Quality of steel used, accuracy of pitch and fineness of fit and finish have steadily improved, and were never at so high a standard as in 1898; accuracy of cutting and scientific shaping of the sprocket teeth have also been constantly studied and show greater advance than ever, so that, as a result, the chains on this year’s product run with a smoothness and “sweetness” not before attained. The chainless movement has naturally contributed to this advance, which is a substantial fact. Quality has improved while cost of production and market price have declined, and the high-grade chain of 1898 may without extravagance of language be called “beautiful.” For instance, in a specimen before us the blocks are nickel steel, straw color, and the links are of bright tool steel; the inner edges of the links are chamfered or beveled to lessen the chance of the chain’s ever “mounting the sprocket” if it is run when too slack, and the ends of the pins are so perfectly headed that the operation has left no trace. This finely finished specimen happens to be from the Lefevre Arms Company of Syracuse, but like praise can be given to the best product of several other makers. As to strength, chains used to be made with a breaking strain as high as 1,800 pounds; we suppose the average with the narrower and lighter product of today is about 1,000 pounds, which is far beyond any driving strain it can receive.
ATTEMPTS TO DEAL WITH CHAIN FRICTION.
THAMES
TWIN-ROLLER.
The friction of the chain is of three sorts and at three places. First is the “block” friction, where and when a few blocks at a time enter and leave contact with the sprockets on the upper side, the action on the lower side (except in back-pedalling) being so free that it need not be taken into account; the second is the “pin” friction, made by the side links as they turn on the rivets; the third is where and when the ends of the links rub on the sprockets while bending.
MORSE ROLLER-JOINT
CHAIN.
There have been many attempts to turn these rubbing frictions into rolling movements. Only a few months ago application was filed for an English patent on putting balls into the chain joints; but the great number of joints and the small size of the parts make this plainly impracticable. A far better and really practical thing is the [Morse roller-joint chain], made in Trumansburg, N. Y., and now in use on several makes, among them the Sterling; it would undoubtedly make its way faster into use except that the parts have to be a little larger, and therefore the pitch a little more than the regular inch, and so the sprockets must be cut specially; sprockets of inch pitch can, however, be recut to fit. As the illustration shows, the principle of this joint is the same as that of scales—the knife-edge bearing. The pin with the two edges is fast to the side link; the pin with one edge is dropped in loosely and the two rock on each other instead of rubbing, producing no wear and so not needing lubrication. The maker claims a frictional loss by his chain of less than one per cent. of the power developed; there is always some loss, it should be observed, and so the advertisement of the Eadie roller-chain, that “it transmits practically 100 per cent. of the force applied,” is somewhat too enthusiastically worded.