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).
Confidential memo discussing design points and issues with a modified gearbox.
| Identifier | ExFiles\Box 137\5\ scan0088 | |
| Date | 23th October 1929 | |
| Btn-2 Oct. 23, 1929. CONFIDENTIAL To: Mr. Bagnall Co- Mr. Olley (Await return) Mr. Beaver Expl.Dept. From: Mr. Burton Modified Gearbox We have today issued some definite instructions for the assembly of the second gearbox, under D-3709. In getting out the first box, we have run across several points in design that we did not realize at the time. 1. Any inaccuracy in double helical gears, whether it is eccentricity or distortion, produces end movement of the mating gear. This is eliminated in the Reo box by having a plain bearing side shaft with all sorts of end movement, letting the helical gears control the locations entirely. This is rather difficult to do in our box as we have housings for ball bearings and a very limited side play in the bearings. It is conceivable that we might fit up a box with a side shaft mounted entirely on Hoffman Roller Bearings but this is rather expensive and would take the hammering of the starter clutch entirely on the teeth of the constant mesh gears. We are laying out a scheme of this nature to see what is involved. 2. By retaining Bethune's pitches, with a considerably larger size of gear, we have run into a high pitched whine on 2nd speed. We do not know whether this is caused by lack of backlash in the teeth, inaccuracies in the tooth form, or whether it is characteristic of the gears running at the speed we get. If the latter, it suggests rather that we should have kept Bethune's number of teeth rather than his pitches, so that we would get the same no. of teeth in contact per minute, giving rise to the same natural note. We shall know more about this when the Nickel Steel gears are running. 3. We are undoubtedly very severely handicapped by the large size and peripheral speed of our gears in comparison with those of other people. This would suggest the biggest argument in favor of the use of the unit gearbox which has considerably reduced short centers, and a corresponding reduction in the size of the gears. Btn. RBB-M | ||