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).
Detailed description of the features, construction, and operation of a special ignition coil.
| Identifier | ExFiles\Box 37\1\ scan 081 | |
| Date | 25th September 1920 guessed | |
| possible faults due to accidental earths. The cam-shaft of the contact breaker can be adapted to any form of drive and be provided either with a shaft coupling, a socket coupling, or with a flange to be bolted to the camshaft gear of the engine. The design of this component is very compact and the weight is small; pressings are used where possible, such as, for example, for the rocker arm. Two lugs carry springs which clip the stabilite moulding to the body of the unit and render it quickly detachable. The Coil. As regards the coil, this possesses several special features. It is built up on a core of square section consisting of laminated plates of special armature steel. On one end is cast an aluminium plate, which acts as a shading coil, the purpose of this feature being to ensure maximum efficiency and a uniform spark at all speeds. This is arrived at in the following manner: On the side of the aluminium plate remote from the coil is a vibrator or moving armature which has a certain time frequency, depending on the voltage in the primary circuit and upon the retardation effect of the aluminium plate or shading coil. Across this vibrator is connected a resistance which is normally short circuited, but when the period of "dwell" at the make and break exceeds a certain interval, the vibrator opens the short circuit and the resistance is placed in series with the primary ignition circuit, thus limiting the current flowing from the battery to a normal standard value. In the ordinary system of battery ignition as the dwell of the contact breaker grows less and less as the engine speed increases, so the ignition value of the high-tension spark grows less and less simultaneously. In the Conner coil, however, as the dwell grows less the resistance short circuiting armature, or vibrator, in the coil also decreases its opening period and thus the magnetic field in the induction coil core is kept at a practically constant value. Robust Construction. As regards construction, the coil is encased in a rigid heat-proof material, and may be mounted either vertically or horizontally on the engine or at any other convenient position. A brass end case secured by three screws contains the resistance and covers the vibrator controlling the resistance. A ring of holes in the end of the casing allows the heat generated by the resistance to be dispersed. At the other end of the coil a casing of insulating material covers the two terminals of the coil and a simple safety gap. It is claimed that the construction of the coil and the arrangement of this gap make it possible for the spark to pass at the gap continuously without causing any damage. A feature of the apparatus is the ease with which it may be adapted for either right or left hand rotation merely by changing over the cam, while engines with various numbers of cylinders can be catered for merely by providing a cam with the correct number of lobes and a distributer casing with the correct number of segments. The apparatus will be exhibited at the forthcoming Commercial Vehicle Show at Olympia on Stand No. 152, while at the Car Show it will be found by those interested at Stand No. 488 at the White City. A special resistance coil and vibrator are mounted on one end of the coil and covered by a brass cap. The Cornwall Press Limited, Coventry. | ||