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).
Production and grinding difficulties of a proposed five-gear motion shaft for the Bentley 50 gearbox.
| Identifier | ExFiles\Box 112\2\ scan0084 | |
| Date | 31th January 1939 | |
| 828 TO Rm.{William Robotham - Chief Engineer} Da.{Bernard Day - Chassis Design}/Hdy.{William Hardy} & HPS.{Horace Percy Smith - Experimental Factory Mgr} c. RHC.{R. H. Coverley - Production Engineer} RHC{R. H. Coverley - Production Engineer}/Wld.1/FH.31.1.39. RE. BENTLEY 50 GEARBOX - Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}9/MH.{M. Huckerby}28.1.39. The 2nd. Motion Shaft with five Gears as proposed for the above piece is not, in our opinion, a practical proposition for the following reasons :- (a) The Production of the Reverse Gear is definitely tied down to one machine - the Lorenz - with consequent serious interruption to Production should the machine break down. In addition some £150 to £200 will have to be spent before one Gear can be cut, and delivery of the special parts may be as long as three months. However, you will appreciate that this Gear cannot under any circumstances be ground. (b) The grinding of the 1st. Speed Gear offers difficulties as a Production job because the diameter of the wheel must be maintained within fairly fine limits and this would mean constantly changing the wheels and maintaining a reliable supply of wheels of the correct diameter which, incidentally, is not the standard diameter. We did not have quite the same difficulties when grinding the Spur 1st. Speed Gear because although we were limited to the same maximum diameter of the wheel as on the Helical Gear, we were able to wear the wheel down very much smaller, because with the wheel head being square with the centre line of the Gear Shaft, we had no trouble with the Overdrive Gear fouling the underside of the wheel head. This is the limiting factor on the minimum size of the wheel which we can use when grinding a Helical 1st. Speed Gear. In this connection we would also point out that the grinding of the 1st. Spur Speed Gear which we have already done, was for Experimental Chassis only. We would not consider it desirable as a Production job due, partly to the time taken to grind each Gear with the consequent High Production Cost, and partly to the relatively high chance of scrap due to the hand Indexing which is necessary when grinding by this method. -cont'd- | ||