SHAPES OF CRANK AND SPROCKET.
The original crank or rectangular section has for some years been generally round, or of an elliptical section tapering to round at its slightest portion at the end; a few makers have used a bayonet section, or have chamfered out the inner side; fluted sections have also been used, and one or two have brought out a crank in the shape of an S, in the not well-founded notion that it is a good point to depart from rigidity in the driving, or perhaps imagining that a longer throw is thus obtained in the effective portion of the stroke. But there is now a decided reversion to the rectangular and even to the tapered square crank; cranks of bayonet or flattened diamond section are also quite in vogue, notably on the Fauber one-piece construction. There does not seem any considerable reason for choice between round and square, on the score of strength, but the round should hold nickel better, which always shows an inclination to peel on an edge. Still another shape may be mentioned, which has some novelty and neatness—a square or rectangular crank that smooths off into round a few inches from the axle.
Although not new this year, we may mention the peculiar Victor reversal of usual construction by putting the axle on the crank, so to speak, instead of the crank on the axle; the axle is hollow, and the crank stands through instead of over its end. The Spalding crank has on its end a lug or boss which fits a sort of heart-shaped end on the axle, the crank proper being very slightly outside the line of the axle instead of exactly across that.
The Racycle continues its well known peculiarity of putting the bearings of the crank axle within the crank ends, so as to increase the distance between the two ball rows and bring the line of chain pull between them. The Cleveland has a similar arrangement for the same purpose.
There is a disposition to return to the fixed front sprocket in a single piece, as was the construction before the central “spider” with a removable rim attached came into use. The spider itself has been strong enough, but the portions to which its arms were screwed and the rim itself have been rather slight of late, and the toothed rim has not always had support enough. There has therefore been a liability in the sprocket to spring under strain or even to take a “set” out of line, and the change is to be approved on the whole, especially as a very easy detachability in the front sprocket is rather a “talking point” than otherwise, since it is rare that any rider avails himself of it in order to make a change of gear ratio.
Hewitt Brothers, of Cumberland, Md., have a form of sprocket in which the central portion, which comprises the whole except a rim just large enough to have the teeth on it, remains fast and immovable on the crank bracket. This rim, being coned on its inside edge to match a coned recess on the outer edge of the fixed central portion, has a row of balls between and runs around on those balls, just as the intermediate spur gear wheel does on the [Hildick chainless], already described and illustrated. For this sprocket device the usual claim is made that it so increases ease of movement that a gear of 120 with it requires no more power to drive than one of 70 without it.