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).
Pros and cons of earthed versus non-earthed electrical wiring schemes for a car.
| Identifier | WestWitteringFiles\E\August1920\ Scan22 | |
| Date | 6th August 1920 | |
| To EFC. from R.{Sir Henry Royce} Copy to CJ. " WOR.{Arthur Wormald - General Works Manager} " HS.{Lord Ernest Hives - Chair} " BY.{R.W. Bailey - Chief Engineer} " DA.{Bernard Day - Chassis Design} Y.4165 ORIGINAL. RE ELECTRICAL EQUIPMENT FOR R.R. CAR. (EFC4/T26/7/20) R2/G3/8/20. 6 6 AUG 1920 RECEIVED X.3659 X.3555 I telegraphed you on the 30th ulto. as follows:- Y.4169 "CLARK CONSULT WITH MR WORMALD AND AS SUGGESTED CONCENTRATE ON SOMETHING THAT WILL MATERIALISE UNDOUBTEDLY YOUR SCHEME THREE SEEMS MOST HOPEFUL Y.4173 BECAUSE YOU SAY SCHEME FOUR NONEARTHED MAKES TOO MANY WIRES BUT SCHEME FOUR IS WHAT I PREFER. WE CANNOT CONSIDER AN EARTH SCHEME UNTIL WE HEAR IF LAMPS AVAILABLE." The point I wanted embodied in our earthed scheme, and mentioned in Mr. Elliott's memo, was that the heavy motor circuit was to be insulated (i.e. non-earth) If this is done, our earth connection on our battery negative lead need only be a 20/30 amp fuse, then in case of any contact between a positive conductor and frame of car of lower resistance than, say, .5 ohms the accidental current would blow this fuse and render the lamps, ignition, and klaxon inoperative, in the same way as the blowing of a fuse on the positive side. The advantages is that in case of breakdown of insulation or the accidental earthing of any part of any circuit, (the whole wiring is either 12 volts above the frame or O, according to the position of the switches) would only give a momentary current of, say, 50 amperes, which should not set fire to anything. In our drawing of the distribution board we intended to shew(but failed to do so) this earth connector on the board via a fuse. If this is done the battery is not earthed at all. In any case we intended that the battery should only be earthed via (Contd.) F' H' S'32' (200 H) (E'D' '408' SE-4-19') BW' S122ELR? | ||