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 A.T. Speedometer Co. Ltd. responding to test results for 40/50 hp speedometers, detailing their own findings on temperature variation.
| Identifier | ExFiles\Box 50\4\ Scan192 | |
| Date | 18th April 1928 | |
| CONTRACTORS TO THE WAR OFFICE THE ROYAL AIR FORCE AND LEADING MANUFACTURERS. A.T. SPEEDOMETER CO. LTD. X4308 Trade Mark. 20, Avonmore Road, West Kensington, London, W.14. DIRECTORS: F. {Mr Friese} T. FISHER, H. {Arthur M. Hanbury - Head Complaints} O. {Mr Oldham} BOOTH, S. D. {John DeLooze - Company Secretary} McKELLEN. Telephone: Fulham 1422. Telegrams: Aytespeedo-Hammer, London. Your Ref. EFC {E. Fowler Clarke - Electrical Engineer} 1/T. Our Ref. GOB/W. 18th April, 1928 PATENTEES & MAKERS OF MAGNETIC SPEEDOMETERS FOR MOTOR CARS AND MOTOR CYCLES. A.T. ELECTRIC SCREEN WIPERS AND PETROL LEVEL GAUGES. MOTOR CLOCKS, TACHOMETERS, MILEAGE RECORDERS. REVOLUTION COUNTERS AND INDICATORS FOR MOTOR CARS, MOTOR BOATS, ENGINES, ETC. ALL CLASSES OF SCIENTIFIC INSTRUMENTS. REPAIRS A SPECIALITY. Messrs. Rolls-Royce Limited, Nightingale Road, Derby. Dear Sirs, re - 40/50 hp Speedometers. Again referring to your letter of the 17th March, we have now completed very exhaustive tests, which we have been carrying out in regard to the above instruments, and we would like to inform you that after testing seven instruments under very carefully devised conditions with a Constant Speed Motor, we find that instruments compensated as they are at present do not show variation exceeding 1.6% which we feel is well within your requirements. Between 18°C and 30° We are at a loss to understand how the two instruments that you have tested show a variation between the same temperatures, of 5% and if it is possible for you to send us these two instruments we should be very pleased to carry out our tests on them and let you have our report. We would like to add that between 14° centigrade and 40° centigrade there is not a variation exceeding 5% on any of the instruments that we have tried and we, therefore, consider that we would be in a position to guarantee our instruments not to vary more than 3% between 18° centigrade and 30° centigrade as asked for in your letter. | ||