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).
Material test laboratory report on the case failure of Bentley V steering cams.
| Identifier | ExFiles\Box 153\4\ scan0095 | |
| Date | 5th May 1941 | |
| COPY Rm {William Robotham - Chief Engineer} /FJH. {Fred J. Hardy - Chief Dev. Engineer} Material Test Laboratory. H1/GLT.S/JK.S.5.41. Case Failure on Bentley V. {VIENNA} Steering Cams. Rm {William Robotham - Chief Engineer} /FJH. {Fred J. Hardy - Chief Dev. Engineer} 1/RH. {R. Hollingworth} 7.1.41. Two steering cams were sent to the laboratory for investigation. They both showed cracking and flaking of the case; failure in both cams had occured entirely on the pressure face at the ends of the thread. Tests for case and core hardness and depth of case gave the following results :- Hardness of Case Hardness of Core Depth of Case. Cam 1. 61 C Rockwell. 349 Brinell. .026" - .030" Cam 2. 60 C " 345 " .030" The case-hardness is normal, but the case is thin; we would say that approximately .050" is a suitable depth. Moreover, the core hardness is low, as the specification calls for 388 - 415 Brinell. We understand that these cams were run on cars with large section tyres, which would cause unusually heavy loading on the cams, especially at the ends of the threads. This heavy loading of a thin case, insufficiently supported by the soft core, resulted in scoring, cracking and eventually, flacking away of the case. H1/GLT. | ||