After evaluating preceding studies and designs of lightweight supports, the all-hydraulic and the hydromechanical concepts were selected for detailed design and fabrication. Further analysis and testing showed that all-hydraulic design was economically justified and met all the crucial engineering, manufacturing, and design criteria identified during the evaluation. Following Bureau of Mines approval of the detailed design, four all-hydraulic support models were fabricated. When functional and structural testing was completed, 40 additional units were constructed and distributed for in-mine testing. The units were acceptable by three demonstration mines. The widespread interest in supports for seam heights greater than 8 feet led to expansion of the design data package. Four basic models were designed to cover the new height range, but no hardware has yet been fabricated.
Bureau of Mines, Spokane, Washington, Spokane Research Center