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).
Trial and comparison of various ignition coils, including Goshawk and 40/50 types, with different turns and ballast resistances.
| Identifier | ExFiles\Box 45\4\ Scan051 | |
| Date | 28th October 1922 | |
| EFC1/T28.10.22. -6- Contd. that the reduction in the number of secondary turns was not desirable. In this case, however, this particular coil with a ballast resistance of 15" (as against 50" which would be the 40/50 standard) functioned remarkably well. This may be a freak result possibly due to the length of time the coil has been made, as we sometimes notice that coils improve with time, or it may be due to the reduced number of turns. On the other hand another coil of the series, with 18000 turns, which was tried. was hopeless. Coils of improved Goshawk construction of 16000 and 18000 turns are now available. The second result of the trial of the 16000 turn coil, which being a 40/50 coil has a different primary winding (360 wż turns in place of 300), was to suggest the trial of further 40/50 coils, it being surmised that the difference might be due more particularly to the bigger magnetising effect on the core for a given primary current. Sometime previously a standard 40/50 coil had been tried with a 32" ballast (previous standard Goshawk) as against 50" standard for 40/50, and it gave no improved result. Today, however, we have compared two 40/50 coils with 20" and 32" ballast with two of the latest Goshawk coils with 10", 20" and 32" of ballast, and we find that the 40/50 coil with the 20" length of ballast is, we might almost say, entirely immune, almost identically the same result having Contd. | ||