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 length of the propeller shaft, position of the cross frame, and engine/gearbox design.
| Identifier | ExFiles\Box 94\2\ scan0099 | |
| Date | 3rd December 1936 guessed | |
| (sheet 2) gearbox this coupling became enclosed in the clutch casing and suffered considerably from deterioration due to heat and also oil. This condition still holds. (4) Length of Propeller Shaft. It is not possible to have the propeller shaft long enough to reach from the gearbox to the back axle in the case of unit construction, and it is, therefore, necessary either to have an extension shaft running in a bearing on a cross member, as was done on Peregrine, or use a tail on the gearbox to keep the length of the propeller shaft down. The Peregrine scheme gave a lot of trouble due to the noise set up in carrying the shaft on a crossmember, and up to the time P.III was designed we had no experience of the effect of a tail on the gearbox and its effect on propeller shaft vibration. P.II. of course was made en prope without such a tail, but the propeller shaft would not be equal to the speeds that we should require for a 12 cylinder engine. (5) Position of Cross in Frame. When Phantom II was first built it was designed with a cross behind the gearbox which gave us a considerable amount of grief and pain before we finally threw it out. If the sidemembers of a frame could be infinitely rigid it would not matter where the cross was placed in the length. As however this is an impossible condition it is desirable to get the cross as far forward as possible, a position which is admirably catered for by a separate gearbox. I have always maintained also that the Phantom III. position is the best relative to the type of coachwork that we normally fit. (6) It was argued from some quarters that a 40/50 engine complete with gearbox made rather a large heavy unit to handle, and that to split it up into two units would be an advantage from this point of view. | ||