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).
Over-drive gearbox, its ratios, and proposed changes to the gear gate layout.
| Identifier | ExFiles\Box 96\3\ scan0179 | |
| Date | 24th February 1937 | |
| 363 Sg.{Arthur F. Sidgreaves - MD} from Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} c. to Cx.{Major Len W. Cox - Advertising Manager} Rm{William Robotham - Chief Engineer}/Gry{Shadwell Grylls}3/R.24.2.37. 36-Ex. We are sending this car to London on Friday, so as to arrive at Lillie Hall about mid-day. The interesting features are the over-drive gearbox and the new stay between the gearbox and engine to reduce chunking. The overdrive box was the best compromise we could obtain without altering the casting and with the minimum of other alterations. The over-drive gear itself is what we think to be the correct ratio. The engine revs. at the same road speeds are reduced to 4/5ths of the direct high gear figure. The first speed ratio is slightly lower than the standard second speed, and the second speed is slightly lower than the standard third speed. The position of the gears in the gate is thus:- If the over-drive is adopted, it will be essential to increase the shaft centres in the box by .3". This is in order to obtain a low enough first gear ratio. We recommend that when a design is made on these lines, the positions in the gear gate are:- This will provide a slightly simpler mechanism in the box than the existing arrangement. Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} | ||