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 memorandum detailing three issues with the 25 HP Synchromesh gearbox.
| Identifier | ExFiles\Box 179\2\ img064 | |
| Date | 15th December 1931 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} c. to SE. Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} Ds. c. to Hy.{Tom Haldenby - Plant Engineer} 25 HP. SYNCHROMESH. We have had, in addition to reverse gear coming out, three troubles with this gearbox :- (1) Noise both idling and running in 3rd. gear. (2) Difficulty of engagement of 3rd. gear. (3) Top gear coming out of mesh. (1) Noise. We started with the idea that other manufacturers had found it easy to make a silent gear and we tested two Chrysler cars that had very silent 3rd. gears. On examination of these boxes we found they had internal or spool gears. We then tried a De Soto car with a constant mesh spur gear 2nd. This was noisier than our box and we were led to believe that they had had trouble with the roller bearing on the sideshaft which was very noisy. We have also tried a Vauxhall car with constant mesh helical 2nd but this was not as good as our best box. On our own box we started with a very bad idling noise most of which vanished on fitting a plain bronze bearing instead of the rollers supporting the 3rd. motion shaft in the 1st. motion shaft. On 3rd. gear the noise we complain of is on the overrun from 35 to 20 and again at 10 m.p.h. and is generally worst at 24 m.p.h. We have tried a cast iron gearbox which effected a slight improvement but not in our opinion one that justified the extra weight. We then tried shrouding the helical gears in an aluminium box, the shrouds being cast integrally with the box and having a .025 clearance round the gears, but this had no effect. A box fitted with plain bearings throughout instead of ball races was considerably quieter but does not seem a practical way of achieving silence. Experiments we have done with different gears and with 3rd. gears absent lead us to believe that the greater part of the noise comes from the constant mesh gears and not from the pair of 3rd. continuous gears. | ||