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).
Manufacturing particulars and alternative gear ratios for Wraith III steering cams.
| Identifier | ExFiles\Box 9\7\ 07-page158 | |
| Date | 7th March 1938 | |
| 650 To RHC{R. H. Coverley - Production Engineer}/SB.{Mr Bull/Mr Bannister} from Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} c. By.{R.W. Bailey - Chief Engineer}___________ Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}10/AP.7.3.38 WRAITH III. STEERING CAMS. We give below the particulars of the Wraith III. steering cams which you require for the Fellows Gear Shaper Co., The Adamant Co. at present produce these cams by an end milling cutter. With this method it is not necessary for the gear ratio between cutter head and cam blank to be an even number. In the Fellows process this ratio must be even as the cutter consists of a complete gearwheel. The original Wraith cam, to Adamant No.M.22166, had a working ratio in the gear of 13.45 to 1 and the cutting ratio was 14.167 to 1. Owing to the trouble experienced with eccentricity of cams on Production the Adamant Co. increased the backlash on the locks by using a ratio of 14.933 to 1, the working ratio remaining at 13.45. This cam is shown on Adamant drawing M.22517. If the Fellows process is more accurate than the Adamant process it may be practicable to reduce the cutting ratio, and so reduce the backlash on the locks. In this case a 14 tooth cutter could be used still with the same working ratio of 13.45 to 1. The alternative is a 15 tooth cutter which will produce a cam almost identical to the present standard, M.22517. We think that the Fellows Co. are the best people to decide which is the cutter to use. If the Fellows Co. consider that neither of the above cutters are practicable they may wish to alter the working ratio slightly. In this case we prefer that the alteration should be in the direction which gives a lower geared steering i.e. the existing ratio of 13.45 to 1 should be made 14 to 1 rather than 13 to 1. An alteration to the working ratio will involve slight alterations to the outer profile of the roller follower. Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} | ||