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 comparing the electrical characteristics of standard and experimental coils and switches.
| Identifier | ExFiles\Box 168a\2\ img014 | |
| Date | 4th September 1930 guessed | |
| W.E.44. contd. (2) Main coil Relay coil Gauge 1.34 ohms (21 SWG) 2.56 ohms (27 SWG) Standard. .77 ohms (20 SWG) 1.92 ohms (26 SWG) at atmospheric temperature. at 12V The current taken by the coils at working temperature i.e 30 secs after switching on was found to be :- Main switch. Relay switch Exptl 76 8.5 amperes. 3.5 amperes. Standard 13.1 amperes. 4.5 amperes. The average pull on current taken by standard main switches on present production (based on results of 12 std switches) is 41 amperes, so there would appear to be still a good margin with the finer winding coils for satisfactory performance. It was found that the switch unit would operate quite satisfacto- rily on a voltage of 7 volts the main switch pulling right down. | ||