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A walk-behind dragline is a heavy-duty machine used for surface mining and civil engineering. It has a large bucket controlled by wires and chains, and it walks with individual spokes. The largest dragline ever created was Big Muskie, weighing 13,500 tons and moving 20 million tons of clean coal. However, the design has limitations, including storage problems and limited digging depth.
A walk-behind dragline is a heavy-duty industrial machine typically used for surface mining and civil engineering applications. It’s similar in design to a crawler crane, but instead of a hook, there’s a large bucket suspended from the long boom. The bucket is controlled by wires and chains to dig up large quantities of earth and deposit it in a place away from the excavation site. A walking dragline literally walks, as individual spokes raise and lower to propel the machine forward. The average foot dragline typically weighs a few thousand tons, but manufacturers have built draglines weighing up to 13,500 tons (approximately 12,250 MT).
The dragline was invented in 1904 by John W. Page for use in the construction of the Chicago Canal. His invention would be modified and expanded by Oscar Martinson in 1913 to create the first walking dragline. Later, advances in hydraulic mechanisms allowed operators to expand the use of the dragline, especially in rough terrain. With increased mobility and ever-increasing bucket capacity, the walk-behind dragline has become an invaluable tool for miners and engineers.
A limitation of the mobile dragline design is that the radius within which excavated material can be discharged depends on the length and height of the boom. This generally leads to storage problems, thus requiring modifications around the excavation site to safely accommodate the large concentration of excavated dirt. Another limitation is the digging depth, which is limited by the length of the tow rope. In addition, walking draglines are inefficient at removing mounds of earth that rise above its base, thus requiring more electricity and time than a standard excavation would normally require.
The largest walking dragline ever created has been aptly named Big Muskie. It was the largest mobile digging machine on Earth, weighing 13,500 tons (about 12,250 MT) and standing nearly 223 feet (nearly 68m) tall. The hydraulically powered machine required 13,800 volts of electricity to dig 325 tons (about 295 MT) of earth with a bucket that had a capacity of 220 cubic yards (about 168 m3). From 1969 to 1991, Big Muskie moved nearly twice the amount of earth that was excavated during the construction of the Panama Canal and more than 20 million tons (about 18.1 million tons) of clean coal. In 1999, the cable holding up the massive boom was severed by explosives, effectively demolishing Big Muskie.
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