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).
Technical report on synchromesh gearbox issues, focusing on top and 3rd gear engagement, and experiments with cone angles.
| Identifier | ExFiles\Box 15\5\ Scan302 | |
| Date | 3rd May 1932 | |
| 87310 To. H.{Arthur M. Hanbury - Head Complaints} from Hw/Gry.{Shadwell Grylls} c. to Sz. for. c. to S. By.{R.W. Bailey - Chief Engineer} c. to Dn. P.II. SYNCHROMESH. It was reported on 19-M in France, that top gear worked out as well as 3rd. The former we could not understand until we discovered that top gear was not being fully engaged. This was due to the chamfering of a taper pin in the operating mechanism. The 3rd and 4th sliding piece, therefore, relying only on friction for its movement, did not accurately follow the gear lever, remaining sometimes in gear, when the lever was in neutral. M.{Mr Moon / Mr Moore} is replacing this pin with a key so that the trouble should not happen again. This also explains the trouble with the selector mechanism when the 3rd and 4th rod moved while in 2nd gear. We first thought this was due to the cones seizing. 3rd gear would occasionally come out on the overrun on both cars. We have fitted to 22-M a new 3rd motion shaft with centralised splines, as was found successful on the 25 HP. This has proved satisfactory, 3rd gear showing no tendency to work out. We shall fit this type of shaft to all production gearboxes. The effort required to change gear has been greatly diminished by the use of a lower oil level and also by the adoption of engine oil instead of gear oil. With 6 pints in the box we carried out several ascents and descents of 1 in 4 hill on both 2nd and 1st gears. At no time did the gears become noisy due to lack of oil. Nor has the 3rd gear become noisier with the thinner oil. We have experimented with various cone angles in the synchromesh to make the change into 3rd easier. With 45°, as on 1-M, we consider the effort required unnecessarily great and so have tried on 22-M, in conjunction with the new oil conditions, a 18° cone and a 30° cone. With the former it was too easy to crash the gears, but the 30° cone we think better than 45°. On this car, however, we are still having trouble due to the cones sticking, making it difficult, and sometimes impossible, to engage the teeth. We shall therefore lap the mating pair of cones together in a machine which we have just started using for overcoming the same trouble on the 25 HP. production boxes. If this is successful in preventing the cones sticking, we shall have a change from top to 3rd up to the 25 HP. standard. At the moment we are not free from trouble with side-shaft noise. We think this is due to the ball races. Hw/Gry.{Shadwell Grylls} | ||