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).
Temperature tests of coils, discussing spark-over E.M.F., distributor discharge, and winding breakdowns.
| Identifier | ExFiles\Box 45\4\ Scan204 | |
| Date | 8th September 1923 | |
| PN.{Mr Northey} from EFC. c. BJ. X 4079 EFC1/T8.9.23. X.4079 - TEMPERATURE TESTS OF COILS IN CASES OF VARIOUS MATERIALS. Answering your PN{Mr Northey}1/DP/7.9.23, the reduction in the spark-over E.M.F. due to gaps being operated at atmospheric pressure is compensated by the use of a greater length of gap. It is agreed to generally that a 6.5 mm. gap in air necessitates a spark-over E.M.F. greater than the E.M.F. required at any time under the worst possible conditions on the sparking plug terminal. In any case, we have shown (this will be reported shortly) that only a little above this length of gap in air, the discharge begins to take place inside the distributor. Though we intend conducting experiments on the road (with the distributor head fitted with mica windows which we have previously used on the bench for this purpose) to ascertain whether such sparking over in the distributor takes place in any circumstances, we have no date no evidence that such has ever occurred. With regard to the breakdown of primary windings, such breakdowns have happened in certain cases leaving the secondary winding intact, but these have been in all cases traceable to poor separation (insulation) between turns in consecutive layers of winding, between which voltages may normally be 200 or even more. EFC. | ||