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).
Micro-examination report on fractured levers from a Phantom III front suspension unit.
| Identifier | ExFiles\Box 95\3\ scan0154 | |
| Date | 2nd October 1935 | |
| Micro-Examination Report. X 346 M.1070. Hs.{Lord Ernest Hives - Chair} from Hl. c to By.{R.W. Bailey - Chief Engineer} c to Da.{Bernard Day - Chassis Design} c to Hs{Lord Ernest Hives - Chair}/Les.{Ivan A. Leslie} HL8/JC. 2.10.35. Laboratory. Re - LEVERS FROM FRONT SUSPENSION UNIT OF PHANTOM III. (Your ref. Hs{Lord Ernest Hives - Chair}/Les.3/KW.23.9.35). Two levers were submitted:- G.81431 - Main Lever. G.81562 - Triangle Lever (Upper). Both levers have been analysed, and found to conform to the material specifications quoted on the drawing. Both levers have been tested for Brinell hardness at points close to the fractures. In each case the figures obtained were within drawing requirements:- G.81431 - 269 Brinell. G.81562 - 260 Brinell. The micro-structure of each lever was examined. It was found that the fractures were approximately at right-angles to the direction of grain-flow. The micro-structure was also examined and found to be quite normal. The micro-examination, fracture tests, and hardness tests, all confirmed the correctness of the heat-treatment. In G.81562, there were two fractures at opposite corners of the square hole. Both were of the fatigue type, due to reversed stresses concentrated at the comparatively sharp corners. It is understood that this part has been modified to eliminate the sharp corners. In G.81431, the open fracture was partly formed in fatigue and partly in tension. On the other side of the splined part, two more fatigue cracks had started, at the roots of the splines. The probable mechanism of failure has been discussed with Mr. Bailey and Mr. Leslie. It was agreed as possible, that the tension break might be due to shock owing to a seizure of the shock damper piston which had occurred previously. It was also agreed that fatigue cracks were developing at the same time, and that the design required Continued. | ||