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).
Calculations for piston position and spark timing relative to a hand magneto.
| Identifier | ExFiles\Box 43\4\ Scan061 | |
| Date | 9th February 1927 guessed | |
| -2- For instantaneous position of piston when hand magneto begins to send sparks to cylinder, we have:- Retard of centre line of trailing brush behind leading edge of main brush = 1.202 {+.113} = 1.315 (relative) Distance travelled by trailing brush from position occupied when main advanced spark takes place to position midway between segments = 1.315 - .044 - 1/2(1-.266) = .904. = 27° This on engine = 54° or 54° - 35° A.D.P. i.e. 19°. A.D.P. EFC. | ||