York/Clayton demonstration of how to beat jack-knifing
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NVINCING demonstrations of the effectiveness of having a load-proportioning valve connected to the driving and trailer axles of an artic were given by Clayton Dewandre
and the York Trailer Co. last week. Three attics were put through manoeuvres likely to produce jackknifing at Hendon aerodrome, London, and this phenomenon did not occur on any when the Clayton Dewandre "g-matic" light-laden valve was in operation.
The surface used for the tests did not have a sufficiently low adhesion factor even when soaked with water to permit any spectacular jack-knifing.
With unladen outfits, only small movements out of line occurred even when the braking effort at the driving axle was not reduced by the "g-matic" to match the load applied to it; there was no sign of swing with the device in action.
But in the case of a Dodge/York outfit which had been deliberately badly laden to make a jack-knife likely the outfit folded fairly quickly when braked and if the road surface had been any smoother it is probable that the cab would have been cleared off.
On a repeat run with the Clayton Dewandre equipment connected up and the outfit again braked to the maximum on the very wet curve, a perfectly safe stop was made although the front wheels locked, and the outfit went straight on, instead of turning, for the last five or six feet.
Operators of p.s.v. fleets as well as goods vehicles were among the audience. They were especially interested in the more consistent braking which might be obtained on buses in laden and unladen conditions by the use of loadproportioning "g-matic" valves.