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).
Analysis of an electrical effect observed when touching ignition coil cases made of different materials like bakelite and mouldensite.
| Identifier | ExFiles\Box 45\4\ Scan064 | |
| Date | 9th November 1922 | |
| EFC1/T9.11.22. -5- Contd. arranged by U.S.A. suitable for the 40/50. It was also noticed that on the coil on the Marmon car which is made up in a bakelite case the phenomenon did not appear to exist, no effect being noticed by touching the coil. This particular effect seems to vary slightly with different coil cases of the same material, (possibly slight differences in the moulding process), but with those made of mouldensite it seems to be decidedly less. We were not able to entirely eliminate the effect by heat insulating the coil from the engine, the atmosphere under the bonnet appearing to be at a temperature equal, or nearly so, to that of the metal of the engine. There is, however, an improvement, when the coil case is not in actual contact with the metal of the chassis. A difference in the amount of effect of touching the coil was noticed according as to whether the holding down bolts of the coil were in place or not, the coil standing on a non-metal packing piece. This would rather go to show that the coil case was to some extent acting as a partial conductor. The effect due to touching the case being noticeable at any point of the case and not particularly more so near the H.T. terminal, this indicating that it was at any rate not a surface leakage effect from the H.T. terminal. There might, however, be a partial conducting film on the outside of the case acting as a second plate of the condenser of which the coil case is the dielectric. Contd | ||