Progress in the Art of Coal Hauling 720797

High labor and operating costs have led to the demand for more reliable and productive equipment. OSHA is further demanding safer, quieter, and cleaner working conditions for the operator.A fleet of Kress 150-ton single unit, rear engine, bottom dump coal haulers, now in operation at the Captain Mine, are an interesting solution in meeting these demands. By eliminating the weight of the gooseneck, hitch, and tractor frame, and using 175,000 psi yield steel, these units have payload to weight ratios of approximately 3:1. This is between 60-90% improvement over conventionally designed tractor-trailer units.This new coal hauler design concept became possible with the development of a dual tire front axle module which includes an oleo pneumatic suspension and 90 deg steering capability.The automatically leveled suspension system has a 20 in stroke, allowing relative deflection rates 1-1/2 times softer than the softest passenger cars. This increases vehicle operating life, improves tire life, provides exceptional driver comfort, and allows safe 50 mph plus operating speed. Sufficient power is available to maintain this high speed when loaded; which results in substantial productivity improvements.The engine in the rear gives 65% traction empty and 50% plus traction on grade when loaded. This engine location isolates the driver from noise and vibration. All removable components are modular. The engine module can be removed and replaced in as little as 3 h. For maximum safety, the dual accumulator hydraulic system allows normal vehicle control even when the engine is dead and one hydraulic system is inoperative.