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).
Secret memo regarding modifications to four-speed gearboxes for India, discussing issues with 1st and 2nd speed pinions.
| Identifier | ExFiles\Box 6\4\ 04-page122 | |
| Date | 1st September 1925 | |
| To CJ. from R.{Sir Henry Royce} c. to BY.{R.W. Bailey - Chief Engineer} HS.{Lord Ernest Hives - Chair} X.5310 S E C R E T. RL/146.S.25 I N D I A.{Mr Adams} FOUR SPEED BOXES. X.5310 With reference to your memo. re. 4-speed boxes it was towards the end of Feb. that Derby were advised of the increased size of the 1st. and 2nd. speed pinions. These have never been tested. We know that any increase in the dia. of these pinions will help to keep them still on the shaft. it only requires a little now to make the 1st. speed satisfactory for ever, because it seems as though with the improvements we have already made, the 2nd. speed which is somewhat larger, is quite satisfactory. Unfortunately Derby have gone on making the boxes, including these two gears, and I think these will have to be scrapped because I do not anticipate the box will be really satisfactory until the small pinion stays quietly on its shaft, and it will be necessary to make some modification to the splines also. This has been forced upon us because the modifications have not quite overcome the 1st. speed trouble. The only modification which has been embodied is the torsionally free pinion and this has proved not quite enough for the 1st. and reverse, so that it is advisable to do all we can by making this slight increase in the dia. unless it proves that the increased angle of the splines, (which can be increased up to 60°, as telegraphed from Le CanadelHenry Royce's French residence direct from Derby), before we should anticipate the slightest trouble from such contd :- | ||