DIESEL WORKSHOP
REAL WORLD COUPLING TESTING PROGRAM Australian Multiple Combinations test truck components to their limits, and a new initiative is setting up a real world coupling testing program, to assess the forces exerted on the connections between road train elements.
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urrently, the Australian Design Rules covering heavy vehicle do not offer any guidance for truck and trailer manufacturers beyond a truck GCM of 125 tonnes. At the same time, overall GCM ratings at higher tonnages are increasing and the Performance Based Standards Scheme (PBS) needs precise data on each articulation point, both fifth wheel and pin type, to design and assess possible configurations for submission to the scheme. Measuring the forces at play between elements of a road train uses what is called the D-value, measured in kilonewtons (kN) and representing the theoretical horizontal force between towing vehicle and trailer, and between trailers. Needless to say, this is a complicated calculation and one which is left to the engineers developing truck and trailer combinations around the world. However, Australia is one of the few places where the combinations on the road go outside of the normal parameters used
globally. As a result, the development of ever heavier road trains has taken those engineering outside of the normal envelope of understanding and created an issue for those developing large combinations. The project is an initiative of the ARTSA Institute as lead, alongside the Australian Trucking Association (ATA), Truck Industry Council (TIC) and Heavy Vehicle Industry Australia (HVIA) and is funded by the Commonwealth Government through the National Heavy Vehicle Regulator’s (NHVR) Heavy Vehicle Safety Initiative. The team behind the project is chaired by Martin Toomey (ARTSA-i) and supported by a Steering Group made up of Chris Loose from the Truck Industry Council, Bob Woodward from the Australian trucking Association, plus ASRTSA-i members Greg Rowe, Rob Smedley and Wayne Baker. there will be three working groups, On Road Testing, Laboratory Testing and Communications. Each of the working groups will have industry representation
as well, from suppliers like Jost, BPW, SAF Holland and V.Orlandi. Project Manager and mechanical engineer Wayne Baker explains the background “We are aware that as a heavy vehicle combination gets heavier and longer, the forces that the couplings are subject to are lower than what a theoretical calculation shows. It is this phenomena that we are hoping to understand and quantify.”
LOOKING AT D-VALUES “Currently, the D-value formula on larger combinations, under the rules, caps out at 125 tonnes GCM,” says Rob Smedley, Director and Senior Engineer, Smedley Engineers. “When the calculation is used in larger combinations it can come out so high that manufacturers don’t even make couplings that meet that D-Value. “However, those same couplings that don’t meet that D-value are being used successfully on our roads. At the moment there’s a black hole, where operators and trailer makers aren’t covered because, technically, they are
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