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 to Mr. Minchin of Messrs. Feto & Radford regarding the testing and adjustment of an instrument's speed readings.
| Identifier | ExFiles\Box 50\4\ Scan319 | |
| Date | 30th October 1929 | |
| X4308 EFC6/AD. 30th October, 1929. Mr. Minchin, Messrs. Feto & Radford, 50, Grosvenor Gardens, London, S.W.1. Dear Mr. Minchin, We found that the adjustment in the instrument was at its maximum value, so we could not increase the reading without remagnetising. This we have done. We have tapped and boiled the magnet down to a stable condition and now adjusted the instrument to read speeds about 3% high in itself when cold. Actually at 600 r.p.m. it reads 54.8 m.p.h. when at atmospheric temperature (18°C) and 53.4 m.p.h. at 25°C. You will remember that the actually correct reading is 53.3 so the instrument will be exactly correct in itself at 25.5°C. Our testing speed of nearly 600 is very exactly ascertainable, as it is a synchronous speed from the Derby mains. We have not checked the instrument at other speeds but we know from previous tests that the scale is quite nicely proportional. We are, from previous experience, doubtful that a loss of magnetism has actually occurred, as any definite observations which we made in this direction have given negative results. We shall therefore, be very interested in the permanence or otherwise of the speed indications of the instrument as now rearranged, to the extent, if convenient, of making a further test on this when it has done 5 to 10 thousand miles. We are having the instrument despatched back to you tonight. | ||