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).
Recommendation on chassis and powertrain design, comparing various car models and future gearbox options.
| Identifier | ExFiles\Box 148\5\ scan0093 | |
| Date | 19th November 1935 | |
| -2- Our recommendation is that the two chassis frames, brake gear, steering, axles and suspension layout should be identical. That the increased accommodation required on the Phantom should be obtained by inserting the required length in the frame. The frame width does not dictate body width, an example being the Cadillac. Therefore, the increased width can be obtained on the coachwork and possibly by the wheels and brake drums being moved out if found necessary. The chief difference between the two cars would be in the size and design of the power unit and gearbox. The big car should have the larger engine of more expensive design to save weight, and a gearbox to deal with the increased torque. If this policy were followed, all that would be necessary to get an improved 20/25 into production would be the design, development and production of a new unit and gearbox. Carrying the simplification of the programme throughout the range, we consider that by our success with the Bentley we have shewn that the engine and gearbox which is suitable for the 20/25 will, with minor modifications, do for the sports car admirably. Briefly, we expect a different head, induction system and camshaft with altered gearbox ratios. The gearbox at present designed and partially manufactured for these two cars is the one intended for the Wraith. We admit that if starting with a clean sheet of paper, we should not repeat this gearbox, because we consider that the four speed box with three synchromesh gears has become too complicated, costly, and bulky for the duty which it is likely to have to perform in the future. Whether or no we can go to a three speed box, however, depends on the type of engine unit employed. We consider that if a 12-cylinder engine is used, then three speeds are adequate, particularly if they have the added advantage of permitting remote control and easy ingress on the driving side. The reason the 12-cylinder allows of this is because its wider speed range permits of a 10 to 15% reduction in axle ratio. | ||