York Produce Third Axle Conversion
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HAVING rapidly established themselves as semi-trailer manufacturers in this country, the York Trailer Co., Ltd., St. Marks Road, Corby, Northants, have now entered into the production of a third-axle conversion for rigid fourwheelers.
Unlike most other proprietary conversions of this type, which employ an additional solid aide with extra leaf or coil springs, the York design utilizes the original rear leaf springs of the fourwheeler to provide the suspension medium for two independently sprung stub axles, as well as supporting the driven unit. The rear pair of spring-hanger brackets is removed, and the shackles are reversed and connected to the forward ends of two robust, hollow-section distributor beams.
At their trailing ends the beams carry welded-in stub axles on which the rear pair of hubs and wheels is mounted. An additional tubular cross-member is introduced into the frame with a central bracket suspended below it. This bracket, combined with two others bolted to the outside of the chassis side members, carries a cross-tube on which the two distributor beams pivot.
Phosphor-bronze bushes are interposed between the moving parts, and are lubricated through, grease nipples on the outer brackets. They are protected from the ingress of dirt by rolled-over flanges on the mounting brackets. The pivot point is approximately twothirds of the way along each beam from its forward end. This gives a static weight distribution of 55 per cent, on the driving axle and 45 per cent. on the two stub axles.
A novel feature is the provision of an extra set of holes to enable the spring shackles at the forward end of the beam to be mounted farther back to vary weight distribution over the bogie. If this rearward mounting is used, weight distribution becomes 60 per cent. on the driv6n axle and 40 per cent, on the trailing unit. This alternative can be used when extra traction is required, as in tipping work.
The trailing axle may be braked hydraulically or by direct air pressure. A second mechanical linkage is provided for the hand brake.
Three conversions have been carried out so far to Thames Trader and Dodge 7-ton chassis. Any vehicle, however, may be converted and the York equipment is offered in medium-weight and heavy-duty versions.
The medium-weight model has 15k-in.diameter brake drums with 5-in.-wide facings, whilst the heavy-duty type has drums of the same diameter with 6-in.wide facings and larger stub axles. The cost of the conversion, complete with wheels and tyres, is £480 for the lighter model and £536 for the heavy-duty version.