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).
Comparison of electrical characteristics for Ballast and Primary & Ballast components from Remy and Delco.
| Identifier | ExFiles\Box 52\3\ Scan269 | |
| Date | 28th April 1917 | |
| -2- BALLAST. Remy 12. Remy 6. Delco Approx. resistance (Ohms)(cold) .610 .40 .37 Approx. resistance (Ohms)(warm) .690 .43 .425 (When carrying current of same heating value as working current at 900 R.P.M. of timer and with platinum gaps set as below under Contact Breaker.) Approx. R.M.S. working current of coil at 900 R.P.M. (amperes) 2.10 1.50 1.60 Approx. average working current (D.C. value) (amperes) 1.76 1.3 1.35 PRIMARY & BALLAST. Approx. resistance (ohms) (ballast cold). .845 1.11 .90 Ditto (ballast warm) .925 1.14 .955 Approx. time constant under working conditions. (sec) (ballast warm). .00325 .0066 .0049 Final current at 6 volts assuming working conditions (amperes) 6.49 5.26 6.29 Ratio (ballast resistance / primary coil resistance) 2.94 1.6 1.8 | ||