A mast assembly for a mobile drilling machine may comprise: a mast frame including a back, a first side, and a second side, the first side and the second side diverging from the back to form an open front along substantially an entire length of the mast frame; a drill motor assembly movably attached to the mast frame, wherein the drill motor assembly is configured to rotate a drill pipe; and a drill drive assembly configured to drive the motor assembly up and down along a length of the mast frame, the drill drive assembly including: a sheave assembly comprising a plurality of sheaves, wherein the plurality of sheaves include a first sheave aligned generally parallel to the first side of the mast frame and a second sheave aligned generally parallel to the second side of the mast frame.
展开▼
