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).
The specifications of an American Bosch ignition coil without ballast.
| Identifier | ExFiles\Box 61b\4\ scan0145 | |
| Date | 26th October 1927 | |
| October 26th, 1927. RE: IGNITION COIL WITHOUT BALLAST X3/29 X4275 With reference to your memo of October 24th, re the above subject, I give below some details of the American Bosch Coil. If Mr. E.F. Clark wishes to make a more detailed study of the coil, I suggest it would be best to give him one or two coils which they can take apart: AMERICAN BOSCH COIL - Primary Winding - 4 layers Outside layer 55 turns 3rd " 63 " 2nd " 62 " 1st " 64 " Total Primary 244 " Dia. of wire .0319 = 18s BandS Enamelled Dia. of outside layer - 2 1/8" outside Dia. of inside layer - 1 3/4" inside Resistance at 26ºC 1.2 ohms Secondary Dia. of wire .0038 over enamel Resistance at 26º 3.950ohms Length of winding 2" Length of paper insulation 2-3/4" Core Dia. of wires in core .0319" Length of wires in core 3.75" Dia. of core over wires .5" Dia. of core over insulation .625" Case Outside dia. 2-3/8" Length of steel cylinder 4 1/16" Thickness of " " .016 " " sheet round inside of case .016 Length of sheet round in- side of case 3-3/4" (Continued) | ||