Bucket-wheel excavators are heavy equipment used in surface mining and civil engineering. They are among the largest vehicles ever constructed, and the biggest bucket-wheel excavator ever built, the MAN Takraf RB293, is the largest terrestrial vehicle in human history.
The excavation component itself is a large rotating wheel mounted on an arm or boom. On the outer edge of the wheel is a series of scoops or buckets. As the wheel turns, the buckets remove soil or rock from the target area and carry it around to the backside of the wheel, where it falls onto a conveyor, which carries it up the arm toward the main body of the excavator. Additional conveyors then may carry it further; in some cases, several long conveyors are placed end-to-end, each supported by a large vehicular base (usually with caterpillar tracks).
The largest bucket-wheel excavators in the world are used in German strip-mining operations. These tremendous earth-movers can cost over $100 million, take 5 years to assemble, require 5 people to operate, weigh more than 13,000 tons, and have a daily capacity of 240,000 tons of brown coal or m³ overburden
. One of them, Bagger 288
, is working in stripmine Garzweiler (Tagebau Garzweiler
), and five others in stripmine Hambach (among them Bagger 293). Bagger 288 (the oldest, assembly completed in 1978) is 240 meters long and 96 meters high. Until 2001 it worked in Hambach, and then drove as a giant caterpillar vehicle to Garzweiler, a distance of 22 km through the fields, crossing a few roads, a railroad, and a river. Bagger 293 (formerly RB293, manufactured by MAN Takraf
), the heaviest among these 240,000ers, was recognised by the Guinness Book of Records (2001-2006) as the largest (heaviest) land vehicle.
In Transformers Cybertron
, the character Metroplex
has the ability to transform into a Bucket-wheel excavator.