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 insulating properties of bakelite in a Goshawk coil and proposals for testing.
| Identifier | ExFiles\Box 45\4\ Scan072 | |
| Date | 10th November 1922 | |
| R.R. 199 (50T) (SD576 19-7-17) M/1806 X4079a To EFC. from R.{Sir Henry Royce} R2/M10.11.22. X. 3485 - GOSHAWK COIL. X.4079.a It was quite unsuspected, if you find as anticipated that the insulating properties of bakelite are very much reduced at increased temperature. The insulation of the secondary winding, lead, terminal, and circuits, must at all temperatures be very high - 10 megohms would be about right. Kindly test the lossesf from this source. I propose the use of an electrostatic (Wimshurst) machine might be useful as a means of testing the leakage properties of such materials. This would remove the risk of wrong conclusions that may be drawn by using altemating current through electrostatic capacity, etc. Regarding the phenomenon of the touch on the coil and the hand around the coil, this might easily be due to the attraction and repulsion due to electrification, but why should this vary with temperatures ? Does also the electro inductive capacity of bakelite vary with temperature; if so, might our condenser (oiled silk) be a source of variation in the efficiency of the ignition ? R.{Sir Henry Royce} | ||