Adzer machine having failsafe head assembly

An adzer machine, comprising:

• a machine frame;
• wheels configured to support the machine frame and ride along a rail located at first ends of a plurality of cross ties;
• track-type crawlers located opposite the wheels, configured to support the machine frame, and ride along second ends of the plurality of cross ties;
• a rotatable cutting head configured to resurface the second ends of the plurality of cross ties and being located between the track-type crawlers;
• skids configured to slide along the second ends of the plurality of cross ties and being located between the rotatable cutting head and the track-type crawlers;
• a lift frame configured to mount the rotatable cutting head;
• parallel lift arms pivotally connecting the lift frame to the machine frame;
• a double-acting lift cylinder disposed between the parallel lift arms and configured to raise and lower the parallel lift arms;
• a plurality of single-acting hydraulic cylinders, each connecting the lift frame to a corresponding one of the skids and to the lift frame, the plurality of single-acting hydraulic cylinders being configured to only extend the skids relative to the lift frame;
• a plurality of springs each connecting a corresponding one of the skids to the lift frame and configured to bias each of the skids back toward the lift frame;
• and
• a shim pack located between the skid and the lift frame;
• wherein:
• the skid includes a stem portion, a generally T-shaped end connected to the stem portion, and a base plate connected to the stem portion opposite the generally T-shaped end;
• the lift frame includes a bracket that encircles a portion of the stem portion;
• and
• the shim pack is located around the stem portion, between the bracket and the generally T-shaped end.