A New Electric Speedometer
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ANEW + electric speedometer has re cently been introdneed by the British Thomson-Houston Co., Ltd., Coventry. It consists of a robust electrical generator driven either by belt or from the gearbox, and a voltmeter,
24 ins, in diameter, which indicates the speed. The device registers up to 50 m.p.h. Connection between the generator and the indicating instrument is made by two insulated wires.
For gearbox drive, the generator mounting can be interchangeable with the usual mechanical transmission, but, for belt drive, pulleys are provided for the generator and transmission shaft, the shaft pulley being split to permit mounting. The drive is taken through an endless rubber belt, ample provision being made for adjusting its tension.
The normal running speed of the generator is between 1,500 r.p.m. and 1,800 r.p.m., when the output is six volts. The generator is of the stationary-armature AC type, the field being produced by rotating permanent magnets of cobalt steel.
The speed-indicating instrument is, in effect, a moving iron voltmeter specially constructed for use on commercial vehicles, and has a high-resistance winding with a large proportion of Eureka wire. The pointer, and the arrow on the dial indicating the 30 m.p.h. position, are luminous.