A roadheader is a self-propelled excavation machine which combines cutting and rubble removal in one vehicle. Driven by a pair of crawler-type tracks, the roadheader consists of a cutting head mounted on a pivoting extension boom. The boom is mounted above a chain conveyor assembly fronted by a dustpan-shaped scoop. The scoop is equipped with two rotating gathering arms that pull cut debris falling from the cutting head onto the conveyor, which then transports them to the rear of the machine and onto a waiting transport. These machines are used in a variety of excavation applications including mining, tunneling and road construction.
Most roadheaders are electrically-powered, driven by tank-like crawler tracks. They feature a large, rotating cutting head mounted on a hydraulically-operated extension boom at the front of the machine. The cutting heads may be shaped like a spiral, cone or ball, and they all feature concentric rows of hardened, removable cutting teeth. As the cutting head rotates, it abrades or gashes material away from the working face, constantly advancing the cut.
The cutting head boom of the roadheader may extend along its own axis, rise up or down or turn through an arc across its axis. This makes the machines some of the most flexible excavators in terms of cutting area ranges. The roadheader also features a cut which disturbs very little, if any, adjacent material, making for accurate and safe cutting. They are also well-suited to applications where frequent changes in direction are required to cut side tunnels.
An inclined chain conveyor, which starts at the front of the machine in a scoop shape much like a domestic dustpan, sits below the cutting head and boom. On either side of the scoop are two rotating gathering arms that run with the conveyor. As the head cuts, debris fall below it and are pulled onto the scoop and into the conveyor channel by the arms. The conveyor then transports the rubble to the rear of the machine, where it is discharged onto a truck, shuttle car or another conveyor for removal from the working area. The conveyor boom is often articulated, allowing it to turn almost like a scorpion's tail to accommodate tight-cutting face confines.
Roadheaders are available in a large range of sizes to suit all applications. The largest machines feature cutting heights of 26 feet (8 meters) and cutting widths of 30 feet (10 meters) and weigh in the region of 120 tonnes and are driven by motors in excess of 600 horsepower (400 Kw). The smallest examples are not much larger than a Bobcat loader, with motors of 40 horsepower (30 Kw).