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).
Description of the features of the 12 volt Lucas type electrical system on the 40/50s model.
| Identifier | Morton\M3.5\ img012 | |
| Date | 9th April 1925 | |
| (19) DAE FROM R.{Sir Henry Royce} SECRET ORIGINAL E.A.C. DESCRIPTION: Copy to HS.{Lord Ernest Hives - Chair} R1/MS 9.4.25. X8780 I am not sure if anyone has written pointing out features of the electrical system other than those on past 40/50s. - i.e. Lucas type. X.4617 - This model retains the same 12 volt electrical system, and we are pleased to say that accumulators, like tyres, are now much more reliable, but still the chief thing to guard against is undercharging, as any lead battery left un-charged is rapidly degenerating, and if possible it is extremely good to arrange that when the car is in the garage, a very small current can be run through it, about 1 amp. or less. RR. have done all that is in their power that is at present known by making the dynamo to cut in at an extremely slow speed, and to fall off at high speed, (therefore favourable for under and over charging.) X8560 - The installation on the car is simply wired because it is believed it is in so many ways simpler to understand and keep in good order, one thoroughly well insulated wire being better than two more doubtful ones. This especially applies to the smaller fittings such as lampholders. It is absolutely impossible to make an equally good and reliable scheme of double wiring. X8730 - The switchbox is extremely well made with multiple wipe contacts which should last reliably the life of the rest of the installation. It controls also the ignition, and can be locked in all suitable positions. It is arranged for running separately on either or both ignitions, for the object of proving if both are in perfect working order, which is so useful in case of trouble, including carburation faults. For safety against fire and an accidental fault on any small fitting putting the installation into difficulties, the distributing box is fitted with a liberal number of fuses which are made of fine copper wire mounted on easily detach-able carriers, of a very superior design for reliability as can be seen from inspection. The starter system is the same as for several years - by press button and magnetic switch and motor connection. This is unusually silent in operation and has been well proved to give no trouble in service. X8604 An extremely nice small point in the installation is the use of different coloured wires for different circuits care-fully labelled with diagrams within the distributing box in-struction book to make the whole installation as easily under-stood as possible. This 40/50 installation is very similar to the one of RR. manufacture, which has been so satisfactory on the 20HP. RR. Naturally there are several points of difference in both size of dynamo etc. and arrangement of the ignition system etc. R.{Sir Henry Royce} | ||