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QINETIO MT TESTING
Page 15
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• With major quarrying companies focusing on even greater site safety, there's growing interest in not only conforming to the IRTE's tipper stability recommendations, but also proving it with rigorous testing. That's why United, along with other trailer makers, has taken its products to the Qinetiq tilt table at Chobham, Surrey.
While Stas, GT Fruehauf and Wilcox are all reported to have attained category A and B status, CM was invited to witness United Trailers' recent 'proof-testing' exercise on an insulated asphalt trailer. Such vehicles feed materials into Barber Greene rollers on road repairs, which slowly push the trailers ahead of them by making contact with the trailer tyres.
On straight-frame chassis with 400mm ride heights suspensions are well clear, but those with very low ride-heights suffer airbag damage.
Although United's stepframe rides at 300mm, the Discos suspension's short arm is lower and ensures the bellows are well clear.
"Discos fits the bill completely," says United's chief draughtsman Barry Scott. And it's one of the stiffest suspensions available."
Having successfully tilt-tested its 38-tonne tipper designs many years ago—with Harsh under-body hydraulics—this was United's first attempt at 44-tonnes GCW, using front-end gear. Coupled to a Foden 3440 6x2 tractive unit, the standard 28.4m3 step-framed semi-trailer had a Penta ram with underfloor stabiliser frame to aid stability.
For extra safety, three heavy steel body baffles were added to contain the load on full 450 tilt, plus some beefy cable brackets on the ram housing and tie-down rings on one side.
The stepped chassis had extrawide 1,400mm main rail centres, DaimlerChnisler's Discos suspension, Bridgestone 11164 385/65R 22.5 wide singles, while the monocoque body had pressed-aluminium sides, headboard and tailgate.
The three-piece alloy floor was lOmm, 8mm and 6mm thick, front to rear, and its forward-sloping split tailgate secured by an air-operated locking bar.
United also added PM Or-Board load-weighing equipment and Dawbarn's insulated Clearspan rollover sheet.
CM verified the United asphalt trailer was laden to 44 tonnes with road shavings before witnessing it comfortably achieving the IATE's recommended minimum tilt angles.
Observing the numerous safety checks, procedures and precautions, Qinetiq's technicians gradually tilted the Foden/United combination sideways, first to 5.0", and then 7.0" and, to counter any slight 'creep' in the tilt mechanism, another half a degree.
In practice, before a tipping trailer is raised fully, most of the load would have shot out but on a test bed, the sight of one lifted to 45° with a full load in place, and then tilted to 7.5°, is truly awesome. But why go to these lengthsP.
"Well, we're certainly not looking for a limit," Layton asserts. "And we don't regard it as a competition either. We've done it simply to assure operators and customers that our trailers will function in accordance with the IRTE's proposed codes of practice on tipper stability.
"Our achievement at Chobham means we can sell confidently into the market place, knowing that our designs are more than a match for the IRTE's category A and B minimum stability recommendations."