"In many underground mining operations the highest cost is the loading and haulage of run-of-mine ore. Ore hauling costs can be reduced significantly with the use of belt conveyors, a common practice in coal and other soft mineral mines, if oversize ore can be eliminated prior to conveying, hence the demand for crushers close to production areas. Portable feeder-breakers are used extensively in conveyorized coal mines, but no such equipment is available to extend the benefits of belt conveyor haulage into hard rock mines of low to medium headroom. A hard rock crusher that could be easily moved would permit the use of lower cost haulage means, and would improve the safety and productivity of all elements in the underground ore handling system. This report describes a study to determine the optimum design parameters, and provide a concept, for the design of a low profile, hard rock, portable underground crusher in order to insure that future development will lead to maximum utilization by the industry. The recommended design is a rotary jaw concept."