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).
Bench tests and analysis of a failed Springfield De Jon ignition coil.
| Identifier | WestWitteringFiles\V\2January1931-April1931\ Scan037 | |
| Date | 9th February 1931 | |
| To R.{Sir Henry Royce} from EFC. c.c. Eg. Wor.{Arthur Wormald - General Works Manager} c. Dy.{F R Danby} E.{Mr Elliott - Chief Engineer} EFC2/AM 9.2.31. X.6101. SPRINGFIELD DE JON IGNITION COIL. Bench tests on one of the above coils have been made in accordance with the specification of ignition coil tests evolved for the purpose of comparatively testing different types of construction of R.R. ignition coils. The De Jon coil failed during the heating test No.6 which test our own ignition coils pass easily. The symptoms were a short circuit or a relatively low resistance H.T. leak in the secondary and it was therefore considered possible, if the windings themselves were O.K., that the insulating properties of the secondary insulation were affected by the heating. The coil did not appear to get so hot internally as the Delco Remy coil recently tested (see report EFC1/AD24.12.30). Our experience of R.R. coils which have failed in service results in the conclusion that there should be a good temperature margin to ensure satisfactory performance in customers' hands in all circumstances. Hence our suggestion that the wheeless position of the coil as on the 20/25 should be reverted to on the Phantom. The U.S.A. coils are all hermetically sealed in their cases and this may affect the rate of heat dissipation. It may be the case that our heat test was too severe but nevertheless our present standard coil passes it and before relaxing conditions of test it is necessary to confirm the severity or otherwise of the test conditions by actual chassis measurements. Such measurements are being made The De Jon coil has now been unwound for examination of its construction and to ascertain the cause of failure and the following is a copy of my assistant's report WE.80 giving details of the design construction observed :- | ||