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).
Testing a soldered ballast resistance, concluding it is suitable for production as a replacement for the previously brazed version.
| Identifier | ExFiles\Box 168a\5\ img052 | |
| Date | 5th February 1931 | |
| E.7.C. X.7720. Date 5-2-31 Ref No WE 79. X NOS. 7720 Standard ballast resistances. We have had handed to us by Mr Brock a standard ballast resistance with the wire soldered to the terminals instead of brazed as hitherto. A number of ballasts have failed in service due to wire breaking at this point, due it is thought to the excessive heat the wire is subjected to in order to braze it to the terminals. We placed this ballast across 14 volts, the current being 2 1/2 amperes, for 3 hours without the solder showing any signs of softening. Upon raising the current to 3 amperes the solder melted. As the normal working R.M.S. current is about 1.70 amperes and the final current on contact about 2.00 amperes we consider ballasts soldered instead of brazed will be quite OK for production. MX{John H Maddocks - Chief Proving Officer} has had this ballast on his car for a considerable time without complaint. HWest | ||