A Trailer-brake Control
Page 59
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of marked simplicity
IN June of last year we referred to the Warben trailer-brake control, which possesses many novel features, one of its most outstanding recommendations being its extreme simplicity, Since that date various improvements have been made and it is now marketed by the Warben Motor Engineering Works, 43, Mayville Road, Leytonstone, London, E.11; the cost is about £4 10s.
The brake control consists of a steel casing which can be clamped to the lorry cab or floor. This houses all the moving parts, and the coupling to the trailer brakes protrudes from its rear end.
A horizontal rack bar is employed. This slides on rollers or on a plain bearing surface, as desired ; it is guided laterally by the casing and vertically by the forward opening in the casing and by a boss between the sides of the ease at the midway point.
Mating with the rack is a doubletoothed pawl member, operating vertically. The double-tooth formation allows the rack to be pulled on by half a tooth at a time, if such fine variation be required. Control is effected by a single lever pivoted on the casing. At its lower end it carries a finger with a radiused tip ; this finger works between the teeth of the rack and it is pressed downwards by a coil spring surrounding the release trigger. When the lever is pulled backwards the finger mates with a tooth space of the rack and pushes forward the lastnamed, a pawl checking it as it goes. The driver may take two or three pulls and the pawl holds the brake in any desired position. When releasing the brake the release trigger is lifted and the lever pulled right back. This causes the finger to clear the rack and by means of a projection on the lever raising the pawl, allows the brake completely to free itself, as there is no check whatever upon the backward run of the rack. If, however. the release trigger be lifted and the lever rocked gently without reaching its extreme backward position, the rack is allowed to run back one or two teeth at a time. It will be seen, therefore, that any degree of application or release can be obtained at will. A point in the design is that, owing to the variation in the leverage obtained by. reason of the action of the finger, the greatest amount of pull is obtained during the initial backward movement of the lever, that is, when the driver has the greatest power available. The leverage decreases, giving slower action, as the lever approaches the vertical, that is, when the driver's power is diminishing.
An inspection of the actual brake control reveals its marked simplicity and robust construction. Provided that care be taken to allow ample space for the rack bar to move forward there is no difficulty in installation; lubrication is necessary only at infrequent intervals.