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 operational speciality of an instrument's compound magnetic circuit and cut-out mechanism.
| Identifier | WestWitteringFiles\F\April1921\ Scan68 | |
| Date | 1st April 1921 | |
| Contd. -2- EFC2/T3. 4. 21. The speciality of the instrument, however, is that the magnetic circuit is compound and that the movable element is pivoted over the top of the central leg of a three-legged magnetic circuit with common yoke, and is attracted at the right hand or left hand variable gap in appropriate circumstances. As regards the cutting-in, the cut-out works as an ordinary cut-out, the shunt coil current through the series turns assisting in causing the flux to traverse the right hand portion of the compound magnetic circuit, and in these circumstances very little flux passes across the left hand air gap. After contact has been made, it appears that at some time in the growth of the series current running to the battery, the flux across the left hand air gap becomes zero and reverses. When the dynamo speed reduces and the series current falls, this flux reverses back again to its original direction and when the series current becomes powerful enough to prevent the shunt coil from producing flux across the right hand air gap, a comparatively large flux is passing across the left hand air gap and assists the spring in causing the pull off quite definitely. A feature that is claimed for this cut-out is that owing to the definite pull off which is produced magnetically, and which is stronger the stronger the reverse current, the cut-out cannot possibly stick. Further, the cut-out will not stick on, as we have verified, if the dynamo be stopped and the cut-out be pushed up by hand with the switch on. [Text at bottom, upside down]: R.R. 235A (50) (T S) H.{Arthur M. Hanbury - Head Complaints} 936. 19-2-21. C-8008 | ||