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).
Preliminary report detailing the history and experience with the Bethune Gearbox D-3709.
| Identifier | ExFiles\Box 137\5\ scan0084 | |
| Date | 6th November 1929 | |
| Expl.-1 November 6, 1929. TO: Mr. Olley (England) FROM: Experimental Dept. cc Mr. Beaver Mr. Burton PRELIMINARY REPORT - BETHUNE GEARBOX - D-3709. SECTION 6030. It is thought that a history of our experience with this gearbox will be of interest at this time. On our first attempt at assembling the box, the continuous gears were found to have a high spot, and to be extremely tight in mesh. Two attempts at lapping in Mr. Buckley's rig, to increase the backlash, improved the situation considerably. There was still a perceptible high spot in the continuous gears, however. It will be remembered that the original design called for removal of the spigot from the starter epicyclic and the locating flange from the bore in the gearbox, so that the second M.S. would be located entirely from the continuous gears. It was noticed that the 2nd. speed gears (which have given us absolutely no trouble) moved back and forth endways, relative to each other, for every revolution, and it was therefore supposed that the continuous gears were trying to do the same thing, but were restrained by friction between the 2nd. M.{Mr Moon / Mr Moore} S. bearings and the case. This was substantiated by the fact that the tightness and noise of the continuous gears could be materially increased or decreased by knocking the sideshaft one way or the other, while running. Easing the bores for the 2nd. M.{Mr Moon / Mr Moore} S. bearings improved the situation somewhat, but did not eliminate the trouble. Hoffman roller bearings were then fitted to the 1st. M.{Mr Moon / Mr Moore} S., and the 2nd. M.{Mr Moon / Mr Moore} S. locked in what appeared to be the best position by means of packing washers. In this condition it was still possible to feel a slight high spot while running on the rig. The gearbox was put in the chassis and has run 2,000 miles since. The tight spot noticed in the continuous gears is very noticeable on the road at certain times. Ordinarily, however, it cannot be heard. As this was thought to be due to hardening distortion, and it was not desired to make special laps for these gears on the Copeland machine, Mr. Burton on Oct. 15th instructed the production of two additional sets of gears, one in Nitralloy and one in S/N206. It was expected that -continued- | ||