A New Magneto Conversion B.T.H. Instrument for Interchangeability with Batteryignition
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Distributor-head Units A WELL-MADE rotating-magnet 1-1.. type magneto, suitable for use oti four or six-cylindered engines originally equipped with battery ignition, has just been introduced by the British Thomson-Houston Co., Ltd., Rugby. Designated the type J, it runs at half engine speed, in respect of its mounting it is interchangeable with the usual type of contact breaker and distributor head, and it incorporates an automatic. advance-and-retard mechanism running In an oil bath.
Mounted on ball bearings, the rotor has four or six poles, according to the number of cylinders of the engine, whilst the four or six-point contactbreaker cam is carried on the upper end of the shaft. At the lower end is situated the timing control gear, leather washers being employed to retain the lubricant.
The laminated iron armature poles are formed integrally with the main housing, which is an aluminium die casting, the armature coil assembly being secured to the poles by screws. Thus replacement of the windings, if it should be necessary, is an easy matter. The coil is protected by a detachable dustproof and watertight cover provided with a terminal in spring-contact with the end of the secondary winding.
A short length of h.-t. cable connects this terminal with the distributor, and an earthing terminal is mounted on the side of the contact-breaker housing. Within the base of the last-named is a tubular-type condenser. The distributor is similar to that used in batteryignition equipment, the brush holder being located on an extension of the cam.
Although light in weight, the magneto is of robust construction and its overall. height has been kept as low as possible to minimize vibration and to render it suitable for use where headroom is limited, e.g. when the distributor is mounted on the engine crown.