A dragline excavator is a piece of heavy equipment used in civil engineering, and surface mining.

Draglines fall into two broad categories: those that are based on standard, lifting cranes and the heavy units which have to be built on-site.  Most crawler cranes with an added winch drum on the front can act as a dragline. These units (like other cranes) are designed to be dismantled and transported over the road on flatbed trailers.  Drag-lines used in civil engineering are almost always of this smaller, crane type. These are used for road, port construction, pond and canal dredging, and as also as pile driving rigs. 

The much larger type which is built on site is commonly used in strip-mining operations to remove overburden that is above and more recently for tar-sand mining. The largest heavy drag-lines are among the largest mobile land machines ever built. The smallest and most common of the heavy type weigh around 8,000 tons while the largest built weighed around 13,000 tons.

A dragline bucket system consists of a large bucket which is suspended from a boom (a large truss-like structure) with wire ropes. The bucket is maneuvered by means of a number of ropes and chains. The hoist rope, powered by large diesel or electric motors, supports the bucket and hoist coupler assembly from the boom. The drag-rope is used to draw the bucket assembly horizontally. 

Quadrasteer operates in three phases.

Negative Phase -- At low speeds, up to 72 kph (45 mph), the rear wheels steer in the opposite direction of the front wheels.

Neutral Phase – At moderate speeds,  about 72 kph (45 mph), the rear wheels remain straight. This is also the failsafe phase in case of system problems.
 
Positive Phase -- At high speeds, above 72 kph (45 mph), the rear wheels turn the same direction as the front wheels. The Quadrasteer control module determines the phasing and amount of rear wheel steering based on the mode switch setting, position of the steering wheel and vehicle speed.

Alignment -- There are provisions for toe adjustment only. Caster and camber are fixed.

Steering Gear Motor – The electric motor is serviceable separate from the steering gear. When the motor is removed, 
the planetary gear reduction set is exposed, so care must be taken to avoid contamination.