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).
Laboratory report recommending the use of 3.5% Nickel Steel over Mild Steel for rear axle casings.
| Identifier | ExFiles\Box 171\3\ img032 | |
| Date | 31th December 1919 | |
| Laboratory. C O P Y. H19/EB31.12.19. X.3.69.-REAR AXLE CASING IN 3 1/2% N.S. From a number of tests made here, it is evident that we take an unusual amount of care in heat treating our Mild Steel, so that I do not think that failure has been due to irregularity in that direction. Since the road conditions are exceptionally bad, especially in France, we should undoubtedly be doing well in changing over from Mild Steel to Nickel Steel for Rear Axle Casings, since with Mild Steel the yield point cannot be guaranteed above about 22 tons as compared with an almost certain 40 tons in a heavily tempered Nickel Steel. Further-more, the fatigue resistance in the case of Nickel Steel is considerably greater. Another advantage that Nickel Steel has over Mild Steel is that it does not require taking to such a high temperature for heat treatment, so there is less liability to local burning or surface cracking in hardening. Nickel Steel is also preferable owing to the fact that it is not water quenched. H.C.H. | ||