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).
The design and wiring of a four-terminal fault detection unit within the vehicle's electrical system.
| Identifier | ExFiles\Box 59\1\ Scan162 | |
| Date | 12th October 1927 guessed | |
| -5- Contd. We have carefully considered as to whether this unit should be made with three or four terminals, and if with three, as to whether the common terminal should be on the top or positive side, or on the bottom or negative side, and our final conclusion is that the unit should be made with four terminals and be connected as shown on the diagram, in which the operating foil or heater, as the case may be, is connected between the dynamo terminals A and B of the distribution box and the contacts which are operated thereby are between the ammeter side of the main fuse in the distribution box and the live terminal of the high water temperature indicator lamp, whose other terminal is connected to earth. It will be seen that the unit will function corresponding to a break in the dynamobattery circuit anywhere as mentioned in (c) above, but not in that portion between the dynamo commutator under the negative brush, and the corresponding A terminal on the distribution board, i.e. it would not show danger when there was a sticking negative brush leading to a high voltage operative upon the dynamo field, (remembering that the auto switch is not, for the present, considered to be included in the diagram). The relay would be set to operate at about 16 1/2 volts and the lighting of the lamp in question, would mean that something was wrong, viz (1) Water temperature too high, (2) Voltage of system too high and charge must be switched off either by main switch or auxiliary dynamo charge switch if install (We may remark in passing that the indepe ent switch for switching off the charge | ||