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).
Extract discussing the materials and performance of the American Bosch Battery Ignition system.
| Identifier | ExFiles\Box 35\6\ scan 031 | |
| Date | 1st June 1922 | |
| X2894 Extract from Oy4/G4.3.21. X.4.75- AMERICAN BOSCH BATTERY IGNITION. Contact Breaker: X.1818. X.1819. X.2894. The points are Tungsten which is used here universally on battery ignition and gives absolute satisfaction so long as the current is not excessive. The running current on the 6 volt ignition was in this case is about 1 amp. (on the 12 volt I suppose it would be about the same). From what I can gather, there is some doubt in the minds of American ignition manufacturers whether tungsten is as satisfactory in the moister climate of England as it is here. Platinum is always used in the better grade magnetos because of the greater current, though tungsten is apparently found satisfactory for trigger-operated magnetos on farm machinery and the like. The rubbing contact is a special bakelite and silk composition with the grain normal to the rubbing surface. This is said to wear very little. The Westinghouse battery ignition makes the entire cam of this material and claims on test a wear of only one thousandth in a bench run equivalent to fifty thousand miles at sixty miles per hour. RRM 3034 (50 T.S.H. 9M. 11-21) 10M 6-22 | ||