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).
Investigation into a constant mesh gear failure on chassis B-5-AE, concluding it was a one-off manufacturing error.
| Identifier | ExFiles\Box 27a\1\ Scan454 | |
| Date | 29th May 1936 | |
| W/P. (Sr). c. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} GRY{Shadwell Grylls}- X1-45 Rm{William Robotham - Chief Engineer} (signature) EY.17/G.29.5.36. FAILURE OF CONSTANT MESH GEARS. CHASSIS NO. B-5-AE. MR. DE LA{L. A. Archer} CUADRA. Referring to your memo VA.2/ET.7.4.36. this is the first failure of a helical side shaft which we have had, although we have been fitting these for the whole period of production of the 20/25 and Bentley cars. My impression was that by a fault in carburising or in cutting the bottom of the tooth had been cleared of the carburised material. An examination of the tooth, by taking a section and etching same proved that this had occurred with the result that the base of the tooth was seriously weakened. Some years ago we had a similar experience with regard to the straight cut spur gears of the 3rd speed ratio on the 20 HP. car, and at that time we instructed that all gears must be carburised completely on the tooth section and the carburised material not cleared from the root in accordance with general practice, as a result we never had another failure. It is evident that the gear on the first motion shaft was peculiar in this respect, as the gear from the same box on the second motion shaft was hardened at the roots of the teeth, and as a result of an examination of gears in the Works it was quite clear that no/series of gears had been produced in a similar manner to the one which had failed, and furthermore it has been our practice long before the Bentley was produced to have the gear teeth outline completely carburised, and therefore one can only assume that a single gear had been treated wrongly either in the process of carburisation or cutting, just how this could have occurred it is difficult to understand, in fact had it not been for the failure I should have been positive that it was not possible for us to produce such a gear, and I am certain that the gear is a 'freak', and does not represent a batch of gears during any period of our production. BY.{R.W. Bailey - Chief Engineer} BM (signature) | ||