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).
Modifications to the wiring layout for a Left Hand Drive car to convert it to a positive earth system.
| Identifier | ExFiles\Box 124\4\ scan0137 | |
| Date | 29th April 1940 | |
| 1046 Ev.{Ivan Evernden - coachwork} from Rm{William Robotham - Chief Engineer}/RC.{R. Childs} Rm{William Robotham - Chief Engineer}/RC.{R. Childs}9/JS.{Mr Johnson's Secretary}29.4.40. LEFT HAND CAR. In order to simplify the drawing up of the wiring layout for the Left Hand car, which will have a positive earth system, we have made some notes on the attached print to DB.{Donald Bastow - Suspensions}2403. The necessary modifications are as follows:- (1.) Any unit having a symbol mark "+" should be altered, and the letter "B" marked in its place. This will make the unit suitable for either system, (with the exception of the dynamo) (2.) No ballast will be required for the ignition. Also a twin contact breaker distributor will be used. B.V. has a single lever unit, and requires a ballast for the coil. (3.) Because the current is passed round the circuit in the opposite direction to standard B.V., the connections to the ammeter will need changing over. (4.) The Battery will be changed round so as to earth the positive instead of the negative terminal. The dynamo and regulator unit will be as standard B.V. as, by changing the battery potential over and initially magnetising the field in the required direction will cause the dynamo to build up its E.M.F. in the right direction. It will be noticed that the theoretical diagram for B.V. to DB.{Donald Bastow - Suspensions}2403 does not agree with the wiring layout to DB.{Donald Bastow - Suspensions}2412 in that, on DB.{Donald Bastow - Suspensions}2403 the cable from the instrument lights is connected to the bottom terminal of No.5 fuse whereas on DB.{Donald Bastow - Suspensions}2412 it is connected to No.5 terminal of the switch box. The latter arrangement is preferred on account of the shorter and easier run for this circuit. We realise that in doing this the 30 amp. fuse is bypassed, but consider that the layout is reasonably safe. The symbol 'C' on the dynamo is a relic of the old third brush machine where we had three terminals labelled A, B, and C. We think it would be better now to mar P.1 | ||