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).
Article from 'The Motor' magazine describing a new ignition system using a condenser charged by dry cells.
| Identifier | ExFiles\Box 37\1\ scan 069 | |
| Date | 14th January 1920 | |
| X.3199 January 14, 1920. 1119 The Motor NEW IGNITION SYSTEM. Charging a Condenser from Dry Cells, the Discharge being Through an Ordinary Coil. WE have been recently afforded the opportunity of examining a new form of ignition, which is applicable to all kinds of internal-combustion engines, at the works of Messrs. Leopold Ward and Co. Dr. A.{Mr Adams} M.{Mr Moon / Mr Moore} Low was present and made an examination of the apparatus which, although experimentally constructed, is very simple. Fig. 1.—Diagram showing the connections. We have asked Dr. Low to make a report on this new system, and the following is his description of it:— In the main the principles involved are quite ordinary, but the apparatus is arranged in quite a different manner to the usual high-tension ignition. The principle consists entirely in the charging of an ordinary condenser by dry cells or other convenient source of electrical energy, and then allowing this condenser to discharge itself through the primary of an ordinary plain induction coil such as is used for non-trembler ignition. A Novel Principle. It is therefore the “making,” and not the breaking, of the primary coil circuit which causes the spark to occur in the secondary circuit at the plug. This in itself is one of the advantages of the system, for when two points approach each other the spark is rather more brush-like in character just before contact, and does not become of the nature of an arc which is experienced when two ordinary coil or magneto points break. Even if slightly more care is necessary for insulation, this is a useful feature. Fig. 1 shows a sketch of the connections in diagrammatic form. B is a dry battery, which will give a voltage of about 30, in the actual experimental model the voltage is 120, but the current consumption is so exceedingly low that if the apparatus is short-circuited the cells do not appreciably run down. The current consumption, we are told, is less than one-quarter milliampere. condenser of four microfarads capacity, non-inductive resistance of 2,000 ohms, series with the condenser and a wipe contact to prevent discharge of the batteries if left. M is an ordinary magneto contact breaker, so arranged that it does not make contact to discharge the condenser through the primary winding (P), producing the spark at the plug, until the wipe contact (W) is just off circuit, having charged the condenser. In the actual apparatus these two contact breakers are combined and are situated under an ordinary distributer, the arrangement being as shown in the diagram Fig. 2, which provides a simple method whereby the heel of the ordinary magneto break is used as a wipe contact by passing over the segment (F). The spark given by this ignition is quite satisfactory, and as might be expected on testing the result of pressure upon the spark; rise of pressure reduces the brush effect and shortens the sparking period, thus tending to raise the spark temperature, which is very satisfactory. The chief idea is, of course, that it will act as a stand-by in cases of dual ignition being fitted, so that it can be kept quite separate and independent from an ordinary accumulator operating a starter or lighting set. With regard to the current consumption, whilst this is exceedingly small, it is naturally the wattage or power that is concerned, and this is increased by the high value of the voltage; in spite of this, however, there is no doubt that dry batteries would last a great length of time; even allowing for shocks or electrical surges, they would probably wear out from chemical disintegration long before any complete polarization took place or they became exhausted from actual use. Fig. 2.—A diagrammatic illustration of the double contact breaker. Even with a plain coil the amount of current necessary to charge up the condenser prior to its discharge is very small indeed, and a considerable amount of magnetic eddy and hysteresis losses are avoided. c21 | ||