1. Q. Give a brief explanation of the Walschaert valve gear.
A. The Walschaert gear has an eccentric crank attached to the end of the main pin on each side of the locomotive, with an eccentric rod from this pin to the connection at the bottom end of the link. This eccentric is located so it serves for both forward and back motion. The link swings on a center trunnion and cannot be moved up and down as the Stephenson link, but the link block can be moved from one end of the link to the other to reverse the engine; or part way toward the center of the link to change the cut-off. A radius rod connects the link block to the valve stem. There are two motions given to the valve stem, one from the link block which regulates the travel of the valve for the cut-off and reversing; the other motion is from a connection with the cross-head which gives the valve a positive motion to take care of the lap and lead. To give this motion there is used a combination lever or a lap and lead lever connected to a cross-head arm by the union link.
2. Q. Is the Walschaert gear direct or indirect?
A. It is direct when the link block is below the center of the link; it is indirect when the link block is above the center of the link.
3. Q. What are the princ.i.p.al differences in the location of the Stephenson and Walschaert gears, and what advantages does this give the Walschaert?
A. The Stephenson gear is placed between the main frames and employs two eccentrics, with straps and rods on each side of the locomotive; one for forward and one for backward motion. The Walschaert gear is placed outside the driving wheels and frame, has but one eccentric, which is a simple arm connected to the outside end of the crank pin for both forward and back motion. The links are set above the wheels on a level with the steam chest, the combination lever next to the cross-head. This gives it an advantage of a better chance to inspect all parts, the eccentric connections are much lighter and direct, which makes them less liable to wear or breakdown, and the valve has a constant lead.
4. Q. How is the lead affected by movement of the reverse lever with the two gears?
A. With the Stephenson gear the lead increases as the reverse lever is hooked toward the center in both forward and back motion. With the Walschaert gear the lead is the same in all positions of the lever, so that the lever is used to reverse the engine or adjust the cut-off.
5. Q. In reversing, how do the two gears differ as to the movement of the link and link block?
A. With the Stephenson gear, when reversing, the link is raised and lowered, bringing the block which is not moved by the reverse lever under control of either the forward or back-up eccentric as is desired to move the engine the proper way. With the Walschaert gear the link is not moved by the reverse lever, but the link block is raised and lowered in the link; the position of the block above or below the center of the link controlling the direction of motion.
6. Q. What would you disconnect if the eccentric crank, eccentric rod, or the arm at the bottom of the link should break?
A. Would remove the broken parts, disconnect the link lifter from the radius rod and block the link block in the center of the link; the combination lever would then move the valve twice the amount of its lap and lead, which would be sufficient to provide for lubricating the cylinder.
7. Q. If the main crank pin was broken?
A. Take down eccentric rod, eccentric crank, main rod and all connecting rods, block cross-head, disconnect from end of radius rod, chain it to running board and block steam valve to cover ports.
8. Q. Broken cross-head pin, main rod, strap or bra.s.ses?
A. Take down main rod, block cross-head, disconnect front end of radius rod and chain to running board and block the valve to cover ports.
9. Q. With a broken combination lever, union link or cross-head arms, what would you do?
A. Would disconnect the forward end of the radius rod and secure it to the running board with a small chain, wire or rope, remove all broken parts, take off the combination lever, even if not broken, secure the valve in its central position, loosen cylinder head to provide for lubrication, leave up main rod and proceed on one side. If valve was blocked to open rear port slightly, this would provide for lubrication and the cylinder head need not be loosened.
10. Q. If the radius rod on Walschaert gear is disabled, what should be done?
A. If broken in front of the link block, take off the broken part by disconnecting from combination lever, take down eccentric rod, fasten valve to cover ports and proceed on one side. If broken back of the link block, block the link block in the desired position and proceed with both sides.
11. Q. What would you disconnect with a Walschaert gear if a valve yoke should break?
A. Disconnect the forward end of the radius rod, suspend it from running board, block the valve, provide for lubricating the piston and proceed.
12. Q. How proceed with a broken reach rod?
A. Remove the reach rod, block links on lower side to hold them in running position for proper direction. Unless radius rod lifters can be uncoupled, leave a little slack in the blocking.
13. Q. How can you tell without opening the steam chest if the valve covers the port with Stephenson gear? With Walschaert gear?
A. Place the rocker shaft vertical with Stephenson gear. Place the combination lever vertical with reverse lever in mid gear so the link block is in the center of Walschaert link.
14. Q. What is the Baker-Pilliod valve gear?
A. It is an outside gear with an eccentric crank, similar to the Walschaert gear, but without a reversing link. The motion is reversed by means of a reversing yoke instead of a link; the cut-off is changed in the same manner. It uses a combination lever connected with a union link to its cross-head arm. In case of breakdown remove the broken parts the same as described for Walschaert gear, blocking the reversing yoke, if necessary, in the proper position.
15. Q. Is the Baker gear a direct or an indirect motion?
A. It is direct, going ahead for an inside admission and indirect backing up, and just the opposite for the outside admission type.
16. Q. What parts of the Baker gear take the place of the link which is used by the Stephenson or Walschaert motion?
A. The radius bars and reverse yoke.
17. Q. What relation to the main pin is the eccentric crank set to?
A. The eccentric crank always follows the main pin.
18. Q. Should the eccentric rod or eccentric crank break how is the engine put in condition to proceed?
A. The disabled side can have lap and lead travel and a port opening equal to the lead for all cut-offs. First block the bell crank by using a "U" bolt (which should be provided) in the holes placed in the gear frame for this purpose. Throwing reverse lever in mid-gear will help to get bell crank in position to block. Second, take down broken parts.
Third, knock out back pin of short reach rod and throw reverse yoke in forward motion against gear frame.
19. Q. What is to be done should a gear connection rod break?
A. Do the same as for a broken eccentric or crank.
20. Q. What is to be done should the upper part of gear connection rod break?
A. If break is close to the middle pin, do the same as for a broken eccentric rod and also tie lower end of gear connection rod to keep it from swinging. If break is near the top and below the jaw, first block the bell crank and wire the connection rod fast to radius bars. If break is through top jaw, do the same as for broken eccentric rod.
21. Q. What is to be done should a radius bar break?
A. Do the same as for broken eccentric rod.
22. Q. If the horizontal arm of bell crank should break?
A. Same as broken eccentric rod.
23. Q. What is to be done should the vertical arm or bell crank break?
A. Take down union link combination lever and valve rod, then block valve over ports by using set-screw in valve stem cross-head provided for that purpose.
24. Q. Should you break cross-head arm or union link, what would you do?
A. If rod be provided to secure lower end of the combination lever to guide yoke, remove broken parts and proceed with full train, working engine at long cut-off. Otherwise would remove broken parts, combination lever and valve rod, cover ports, and proceed on one side.
25. Q. What do you do if a union link should break?
A. Same as for a broken cross-head arm.