A power feed system for a rotary drill includes a hollow tubular derrick having a powerhead connected to a flexible cable moved by a double rod hydraulic cylinder assembly. The derrick includes fixed and movable sheaving assemblies. The hydraulic rod assembly, the fixed and movable assemblies operate substantially within the derrick interior. A guide wheel on the movable sheaving contacts the derrick to maintain axial alignment of the hydraulic rods. Pivotable connections between the cable and the movable sheaves automatically adjust for cable fleet angle change, as the movable sheaves travel, maintaining axial alignment of the hydraulic rods and avoiding introducing torque into the cylinder rods.
A field adjustable block for use with a bridge crane having a rotating cylindrical drum for rope. The block includes a cylindrical center pin having a key way recess parallel to an axis of the center pin. An inner side plate has an opening therethrough and an extending key receivable in the key way recess to prevent rotation of the inner side plate. Multiple sheaves are receivable over the center pin. At least one toroidal spacer is receivable over the center pin. A lock washer has an inwardly extending key receivable in the key way recess of the center pin and has a plurality of radially extending tabs. A nut has at least one notch to receive one of the extending tabs therein. An outer side plate is removably attached to the inner side plate by fasteners.
