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).
Coil temperature tests comparing the cooling effect of metal versus bakelite ignition coil cases.
| Identifier | ExFiles\Box 164\5\ img345 | |
| Date | 12th May 1938 | |
| To BY.{R.W. Bailey - Chief Engineer} c. to BY/RD. 6017. Rm{William Robotham - Chief Engineer}/RC.{R. Childs}8/JH.12.5.38. COIL TEMPERATURE TESTS. In order to ascertain whether on ignition coils, a metal case has any advantage over the bakelite case, we have carried out a number of tests using various types of coils, with and without their respective cases. The following results prove that the metal case has a marked cooling effect which the bakelite case does not possess. Test (1) 2 hours run on the ignition rig at a distributor speed of 800 r.p.m. make ratio .55 primary volts kept constant at 12.5 volts. Ambient temp. 19°C. | | Delco | Wraith 20,000 | R.R. SPECIAL | Lucas. | |---|---|---|---|---| | With case. primary temperatures. | No ballast. 92.2 °C. METAL | 63.8 °C. BAKELITE | No ballast. 85.4 °C. BAKELITE | To our specification. 49.1 °C. BAKELITE | | Without case. primary temperatures | 124.2°C. | 55.2°C. | 86.0 °C. | 44.9°C. | Test (2) Constant current of 1.75 amperes was passed through the windings for a period of 2 hours the coil being placed in an oven. During the latter part of the test the ambient temperature was 36°C. | | Delco | Wraith 20,000 | R.R. SPECIAL | Lucas. | |---|---|---|---|---| | With case. primary temperature. | No ballast. 81°C. | 50.2°C. | No ballast. 90°C. | To our specification. 42.8°C. | | Without Case. Primary temperature. | 100.5°C. | 40.2°C. | 88°C. | 42.8°C. | | ||