Propeller shaft modifications for the 20/25 model, comparing performance to the Bentley.
| Identifier | ExFiles\Box 105\2\ scan0146 | |
| Date | 27th May 1935 | |
| To E. {Mr Elliott - Chief Engineer} from HDY. {William Hardy} c. Hs {Lord Ernest Hives - Chair} /Da. {Bernard Day - Chassis Design} HDY. {William Hardy} 1/HP.27.5.35. Propeller Shaft. 20/25. Recent modifications to the axle and tyre size have increased the length and speed of the propeller shaft. We have set out the position in comparison with other shafts in the table attached hereto. It will be seen that the new shaft will be on the limit which we work to of 70% of the theoretical whirling speed, but is not appreciably worse than the Bentley with 10/41 axle (present standard) and is better than the Bentley with the new 10/43 axle, assuming that in the latter case the same car speed is reached. We understand that at 4300 the existing Bentley shaft ceases to run truly, but that there is no noticeable vibration from the shaft at speeds so far reached. The diameter of the shaft on the 20/25 is limited by the crossmember which surrounds it, and no increase can be easily made. HDY. {William Hardy} | ||
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).