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).
Response to an enquiry regarding the modification of an electrical system from double pole to single pole connections for lamps.
| Identifier | ExFiles\Box 61\2\ scan0194 | |
| Date | 4th December 1922 | |
| PN.{Mr Northey} from EFC. X. 3374 EFC1/LG4.12.22. X.3374- RE. ENQUIRY FROM MESSRS. J.W.ATHA & CO. X.4087 Answering your PN{Mr Northey}11/DN30.11.22, or rather the attached letter, it is certainly not impossible to fit lamps with single pole connections to our 40/50 chassis, but in doing so the electrical system must become more nearly an earthed system. It would be necessary to ensure that that wire (negative) of the twin conductor going to each lamp, electrically in connection with the lighting switch, should be the one connected to the central pole of the lamp - this being correctly marked as "-Pol" on their sectional diagram. We consider that the method of changing the double pole to a single pole connection, shown in their diagram, is satisfactory. Although the electrical system as standard is earthed on the positive side, it is only earthed through a fuse for the ignition circuit. It is only a semi-earthed system in that protection is afforded by this fuse against short circuits on the live negative wires. This protection is not lost in converting the system in the way described into a more completely earthed system, if this positive fuse is retained as we suggest should be the case, as the difference being that a fault causing failure of this fuse will now put out the lamps in addition to cutting off the battery ignition and if this is not objected to, in other respects the result should be satisfactory. As to whether the double pole or single pole system is preferable, that is the advantage of the double pole, that an contd:- | ||