THE “CUP” OR “DISK” ADJUSTMENT.
Of the highest importance is also “cup” adjustment, as opposed to the usual “cone.” As seen in the cut of the three-point bearing, in the latter form the cup is pressed into the hub and stays fast there, as a seat for the balls, with its coned surface facing outward. The adjusting cone faces inward and screws on the axle. The “cup” form reverses this, facing the axle cone outward and leaving it fast on the axle; the cup faces inward and adjusts by screwing into the hub end, as shown in cut of the bearing last described. The practical advantages of this method are very real and are these, as may be indicated by the somewhat rude cut:
1. When the cup is pressed into the hub it may not be quite true across the axle line—all the more if it is afterward removed and replaced, as in changing the rear sprocket. Any nut has some degree of side-to-side movement on its thread, however nicely fitted; an adjustment cone on the axle can also never be held quite firmly in position, and the grip of the fork ends upon it is even liable to cant it to one side to the slight extent of its looseness in the thread. This interferes with accuracy in the bearing. But the cup is of larger diameter and hence is steadier in the fit of its thread, and it is also practicable to lock the adjustment more firmly on the cup. Moreover, in the “cone” form the cone has to run on the same thread with the outer nuts which hold the wheel in the fork, and this thread must be coarse, because a fine one would not have sufficient strength to bear the strain of locking the wheel; so the adjustment must be on the coarse thread. But when the cup screws into the hub as proposed, it has its own separate thread, which may be as fine as desired; thus it gains in steadiness by fineness of thread as well as by larger diameter.
2. Dirt cannot enter through the thread, but only through the open joint. The opening close to the axle is obviously a smaller circle than at the edge of the movable cone on the old method; hence the cup form excludes dirt better, and if a felt washer is used the friction from that is less when put close to the axle than when farther away.
3. The cup adjustment has the great and obvious advantage that the adjustment is wholly independent of the fork, being only on the hub itself; hence the adjustment can be made more easily and accurately, and after being so made once for all the wheel can be removed and replaced without danger of disturbing it.
4. In the other form of hub, oil naturally runs out; with the cup adjustment, the parts are readily and naturally arranged so that oil is held at the bottom as in a reservoir, and the balls can run in it. Reservoir hubs of this pattern are quite well known in England, and the makers of the “E. & D.,” who use a felt washer as indicated in the cut, claim such a perfect exclusion of dirt and retention of oil that the latter is found still in its place at the bottom, not discolored, after over a thousand miles’ running.
In England the cup adjustment has long been standard, although perhaps not invariable; the tardiness of its adoption in this country must be ascribed to an insufficient study and appreciation of the practical importance of bearings, and to the considerable investment already made in parts and tools on the other plan. The first step in adopting the cup form here was at the crank-hanger, where it has been quite largely in use for several years; but it is being applied to the wheels as well, and among the makers using it all over we note such well-known concerns as the Liberty, the Sterling, Humber, Victor, Howard and Lyndhurst. This is not an exhaustive list, for we have not studied every catalogue; moreover, it is impossible to determine the point in all instances, and many who do not use this form on wheels have it on the crank bearings, as also some others screw the cup into the wheel hub and “back out” the axle cone for adjustment—this last is good as far as it goes and is a half-way step. After having constantly advocated the cup adjustment for several years past it is a gratification to find it thus making progress, and we note this as the chief step in improvement of bearings in 1898.