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).
Design proposals and specifications for the Wraith II gearbox.
| Identifier | ExFiles\Box 8\11\ 11-page029 | |
| Date | 26th June 1936 | |
| GRY{Shadwell Grylls} XTOFF 628 30 C. [REDACTED] He/Em. /HDY.{William Hardy}1/HP.26.6.36. Wraith II Gearbox. We send herewith N.Sch.4838 which shows the gears, synchromesh pieces, shafts and bearings for this box. The shaft centre distance is 3.2" which is .85 of the 3.75" Phantom III centre distance. On this basis the Wraith II box should weigh .615 of the weight of the Phantom III, i.e. 134 x .615 = 82.5 lbs. However, there are differences mainly due to the box being integral with the engine on the Wraith. The 3rd and 2nd speed gears are 9 D.P. and the constant mesh 11.45 D.P. The former are relatively coarse. The latter are made finer to accommodate the synchromesh cone fixing pins. Alternatively the constant mesh ratio could have been raised, but this is undesirable on the grounds of side shaft noise. All gears except 1st and reverse should have the Cadillac correction of pressure angle as on the Phantom III. We are proposing to use, for the first time, the spring ring location of the outer ball bearing races, which is universal on American cars. The object is to save cost in machining the box. Messrs. Hoffmann or Ransome & Marles will make these bearings for us, but so far they cannot be regarded as standard productions of these companies. We shall be sending a scheme giving dimensions for the three bearings concerned. We are also proposing that the splines on the shafts should be brought into line with American practice except in the case of the rear end of the 3rd motion shaft. The modifications consist in an increase in the number of the splines, and provision of clearance both top and bottom. The splines at the rear end of the 3rd motion shaft must be a fit on the shaft at the bottom as the oil feed from the scoop will escape otherwise. | ||