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).
Analysis of gearbox noise and gear changing issues, with suggestions for alternative gear materials and treatments.
| Identifier | ExFiles\Box 137\5\ scan0085 | |
| Date | 23th October 1929 | |
| -2- these gears would be free from distortion, and enable us to judge the design without being adversely affected by the material. In running on the road, the tone of the second speed gears is very high pitched, although quite even. It is felt by most of those who have driven the car, to be rather pleasanter than standard. This opinion is not unanimous, however. SK-370, attached, shows the relative tone of our standard gearbox, the experimental gearbox, and the Bethune design as used on Reo. Naturally, since the tone is higher, the volume of noise is less, and this is thought to be the secret of the quietness of the Reo box. Although their gear tooth frequency does not approach the limit of audibility, it is enough higher, than ours that the concurrent decrease in volume of sound may well make the gears practically inaudible. The gear changing on the first experimental box has been a disappointment, as it is no easier than standard, and is enough different to be troublesome until one is used to it. It was proposed to make the second gearbox with alternate teeth on the sliding collar and its mating gears cut back .100" to improve this feature. In connection with this report, Btnl & 2, 10-23-29 give some useful suggestions. For the sake of having the situation squarely before us, we give below some alternative suggestions to what we have already tried, with the sympton they are expected to cure. 1) Uneven Continuous Gears. A.{Mr Adams} Lapping of gears in Copeland machine before fitting. This seems essential if we are to have any success with case-hardened gears. B. Use of Nitralloy gears. The nitriding process is supposed not to give any hardening distortion. We have proven that this material is excellent in other locations, and it offers a useful alternative to case-hardened gears which must be lapped. C. Use of S/N206 Gears. These gears, not being case-hardened, may be made very accurate. Experimentally, this seems the best material to use, either alone, or in connection with Nitralloy, as we can pass upon the design without being confused by the effects of hardening distortion, and without going to the expense of making chills and laps for a number of odd-sized gears which we may never use. -continued- | ||