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).
Issues of overheating and wet varnish in ignition coils and proposing solutions involving ballast resistances.
Identifier | ExFiles\Box 69\1\ scan0076 | |
Date | 10th February 1928 | |
X8710 To EFC. BY/RD5/ML1 10.2.28. IGNITION COILS - EFC2/T.4.2.28. X.8710 X4653 COIL 4405.- The finding of wet varnish in this coil is I think no isolated case, it is extremely difficult, nearly impossible, to dry out the varnish of a secondary winding. COIL T.145X, which shewed signs of heating, I am very surprised to note from your remarks that if a coil was left on circuit the heat produced should be of such magnitude to cause this weakening of the insulation, the leaving on of the ignition switch I should say is a common occurrence and may very possibly be the cause of the unexpected heating in the coils. I suggest that you test coils having 22 S.W.G. and 25 S.W.G. Primary windings in circuit with the late standard ballast resistance (not double length) in conditions similar to leaving the ignition switch on and the contact breaker closed, the coil being up to 80°C. to start with, if the coil will not stand this treatment, then we should fit the double length ballast or make some other alteration which will enable the coil to withstand any such treatment. If the foregoing is a correct review of the situation we propose to instruct the Repair Dept. to change over Ballast Resistances on all cars which they get hold of to the double value. BY/RD (Signature) | ||