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).
Condenser capacity for the battery ignition system of 40/50 & Goshawk engines.
| Identifier | ExFiles\Box 34\1\ Scan302 | |
| Date | 29th December 1921 | |
| X 2172 Extract from EFC2/EG29.12.21. X.3485. BATTERY IGNITION FOR 40/50 & GOSHAWK. X.4430. Z.2512. X.4423. As regards the condenser capacity, it would appear that other things being the same (supposing that it is already arranged to effectively quench the primary sparking at break) this, for the best results, should vary with the magnitude of the current at the instant of break. The current at break is small with the ignition running at high speed, or with the ignition running at very slow speed when the ballast resistance is hot or if the battery volts are low due to the starter motor current, and it is in these circumstances that the condenser capacity may be too big to allow the secondary to produce the necessary voltage and a good deal bigger than necessary to quench the primary spark. In increasing the capacity of the condenser, therefore, we must be careful not to meet these conditions as far as possible, in fact, to effect the most satisfactory compromise. For instance, at 1500 distributor speed or 3000 r.p.m. engine speed, our present standard capacity (.21mf) will allow of a regular firing gap of 6 mm. With the proposed increase of 50% condenser capacity, this, at that speed, is reduced to 4.5 mm, though in the first case the capacity is amply sufficient for quenching the primary spark. We are, however, preparing a 40/50 HP. condenser of this increased capacity both with mica and with paper. We have an idea that the damage to the primary ignition points, Contd. | ||