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).
Modifications to the Phantom III gearbox's 3rd speed driven gear to strengthen it.
| Identifier | ExFiles\Box 94\1\ scan0299 | |
| Date | 13th January 1936 | |
| X326 L.E. Smith EY. C.E.L. MS. DA.{Bernard Day - Chassis Design} MHC. Hs{Lord Ernest Hives - Chair}/Fm. Gearbox - Phantom III. E/HDY.{William Hardy}1/HP.13.1.36. We send herewith N.Sch.4734 which shows what we suggest to strengthen the neck in the 3rd speed driven gear between the clutch teeth and the gear. We have obtained a 50% increase of thickness by reducing the present .035 root clearances to .022 and by reducing the clearance for the shaper cutter to .010. The depth of engagement is reduced from .107 to .100. We are aware that the present .035 root clearances were asked for by the Experimental Dept. in 1931 to facilitate engagement of the teeth, but we think that some reduction of this can be safely made as we cannot visualise the teeth being as much as .022 eccentric to one another nor can the raising of burrs in the teeth be likely to cause more loss than 3/1000" according to our measurements. We have truncated the teeth on the inner sliding piece. Any interference when cutting is now reduced. The cutter for the teeth on the gear must be topped, but it is otherwise standard. The oil holes in the gear are rearranged. It is essential that all cars that will pass into customers hands should have these modifications. N.Sch.4734 herewith. E/HDY.{William Hardy} | ||