The Modern Bicycle and Its Accessories

by Alex Schwalbach; Julius Wilcox

VICTOR CHAIN TEST.

If an accurate measure of the pressure required on the pedal in order to overcome the varying resistances of surface, grade and wind, or what not, could be found, then the resistance in each case could be weighed and recorded in pounds. The Victor dynamometer—which is a peculiar pedal, containing a pair of springs, with a recording pencil and a moving roll of paper for making a record—does this weighing. Obviously the first effect of pressure on this box-like pedal is to depress the springs; and the wheel will not be moved at all until the springs have been depressed enough to represent the resistance. Suppose the total resistance is equal to lifting a weight of ten pounds, then press on the pedal; the springs will first yield until the equivalent of ten pounds is reached, then the pedal will move and the wheel will turn. If the resistance changes to fifteen and then to five pounds, the springs will yield more and then less, and the pencil attached will register accordingly, the result being an irregular line similar to that on the steam engineer’s “indicator card.”

If the dynamometer pedal were used on the road the irregular line on the card would show resistance fluctuations, but would not show the various times and causes of resistance encountered. So, for a test of the peculiar sprocket, a bicycle fitted with it was put on a stand and a resistance equal to seven and six-tenths pounds at the rim of the wheel was arranged. Then mud was daubed on the chain, and pressure was put on the dynamometer pedal. The height of the wave line above the straight or zero line in the diagram indicates the power required to turn the wheel. It ranged from 88 to 94 pounds, and was nearly uniform. Then another bicycle, with usual sprockets, was set on the stand, with the same resistance at the wheel rim. The same chain used before was put on (for this is a matter of sprocket only, and any usual chain both fits and answers the purpose), mud was again daubed on the chain, and the test was made. The pull required to turn each ranged from 96 to 160 pounds, and fluctuated greatly, as indicated in the other diagram. When the tests were carried further and the resistance at the tire was brought up to 11¼ pounds the ordinary sprocket clogged under the mud and could not be turned at all, while the straight-line sprocket moved about as before, the card indicating a pull of 128 to 131½ pounds applied.

WOLFF-AMERICAN
CHAIN ADJUSTER.

At the Victor branch in Warren street, a bicycle with these sprockets rests on a stand, with a box of Jersey mud and a dish of water and a trowel underneath; anybody is free to mix the compound to suit, and to load on all the chain will carry. Then he may get on the saddle, there being an adjustable brake for the rear wheel to represent road resistance, and pedal away; or he may turn by hand. When the mudded slack of chain reaches the rear sprocket, the first effect is a crunching noise and a partial stoppage; this ceases when one revolution has been made, and directly the wheel (the brake being off) spins as freely and quietly as does another bicycle with the like sprockets which is mounted, all clean, on another stand. The mud test is actual and fair. The snapping noise which every rider knows is produced by mud on the chain, especially when the bicycle is new and the fit is at its best, comes because the mud acts as a wedge between sprocket and chain and the latter is temporarily put “out of pitch.” The surprising performance of this sprocket under the severest possible mud test can have only this explanation: that the spaces cut away allow some room for mud without jamming, and that the sprocket clears itself by throwing out the intruder. It is certainly one of the most remarkable things of the season, and seems quite independent of outside disturbance, hardly needing a case except for cleanliness and length of wear.

CHAIN BOLTS AND REPAIRS.

Of course, the ends of the chain have to be joined, and sometimes they need to be separated for removal. The customary way has been to use a screw-bolt, threaded into the link-plate on one side, and fastened with a small lock-nut. As this small nut was liable to loosen and be lost, and as there was also a possibility of the screw itself working out (in which case it might strike something as the chain moved or might drop out on the road) some securer fastening became desirable. The [“Diamond” B] chain now dispenses with the nut (as shown in the cut of that make of chains) using in place of it a swinging “latch” of thin steel; the head of the screw fits nearly flush into the side-link, and the latch has a place raised up in one end to fit the screw head, so that when this latch is turned down it snaps into place, preventing the screw from backing out and being itself held fast by its own elasticity. The Humber carries on its chain a similar latch, but slightly different in shape at the end, which has a hexagonal hole that fits the head of the screw. The [Crescent] meets the case by dispensing with the screw-bolt. As shown in the cut, the side links are slotted, and in the centre of the slot is an enlarged place through which a special pin with grooved ends can be slipped in or out by slacking the chain for the purpose.