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).
Comparing the capacity and construction of various condensers for battery ignition systems.
| Identifier | WestWitteringFiles\G\September1921\ Scan87 | |
| Date | 27th September 1921 | |
| R.{Sir Henry Royce} from EFC. c. CJ. c. E.{Mr Elliott - Chief Engineer} c. Da.{Bernard Day - Chassis Design} c. Hy.{Tom Haldenby - Plant Engineer} ORIGINAL EFC2/T27.9.21. X.2012 - CONDENSERS FOR BATTERY IGNITION. Further to Mr. Hives' note Hs{Lord Ernest Hives - Chair}7/LG16.9.21, we have gone into the question of the possible capacity of a mica condenser for a given volume, comparing this with the actual measured values of our own, a Liberty Delco, and a U.S.A. Bosch ignition condenser. In the case of a mica condenser, if we take the maximum possible dielectric inductivity as 6.7, and the thickness of the micas as .0015" uniformly, and of the foils .0005" uniformly, so that there are 500 dielectrics per inch of depth, we find that the possible capacity per useful cubic inch of condenser is almost exactly .5 mf. We do not think it would be practically possible to obtain a greater capacity than this. In the case of our own chassis condenser, the useful volume is .86 cu.in; the average capacity we realise is about .21 mf., so that the capacity per cu.in. is .244 mf. or rather less than half the ideal. The observed and calculated capacity correspond when the thickness of the micas is taken as uniformly .002". X3296 We have taken out a condenser from one of the Liberty Delco aero ignition sets; the actual condenser is made in two halves, one of which we are sending on to Mr. Royce for examination. The capacity of this portion (upside down text) R.R. 235A. 100 (T) (S.H. 798, 10-12-20) C 2947 | ||