From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Producing quiet gears using the cyanide hardening process and its advantages.
Identifier | ExFiles\Box 136\1\ scan0079 | |
Date | 2nd September 1933 guessed | |
-2- to the applied load. In service, once having obtained the correct material, there has been very little complaint of wear; They have, however, found that with increasing engine speed, the metal gear tends to wear, and they have had to increase the hardness to cope with this condition. Their method of obtaining hardened gears without distortion is most interesting and has advantages over our own procedure. PRODUCING GEARS BY THE CYANIDE PROCESS. The general procedure for obtaining quiet gears is as follows. The materiel used is a chrome steel which has a brinell of over 300 in its normal condition. The gears are hobbed in the ordinary way, numerous inspection operations being carried out and the gears being marked according to their plus or minus dimension on the pitch diameter. After being cut they are shaved on a rack which produces a finer tooth contour. The gears are then burnished by an ingenious machine in which they run against two glass hard master gears. During this process the gear is moved up and down its axis to spread its burnishing over the face of the tooth. The gears are then hardened by the cyanide process which consists of suspending the gears in a bath of sodium cyanide at about 700°C. for quite a short period, we understand about one to two hours, and then quenched in water or oil according to the hardness required. This method of hardening produces practically no distortion, we actually measured up, in its soft state, and then hardened, a gear, on checking there was no appreciable distortion. After hardening the gears are run in a silence chamber in pairs, and about 90% are passed without further work being done on them. The remaining 10% are brought up to the required condition of silence by lapping against a cast iron lap. Our impression is that the degree of silence of the Ford gearbox is exceedingly high, particularly considering the fact that they use a coarse pitch gear. Therefore, it occurs to us, in the case of timing gears, where we harden the steel gears and do not grind them, this cyanide process would be a definite advantage in obtaining absence of distortion. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||