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).
Magneto timing, comparing the make and break periods of different magneto types to optimise performance.
| Identifier | ExFiles\Box 48\2\ Scan352 | |
| Date | 27th January 1926 guessed | |
| EFC {E. Fowler Clarke - Electrical Engineer} 3/T27.1.26. -3- Contd. in a magneto without a sleeve. That means to say that approximately we have only to consider one timing of the make, i.e. that in relation to the sleeve, for all positions of the contact breaker lever, though of course in the case of non-sleeve machines a compromise would have to be made between times of make suitable for the retarded and advanced positions. However, it is a fact that whereas the time of make of the Watford magneto with flat cams is 156°, the time of make of the B.T.H. (with sleeve) is 97°, and the times of the Simms and Lucas are 77° and 79°, respectively. There seems no doubt that the general performance of the Watford magneto would be better if the time of making were reduced to the neighbourhood of 100°. Only one time of make has to be considered. The approximately right amount on principle must be in the neighbourhood of 100°, though, as previously stated, the variation of ± 5° is not of much consequence. It is also considered that the instant of break is too early for the best all round results, and that it would be better about 15° to 20° later. Summing up, therefore, we think that the make occurs far too early and the break a little too early, and that the whole period of make is to large by an amount represented by the difference of these earlinesses. | ||