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).
Advantages and disadvantages of different ignition control systems, including magneto and battery options.
| Identifier | Morton\M3.2\ img013 | |
| Date | 1st January 1925 | |
| TO HS.{Lord Ernest Hives - Chair} E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} BT.{Capt. J. S. Burt - Engineer} CJ. BJ. PN.{Mr Northey} CWB. FROM R.{Sir Henry Royce} SECRET E.{Mr Elliott - Chief Engineer} A.{Mr Adams} C. 'V' SERIES - IGNITION CONTROL. X8685 X4187 X8680 X8690 I have written at various times my reasons for this scheme, and my objections to the Scintilla magneto. I do not agree that there is much difference in complication and cost between two separate governors and our single governor and relay, but since the Scintilla mechanism is buried it is not as obvious. Some of the centre scheme is due to difficulties with all magnetos available, which is not met in the Scintilla combination. When we have two ignition plugs well apart as intended later (new head) it is imperative for these to fire exactly together, both for their proper working, (i.e. both must fire before pressure rises) and also to avoid disastrously objectionable detonations. This is why I wanted the ignition to depend on one governor and control. I also understood that Scintilla was the only automatic advance magneto available, and it was foreign and would cause much trouble in spares throughout our business. It had a type of advance that caused it to be feeble at slow speeds retarded, therefore not good for slow speeds, and could not be used for hand starting the engine, should the battery be run down. I am not sure that the Watford sleeve magneto is entirely satisfactory for the above, but we could not get over the trouble of hand starting by fitting a hand magneto as in aero engines. There is still another combination which is fairly safe and good, that is to use two battery towers and a magneto to standby as we do in Goshawk. We did not think much of this because of current consumption and complication, but I now understand that coils can be made to take less current, and if the two schemes are objected to, I think BY.{R.W. Bailey - Chief Engineer} E.{Mr Elliott - Chief Engineer} & HS.{Lord Ernest Hives - Chair} should meet and decide what is best to offer Sales officials. SS.{S. Smith} R.{Sir Henry Royce} could I believe quickly arrange the two battery towers was done by us for the American car. I thought our scheme was good because it permitted any magneto to be used (don't use sleeve type if too much friction in control) also when once fitted up in synchronism it ought not to get out. It had a selling point namely, of calling attention to the loss of lubricating oil to the engine. But experience would soon shew if it was sufficiently reliable - my only anxiety. In the case of 2 separate governors one may act more quickly, and also both may be somewhat erratic and cause inexplicable detonations especially if we had two separate wide apart plugs as in the new head, when detonations would be very bad. Ask the critics to learn all the facts and then be very anxious not to hurt the feelings of those who have tried to produce something by suggesting they are very foolish people. E.{Mr Elliott - Chief Engineer} and I gave our best blood to try to get a good scheme. R.{Sir Henry Royce} | ||