Читать книгу The Modern Bicycle and Its Accessories - Julius Wilcox - Страница 49

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At the Stanley and the National shows in London, chainless driving—with the exception of a few which are close upon or within the freak line and do not need mention here—was represented by the Columbia bevel-gear and by the Lloyd cross-roller as exhibited by the “Quadrant” makers. This latter is like the bevel in using a shaft to reach from crank axle to rear-wheel axle, and so might in a general way be classed in the bevel-gear type; yet in important details it is materially different, the gears themselves being replaced by roller-and-pin wheels. This is an adaptation, with some changes in the shape of the rubbing parts, of the old crown wheel and of its pinion constructed of wire pins instead of cut teeth, this form of pinion being now in use in clock trains by the million. The large wheel on the crank axle has horizontal pins or studs projecting from its rim, the bottom ends of the pins being seen in the cut but the pins themselves being behind the wheel; these pins mesh into a roller pinion on the shaft, the common fixed pins being replaced by rollers turning on pins in order to substitute rolling for rubbing friction. The same construction is at the rear end, only reversed in position. In front, the pins drive the roller pinion; at the back end of the shaft, the roller-pinion drives the wheel by meshing with the pins on its hub.

It is impossible, from only the cuts and descriptions in the English trade journals, to be entirely sure of the precise shape of the engaging portions of this device, but the foregoing is substantially correct. The best authority in those journals, which expresses a high opinion of it, says: “The cross rollers act in practice more smoothly than the idea would seem to suggest. The gear is in effect almost the same thing as a bevel-gear, since the ends of the rollers which impinge nearest upon each other are slightly tapered and rounded. There seems, however, to be less tendency for the gear to force itself apart than when bevels are used, and the rollers of course remove a lot of the rubbing friction inseparable from plain bevel-gears.”

On the other hand, the same writer says of the bevel: “Bevel gearing has been almost universally condemned by experts generally, but we do not think that the latest patterns of bevel-geared machines have been put to a really practical test. Taking the Columbia as one of the most perfect examples of this class of machine, the cutting of the teeth and the general construction of the gear is so vastly superior to anything before turned out that previous tests are really very little guide. No other firm has given so much attention to the matter as the Columbia people, and we hope at an early date to have an opportunity of testing one of their machines. If the loss from increased friction is only slight, bevel-gears will have a considerable run—it all hinges on that.”