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).
Ignition coil performance tests and a recommendation for future coil winding specifications.
| Identifier | ExFiles\Box 164\5\ img302 | |
| Date | 25th August 1937 | |
| To Rm.{William Robotham - Chief Engineer} c. to By/RD. c. to Rm{William Robotham - Chief Engineer}/FD.{Frank Dodd - Bodies} 6017 Rm{William Robotham - Chief Engineer}/RC.{R. Childs}4/JH.25.8.37. Re Coil performance tests carried out on 25-G-V1. Recently road tests were carried out in which the performance of the R.R.D.75672A Ignition coil was compared with that of the Delco-Remy coil: the R.R. coil was found to be superior giving a better slow running performance. The D.75672A coil was then replaced with a D.75672 type, the latter having a secondary winding of 15,000 turns of 42 S.W.G. wire instead of 20,000 turns of 44 S.W.G. wire, as in the former case. This modification was introduced to increase the output of the secondary; the resulting coil was quite satisfactory, until recent engine developments made increased plug gaps necessary; this increase of gap caused the coil to give a poor performance on slow running. The former D.75672A coil was refitted and no further trouble was experienced, proving the D.75672A to be a better coil than the D.75672. In view of this, we recommend that any further coils made to LOP.D.75673 be wound with a secondary of 20,000 turns of 44 S.W.G. wire. Rm{William Robotham - Chief Engineer}/RC.{R. Childs} | ||