Fifth-wheel drawbar coupling improves stability
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• Improved trailer stability, strength of the towing connection, and quicker on-and-off loading are the principal advantages of an unusual form of truck and drawbar trailer car transporter which has just been put into service by Latham Transporters Ltd, Coventry, at its Preston depot.
The transporter uses a fifth-wheel coupling as the towing link between the two-axle rigid prime mover and its close-coupled two-axle trailer, the coupling being mounted low down on the back of the truck.
Although the York fifth-wheel is subject to occasional extra loads from the trailer — the up and down directions, when the vehicle is on the move — the coupling's primary function is to act as a safer form of drawbar connection than the normal pin and eye type. It also allows greater articulation of the trailer.
The prime mover is an 18ft 4in. wheelbase Atkinson, powered by a Gardner 8LXB which drives through a Fuller nine-speed gearbox. A pto and hydraulic pump fitted to the gearbox provide power for raising and lowering the rear of the top deck of the trailer.
Whereas earlier truck and trailer outfits in the operator's fleet with normal towing hitches have their hydraulics on the prime mover, the latest transporter has its hydraulics on the trailer. This can be done because the extra stability imparted by the fifth-wheel in the Latham design allows the trailer's top deck to be tilted with perfect safety. This, in turn, permits quicker loading because the deck need be let down only once in order to load both top decks.
With existing drawbar transporters, the truck's top deck has to be swung down twice for loading — once for bringing up cars to the level of the trailer's top deck, so that they can be reversed on to it, and a second time for picking up its own load. The same procedures, but in reverse, apply to both types of transporter when it comes to unloading.
Bridging channels have to be placed between the two bottom decks of the latest vehicle, over the fifth-wheel, during loading operations but the adjacent ends of the top-deck wheel tracks are fitted with extension pieces to eliminate the need for any bridge. The complete trailer and the bodywork of the Atkinson were constructed by Municipal Trailers Ltd, Bamber Bridge.
Maximum length of the new Latham transporter is the legal limit of 18 metres (59ft lin.) and it weighs 13 tons 16-cwt unladen, of which the truck contributes 9 tons 3cwt. The vehicle can carry either nine small cars or eight medium cars, or a mixed load of six vans and two medium cars. Overall height varies from 13 to 14ft with cars on board, and is about 15ft 7in. when vans are being carried.