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).
Improvements to headlamp wiring and changeover switches to accommodate higher wattage lamps.
| Identifier | ExFiles\Box 168b\2\ img225 | |
| Date | 6th March 1931 | |
| -3- from switchbox to distribution box had to carry the current of both head lamps and also on the fact that the current demands of the head lamps were increased by raising these from 36 watt to 60 watt. Even now, however, as will be seen from the figures, the drop on this portion of the circuit is not very serious when there is no changeover switch. When there is a changeover switch, it appears that a (single) 40/36 wire has still been adopted from the distribution box to the changeover switch in which case there is this further length of 40/36 wire which has to carry the current of both head lamps. Not only is there an additional loss of P.D. due to this cause, but the fact that a changeover switch is in the circuit is itself responsible for an appreciable loss of P.D. before the current arrives at the head lamps. We have all along emphasised the necessity of very superior design of switch for this changeover purpose -- we have condemned certain switches such as the "Court" which had been used to a limited extent, we are not by any means satisfied with the Lucas switch and, as you may know, we are still awaiting an R.R. design of switch from Mr. Elliott. It seems probable that in the case of the car referred to by Mr. Salamanca, there may be a central lamp scheme with some changeover switch and that would probably account for the increase of light observed when heavy wires were connected direct from the battery to the head lamps. We are in complete agreement that every possible step should be taken to improve the conductance of the head lamp supply between the switchbox and the head lamps. The 40/36 wire between the switchbox and the distribution box ought to be 90/36. Any single wire from the distribution box to a changeover switch also ought to be 90/36 and preferably, especially in the case of 60 watt lamps, the feed wires to the lamps themselves ought separately to be 90/36 in place of the present 40/36. At the same time as the above, it will be our intention to watch that any changeover switch which may be standardised or considered standard shall cause no undue loss of P.D. due to the passage through it of the 10 ampere current of two 60 watt head lamps. As PNL/PH10.2.31 on this matter was addressed to yourself we are sending copies of this memo in triplicate to enable you to forward them as you think advisable. EFC. | ||