Secret memorandum discussing the procurement and manufacturing process for the Wraith gearbox.
| Identifier | ExFiles\Box 8\11\ 11-page058 | |
| Date | 28th January 1937 | |
| 105G 628 SECRET. Rm {William Robotham - Chief Engineer} /FJH. {Fred J. Hardy - Chief Dev. Engineer} from Rm. {William Robotham - Chief Engineer} Rm {William Robotham - Chief Engineer} 22/R.28.1.37. WRAITH GEAR BOX. We want to get some unground gears for the Wraith box. As far as we can ascertain the most satisfactory unground gears are made from steel which does not case-harden but is tempered to a fine Brinnel of 450 after machining and that this tempering process does not cause distortion. The crux of the matter, therefore, is to get a tooth form which is correct when the gear is cut. It appears to be generally assumed that the Fellowes machine gives an accurate tooth form but that this may not be sufficiently accurate and that a shaving operation is necessary. The National Broach Co. of Detroit supply a machine for this job, and Ford's have one. We want to start with continuous gears on the Wraith, and when we get something which is sufficiently silent we can apply it to the rest of the box. We recommend that we first get a set of gears cut on the Fellowes only, but with a fine finishing cut, have them Cyanide tempered, and try them out. If we have not a Fellowes machine at the Works, we shall have to get somebody outside to do the job. If it is necessary to alter the gear ratios to use existing tackle, we do not mind doing this. If the gears are not sufficiently quiet, we shall have to try and get them shaved, either by (1) Buying a rack from America and getting our gears done on a machine which is at present in the country. (2) If this is impossible, buying a machine and carrying out the experiment ourselves. By tackling the Agents for the machine you will find out how many there are in the country. It may be necessary to burnish, but you can decide this yourself. We should like you to let McWilliams, who is RHC {R. H. Coverley - Production Engineer} 's man on the job, know what you are | ||
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).