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).
Arguing against a fully automatic charge control system, proposing a simpler, driver-operated alternative.
| Identifier | WestWitteringFiles\R\January1928-March1928\ 69 | |
| Date | 22th February 1928 | |
| EFC. } FROM R.{Sir Henry Royce} HS.{Lord Ernest Hives - Chair} } (At Le CanadelHenry Royce's French residence.) BT.{Capt. J. S. Burt - Engineer} } REC'D.{John DeLooze - Company Secretary} R1/M19.2.28. DESPATCHED FROM WW. 22.2.28. PHANTOM & 20HP. AUTO: CHARGE CONTROL. X40DE X40MO. Cc to BT.{Capt. J. S. Burt - Engineer} WOR.{Arthur Wormald - General Works Manager} E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} RO.{C. C. Rose - Export Manager} C. CMB. SG.{Arthur F. Sidgreaves - MD}FN. You will remember that I feared to fit this as an entirely auto: device. I am still of that opinion. Owing to the extreme difficulty of tracing out and correcting any failure to function by the average garage mechanic I think we should keep the electrical system as simple as possible, and also if it fails it should do as little harm as possible. Any auto: device throws the responsibility upon the maker, and it is principally from this point of view that we do not fit thermo: control of the water temperature. Often it is impossible to avoid automatic parts, and get the work done well enough (i.e. carburetter and ignition) but in this case we have a very good alternative which will shew the driver when he has got a full charge, and leave it for him to switch off, so that if our apparatus fails he can ignore it; its failure should not make it impossible to get any current from the dynamo. I believe I have written all this before but little or no notice has been taken of it. In my earlier memos. I gave the alternative schemes and why I feared the entirely auto: device. My observation on the two cars with which our modified Midgley system is fitted has not increased my confidence: they have not worked the same on each car - ours on EAC.7., 14-EX., cuts in and out every time the klaxon is sounded. I think the simplest and safest scheme is to let the magnetic contact maker light a green lamp when the volts arrive at the maximum pre-determined amount, and ask the driver to turn off the charge. I believe E.{Mr Elliott - Chief Engineer} suggested or re-suggested this. You will realise that there are so many things to make the magnetic arrangement work wrongly that it would be dangerous to leave it to the auto: device, and take it entirely out of the driver's hands. I know very many ways of attempting to correct the temperature fault but I do not know one simple and effective. My impression is that if we could make a bi-metal strip that would bring the armature nearer to the core when hot, it might be the simplest. Another way is to make a hold off spring to weaken with temperature rise. On the auto: lighting plants (Austin and others) a permanent magnet type of instrument is used to make contact at an exact voltage, practically independent of temperature. This moving coil contact maker has a resistance in series with it made of one of the alloys which has a small negative temperature co-efficient. We much thank Mr. Clarke for his care, skill, and perseverance with this apparatus, but I fear it is not quite in the right direction, and I cannot help asking him to turn his attention to the alternative scheme mentioned in this memo. R.{Sir Henry Royce} | ||