The former is a standard-type cutting machine with the horizontal cutting arm at floor level, and an additional overhead cutting arm or "riffle," both powered by a 50-h.p. electric motor. A second 50-h.p. motor drives the loading and vertical cutter portion of the combination. The loading mechanism consists of rotating bars fitted with teeth and a small slatted belt which loads the coal as it is cut on to the face convey or-belt.
The machine weighs 10 tons, and is 16 feet long and 3 feet high, with horizontal cutting arms of a length between 4 feet 6 inches and 5 feet 6 inches. The vertical cutter (or shearer) varies according to the thickness of the seam, but is usually from 4 feet to 5 feet 6 inches in height.
To begin operations, the extreme ends of the coal face are cut into a depth of 10 or 12 feet, forming boxes or "stables" in which the cutter-loader can be manoeuvred into a starting position, and the machine starts to work, pulling itself along the face by a wire rope. As the coal falls after it, cut horizontally and vertically by the cutters, it is assisted by the teeth of the rotating bar on to the traverse belt, and so to the face conveyor, and on outbye.
The machine moves forward at a rate of up to27 inches per minute. Immediately in its wake a row of props are erected, and on reaching the second "stable" at the far end of the Face, the cutter portion is detached and manoeuvred round to the other end of the loader, while the vertical cutter, which is on a swivel joint, is reversed. The cutter is then ready for the return journey, each journey occupying one shift out of the three-shift cycle of operations.
Initial difficulties in supporting the roof have been overcome by slight variations in technique. An indication of the cutter-loader's performance may be gained from observations taken by Messrs. T, E. B. Young and W. H. Sansom, embodied in a paper presented in the Institution of Mining Engineers. "The machine cleared 108 yards in an average of six to seven hours to a depth of 5 feet 6 inches, the actual operating period being little more than four hours and a team of thirteen men produced an output equal to that of twenty-four men engaged in hand-loading under similar conditions."