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).
Investigation into the effect of headlamp load on the electrical system's auto switch, proposing the removal of the series coil.
| Identifier | WestWitteringFiles\R\2October1927-November-1927\ 149 | |
| Date | 17th November 1927 | |
| To R.{Sir Henry Royce} from EFC. c. BJ. CWB. c. BY.{R.W. Bailey - Chief Engineer} Wor.{Arthur Wormald - General Works Manager} c. E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} AUTO SWITCH. XCC025 In investigating the effect of the headlamp load on the operation of the electrical system with the auto switch, we have arrived at the fact that the series coil can probably be entirely dispensed with, with the added advantage that the risk of burning out the headlamps (on open battery circuit) due to the negative ampere turns of the headlamp through the series coil putting the auto switch out of action, is eliminated. In any case only a very small number of negative series ampere turns would be required because the Reg load of the headlamps reduces the voltage of the system and therefore the voltage operative on the shunt coil of the auto switch by a relatively large amount. The fact that at the instant of switching on the headlamps their filaments are cold and therefore of much less resistance helps us materially in giving an additional and instantaneous lowering of the voltage which enables the auto switch to re-make contact when the headlamps are put on. There is no difficulty in arranging the auto switch mechanically so that the operating and returning voltages cover a suitable range. We are aiming tentatively at an operating voltage of the auto switch of 17.0 after having been heated up on 17.0 volts in a normally warm atmosphere, also at a letting back voltage of round about 12.0. We want this voltage to be such that the system will carry a small load such as the ignition for a considerable time (or the side | ||