|Bucyrus-Erie 120-B removes overburden for coal for contractor A.E. Dick Construction in Pennsylvania|
In the 1920s, quarries and hard-rock mines were expanding their use of shovels to load haulage vehicles with larger quantities of material than ever before. The only shovels heavy and robust enough for tough quarry work were the old-faithful steam railroad shovels, many of which had found their way into large quarrying operations. Although some had latterly been converted to crawlers, freeing them from restrictive railroad tracks, their working capabilities were still severely hampered by long steam boilers at the rear, and boom and dipper assembly with swing limited to about 180 degrees. Shovels with 360-degree swing were available, but these were either small construction-sized units or long-boomed gangly stripping shovels not robust enough for hard digging. Clearly there was a need for a machine that combined the railroad shovel's robustness with the stripping shovel's full-swing capability.
In 1925 Bucyrus answered the call with the 120-B, announced as the world's first mine and quarry shovel designed for loading rail cars or trucks. Initially introduced as a 4-cubic-yard shovel, the 120-B tipped the scales at 170 tons, and its robust construction and “over-design” earned it an enviable reputation for reliability in the toughest digging. It was ruggedly built, utilizing massive castings and riveted construction in an era when welding was not yet established. It moved on standard 36-inch-wide crawler shoes and sat firmly on a substantial undercarriage measuring 17 feet wide by 19 feet 4 inches long. Its 32-foot-long boom and 22-foot dipper handle provided a maximum dumping height of 21 feet 6 inches at 39 feet 3 inches radius. The twin dipper handles were mounted outside the boom, and the crowd motion was driven by rack-and-pinion from a boom-mounted motor.
When electric welding came of age in the mid 1930s, the 120-B shovel graduated from riveted to electric-welded construction. While retaining its rugged steel castings for carbody and revolving frames, its welded boom and other assemblies permitted increased dipper capacities to 5 cubic yards with no significant gain in overall machine weight. Some of the 120-Bs were steam driven, and the last two sold in 1939 were the very last steam shovels built in America.
The electric 120-B shovel utilized separate DC motors for its various motions and employed the Ward-Leonard system of control. This system, used on all Bucyrus shovels until recent times, replicated the precise control of the former steam shovels and provided maximum torque at stall speed. AC power was supplied to the shovel via a trailing cable which drove a 275-horsepower motor-generator set. This in turn provided DC power to the hoist, crowd and swing motors, with crawler propel driven from the main hoist motor through a train of gears, shafts and clutches.
About 330 of the 120-Bs were sold around the world over a period lasting almost three decades. During this time, other shovel manufacturers and Bucyrus themselves developed full lines of different sized quarry and mine shovels based on similar design parameters, and it's on these that today's high-capacity electric mining shovels have been developed.
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Learn more about machines built by Bucyrus in Keith Haddock's just-released and fully illustrated book: “Bucyrus Construction and Mining Machines 1880 to 2008”, now available in bookstores. Also, consider a membership in the Historical Construction EquipmentAssociation, www.hcea.net, and be sure to visit ConstructionEquipment.com for past Iron Works features.