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).
Rheostatic switches for Clayton car heaters, including cost, testing, and recommendations.
| Identifier | ExFiles\Box 137\2\ scan0144 | |
| Date | 3rd September 1938 | |
| 1158 To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Std. c. By/RD. c. Hn.{F. C. Honeyman - Retail orders} RHEOSTATIC SWITCHES FOR CLAYTON CAR HEATERS (S.2.C.A. TYPE). We have obtained a cost figure for the car heater rheostatic switch to DCD.709 - this is 4/4d. per switch (black finish) with approx. £70 tool cost. We have also tested a switch with the same maximum resistance as that of DCD.709 and it gives a speed range on the Clayton S.2.C.A. type heater of 1750-2800 r.p.m. when the heater motor is warm. Messrs. Lucas have a rheostatic switch which appears a sound job mechanically and which can be bought for approx 2/6d. without any tool cost. By/RD. has had one of these switches specially built up with a 6 ohm resistance wire in it and we have then tested it on a Clayton S.2.C.A. heater measuring the speed obtained at various switch positions, temperature which the switch reaches, resistance of the switch for the various positions and relative noisiness of the motor and fan at the various speeds - for results see attached sheet. From these results, it appears that with the Lucas switch it is not safe to use a resistance wire of more than 2.55 ohms (max. temperature reached is 60°C. with 25° ambient temperature) which gives a speed range of 2170 r.p.m. to 2800 r.p.m., which will give a fair degree of heating control and will permit the noise level of the heater (with the car stationary) to be reduced to a degree which will not cause annoyance. We recommend therefore, that for the heaters which are being fitted up on Wraith bodies, the Lucas switch fitted with a 2.55 ohm resistance, black knob and the necessary modifications to accommodate an "on off" dial etc. should be used - will By/RD. please make the necessary arrangements with Messrs. Lucas and Hn.{F. C. Honeyman - Retail orders} accordingly. Rm{William Robotham - Chief Engineer}/Std. | ||