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 history, testing, and known faults of the 20/25 HP synchro-mesh gearbox.
| Identifier | ExFiles\Box 104\4\ scan0120 | |
| Date | 29th April 1932 | |
| To Sg.{Arthur F. Sidgreaves - MD} From Hs.{Lord Ernest Hives - Chair} c. to Wor.{Arthur Wormald - General Works Manager} 85310 Hs.{Lord Ernest Hives - Chair}5/MJ.29.4.32. 20/25 HP. SYNCHRO-MESH GEARBOX. Replying to Sg.{Arthur F. Sidgreaves - MD}5/E28.4.32. The history of the 25 HP. synchro-mesh box is as follows :- 18-G4. car which ran 10,000 miles in France started the test with a design which had the following known faults - (1) Liability of top gear working out. (2) Reverse working out. (3) Noisy gears when idling. 18-G4. car completed 10,000 miles test by the 22nd. of December, but actually we did not found a solution to the above difficulties until 18.1.32. The box fitted to R's car at Le CanadelHenry Royce's French residence has the known original faults. You will remember that you criticised the noise of the gears before the car went away. We have not had any complaints as regards the top gear or the reverse coming out, but as R.{Sir Henry Royce} and Bodd knew that with the box on 20-G4 there was a possibility of this occurring, it may not have been reported on. The modifications decided upon to overcome the faults had to be put into production right away; there was no alternative. Tests were carried out on the dynamometer and on the road, to confirm the results and on 24.2.32 18-G4. car was fitted with this gear box and has since run nearly 5,000 miles. The fault of the third speed working out was not reported on this car until 3,000 miles had been run. The third gear on this box can still be made to work out, but on the other hand under normal use we think it would be easily possible to run for six months without it ever occurring. Of all the faults we have had with the synchro-mesh box we think the working out of the third speed is the least to worry about. It does not occur if any power is going through the gear. That is, there has never been a case of it working out on the dynamometer or when climbing a hill. The trick to get it out, is to go fast down a hill on third speed with the throttle shut (a customer is not likely to do this.) | ||