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 The British Thermostat Co. Ltd. discussing thermostat design and temperature specifications.
| Identifier | ExFiles\Box 156\1\ scan0094 | |
| Date | 16th May 1935 guessed | |
| - 2 - Messrs. Rolls-Royce Limited. 11°C. whereas you specify 7°C. We feel that it is a great pity that the orthodox methods of construction cannot be followed in your case, since these prove entirely satisfactory both from the point of view of manufacture, and also of subsequent service on the vehicle. As we have told you, the thermostats which we are at present manufacturing will keep the water temperature constant within a degree or so, and we think you will agree that such control is up to the high standards which you have set in the motor vehicle industry. In the circumstances we can see no object in complicating the design and manufacture when the ultimate control cannot be improved. As we have already explained the bad feature in your design is that you ask us to make a temperature sensitive element which shall be accurate at each end of a temperature range without providing any adjustment. While it is true that you might obtain from us 100 instruments which all give precisely the same characteristics, you will appreciate that the slightest variation in the springiness of the bellows would upset this temperature range, and no satisfactory check of this could be made until the instruments were assembled ready for testing. We are enclosing copies of Drawings, Nos: BGA. 1743C, 1982, 1882 and 3040 showing various designs which are in production, and which you will agree are as simple as they could possibly be. Any one of these designs will give the control described, and we would suggest that you check over once more whether the constructions shown cannot be embodied in your own design. Yours truly, THE BRITISH THERMOSTAT CO. LTD. W. Martin-Hurst. ENCLS: | ||