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 specifications and stress calculations for the Wraith II back axle pinion and crown wheel.
| Identifier | ExFiles\Box 7\3\ X 602 Axle Rear-page04 | |
| Date | 20th June 1938 | |
| x104 602 GRY{Shadwell Grylls} - C. [REDACTED] Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} E/HDY.{William Hardy}1/HP.20.6.38. Wraith II - Back Axle. We send herewith W.Sch.4831, which gives particulars of the pinion and crown wheel for this axle. The ratio is 4.625:1 (8/37), the crown wheel pitch diameter 9.250", and the amount of hypoid 1.625". According to our calculations these gears are less highly stressed than the 8/34 ratio for Phantom III. One factor in this matter is the pinion nose bearing bridge, which, with the large amount of hypoid, has determined the inside diameter of the crown wheel. But for this we should have made the crown wheel 9" pitch diameter. To avoid a needlessly large pinion bearing housing, the pinion teeth are truncated, and in a higher ratio gear, which may be required, still more truncation will be required E/HDY.{William Hardy} W.Sch. 4831 herewith. | ||