The 4042 model, explained president Dana Getman, reduces damage to roads that other haulers produce when heavy weight, such as that of longwall shields, is concentrated in the tires.

Published in the August 2007 American Longwall Magazine

The damage to the roadway is more serious than a road rut - it can affect productivity and safety.

The unit, an updated version of the trailer in the company's tractor-trailer set, also improves frequent problems with shield movers.

"When using shield movers, the shield's weight shifts the center of gravity far in front of the mover's front axle," Getman said.

"This places tremendous weight on the mover's front wheels, which dig ruts into the road, and little weight on the back wheels, which then don't provide good traction." He added that counterweights are often needed when using loader-style haulers.

Getman's unit, he explained, has the sturdiness of a track-based structure that allows the weight to be more evenly distributed. With a 42 short-ton capacity that comes in at less than 30psi when fully loaded with heavy shields, the unit's throat size is 168in by 90in.

It can also properly take on shields of various dimensions, as four-hook points help to put the proper load pressure on its hitch for sufficient traction and braking. To prevent overheating and to keep brakes working as needed in graded environments, the Hydrahauler also includes wet disc brakes on all four main undercarriage wheels. Forced cooling ensures cool brakes at all times.

Because no mine is completely flat, straight or without obstacles, Getman has included a pivoting gooseneck design, to allow the amount of lift on the trailer's leading end to vary by as much as 13in. Similarly, the hydraulic frame-payload lifting mechanism provides 13in of lifting range.

"Each function has its own control so they can be operated independently [and] not have to be raised all together," he said. This design permits the lifts to be completed hydraulically so the unit can maneuver over or under an obstacle.

A specialized cylinder-accumulator system deals with debris issues. "The track retains tension through an accumulator," Getman said. "If debris gets between the friction wheel and track, the cylinder-accumulator system allows the track to give until the debris exits."

As well as ensuring a better post-move roadway, the Hydrahauler - part of Getman's GUTS (Getman Underground Transport System) - makes longwall moves more efficient and rapid. "[It] moves longwall sections faster than shield movers, which are of limited use in longwall moves because they are not designed for high-speed, long-distance transportation," said Getman.

When it's not in use for a move, the unit can be used as a general supply and material trailer.