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).
Particulars of construction for the present standard ignition coil.
| Identifier | ExFiles\Box 69\1\ scan0224 | |
| Date | 18th July 1929 | |
| X8710 18.7.29. X.8710. PARTICULARS OF CONSTRUCTION OF PRESENT STANDARD IGNITION COIL. Core built up of 24 S.W.G. (.022) Iron (Stalloy) wires. Core insulation .006 Oil silk .750 wide 1/2 Lap = .012 thick. Primary winding 300 turns of 22 S.W.G. (.028 dia) S.C.C. enamelled wire (.036 overall dia) Ends of Primary Winding insulated with 2 layers of .006 oil silk .500 wide, length = 42 inches. .00225 total thickness of Insulation, 3 layers of .00075 Oil Paper between each layer of primary 2.850 wide, 2 ft long. Packed up to largest diameter of primary with oil silk and finished off with .00075 oil paper. Primary winding vacuum varnish impregnated. 20 layers of .00075 oil paper between primary and secondary 2.850 wide, by 6 ft long. Secondary winding 18,000 turns of 42 S.W.G. (.004) enamelled wire (.00475 overall dia.) .00225 total thickness of Insulation, 3 layers of .00075 Oil Paper between each layer of secondary 2.850 wide, by 50 ft long. Secondary coil winding covered with 4 layers of oil silk .750 wide x .006 thick. EFC. | ||