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).
The examination of Goshawk supercharger gears and proposed modifications to prevent fatigue cracks.
| Identifier | ExFiles\Box 10\3\ 03-page060 | |
| Date | 28th June 1938 | |
| COPY. PRIVATE & CONFIDENTIAL. S.P.T/S.2/EAG/LBG. 28. 6. 38. MEMORANDUM to Mr. Sinclair. GOSHAWK SUPERCHARGER GEARS. We have now had an opportunity of examining the supercharger gears ex Kestrel XVI engine No. 64228. These gears have run for 167 hours and were removed on account of the condition of the pinion teeth. Both the pinion and the wheel show fatigue cracks on the tooth roots, but the condition is not nearly so bad as in some cases we have seen. The most interesting feature of this set of gears is that the pinion teeth have been ground with a protuberance hob to give tip relief. This pinion, unlike all previous ones we have seen, does not show any signs of the tip of the wheel tooth digging in at the root. This modification therefore appears to be a success as far as it goes. It should be possible to increase the life of the gears considerably by eliminating the stress concentration at the root of the teeth caused by tool marks. We would therefore suggest that in future both pinion and wheel teeth should be polished at the roots. The pinion should have the teeth ground with protuberance hob, the wheel teeth should be polished, and we see no reason why the life of the gears should not be satisfactory. (Signed) E.{Mr Elliott - Chief Engineer} W. HIVES. EXPERIMENTAL DEPARTMENT. | ||