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. regarding sample thermostats, bellows, and heater switch wattage.
| Identifier | ExFiles\Box 156\2\ scan0069 | |
| Date | 13th April 1938 | |
| 1328 Telephone: SUNBURY-ON-THAMES 456 (6 LINES) Telegrams & Cables: THERMOSTAT, SUNBURY-ON-THAMES. CODE: BENTLEY'S THE BRITISH THERMOSTAT CO., LTD. Makers of Scientific Instruments. DIRECTORS: COL. N. HUDSON. J.{Mr Johnson W.M.} E.{Mr Elliott - Chief Engineer} SHERLOCK } MANAGING. W.F.F.MARTIN-HURST L.S. SWINNERTON DYER. F.G. POPLETT. TEDDINGTON WORKS. Windmill Road, Sunbury-on-Thames, Middlesex. WMH/GN: Your Ref: Rm{William Robotham - Chief Engineer}/Std.3/AP; April 13th, 1938. Messrs. Rolls-Royce Ltd. DERBY. Dear Sirs, For the attention of Mr.Steadman. We thank you for your letter of April 12th. We shall be very pleased to supply the two sample thermostats free of charge for trial purposes. We have taken particulars of the bellows used in these thermostats, but unless you particularly want them we had not proposed to send them to you, in view of the possible confusion which might arise due to different methods of measurement. If you require these dimensions please let us know. With regard to the Heater Switches, we repeat that they are only intended to dissipate 5 watts. The fact that our heater motor uses 16 watts does not imply that the resistance must be capable of dissipating this heating load. When a resistance is introduced into a motor circuit the total wattage is reduced, and this is divided between the motor and the resistance according to their respective resistances. The following example, we hope, will make this clear. Watts on Resistance. Watts in Motor. Total Watts. Motor with all resistance in (5 ohms). 5. 7. 12 " " 3/5 " " (3 ohms). 3.5 10.5. 14 " " 1/5 " " (1 ohm). 1.5 14.5 16 | ||