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).
Cost reduction features of the Phoenix gearbox design.
| Identifier | ExFiles\Box 112\2\ scan0040 | |
| Date | 28th September 1937 | |
| SECRET By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} Hs.{Lord Ernest Hives - Chair} Da.{Bernard Day - Chassis Design} Hdy.{William Hardy} 1044 Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}12/AP.28.9.37 828. PHOENIX GEARBOX The primary objective of the Phoenix gearbox is reduction in cost. There is no doubt that the most expensive feature of present R.R. gearboxes is the centre bearing which necessitates a side shaft assembly of about nine pieces of which five are splined gears, and one a splined shaft instead of one solid piece. To achieve the desired cost reduction we think that the following major departures from R.R. practice will be necessary:- (1) No centre bearing. (2) Integral side shaft. (3) 2nd. speed synchromesh on 3rd. motion shaft. (4) Non-positive synchromesh for top and 3rd. (5) Unground 1st. speed gears. As the required torque capacity of this box is about .65 of the P.III, the stiffest assembly would be obtained by scaling down the universal box .65 lengthways only. The constant mesh and 3rd. speed (or overdrive) gears will be at either end of the box in which case a positive synchromesh would be more costly than now. No one has yet brought forward any evidence that rigidity of gear mountings is an essential of silence. We have examples of 3rd. and 2nd. speed gears which after prolonged testing have considerable slack on their mountings, but are no noisier. In every case, gear noise in new designs or production boxes has been overcome by better finish of the gear teeth. We do not think the lack of central bearing will adversely affect silence. Whether or not we can get away with a non-positive synchromesh for top and 3rd will shortly be known by the result of an experiment we are doing on 22.C.V. Obviously, if no departures are made from the usual R.R. standards no cheapening will result. Our investigations on P.III. and Wraith have shown that changes in material provide only a few shillings reduction and are more liable to failures. continued | ||