MAIN FRAME

The main frame is a steel fabrication, designed to withstand the strain imposed by operation over adverse terrain. The main frame provides a mounting base for the various components of the rock drill.

Track oscillation is controlled by two hydraulic cylinders, connected to brackets welded to both sides of the main frame and to brackets welded to the track ^frame. The cylinders permit 20-percent track oscillation, dampen sudden oscillation shocks when tramming over rough terrain, and stabilize the unit when setting up on uneven ground.

TRACTION DRIVE

The tracks are driven by a traction device that consists of a parking brake, an axial piston motor, a brake valve, and a planet gear reduction. The traction drive is equipped with spring-loaded, hydraulically released brakes. The brakes are released automatically when hydraulic fluid is directed to the motors to move the unit. The brake valve, located within each of the motors in the hydraulic circuit, prevents the unit from ^uncontrolled runaways on grades. Each brake is

Figure 14-21.-Crawler-mounted rock drill.

controlled by the tram valve, mounted on the main frame.

POWER UNIT

The Power unit supplies the rock drill with hydraulic and pneumatic power.It consist of an engine four-coupled gear pumps, compressor air end, receiver tank, inlet manifold, return manifold, and hydraulic/ pneumatic piping.

Hydraulic System

The boom/guide set-up control valves and drill control valves are located at the side by the drill guide. Other control valves are located at the front side of the power unit, and the relief valves are located at the inside of the left door. The return and suction filters are located at the top of the hydraulic tank.

A pressure-compensated valve to change rod rpm according to drilling conditions is located at the inside of the left door.

The four pumps provide oil as follows: l Pump one provides oil for right side tramming and slow and fast feed drilling.

. Pump two provides oil for left side tramming, drill, and fast feed.

. Pump three provides oil for high-speed tramming, rotation, and cooler.

. Pump four provides oil for high-speed tramming, dust collector, centralizer, cylinders, and auto rod changer (if so equipped).

Oil Cooler

The oil cooler maintains safe temperatures for hydraulic oil and compressor oil in all climates and is located at the top of the power unit. At low temperatures, the oil bypasses the coder through the cold bypass valve.

Air System

The air system consists of a compressor air end, receiver tank, blow air circuit, dust collector (if so equipped), and air lube system.

The air end is connected to the engine with a flexible coupling. The compressed air is delivered to the receiver tank, located at the backside of the power unit. The compressed air, mixed with compressor oil, is separated from the oil in the receiver tank and is distributed to each system. The separated compressor oil is sent to the oil cooler from the receiver tank under pressure. The compressor discharge air volume is 230 cfm, and the discharge air pressure is 100 psi.

NOTE: A common cause of low discharge air pressure is a clogged orifice muffler, located on the upper rear left comer of the rock drill.

The dust collector is equipped with a stepping pulser that sends discharged air every 20 seconds to knock off the cuttings on the filter into the dropout chute, located at the bottom of the collector.