Dynamic loads beat couplings
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• Runcorn-based VBG is calling for body and trailer makers to consider dynamic loadings when specifying drawbar eyes and couplings for centre axled trailers. Operational dynamics can impose forces up to 30 times the static weight of the vehicle on the cow pling equipment, it says.
Although VBG is unaware of any accidents in the UK to date, it believes that under-specification could ultimately lead to coupling failure and lost trailers. Early experience with logging outfits in Scandinavia has enabled VBG to develop a formula giving a dynamic load figure.
It uses gross trailer weights, platform lengths, cargo or body heights, the height of the CofG over the drawbar eye and the distance between them and expressed as a Pc value in IN for each drawbar application.
VBG produces ratings for all its coupling equipment to ensure customers have the right coupling for the application. Dynamic load ratings are included among the specific requirements of a new EC directive (94/20/EC) relating to mechanical coupling devices.
Once implemented later this year, all drawbar equipment will have to be plated or stamped with dynamic load ratings.