VBG draws up specification check
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• by Bryan JarViS
Specifying drawbar equipment remains a bit of a black art in some parts of the transport industry, according to coupling manufacturer VBG. It believes there are only a handful of bodybuilders which are capable of properly designing drawbars.
For this reason it carries out a full specification check on every installation it is involved with, and works with suitably qualified installers such as Abel Demountable Systems to ensure that all components are compatible for a particular application.
VBG area sales manager George Ostle stresses the importance of checking that the design capacity of drawbar components such as the coupler, eye, frame and the beam itself are compatible with the application. "What may seem to be minor changes to the coupling geometry car have a significant effect on the dynamic loadings imposed on centreaxle trailers,' he warns.
VBG offers its .Pe formulae to help drawbar manufacturers calculate dynamic loadings. These takes into account a trailer's gross weight, platform length, cargo or body height, and the height of the centre of gravity.
The resulting Pc figure is expressed in kN (kilonewtons). The Pc figure must be within the design rating of the coupling equipment.
Pulling capacity
All of VBG's drawbar gear carries a plate showing its Pc (or the recently introduced V) value as well as its horizontal pulling capacity, or D value.
Abel tends to standardise on the VBG 627 coupling and the 57.5mm towing eye for most centre-axle trailers up to 16 tonnes, or the heavier duty 623 coupling with a beefier eye for larger trailers.
It uses four basic drawings from which to develop the optimum configuration within the overall dimensions. Maximum length is 18.75m, but the minimum 2.35m cab depth and 750mm coupling gap requirements have consigned the expensive and complicated close-coupling devices to history.
More than half the drawbars built by Abel require tail-lifts where the real challenge, especially on high-cube outfits is to maintain adequate clearance, particularly where chassis heights are as low as 870mm. In these cases the coupler mountings are fitted some 400mm below rail height and integrated within the entire fabrication.
In the past year Abel has edoyed a 50% increase in orders from customers looking for more bulk and greater operating flexibility. Typical of these is Moores Furniture group of Weatherby, West Yorks, which produces kitchen, bathroom and bedroom furniture.
Two years ago it converted from artics to drawbars in a bid to become more efficient and to Out the amount of empty running.
The replacement rigs provide total body lengths of more than 15m (50ft) per trip,
compared with 12.2m (40ft) for an artic and 8.84m (29ft) with an earlier truck. They return better fuel consumption than the artics and the rigids that they've replaced," says fleet engineer Peter Wilson.
'Operationally we're far more productive.' Moores now runs 27 drawbar units with 106 swap bodies. Most of the prime movers are MAN 18-tonners, which are about to be joined by six new MercedesBenz Atego 1828s. They use V80627 couplings to pull 16-tonne centre. tandemaxled trailers.
Each shunt vehicle has an electronic on-board weighing system which determines the CofG of every loaded body so the driver knows which to load on to the unit and the trailer.
Driver-friendly
Other driver-friendly devices include VBG's easy-couple air actuators which can be operated remotely from beside the chassis instead of scrambling about underneath it; Duomatic air couplings; and a single-plug electric connector.
Like most new drawbar outfits, Moores' vehicles operate at 18.75m overall and carry two 7.7m-long, 2.37m-high swap bodies grossing out at no more than 7.0 tonnes. They also stay within the 4.0m overall height limit set for European operation.