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).
The use of four-speed gearboxes with overdrive in early car models from 1905 to 1910.
| Identifier | ExFiles\Box 148\5\ scan0209 | |
| Date | 28th October 1937 | |
| To Sg.{Arthur F. Sidgreaves - MD} from Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler} c. to By.{R.W. Bailey - Chief Engineer} 1260 also 1153 Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler}17/JH.28.10.37. re Early Rolls-Royce Cars. By.{R.W. Bailey - Chief Engineer} has handed me your Sg.{Arthur F. Sidgreaves - MD}17/E.27.10.37. Four speed gearboxes, with direct on 3rd. and overdrive on 4th. were used on :- All 30 H.P. 6 cyl. cars of 1905/6. Some 20 H.P. 4 cyl. cars of 1905/6. All 40/50 H.P. Silver Ghosts from early 1907 about the end of 1910 (the chassis Nos. of the 40/50's of this type being from 539 to 1015, the total number of 40/50 chassis in these series being about 275). All these cars from 1905 to 1910 used almost the same gearbox with only detail modifications. The overdrive gave an increase in roadspeed of about 24½% at constant engine speed. We hope to send you tomorrow a diagramatic sketch showing the arrangement of the gears. It is interesting to note that very high axle ratios were used on these early cars, 2.96 to 1 being quite common, and some were built as high as 2.5 on the direct drive ! Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler} | ||