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).
Technical comparison between Remy 12 and Remy 6 ignition coils.
| Identifier | ExFiles\Box 52\3\ Scan315 | |
| Date | 4th March 1920 guessed | |
| -2- Contd. Comparison of coils. Although the time of make for Remy 12 is only about half that for Remy 6, owing to the fact that its time constant is so much smaller (and that the final current is larger) the actual current broken in Remy 12 has a larger value than that for Remy 6 in the proportion of 9 : 7 roughly. The actual collapse of magnetic flux, in spite of the larger current broken, is, owing to the lesser inductance, smaller in Remy 12 than in Remy 6, and necessi tates the employment of a larger number of secondary turns, and therefore a greater step up ratio, in order to produce the necessary secondary voltage. At the same time the current density of the spark from Remy 12 must necessarily be less than that from Remy 6. Owing to the fact that Remy 12 has to supply 12 cylinders with sparks following one another at the rate of 180 per second, it is not permissible to allow the period of break to be very much longer than the time necessary to produce a secondary spark, else the intensity of the second ary spark will suffer. Hence the smaller the gap of the contact breaker, consistent with a reasonable primary current consumption, the better the secondary spark effect, up to a certain point. It should be stated that the secondary spark does not occur at the precise mathematical instant of break, but actually at an instant shortly following this, so that it is conceivably possible for make to follow break so nearly that a spark is not (Contd). | ||