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 on the failure analysis of a Bentley back axle pinion.
| Identifier | ExFiles\Box 83\2\ scan0317 | |
| Date | 21th March 1938 | |
| ✓Rm.{William Robotham - Chief Engineer} from H1/EJW. C BY ---- M.1,556. LABORATORY. H1/EJW.2/GS.21.3.38. BENTLEY BACK AXLE PINION. Your Ref: Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}4/AP.26.2.38. This pinion failed on chassis 6.B.IV. during test in France, after 4972 miles. It was made in U.S.A. owing to lack of a suitable cutter required on account of a change in ratio. The pinion was marked : made in U.S.A. G37. 4620. 10-43 1835 M.D.4.526 to shoulder. The failure of the roller track is illustrated in the attached photo. No.M.1,556/1. As requested in your memo, we examined the material in the damaged part for slag inclusions but could not find anything abnormal. The condition of the case was very unsatisfactory. It had an extremely coarse structure, which is sufficiently indicated by the fracture - see photo. M.1,556/3. A transverse section through the track gave the photo. M.1,556/2 indicating variations in the condition of the case. Rockwell hardness tests on the case at the side of the track gave figures varying from C44 to C53. The highest figure is thus considerably below the desirable hardness for a good case. The lowest figures, C44 - C49, were obtained adjacent to the left part of the damaged region as seen in photo. M.1,556/1. The steel used was of the following composition :- Carbon ................ 0.15% Manganese ............. 0.52% Nickel ................ 3.36% Chromium .............. 0.25% This could be S.A.E. 2315 or 2320. The Brinell hardness of the core was 273 - 281 beneath the failed track. H1/EJW [Signature] | ||