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).
The development and performance of a double ballast resistance using various gauges of nickel wire.
| Identifier | WestWitteringFiles\P\2July1926-September1926\ Scan123 | |
| Date | 2nd September 1926 | |
| To R.{Sir Henry Royce} from EFC. c. BJ. PN.{Mr Northey} c. RV. Wor.{Arthur Wormald - General Works Manager} c. EP.{G. Eric Platford - Chief Quality Engineer} E.{Mr Elliott - Chief Engineer} X.8720. DOUBLE BALLAST RESISTANCE. Further to our EFC1/T24.6.26, we have now several ballast resistances of cold value double the standard. These are made up of various gauges of nickel wire, viz. 31 (standard), 32, 33 and 34 S.W.G. the length being less as the gauge is finer, because the length of the standard gauge of wire for this double ballast resistance is rather great for the carrier. Attached please find photostat copy of the volt-ampere characteristic curves of these resistances, also a copy of volt-ampere characteristic of two present standard ballast resistances taken in a similar way, but it will be seen from these curves that the working point (contact points on contact) of the double ballast resistance occurs approximately just before the upward bend, whereas in the case of the standard it does not. This we consider to be more the right condition for the ballast resistance generally and we think that a double ballast resistance of wire of a suitable gauge, yet to be selected, will be an improvement generally, because the short circuit current will be more than proportionally smaller and also that the ignition current generally will be smaller. Double ballast resistances will be run on various experimental cars. We have had one running on a 20 HP. car for nearly 1000 miles and there has not been any suggestion of failure of ignition due to this extra resistance. Contd. | ||