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).
Winding temperature tests of ignition coils under various conditions.
| Identifier | ExFiles\Box 69\1\ scan0122 | |
| Date | 6th July 1928 | |
| X8710 To EY. from EFC. c. EY/RD. WINDING TEMPERATURE TESTS OF IGNITION COILS. X4079 In our EFC3/T11.5.27, entitled "Finer Primary Ignition Coils", we gave some results of tests of the average rise of temperature of the secondary winding under two conditions of ballast (double and single), and in each case under two conditions of heating, i.e. standing on contact with a 12 volt battery, and running for five hours continuously with a distributor make ratio of .55 and a battery voltage of 17.5. The results were presented in tabular form and it was observed that the hottest condition under which the coil would have to function, excluding heat transmitted from engine, was when left on contact on 12 volts with a single ballast. A further observation on these figures, however, might have been made, viz. to the effect that whereas with a single ballast the temperature attained by the coils (all finer primary) was greater when standing on contact on 12 volts than when running on 17.5 volts. With the double ballast, the temperature attained was higher when running on 17.5 volts than when standing on contact on 12 volts. This therefore shows that the use of the double ballast means that the heating of the coil standing on contact is normally not so great as with the coil in normal operation. We have now made some further tests, this time on two ignition coils with the secondary windings packed out to the inside surface of the bakelite case, thus eliminating | ||