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).
The resistance specifications and operational voltage testing for a Green Lamp Switch M, noting material composition and performance variations with temperature.
| Identifier | WestWitteringFiles\S\March1928-May1928\ Scan146 | |
| Date | 30th April 1928 | |
| EFC. AD.6. 30.4.28. GREEN LAMP SWITCH M.{Mr Moon / Mr Moore} --- This instrument has the resistance bobbin wound with manganin wire. The copper winding has a resistance of 6.25 ohms and the manganin 31.25 ohms. Total 37.5 ohms. Ratio of manganin to copper resistance 5.0. It has been set so that after heating on 16.8 volts, the points close at 16.8 volts. They then open at 9.7 volts. At 18ºC, the closing voltage is 16.5, and it was noted that the opening voltage was higher than when hot, viz. 10.0 volts. This effect may be due to distortion of the ebonite base on which the magnet cores and the fixed point pillar are mounted separately. The switch is now being fitted on 9-G3. EFC/F.J.Allen. | ||