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).
Gearbox for 'Japan 3', comparing ratios and design changes with existing models.
| Identifier | ExFiles\Box 104\4\ scan0201 | |
| Date | 4th September 1933 | |
| X5310. To EY. from HDY.{William Hardy} c. For W. S. De. HHG. [Text has been struck through] Gearbox - Japan 3. We send herewith N. Sch. 3788/9/90/91, 3797, 3805/6, which we think give all the information required for detailing the rear half of the gearbox with synchromesh 2nd, 3rd and top gears. We also send N. Sch. 3808 which shows the gears in the front compartment. The actuating gear and casing for the front half will follow within two days. Compared with the 20/25 box the shaft centres and pitch of teeth are the same but increases of strength have been made to the 1st and 3rd motion shaft with the idea that this box may be suitable for use on the SpectreCodename for Phantom III. The gearbox ratios suggested for J.3. are: Present 20/25 .743 .485 .308 R .314. For SpectreCodename for Phantom III .727 .475 .302 .308 Present Phan: .748 .503 .317 R .323 It will be seen that the 1st and 2nd speed gears have been interchanged in position. The advantages gained by this arrangement are: (1) Shorter reverse shaft. (2) The reverse shaft does not limit the dia. of the 2nd speed clutch which can, if necessary, be made as large as the layshaft will permit. The gearbox casing is to be made to take the large 2nd speed clutch as shewn by N. Sch's 3805 and 6, but the first box should have the small clutch in order that it may be determined whether the small one will do. | ||