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 ignition issues, coil insulation, and spark plug gap settings for 25HP and 45HP cars.
| Identifier | WestWitteringFiles\V\October1930-February1931\ Scan236 | |
| Date | 23th January 1931 | |
| HS.{Lord Ernest Hives - Chair} ~~EFC. EP.{G. Eric Platford - Chief Quality Engineer}~~) FROM R.{Sir Henry Royce} ~~E.{Mr Elliott - Chief Engineer} BY.{R.W. Bailey - Chief Engineer}~~) (At Le CanadelHenry Royce's French residence.) ~~C. to - SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} PN.{Mr Northey}~~ CAR WORK - MAGNETO IGNITION. X6097/8 X6058 X8970. [Stamp: CANAL.] It is understood that both the 25HP. and 45HP. cars will start on the magneto ignition if the battery and starting motor are normal. Also that probably owing to our battery distributor the 25HP. does not run backwards but starts forwards even by a spark on the make side while moving backwards (recoil.) If the 25HP. is possible perhaps we ought to be able to make the 45HP. also. If not what would be the cost of a hand magneto? For some time the American cars carried a spare coil when touring (I believe I can remember hearing this to be so.) I believe coils break down because there is no proper safety gap. Under certain circumstances the secondary EMF. may be very high indeed. If this is so it ought to be limited by a safety gap or the coil so insulated as to stand the maximum EMF. on open circuit for a long time, as may occur with certain condition of plugs etc. Does our jump spark distributor increase the stress upon the coil insulation? I have said elsewhere that I do not approve of more secondary turns. I am in definite favour of plugs set with closer points - i.e. between .015" and .020" i.e. 1/2 m/m as gauge for contact maker. Even .025" is too great, and .030" very excessive, and I think the cause of much of our trouble here and in USA. for some years, in complaints of cars missing fire first on magnetos, (which had short safety gaps,) and more recently on battery ignition miss-fires on 20HPs.{Horace Percy Smith - Experimental Factory Mgr} If the foregoing is in correct will HS.{Lord Ernest Hives - Chair} and EFC. point out my errors. [Stamp: RECEIVED 28 JAN 1931 R.{Sir Henry Royce}] | ||