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).
Gearbox improvements, focusing on reducing second gear noise and enhancing the ease of shifting.
| Identifier | ExFiles\Box 137\5\ scan0086 | |
| Date | 11th February 1929 guessed | |
| -3- 2) Audible Second Speed Gears. A.{Mr Adams} From a consideration of axle ratio and tire size, we know that the ratio of the speed of the Reo propeller shaft to the speed of the RR propeller shaft is 129/77. To give the same gear tooth frequency, therefore, the ratio of the number of teeth on the Reo 2nd. speed driven gear to the number on the RR 2nd. speed driven gear should be 77/129. Since the number of teeth on this gear in the Reo box is 30 ( on the half having the fewer teeth), the number we should use to get the same tone is approximately 50. On the other half of the gear we should expect to use about 67 teeth. Inspection of SK-370 discloses that we have gone only halfway toward the degree of silence obtained with the Reo box, and it is thought that the use of gears having a larger number of teeth is the logical next step. B. In this connection also, it will be remembered that Bethune suggested the expedient of turning the gears around to rotate in the opposite direction. We do not know what effect this has on the sound, but have his word that it is apt to make some difference. It is interesting to note that the published photographs of the Reo box (Automotive Industries 8-31-29) show the V pointing in the direction of rotation of the continuous gears, and opposite to the direction of rotation of the 2nd. speed gears. 3) Ease of Gear Shifting. A.{Mr Adams} We have proposed cutting back alternate teeth on mating parts of the dog clutch. B. Pearson's scheme, of cutting two out of three teeth on the gear completely away, and cutting back two out of three teeth on the sliding internal gear, to a distance equal to about 1/3 the total amount of engagement. It is claimed that it is impossible to miss the shift with this arrangement of parts. We believe that the production of a silent, easy changing gearbox is one of the most urgent jobs we have on hand, particularly in view of the sweeping claims which are being made by manufacturers of cheap cars. It is though most advisable to carry on our experiments along the lines outlined above, so that we may have advance information on the subject when it becomes advisable to standardise some such scheme. Experimental Dept. [Signature H.{Arthur M. Hanbury - Head Complaints} F.{Mr Friese} Pullan] | ||