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).
Specifications and construction details for a coil, detailing windings, insulation, materials, and weights.
| Identifier | WestWitteringFiles\V\2January1931-April1931\ Scan039 | |
| Date | 9th February 1931 | |
| -3- The secondary was insulated from the primary by a paper tube .019" thick 1 1/2" diameter and 3 3/4" long which also formed a suitable base for the primary winding. The length of secondary winding was found to be 2.35" leaving a distance at each end of .400". Enamelled wire .004" diameter was used for the winding, the interlayer insulation being as follows :- Between first 3 layers next to primary .008" thick Remaining layers except last, .003" thick. Last layer .009" thick. The grade of paper used did not resemble wax or varnished paper but appeared to be a plain white paper impregnated with some kind of bituminous compound. Each layer of paper had been apparently machine cut as the edges were clean and straight. Weight of secondary wire 3 1/4 ozs. The secondary was wound on a paper tube over the core which consisted of iron strips 3.800" long .410" wide and .016" thick assembled to form a square section of iron 1/2" square. Total weight of iron core including outside cheeks 8 1/4 ozs. As mentioned previously, the whole coil had been impregnated with bitumen which appears effectively to fill up the ends of the secondary winding and thus prevent spark overs occurring, the end distance being very small. The weight of the coil complete was 1 lb. 13 ozs. E.7.C EFC. | ||