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).
Methods for drying and treating coils, referencing wax baths, vacuum processes, and issues with varnish.
| Identifier | Morton\M7\ img021 | |
| Date | 15th September 1911 | |
| -2- Mr Bentley (contd) quickly dried without using a very high temperature. The air can be heated before entering the trunk pipe or within the trunk pipe and if you want to make the drying very rapid the air should be cooled by the refrigerator pipes previous to being heated. It would then be very dry and have a very powerful tendency to take up the moisture. We at Rolls-Royce immerse our sparking coils in a bath of wax heated by steam to 212°F, and the bath of wax (fitted with a cover) has the air pumped out. This arrangement had given excellent success, and we are getting quite a surpris- ing quantity of water out of each coil. Would it not be poss- ible for you to heat your coils in your bitumen compound and use a vacuum in a somewhat similar way? With reference to the varnish with the oil base turning the coils green, I suppose this does not happen to the coils by moisture alone, otherwise it seems to me that they would very soon be always green. It must, therefore, come from the varnish and I should not take any notice of the Americans who, of course, will wish you to go on using their varnish, and would only say such things as would induce you to do so. It seems to me that the acid must come from the varnish and not from anything used to clean the copper, or from the moisture. This is a point which first of all must be settled. I think your present schemes appear to be giving disas- trous results, and I should certainly make a change for something different in the hopes that it would turn out better. Are there not considerable coils outside the field coils which would be benefitted by the solid impregnating system? If so, it would | ||