New era of mine haul truck giants

Diesel Progress North American Edition, March, 1999 by Mike Mercer

"The fact of the matter is that every mine in the world is different and in a sense is its own world," continued Holman. "Not every application will benefit from a larger truck. It depends on the mine infrastructure such as the lay out, the type of roads, and the loading and dumping or crushing system that is in place in the mine. It is not automatic that if a mine gets larger trucks the hauling costs go down."

Unit Rig, a division of Terex Corp., is in development of a 340-ton mine haul truck, the MT5500, which is due to be introduced sometime this year.

The MT5500 truck will utilize an a.c. electric drive system. The drive system is subcontracted to Power Conversion Systems, a division of General Atomics. Many components of the drive system are spinoffs from other applications and will be modified and adapted for the MT5500, Unit Rig said.

According to the company, the frame, axles, dump body, suspension and hydraulic systems are all based on the existing MT series trucks. The current Unit Rig MT product line includes five d.c. diesel electric trucks with capacities from 120 to 260 tons.

The MT5500 truck's statistics include a gross vehicle weight of over 1,100,000 lb. The truck is 46 ft. in length, 30 ft. wide and 24 ft. tall and will be powered by a 16-cylinder Cummins diesel rated 3000 hp.

The design of the a.c. drive system will give the truck a top speed of 40 mph, Unit Rig said. The drive system has the capability to switch from propulsion to dynamic retarding in one second and the dynamic retarding is effective down to zero mph, according to the company.