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).
Experiments on the Phantom III gearbox to determine the cause of unsatisfactory gear changes.
| Identifier | ExFiles\Box 94\2\ scan0215 | |
| Date | 22th April 1937 | |
| 328 Da.{Bernard Day - Chassis Design} from Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls} c. Sg.{Arthur F. Sidgreaves - MD} c. Hs.{Lord Ernest Hives - Chair} c. E.{Mr Elliott - Chief Engineer} c. By.{R.W. Bailey - Chief Engineer} Rm{William Robotham - Chief Engineer}/Gry{Shadwell Grylls}9/R.22.4.37. P.III GEARBOX. With regard to the memo from Hdy{William Hardy} - H/Hdyl/EP.{G. Eric Platford - Chief Quality Engineer}13.4.37., we disagree with the statement that the unsatisfactory gear change on the P.III is mainly due to the inertia of the clutch plate. In the early days of the P.II Synchro-mesh gearbox, we found that the effort to change gear was considerably more than on the 20/25. We did several experiments to determine the cause of this. We fitted to a 20/25 car a clutch disc having five times the usual inertia. Our figure is in excess of the present P.III clutch disc. Nobody could tell any difference in the gear change. The second experiment was to run a P.II car with no oil in the gearbox. We reported that the gear change was as good as the 20/25. The third experiment was to run with all the continuous gears absent. We found the effort required to speed up a stationary clutch plate in top gear was very small, whereas when the gears were present, it was considerable. All this evidence supports Rm{William Robotham - Chief Engineer}'s contention that an easy gear change is achieved by a small gearbox and not a small clutch plate. As regards 9° cones these may give a mathematical advantage of 11% if the entire effort to change gear is caused by speeding up the clutch member. Actually, although we have 9° cones on several experimental cars, we cannot say that they lighten the operation, but merely make it more crash proof. For this reason 9° cones are running on 35-EX in France and could soon be standardised. The increased leverage,we agree, will effect a slight improvement whatever is the cost of | ||