IMPORTANCE OF HAVING WEDGES PROPERLY FITTED.
With the pedestal face in a proper condition to avoid displacement of the wedge, when moved to different positions on it, we should consider what will be the method of lining the wedges, and what duty they have to perform. This duty is merely to take up the lost motion between the pedestal and boxes; and that, from their shape, they readily do from time to time. While this duty is simple, the wedges ought to do it without affecting any of the other parts of the locomotive,—a condition of perfection that can be reached only by having all the wedges perfectly parallel with the pedestals and with each other. If the first condition is not complied with, the result, as stated, will be the box swinging in the wedges. If the latter, then with the varying position of the boxes in the pedestal due to the engine settling on the springs, or to the change of position from the motion of the springs when the locomotive is running, we will have a varying distance between the centers of the wheels and length for the side rods.
Many of the complaints we hear of rods not working properly, are owing to this defect in wedges not being parallel, by which the distances are varied, and a strain thrown upon the rods that not only affects them, but causes them in turn to bind the boxes against the wedges by trying to compress or extend to a length varying as often as the motion of the springs. While the motion of the springs is not much in proportion to the length of the wedges, and the varying distance between centers of wheels is in ratio to that proportion, if the wedges are not parallel, we must remember how often the motion is occurring, and that, no matter how slight the strain upon the rods may be, we are putting it on a part of the locomotive that requires the minutest adjustment to enable it to do its work properly and safely.