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 failure of camshaft and magneto drives on a hangar test, suspecting torsional vibration as the cause.
| Identifier | ExFiles\Box 43\3\ Scan139 | |
| Date | 10th March 1927 | |
| Hs{Lord Ernest Hives - Chair}/ACLL/GLG10.3.27. F.10. A FAILURE OF CAMSHAFT AND MAGNETO DRIVES ON HANGAR. Due to such troubles as shearing the splines of the upper vertical camshaft drive and driving pegs of the magneto brass driving pinion which have been manifest on the hangar test, and much more frequent than failures on the test bench, we suspected torsional vibration as the cause. As a first step we made some experiments in the endeavour to find the difference which existed between the test bench and airscrew driving conditions in respect to this trouble. Considerable more running has been done on the test bench and with less failures than on the hangar, therefore the matter seems all the more important. Torsional vibration diagrams were taken from the timing gear end of the crankshaft in precisely the same way as this was done on the 20 HP. and Phantom and although at present we are not entirely satisfied with the results, we have obtained the following general information :- On the hangar test with the engine driving a two-blade propeller there was evidence of a synchronous speed at approx. 1470 r.p.m. which gave a polar diagram shewing a vibration of six complete cycles per revolution. This is apparently the 'master' period of the shaft being the equivalent of the 3 cycle vibration at 3300 RPM. contd :- | ||