Читать книгу The Modern Bicycle and Its Accessories - Julius Wilcox - Страница 45

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Mr. J. C. English of No. 141 Centre street, this city, formerly of Edison’s staff, has produced a sample of a chainless for which he has neither name nor facilities for production as yet. It uses the Crypto internal gear in principle of operation, the same as on the Bantam. The principle of this gear is that when a pinion on a crank or arm is carried around while in mesh with an internally-toothed rack or ring, which is itself held fast against revolving, the pinion rotates on its own axis with an accelerated velocity, and of course it must impart such increased velocity to any wheel with which it is “in touch.”

This may sound complicated, but if the reader will carefully examine the cut he will not find it hard to understand. Here the gearing is within what appears to be a box-like hub. The disk in which the spokes are headed is independent of the toothed rack, but is fast to the central pinion; the toothed rack is a part of the framework and cannot turn. Now, when the pinion which meshes in the rack is carried around the circle by the short arm or crank which holds it (within the “box”) it is plain that this pinion rolls around upon the teeth of the rack. Rolling thus, as the rack is larger than the pinion, having 3½ times as many teeth, the pinion must make 3½ turns on its own axis while it is carried once around upon the rack. But this pinion cannot turn without turning the central pinion with which it is in mesh (just as on the Bantam), and the central pinion is fast to the driving wheel; so the wheel itself is driven, too. The sample gear ratio is 93⅓.

THE “ENGLISH” CHAINLESS.

The lever measures 4⅝ inches between its fulcrum and the point of attachment to the crank, and 14 inches between the crank pin and the pedal. The crank itself is only 1⅞ inches long, being singularly short as compared with usual crank lengths in direct driving. The pinion on the crank is 1 inch in diameter, with 14 teeth; the central pinion is 1½ inches in diameter, with 21 teeth; the fixed rack is 3½ inches in diameter, with 49 teeth, all the teeth used thus being of “14 pitch.” The stroke of the pedal is 7¼ inches in each direction. Having a rocking movement necessarily, the path of the pedal is not an arc of a circle, but is peculiar, being somewhat like a bow and its string in shape, the down stroke being in the “bow” and the return stroke in the “string,” as shown in the accompanying cut. The pedal also has the somewhat irregular motion and the “quick return” characteristic of the old Facile, and of all levers which are attached to cranks. The fulcrum of this lever, as appears in the cut, and as evidently must be the case, is not fixed in all directions, but slides back and forth, giving the pedal a part of the peculiar motion of the latter.

Summing up this device, we must say that its disadvantages are in the direction of some complexity of structure, weight, and what seems at present view insufficient crank throw, with the inseparable drawbacks of lever-driving. On the other hand, the lever has some good points, among them all that is in the vertical position of the rider, the gear construction supplies its own enclosure against dirt, and the gears are of the simple spur variety, thus escaping any distinctive troubles of the bevel-gear. Arguing from the full trial on the Bantam, this gear may be expected to run well and have good endurance if properly made.