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).
Letter to Cadillac Motor Car Co. discussing calculations for the whirling speed of a Phantom II propeller shaft.
| Identifier | ExFiles\Box 170\2\ img097 | |
| Date | 1st October 1931 | |
| Expl. Dept. Ha/Gry.{Shadwell Grylls}2/MJ. 1st. October 1931. M.{Mr Moon / Mr Moore} Olley Esq., Cadillac Motor Car Co., Detroit, Michigan. Dear Mr. Olley, Hs.{Lord Ernest Hives - Chair} has asked me to reply to your query about the Phantom 11 propeller shaft. We have found one of these shafts on measurement to be 59" between mechanics joints which, assuming the formula w = (π/l)² √(EI/m) should whirl at 4100 RPM. We think there must be some mistake on the drawing from which you quote the length as 64". Even if it were, by our formula the whirling speed would be 3480. We should be interested to hear, therefore, whether your experts employ a formula giving a lower and hence probably more accurate estimate of the whirling speed We have run a Phantom 11 propeller shaft up to 3500 R.P.M. at which speed the centre of the shaft was beginning to run out of truth. We should not expect the maximum amplitude to be reached until 500 R.P.M. above this speed. Yours faithfully, | ||