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).
Comparing propeller shaft specifications and performance for the 25/30 HP car.
| Identifier | ExFiles\Box 105\2\ scan0147 | |
| Date | 20th December 1935 | |
| HS{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer} (crossed out) 1537 C.BY. G.W. Hancock Rm{William Robotham - Chief Engineer} Please let me know Rm{William Robotham - Chief Engineer} E/Lid.{A. J. Lidsey}2/HP.20.12.35 Propeller Shaft for 25/30 HP. Car. The propeller shaft for the 25/30 HP. chassis will be 1.6" longer than the one used on the 20/25 HP.chassis because of the hypoid rear axle. The comparative figures for the two are as follows:- Length Dia. Whirling Speed. 70% whirling speed/safe speed. Max. R.P.M. Ratio. Safe Speed/Max Speed. 20/25 HP. 54.912 3.000 6500 4550 4000 1.137 25/30 HP. 56.512 3.000" 6150 4300 4000 1.075 From these figures it is apparent that if we make no alteration in the diameter of the propeller shaft we shall be 6% worse off as regards propeller shaft roughness. Before the shaft is instructed, therefore, will you kindly confirm that no unpleasant periods, ascribable to the propeller shaft, are apparent up to the maximum revs of 4,000. This propeller shaft was run for 10,000 miles in France on 21-G-4 with smaller wheels than we are going to use on the 25/30 HP. but we cannot trace any report as to its freedom from roughness. E/Lid.{A. J. Lidsey} (Signature) | ||