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 union 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. INDEX A ACCESSIBILITY of Walschaert gear, 131, 132 Adaptability of Walschaert valve gear, 142, 143 Adjustment of Walschaert valve gear, 102 Advantages derived from the use of Walschaert gear, 129–148 B BAKER-PILLIOD improved valve gear, 228 Advantages in securing the short travel of the valve on Combination lever, if broken short, how arrange, 235 Engine disabled on one side, how to block the valve, 233 Valve rod, if broken, how repaired on the road, 235 Baker-Pilliod valve gear, 222 to 236 inclusive Original style with outside admission, 224 With inside admission, 228 Baldwin engine with Walschaert gear, 65 to 67 inclusive Belgian engine with Walschaert valve motion, 80 to 87 inclusive "Blocking the valve"-what is meant, and how it is done, 171 Breakage of lower section of combination lever, or its link to the Break-downs on the road. Difference in methods of disconnec- tion of Walschaert and Stephenson gears, 170, 171 Broken radius-rod hanger, 178, 179 Broken valve-stem, 179, 180 Building up the Walschaert gear: The start, 28 C CASE of broken or detached piston-what to do, 182 Combination lever, 29 Combination lever (lap and lead lever) for inside admission valves, Combination lever (lap and lead lever)—to determine proper Comparative weights of Walschaert and Stephenson valve gears, Confusing in the meaning of lead, 158 Connections of the eccentric rod, 43 Constant lead with reverse lever in any notch, 38 Continuing the layout of the gear, and formulas, 105 to 109 Correcting the built-up motion, 40, 41 Correction of one error introducing others, and their relief, 167 "Cut-off," meaning of, 160 D DE GLEHN compound engine with Walschaert gear, 67 to 69 Derivation of lead through the Walschaert combination lever, 157 Designing and erecting the Walschaert valve gear, 95–126 Details of the Walschaert link, 44 to 49 inclusive Difference between Walschaert and Stephenson motions, 151, 152 Different methods of erection, 49 to 51 inclusive Directness of Walschaert motion, 138, 139 Direct valve motion, 20 Disconnection of radius rod. Method of doing it, 176, 177 Disconnection of Walschaert and Stephenson gears, 170, 171 Does the radius rod give motion to the valve, with reverse lever Does the rise and fall of the engine on springs affect the valve's E ECCENTRIC rod broken. How to proceed, 179 Eccentric-rod connections, 43 Eccentric rod, testing for length of, 192 to 194 inclusive Effect of valve advance to secure lead, 25 Engine standing as last mentioned, if valve is not exactly cen- Enumerating the chief advantages of Walschaert gear, 129 to Equalized cut-off, Walschaert vs. Stephenson gear, 161, 162 Erecting and designing the Walschaert valve gear, 95-126 |