POUNDING IN DRIVING-BOXES AND WEDGES.
But we will deal now with the pounds in a locomotive, and will take the location in which we find the most and serious ones,—namely, in the driving-boxes and wedges,—and see why they pound, and what will prevent them from doing so. The cause we will find, if in the wedges, is due to a rocking of the box in them, or from causes arising from imperfect fitting when they were put up, or lined up when the engine was in the shop. This fitting of wedges on a locomotive that has done service is a matter of importance in the immediate present and future working of the parts themselves, and of other parts of the locomotive as well. On stripping a locomotive that has done much service, it will be found that the working of the wedges on the face of the pedestal has worn it hollow, or pounded furrows on it, or has done both. This occurs so frequently on the “live” wedge side, that it may be taken as the rule, rather than the exception, to find the pedestal in this condition. While it does not happen so frequently on the “dead” wedge side as on the other, it will be found there also if the wedge has not been held by a fastening to the pedestal, or securely fitted between the top of the frame and the pedestal binder-brace. These defects will be found on the back of the wedge also, and are produced by the same cause and same motion as those on the pedestal face. These defects are the most frequent cause of the driving-box pounding, or of the wedges rocking; since thereby the wedges get thrown out of parallel to each other, when it becomes necessary to adjust them during the service of the locomotive.
In refitting wedges, these defects should be removed, the pedestal face carefully straightened its entire length, and the wedge-back fitted to it. It is not only necessary that the pedestal face should be smooth, but that it should be straight its entire length. If not, when it becomes necessary to adjust the wedge, if the pedestal is high on the top end, the wedge is thrown out at the top, binding the box at that point, and allowing it to swing at the bottom.