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).
Graph showing maximum cap-speed curves for a present production battery ignition coil.
| Identifier | WestWitteringFiles\D\May1920\ Scan23 | |
| Date | 5th May 1920 | |
| MAXIMUM CAP-SPEED CURVES FOR PRESENT PRODUCTION BATTERY IGNITION COIL (X3445.) I CURVE (b) CURVE (a) (INCHES) 0 100 200 300 R.P.M. OF CONTACT BREAKER 400 600 800 1000 1200 1400 1600 1800 Recd. 5/5/20 3/73 8/5/20 | ||