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).
Transmission improvements, comparing a General Motors epicyclic gearbox with a Warner box.
| Identifier | ExFiles\Box 126\1\ scan0102 | |
| Date | 26th November 1938 | |
| To By.{R.W. Bailey - Chief Engineer} c. to Hs.{Lord Ernest Hives - Chair} c. to Da.{Bernard Day - Chassis Design} c. to Hdy.{William Hardy} c. to Mx.{John H Maddocks - Chief Proving Officer} Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}10/JH.26.11.38. TRANSMISSION IMPROVEMENTS. G.E.T. Eyston has lent to us for a few days his 8 cylinder Oldsmobile which is fitted with the General Motors epicyclic gearbox. The great interest of this gearbox is that changes between overdrive and top are effected by position of the throttle pedal. This is a real advance in easy gear changing. The Olds. transmission consists of two two-speed boxes in series, the change from one box to the other being done by manual operation and the change in one of the boxes by throttle pedal. Four speeds therefore exist. Starting in 1st. gear, 2nd. automatically engages at some speed below 25 m.p.h. depending on the throttle opening; the more throttle the higher the speed. From 2nd. to top can be done at any speed by moving a lever and declutching in the ordinary way. When in this position or the high range, overdrive is always automatically engaged when overrunning. At a throttle opening depending on the speed, the box changes down into top. Therefore when travelling in overdrive a change down for overtaking is made by depressing the throttle pedal, fully, thus providing maximum acceleration. The clutch is not touched and the hands are not moved from the steering wheel. Above 70 m.p.h. direct cannot be engaged and where accelerating in direct, overdrive automatically cuts in at 70 M.P.H. This provides a safety feature for the engine. The G.M. method of achieving this gear change is complicated but the new Warner box gives the same result more cheaply, the throttle pedal operated overdrive being a series with a normal 3 speed synchromesh box. We have one of these on order from America. | ||