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).
Experimental proposition to double the value of the ballast resistance for ignition coils.
| Identifier | WestWitteringFiles\O\2April1926-June1926\ Scan184 | |
| Date | 8th June 1926 | |
| To R.{Sir Henry Royce} from EFC. c. BJ. E.{Mr Elliott - Chief Engineer} BY.{R.W. Bailey - Chief Engineer} c. Da.{Bernard Day - Chassis Design} Rg.{Mr Rowledge} Wor.{Arthur Wormald - General Works Manager} ORIGINAL X.8721 DOUBLE BALLAST RESISTANCE. In addition to the development of the finer primary winding ignition coil and the good results obtained therefrom, a further experimental proposition is now to double the value of the ballast resistance. There are two reasons for doing this :- (1) For the Phantom, at any rate, the ballast resistance has always been of less value than intended because the amount of wire desired of the size standardised could not readily be got on the designed porcelain carrier. The ballast resistance was thus made uniform with the 20 HP. ballast resistance containing 25", whereas it was intended for the 40/50 HP. to contain 45". (2) Now that we have experimentally satisfactorily increased the inductance 50% (and also the primary resistance by a corresponding amount) it would be logical to increase the ballast resistance at least to a similar extent. Road tests have recently been made on a 20 HP. chassis with double ballast resistance (two standards in series) and so far as this preliminary test went no adverse effect was noticed, in fact a good deal more ballast resistance could be inserted without causing misfiring or producing unfavourable conditions, even with a supply equivalent to five cells in normally good condition but not charging. (This was actually realised by putting an additional cell in opposition in the tapping from the ignition circuit taken from the distribution board into which the additional ballast resistance was inserted). | ||