Now here’s a serious dump trailer: Smithco’s 85-Metric-Ton Gooseneck Tipper, one of the pieces of equipment recently demonstrated by Western Star Trucks at the Michelin Proving Grounds in South Carolina. It was pulled by a 6900XD from Western Star, which was showing off its line of off-road vehicles that compete with “haul trucks” from Caterpillar, Kumatsu, Terrex, and others.

While pulling the Smithco tipper, the 6900XD acted as a tractor, but it’s really a straight truck fitted with a fifth-wheel kit. It’s part of the MBT-40 Multi-Body Transformer system from Carco Industries, using a Palfinger extreme duty model G68 hooklift that picks up bodies and puts them back down. This gives a truck multiple roles at a mine or heavy construction site.

Hook-lift systems are not new, and I recall writing about them in the 1980s (Palfinger offers many models of its own). But those are comparatively small, on-highway products, while the MBT-40 is capable of lifting and supporting larger and heavier bodies, and therefore loads. At this demo, Carco had steel dump and water tank bodies present and showed how they can be interchanged as needed by an operator.

The fifth wheel kit includes a subframe on which the coupling device is mounted. That raises the fifth wheel’s height by more than a foot, and the Smithco trailer’s gooseneck is correspondingly higher than it would otherwise need to be. Partly because of a higher center of gravity, this trailer’s capacity of 85 metric tons (93.7 standard or "short" tons) is somewhat less than the 100 metric tons (110 standard tons) it might otherwise be rated for, a Smithco rep said. The trade-off is versatility.

For the demonstrations, a big Cat wheel loader filled the trailer to the gills with gravel, and when the rig returned from a demo run, attendees watched as the trailer tipped to its left, spilling the gravel onto the ground. Western Star reps said rigs like this – though with standard-height fifth wheels and larger-capacity trailers – are operating at mines in northeastern Canada and in central Australia.  

Western Star says its 6900XD 40-ton dump, and now a new 4900XD 25-ton dump, cost less to buy and maintain than a haul truck and is easier on fuel. They're better for long-distance running over graded gravel and dirt roads. But haul trucks can walk over tall obstructions that would stall the ‘Stars, said an attendee, a Georgia quarry operator who runs a group of Deere haulers.

The Western Star-Smithco rig was a handful to drive, I can tell you. That’s not because of its size (about 116 inches wide and close to 100 feet long) or weight (about 220,000 pounds gross), but its stiff power steering. I needed two hands on the wheel to make all turns, and the wheel didn’t automatically center; I had to twist the wheel to return it to a straight-ahead position.

However, a Detroit DD16 provided the grunt and a 7-speed Allison automatic transmission did much of the operating work. The rig imparted a sense of really getting something done. Maybe this is what I want to do when I grow up.