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).
Letter from H.M. Hobson, Ltd. discussing angular tolerances and adjustments for a special gauge.
| Identifier | ExFiles\Box 44\3\ Scan170 | |
| Date | 22th January 1929 | |
| Messrs.Rolls-Royce,Ltd., Date 22. 1. 29. Page 2 from the vertical is a small one, then quite wide tolerances are permissible without appreciably affecting accuracy, that is to say, up to 10° a variation of plus or minus 5 would be quite permissible, but over this figure, the degree of angularity becomes more important. We originally established our tolerance and facia board angle on a standard gauge; the rise and fall in the back and front tube being approximately equal. However, with the special gauge which we have made to meet your requirements, with a much larger proportion of rise in the front glass, and increased capacity, and so a smaller amount of fall in the back of the "U" tube, the variation of the facia board angles is not so important. We are making some actual tests on your gauge, and we believe that it would be perfectly practicable to assume an all-round angle of say 7½°. The instrument need not be re-shimmed unless the angle from the vertical was less than 2½° in one direction, and 12½° in the other. We have just received your letter of the 21st inst., to which we will reply fully to-morrow. We remain, dear Sirs, Yours faithfully, H.M.HOBSON,Ltd., T.P.Searight Joint Managing Director. | ||