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).
Distributor dimensions and ignition timing calculations.
| Identifier | ExFiles\Box 65\3\ scan0430 | |
| Date | 15th January 1931 guessed | |
| WE 72 contd. (3) Distributor dimensions taking the pitch as 1.000 (Actually 1.267") Make Ratio .58 Range .34 Forward overlap at full advance .16 ditto at full retard .50 Backward overlap at full advance .18 - ditto - at full retard -.16 Brush .15 Segment .61 It will be seen that the contact breaker timing relative to the armature is 10° later in the advance position than our recommended figures and the make ratio being higher the retard figure is 16° later. This makes the timing for a reverse rotation retarded about the same as for a forward (normal) rotation fully advanced, thus enabling the magneto to function as well. If the magnetos was timed more equal to our recommended figures a good spark | ||