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).
Modifications to the hypoid rear axle for the 20/25 and Wraith models.
| Identifier | ExFiles\Box 102\4\ scan0090 | |
| Date | 31th January 1935 | |
| x5350 SECRET. To BY.{R.W. Bailey - Chief Engineer} from Da.{Bernard Day - Chassis Design} c.c. -Wor.{Arthur Wormald - General Works Manager} E.{Mr Elliott - Chief Engineer} Hs.{Lord Ernest Hives - Chair} Hdy.{William Hardy} RMC. Da.{Bernard Day - Chassis Design}1/HP.31.1.35. 20/25 and Wraith Hypoid Rear Axle. It is intended to use the centre casing of the Wraith axle to provide a lower gear ratio on 20/25. There is also the possibility of Wraith having a capacity of 4 1/4 litre with a low gear ratio. To deal with these it has been decided to increase the diameter of the crown wheel to 9". N. Sch.4352 herewith shewing the new gear, and casing. We have increased the diameter of the pinion thrust bearing housing to allow for a high gear ratio - 4.222 and have ascertained that a lower ratio than shewn, viz.5.145 can be fitted, but the gears required are the 4.86 ratio shewn. We have taken the opportunity to strengthen the differential. Used on the 20/25, the loads and stresses are low compared with either Bentley or SpectreCodename for Phantom III; on the 4 1/4 litre Wraith, the load per inch is less than 1600 lbs and therefore superior to SpectreCodename for Phantom III. Da.{Bernard Day - Chassis Design} | ||