Abstract: A drum-cutter mining machine is propelled along a course of travel at the working face of a mine by a winch carried on the machine. The winch drives two sprocket wheels each pivotally carried by a pivot arm to position the sprocket wheels so that their teeth mesh with the teeth of a stationary rack. A roller or skid runner is carried by each arm to engage the lower surface of the rack and maintain the desired meshing relation between the sprocket wheel and the rack teeth at the upper surface of the rack. In a second embodiment, single-acting piston and cylinder assemblies deliver a biasing force to opposite sides of a level coupled to each pivot arm for controlling its position in a dependent relation to the direction of travel by the mining machine along the rack.