Six artics shift 16,800 tons a week
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• To supply the needs of a large cement factory, six new AEC Mandators with special Dyson /Freight Bonallack double hopper semi-trailers are working round the clock ferrying crushed limestone from a nearby quarry to the factory of Tunnel Cement Ltd at Padeswood, near Mold in Flin tshire.
The six artics are doing the 15-mile round trip continuously and shift about 16,800 tons a week. Each vehicle manages eight round trips on each of its three daily shifts. so no time can be wasted on loading or unloading.
Crushed stone is conveyor-fed into tail towers from which the big artics are gravity loaded by hoppers. At the factory, the vehicles are driven over an unloading chute, and when the trailer's hopper doors are opened the entire load is discharged in about 20 sec — a ton a second. Elevators then carry away the limestone directly into the factory.
To meet the requirements of this intensive working — each trailer has 510 tons dropped into it every day, 51 days a week — R. A. Dyson and Co, Ltd and Freight Bonallack Ltd collaborated with Tunnel Cement to produce special tandem-axle semi-trailers.
The Dyson trailer is based on the standard Integravan chassis, which has a perimeter frame to make it adaptable for frameless vans or other special applications. In this case the cross-members distribution leaves unobstructed space in the centre for the hoppers. This method of construction has permitted the correct hopper slope to be accommodated within the short wheel spread required by the operator.
Air suspension, using Dunlop bellows, is employed, and apart from obvious benefits makes for a quieter running vehicle; this is important as the vehicles pass through the narrow streets of Mold twice on each round trip. Exhaust brakes have been specified on the AEC tractive units to assist when returning loaded down the two-mile descent from the quarry.
The hopper superstructure, built onto the trailer by Freight Bonallack, is made from alloy plates supported by vertical steel pillars. Practically all the load is carried within the wheelbase. The external sloping panels are there only for the sake of appearance.
The sliding hopper-doors are hydraulically operated from a combined pto pump on the tractive unit. Even with the engine running at tickover speed the doors can be fully opened in lOsecs and closed in hall that time.
Under present regulations, the axh spread of the outfits limits their gross weigh to 30 tons, giving 19+ tons payload, bu Tunnel engineers have carried out loadini tests at 32 tons gross and the weigh distribution was found to be perfect. Al individual axle weights came within the legs requirements.