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).
Test report on a modified instrument board dimmer switch unit, detailing resistance, temperature, and noise improvements.
| Identifier | ExFiles\Box 168a\1\ img061 | |
| Date | 11th December 1936 | |
| Hm{Capt. W. Hallam - Head Repairs}/Wst.13/AP.11.12.36. INSTRUMENT BOARD DIMMER SWITCH UNIT TO RR.SCH.1007 We have now tested this modified dimmer switch unit and find it to be an improvement as regards heating over the previous switch tested. The windings were wound with a strand of twine between each of the turns, to give better spacing and also increase the heat radiation. This reduces the resistance from a possible 7.67 ohms to 5.2 ohms, but we found the diminution of light when coupled to an instrument panel was quite reasonable and effective. When more resistance is introduced in the external circuit, the smaller instruments become indistinct, the speedometer alone being just visible. It is considered therefore, that the resistance we have chosen above i.e. approximately 5.2 ohms. is about right. We connected the units up for test, in order to measure the temperature rise, and we found this was only 40°C. rising to 46°C. when the voltage was increased from 12 to 14. This is 20° less than the previous switch and is now considered to be satisfactory. One of the switches was very noisy due to the contact blade travelling over the resistance, producing a harsh, rasping sound. This is caused by the Vee section of the blade which we consider should be made with a broader contact surface and less angle of approach. We are now making arrangements for these three units to be fitted to Experimental cars as soon as possible for further test. Hm{Capt. W. Hallam - Head Repairs}/Wst. | ||