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DEMOUNTABLES
Page 33
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There are two types of demountable body system: the straight-lift, and the contact or guide-rail demountable system. In a straight-lift system, the legs are lowered and the body raised by hydraulics or by air bags at the front and rear simultaneously. It is said to be quicker to operate.
With a guide-rail system, the rear Is raised first. The driver then returns to the cab and pulls forward. As he does so, rollers at the front of the body run along a track on the chassis. The front legs are then lowered.
Straight-lift experts Abel and Cartwright maintain that theirs are the simpler systems to operate, arid place less strain on the body. Ray Smith, which pioneered the guide-rail design, says its system has fewer moving parts and is light because the chassis rear air suspension can be used to lift the body. "The legs are on-board, so less subject to damage from fork-lift trucks," says David Browning,joint managing director.
However, guide rails are slower in drawbar operations, because the driver has to demount the bodies separately, so Ray Smith also makes straight lift systems. It supplied the base frames for the drawbar system developed by Don-Bur for Christian Salvesen's five-year contract with Goodyear Dunlop UK. The operation comprises 12 DAF 85 prime movers, 29 trailers and 102 boxvan bodies. After analysis of delivery routes, Salvesen decided three 5m bodies were the optimum and, although weights might vary between one and six twines per body, it also wanted to avoid the drivertraining implications of turntable-steered drawbars.
The solution has been an unusually long centreaxle tri-axle trailer with a wide beg% spread of 4/m. This eliminates the see-saw effect that uneven loading might cause and also increases stability. The front two axles steer to minimise tyre scrub, locking once 40km/h is reached (and also when reverse gear is engaged).
Ocado's demountable bodied home delivery system for Waitrose supermarkets has attracted interest since it was unveiled last year. Paneltex, which helped developed the system, also built the temperature-controlled pads, each of which has its own Hubbard generator-powered refrigeration unit. The pods are 2.6m long and 2.02m wide, allowing six bodies to fit on a 13.7m semi-trailer. They are secured with a fifth-wheel style location system and have fork-lift pockets In the base for loading and unloading. The bodies are transferred to 3.5-twine Mercedes-Benz Sprinter chassis for home deliveries.