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).
Suitable insulation materials for electrical coils, comparing stabalite, ebonite, rubber, and bakelite.
| Identifier | ExFiles\Box 39\3\ Scan206 | |
| Date | 11th November 1922 | |
| Contd. -2- R1/M11.11.22. Would you please let us know what material you think could best be used in which the phenomenon found would be least likely to occur. Apparently the smaller the amount of any known material the better; and metal outside the insulation would be disastrous. There seems little to choose between stabalite and ebonite and pure rubber, and paraffin wax. Of these the only one mechanically suitable appears to be stabalite. Assuming then that this material is as good as any. Records then would suggest that a fair air space be left between a bakelite case and the coil. We can therefore only conclude that the space is no use except to keep the secondary wire away from underiable materials, so that the best coil would be one that was surrounded on the outside and at the ends by air only, all the metalwork being as far away as possible. Assuming that this is not practical, the smaller the amount of any material the better. An experiment I would suggest would be to use bakelite ends and cover, central L.T. wires, and a tube of various materials carrying the H.T. connections. This tube must be mechanically strong and capable of standing heat and moisture. I cannot think of any material that we can use, or any design that can be adopted for the coil that is more suitable than stabalite, if this material is found to be as good as any other material for electrical efficiency. In the Goshawk we use highe secondary electromotive force, because EP.{G. Eric Platford - Chief Quality Engineer} li/es plugs with wide gaps, and the | ||