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 issues causing backward running and potential cures for EW6 type magnetos.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan147 | |
| Date | 6th January 1931 | |
| -2- EFC2/ADL6.1.31 contd. In regard to firing the right cylinder to produce backward running, it may be remembered that as long ago as 1919 we produced a model contact breaker and distributor upon which all phenomena connected with make and break and distributor timing can be analysed. This model has been used in the present connection and shows very readily that with the combination of make ratio quantity of the magneto and equivalent rotor periphery of the magneto in relation to distributor pitch, how, when the engine runs backward the spark will take place to the wrong cylinder for correcting the engine to forward running, particularly if the distributor brush is erroneously too far advanced. A cure for this would be to increase the make ratio of the magneto but this would be wrong as regards the first portion considered. Another cure would be to increase the circumferential length of brush plus distributor segment in relation to distributor pitch but this cannot be done with present distributor dimensions at the same time as retaining a reasonable insulation distance in the distributor. The only possible cure apparently, therefore, for this backward running as described is in making the make and break timing of the magneto in relation to the armature functioning more nearly correct in accordance with principle and possibly with a bias over in the other direction. It will be remembered that the magneto in question is of the EW6 type and not of the later EW6A type with improved slow speed functioning. A magneto of this later type has replaced the EW6 magneto on the car and therefore trials will be made because if the magneto speed is great enough to cause the cylinder to fire when the engine is cranked over top centre, the bouncing back condition should never arise. We are arranging to return the EW6 magneto removed to the makers and asking them to arrange it in accordance with our recommended timing. EFC. EFC. | ||