Test results for a 6-volt armoured ignition coil (DeJon coil) run without a ballast for 15 and 44 hours.
| Identifier | ExFiles\Box 53\3\ Scan136 | |
| Date | 2nd November 1927 | |
| OY1O.R.11227. X4581 November 2nd, 1927. Mr. E. {Mr Elliott - Chief Engineer} F. {Mr Friese} Clark, Rolls-Royce Ltd. Derby, England. Dear Mr. Clark: RE IGNITION. COIL WITHOUT BALLAST. X.3129 X.4581. Completing recent correspondence on this matter we have now left a 6 volt battery connected to an armoured coil without ballast (DeJon coil) for two periods of 15 hours and 44 hours respectively. 15 hours: Battery Spec.Grav. Start 1250 Finish 1175 Room temp. " 24oC " 20oC Coil " 24oC " 58oC 44 hours: Battery Spec.Grav. Start 1250 Finish below 1100 Room temp. " 22oC " 12oC Coil temp. " 24oC " 23oC. In neither case was there any damage to the coil. Yours very truly, Maurice Olley MO/R. | ||
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).