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 the complex and costly construction of thermostat E.86612.
| Identifier | ExFiles\Box 156\1\ scan0071 | |
| Date | 15th April 1935 guessed | |
| - 3 - Messrs. Rolls-Royce Ltd. In such a thermostat it is customary to keep the bellows movement to a minimum, which further simplifies the adjustment. In the case of your Thermostat, E.86612, you have adopted the exact opposite of the normal procedure by requiring the bellows to be of an exact spring rate, and by taking from the bellows the absolute maximum safe movement obtainable. You have no doubt very good reasons for following this procedure, but in so doing you make the construction so exceedingly difficult that such units could scarcely be produced commercially and in experimental quantities must be exceedingly costly. For your information, our head tester has spent 2 1/2 days in getting these six units to their present stage. If it were necessary to allow this length of time for testing each six units, the selling price would be at least four times the figure which we quoted you. If you care to let us have a description and a drawing showing the purpose for which this thermostat is used, we shall be pleased to review the matter and to make any suggestions which, in our opinion, would simplify the construction. We hope that you will be agreeable to take this step. Yours truly, THE BRITISH THERMOSTAT CO. LTD. W. Martin-Hurst. | ||