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).
Modifications to the battery ignition coil for the Goshawk engine due to high-speed performance issues.
| Identifier | ExFiles\Box 54\5\ Scan171 | |
| Date | 29th December 1921 | |
| R & E from EFC. {E. Fowler Clarke - Electrical Engineer} c. to CJ. and PN. {Mr Northey} c. to BY. {R.W. Bailey - Chief Engineer} and EP. {G. Eric Platford - Chief Quality Engineer} c. to Rg. {Mr Rowledge} and Da. {Bernard Day - Chassis Design} c. to Wor. {Arthur Wormald - General Works Manager} X3485 EFC {E. Fowler Clarke - Electrical Engineer} 2/LG29.12.21. X.3129 X.3485 - BATTERY IGNITION FOR 40/50 AND "GOSHAWK". Owing to the greater range of speed over which it it required to operate the battery ignition on the Goshawk as compared with the 40/50 H.P., it may be necessary to wind the primary of the coil with fewer turns for smaller inductance. Mr. Hives has already reported some missing on the Goshawk ignition at high speeds. This will not necessarily occur in every case as, undoubtedly, the coil performance varies a little from coil to coil (see later). You will remember that when we were first considering ignitions for the Aero engines, we had a number of coils made up which we called "B" coils; these having a fewer number of primary turns (about 300) of the larger gauge of wire, namely, 19 S.W.G. The inductance of these coils is about 40% less than the present standard and we have one or two of them (not built up in cases.) If Mr. Hives reports further trouble on this account, we must arrange to have one of these put in a case for trial on the Goshawk. The coil resistance is, of course, considerably less but owing to the large proportion of the ballast, this will not make a considerable percentage difference, although owing to the reduction in ballast resistance from 40/50 to Goshawk, the increase in current taken, due to this, will be rather more than it would have been for a similar change on the 40/50 H.P. contd:- | ||