Ursa Major (excavator)

The Ursa Major (lit. Great Bear) at Black Thunder Coal Mine, Wyoming, is the largest dragline excavator currently in use in North America and the third largest ever built.[1][2] It is a Bucyrus-Erie 2570WS model and cost US$50 million. The Ursa Major was one of five large walking draglines operated at Black Thunder, with the next two largest in the dragline fleet being Thor, a B-E 1570W - which has a 97.5m boom and a 69m³ bucket - and Walking Stick, a B-E 1300W with a 92m boom and a 34m³ bucket.[1]

Ursa Major in 2009

Its bucket is 160 cubic yards (120 m3), and it has a 360-foot (110 m) boom. It weighs 14.7 million pounds (6,700 t).[3][4]


Shortly before the scrapping of Big Muskie in 1999, the largest dragline ever built, construction of another ultraheavy dragline excavator soon commenced. Although not as large as the Big Muskie, the Ursa Major was still a large and substantial excavator.

It first began operation around early 2001, the 160 cubic yard bucket which was newly casted at the time, was delivered at Black Thunder Mine. Operation to deliver the 165,000 pound bucket (82.5 tons) Bucyrus had to obtain special permits for an overweight and oversized load for it to be permissible to be transported. The company also had to check with the power company to make sure it won't hit any power lines on the way to the mine.[5]


  1. ^ a b "Black Thunder Thermal Coal Mine, Wyoming". Mining Technology. Retrieved 11 January 2019.
  2. ^ Orleman, Eric. "Bucyrus Erie 2570WS "Ursa Major"". Stripmine.org. Retrieved 11 January 2019.
  3. ^ "Black Thunder and Coal Creek mines". Engineering News. 7 May 1999. Retrieved 11 January 2019.
  4. ^ Modern Marvels: Earthmovers[full citation needed]
  5. ^ Stephanie Cooper. "Black Thunder to operate world's largest dragline bucket".