The Modern Bicycle and Its Accessories

by Alex Schwalbach; Julius Wilcox

THE LINK FRICTION ON SPROCKET AND PIN.

EWART CHAIN.
(Used by the Pope Co., 1888.)

As to the third of the three chain frictions above described—that of the ends of the links on the sprocket as they bend into or out of the straight line—a serious practical question is involved. Plainly, as the chain is pulled hard toward the centre of the sprocket, it must come to a firm rest on something; what shall that something be? The ends of two adjacent blocks may come to a stop on the sloping sides of the tooth or either the ends of the blocks or the ends of the side-plates (or possibly both) may rest on the space on the sprocket between the teeth; or the side-plates may have a resting place outside the teeth. There has been a flange on the sprocket, just at the base of the teeth, sometimes on both sides and sometimes on only one; this flange, called a “shroud” in England, has been quite a subject of discussion there, as to its proper purpose, and even whether it should be on the sprocket at all. All agree that it is useful in stiffening the sprocket laterally, and some, including some of the best chain makers, argue that it ought to be placed below the reach of the chain, for if the chain touches it and wears it away, the chain will sink below its correct pitch line and cause trouble. Others claim that the chief object of making a shroud was to give the chain as much bearing surface as possible. Practice is not uniform in either country. Sometimes the shroud has helped support the chain; sometimes it has been kept out of reach of the chain, and sometimes it has been cut away where the ends of the side-plates come.

BRIDGEPORT
DETACHABLE.

The pins are, of course, fixed in the links, but form a bearing within the ends of the blocks. To have these pins hard and yet be able to “upset” their ends to make a “head” has been a matter of difficulty. Some of the best English makers avoided this by using a soft pin and putting a hard bushing of pen steel over it to make a bearing. As the links do not need to be hard, the makers of the Cleveland use a hard pin with a groove at the end, and force the end of the side-plates into this groove to hold the pin in place. Other chain makers have contrived methods of getting the pin hard and still having its ends capable of being headed over. The Myers Detachable, made by the Bridgeport Chain Company of Bridgeport, Conn., and the [Baldwin Detachable], made by the Baldwin Chain Company of Worcester, Mass., avoid the difficulty by hardening the entire pin and slotting the link plates, as shown in the illustration. Any broken piece can thus be replaced, or the chain can be made longer or shorter at will, without needing any tools. The Baldwin pattern is reversible, and the makers publish a certificate of one of their chains, which has a record of 29,573 miles; of this, 13,771 miles were done without any attention or repairs being required, the remaining mileage requiring replacement of a broken part but twice.

LIBERTY SPROCKET.

We find in one of the British trade journals a mention of a “spring chain,” but there is neither cut nor detailed description. The maker claims that by inserting a dozen or so of his spring links in any suitable chain “it will be made to run as easily and smoothly as a leather driving band, and that it may be adjusted so tightly as to practically do away with all slackening on top, so that every ounce of driving pressure applied to the pedals will be reproduced on the rear sprocket wheel, thus getting rid of all backlash and consequent friction and waste of power, even when ridden over the roughest roads and by the most inexperienced pedallers.” The editor thinks it impossible, without some dynamometer test, to say whether there is any gain in driving ease, but after having one of the chains in use for a good many months he can bear out the claim of smooth running, and has found that it can be run on a tighter adjustment than the usual chain; so “it certainly seems to be satisfactory.”

CRESCENT
CHAIN ADJUSTER.

The [circular chain] is another peculiar English device, and is pronounced by its maker to be the best and easiest running, wear-resisting and cleanest he has ever tried. His claim is: “The circumferential speed of the block chain is in excess of the corresponding speed of its chain wheel teeth, hence the contradictory friction between tooth and block. The circumferential speed of this chain and its wheel are similar; entirely does away the frictional contact between the teeth of the chain wheel and the chain blocks.”

His first statement cannot possibly be correct so long as the pitch line of the sprocket and of the chain correspond, as is the case with any reasonably good fit. His chain consists of simple and uniform links, turned from the solid and joined by rivets. It suggests the old chain of the chain pump, and, of course, requires a peculiar sprocket.

The Tacagni standard pivot or rivetless is a recently offered English article. It is light, weighing 7¾ ounces, against the usual 14½. Less friction and greater strength are also claimed for it, the maker offering the report of a testing firm that the elastic limit of the sample used was 900 pounds and its breaking stress was 1440. Of course, a special sprocket grooved in the rim must be made for it.