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).
Description of the operation and features of the relay switch and the associated earthed return wiring system.
| Identifier | ExFiles\Box 31\1\ Scan112 | |
| Date | 10th December 1920 | |
| -7- Contd. Relay Switch. This switch shown in Section Fig.10a (an external view is given in Fig.10) closes the starter circuit and, as the current necessary to obtain the required torque, is very considerable, the contact surfaces have to be large. It is, of course, very important that the voltage drop be as low as possible. The switch is operated by a solenoid and the fixed contacts are self-adjusting as they are bedded on hemi-spherical seatings. In this way any trouble due to defective alignment is entirely obviated and intimate contact is obtained over a considerable area of the metallic surfaces. The main contacts are protected from pitting by subsidiary carbon sparking buttons. The relay switch is conveniently fitted to the chassis side member in a position directly between the starter and the accumulator. The amount of heavy cable is thus reduced to a minimum as it is only necessary to connect the relay switch to the push button of the switchboard.by small section leads. Wiring. The system is generally arranged for an "earthed return" and accordingly only single core cable is required. The advantage of "earth return" is that it allows better contacts and insulation to be used on bulb holders, lamp connections, etc. It is, however, very necessary to take special care with the insulation of the cables. A special type of covering has been developed which not only fulfils this conditions, but also has a very pleasing appearance and is much more durable | ||