crosshead, should get broken, what should be done?
A.-Detach the pieces of the link bar, or the brokenoff, lower piece of the combination lever; disconnect the radius rod as explained before, and centre the valve. The remaining stub of the combination lever must be drawn out of the way, forward or back, so that it will not be struck by the pin in the crosshead to which the main rod is connected, when the main rod is not taken down and the crosshead has its regular motion in the guides.
Q. 56.-In all of these cases of breakage it has been assumed that we proceed, after doctoring up the temporary disability, by using steam on the other side of the engine but running with the main rod in place on the disabled side, and the reasons for it have been given; but suppose that the disability is the result of a broken main rod, and no other damage has followed: What should be done?
A.-In case of a broken main rod on an engine equipped with Walschaert valve gear, take down the parts of the broken rod and disconnect the radius rod as has been detailed before; if the valve is of inside admission, push it to the forward end of the steam chest and clamp the valve-stem or block the slide to hold it in that position, or, if the valve is of outside admission it should be drawn to the back end of its travel and secured there, the intention in either case being to keep the front admission port open for steam to enter the cylinder and the back port open to the exhaust. Then, with a bar, draw the crosshead as far as it will go toward the back end of the guidesuntil the piston is against the back head of the cylinder. This is termed "steam blocking,” and while steam is being used the piston will stay placed, but in drifting down hill, or receiving a jerk from the rear end of the train at an application of the air brakes—bumps in switching, etc., while steam is shut off, the piston
is liable to get moved ahead and a sudden opening of the throttle would send it back with force enough to break the back cylinder head and ruin the guides; so, after placing the valve and piston as directed, it is best, also, to block the crosshead in that position. There will, of course, be no movement of the combination lever, and it should not be disturbed; the only motion of the valve gear on the disabled side will be that the eccentric rod will continue to give the regular motion to the link, but with the radius rod disconnected from its suspension bar and the combination lever, and centred in the link, the action of the link will have no effect.
Q. 57.—Suppose that the piston should get broken, or detached from the piston rod in the cylinder: What should be done in that case?
A.-Usually the result of this accident is to carry away, or break, the front cylinder head; the head should be removed, in either case, and the piston taken from the cylinder. If the piston rod is not bent leave the main rod up and disconnect the radius rod in the recommended manner, centre the valve, and go on. The cylinder cocks, in this case, need not, of course, be taken down as the cylinder is opened through the removed head and piston.
Q. 58.—In connection with the preceding accident suppose that the piston rod should be bent in the cylinder: Would you leave the main rod up in place in that case?
A.—Certainly not. In addition to disconnecting the radius rod and covering the ports by centering the valve, as before stated, the main rod should always be taken down-no matter how slight the bend may be in the piston rod.
Q. 59.–What should be done in case of simply blowing out a front cylinder head?
A.—The radius rod should be disconnected in the regular manner, the valve centred, and the back cylinder cock, only, removed. About the only objectionable featurein running with the main rod up on the disabled side of an engine is not present in this case: It is not an easy matter, usually, to keep the piston lubricated, but with the cylinder head removed, oil can be introduced as often as may be necessary.
Breakage, or blowing-out, of the back cylinder head is of rather infrequent occurrence, but when it does happen, if the head is so slightly broken-say a piece knocked out—that it will stand the pressure of the piston under steam, the main rod can be taken down (for undoubtedly the piston rod would cramp in the stuffing-box if allowed to work) and the same process followed as with a broken main rod, as previously described, steam-blocking the piston, etc., as this saves time. In case the back head is completely destroyed, however, the valve should be centred, covering both steam ports, the main rod taken down, and the radius rod disconnected and centred in the usual manner.
Q. 60.-If the link bar connecting the lower end of the combination lever with the crosshead should get broken and lost, from both sides of the engine, how could you measure for new ones?
A.-The length of these link bars could be closely approximated as follows: Move the crosshead into a central position that would indicate that the piston was in the exact centre of the cylinder, and place the reverse lever in the centre notch of the quadrant so that the link-block pin and the link fulcrum pin, or trunnion, are centred together; then move the lower end of the combination lever until the lever is in an exactly plumb, perpendicular position, and measure from the pin hole in its lower end to the pin hole in the crosshead arm to which the link bar should be connected, this distance being the required length of the link bar.
It is to be presumed that any one who is thrown into association with the Walschaert valve gear is familiar with the locomotive in general, and is already wellinformed as to the methods of procedure in cases of breakdowns of the different parts of the machinery other than the valve gear, and for that reason no