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).
Performance comparison report between a standard 40/50 coil and Mr. Brock's No.1 coil.
| Identifier | ExFiles\Box 45\4\ Scan113 | |
| Date | 6th December 1922 | |
| X.4079b 6.12.22. COIL COMPARISON - 40/50 STANDARD AND MR.BROCK'S No.1 COIL. Tests made on 3-G.II. K.L.G. sparking plugs fitted with gaps set at .030". Low tension make and break set at .010" when fully open. Coil placed in standard position. Coils considered hot after running car for 1 hour with water temperature from 90°-100°C. Mr. Brocks No.1 Coil. With an outside spark gap of .050" and over, this coil can be made to misfire badly by touching the coil case. With gap above .030" the coil misfires on the pick up, with retarded ignition and a weak mixture. This missing can be considerably accentuated by touching the coil case. Leakage can be felt through the coil case with a gap of .030" but not enough to cause the coil to misfire when touching it. - Coil hot. No missing occurs when the coil is cold. Low tension current taken by coil (read from ammeter on the dash) 1 1/2 amperes at high speeds. 2 amperes at low speeds. 3 amperes with engine stopped and contacts closed. A standard 25" ballast was used. High speed running is good. Standard 40/50 Coil. Misfires with an outside gap exceeding .025" (when hot) at slow speeds running light, slow speed on the road and picking up with retarded spark and weak mixture, also with spark advanced. This misfiring is not very marked or frequent when the coil is hot, but when coil is cold is very bad above .025" outside gap. Coil misfires at high speeds | ||