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 performance, detailing issues with gear noise, 3rd gear engagement, and top gear disengagement.
| Identifier | ExFiles\Box 179\2\ img065 | |
| Date | 15th December 1931 | |
| (2) We copper deposited a set of gears to examine the bedding after some hard use and found the bedding to be good. This set of gears in whatever box, has always been the best. We have also made sets of coarser pitch gears namely of 12.DP and 10.DP (those to the M.scheme being 14.DP). The 10 pitch gears were left soft and proved to be extraordinary noisy both on the drive and overrun up to any speed, the same high pitched note being audible on any gear including top which latter was as noisy as a production 3rd. gear. On examination the teeth were found to be ridged accounting no doubt for considerable noise. The 12 pitch gears have had considerable work done on them including stoning, but are not as good as the best 14 pitch gears, the continuous gears being plainly audible up to 40 m.p.h. in top. We conclude, therefore, that we shall attain a more silent box by attention to the gears and not by alterations to the box, which might deaden the sound. From what we can find out about other gearboxes, we find the gears always have a 20° pressure angle, whereas we use 14½°. We have, therefore, put in hand a set of gears 14.DP, 20° pressure angle and the addendum increased by .009". We are also having a set of gears ground by the Birmingham Gear Grinding Co. as we cannot grind them in the works, but we do not expect much improvement from this. (2) Engagement of 3rd. gear. We have had difficulty of engagement of 3rd. gear when the teeth were just entered, but this has been overcome by giving the teeth a .035" radial clearance and also by lapping in the cones. (3) Top gear coming out. Top gear has come out of mesh on 2 out of 4 boxes on the overrun only. A considerable force on the end of the gear lever is required to keep it in mesh. Ha/Gry.{Shadwell Grylls} | ||