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).
Investigation into ignition coil trouble causing misfiring on a Wraith experimental chassis.
| Identifier | ExFiles\Box 142\1\ scan0001 | |
| Date | 1st October 1937 | |
| 1204. By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/RC.{R. Childs} (text is crossed out) c. Rm.{William Robotham - Chief Engineer} c. By/RD. (text is crossed out) Rm{William Robotham - Chief Engineer}/RC.{R. Childs}9/AP.1.10.37 RE. IGNITION COILS Trouble has been experienced lately on the Wraith experimental chassis, due to misfiring on 'pick-up'. This was investigated and found to be due to coil trouble. This trouble was not apparent when using the D.76572.A. coil, wound with 20,000 turns on the secondary. We have three types of coils in the experimental stage, the Lucas, the R.R.D.76572 (15,000 turns on the secondary) and the R.R.D.76572.A. (20,000 turns on the secondary). In order to determine the most suitable of these, for the Wraith, a road test was carried out in which the three coils were subjected to the worst conditions. Tests carried out in the presence of Rm{William Robotham - Chief Engineer}/Wym{G. Harold Whyman - Experimental Manager}, Rm{William Robotham - Chief Engineer}/Brazier and Rm{William Robotham - Chief Engineer}/RC.{R. Childs} D.76572 (15,000 turn secondary) When connected normally, missing occurred on pick-up, but by reversing the primary connections the trouble was cleared. This changing of connections was repeated several times, giving the same results each time. Lucas (In R.R. Bakelite case) We obtained exactly the same results with this coil, i.e. missing when connected normally, but OK. when the primary was reversed. D.76572 (20,000 turn secondary) This coil gave good running whichever way the primary was connected, which tends to prove it the best coil of the three. We then subjected the Lucas coil and the R.R.D.75672 (15,000 turn) to a bench test, to determine the polarity of the H.T. lead. In each case this was found to be positive when connected according to the primary markings. Thus, for good running the H.T. lead should be negative. This arrangement of the windings, by which the H.T. lead to the plug is made negative was standardised recently, and the results obtained are due to the fact that less voltage is required to operate the sparking plug when the hottest electrode is made negative. Apparently the Lucas coil is not wound correctly to obtain this condition. continued | ||