It was not a case of reinventing the wheel when Marion Power Shovel Co., one of America's top three mining-shovel manufacturers, announced its revolutionary Superfront shovel in 1974. It was an attempt to combine age-old principles of physics with modern technology to produce a more powerful and efficient cable-operated mining shovel. When released, the machine had already undergone many years of development and testing. It was back in the mid-1960s that Marion's engineers began to develop a totally new concept of shovel design, and build a prototype based on one of Marion's standard shovels.
They took a Marion 101-M, normally carrying a dipper of 3-cubic-yards capacity, and retrofitted it with the Superfront attachment. The machine could then operate safely with a 5-yard dipper, a capacity increase of 66 percent.
The Superfront design was based on a clever arrangement of moving triangular frames and components based on simple geometry. In a normal rope shovel, the angle of the dipper is fixed relative to the handle, and the hoist and crowd forces tend to oppose one another, making the digging less effective. The crowd force also produces an undesirable bending moment in the boom. But on the Superfront, the boom was replaced by a moveable stiff leg, eliminating any bending. In addition, the dipper was able to rotate — similar to that on a hydraulic shovel — allowing the dipper teeth to penetrate at the optimum angle. The dipper rotation was accomplished by a pair of non-powered hydraulic cylinders linked through cables and a bell crank system on the dipper. The degree of rotation was adjusted by the operator with control through a check valve. When in operation, the Superfront was able to exert maximum penetration at the toe of the bank, not always possible with a conventional cable shovel.
After three years of testing, the machine came through with flying colors, prompting Marion to move to the next stage of development. In 1972, two existing 15-yard electrically powered Marion 191-M shovels were retrofitted with the Superfront, again boosting their capacities well beyond the normal ratings. With full-scale machines actually working in mining conditions, Marion's design engineers were able to fully prove the Superfront and obtain feedback on productivity, reliability and operator acceptance.
With a working weight of 1,550,000 pounds, the electrically powered machine, designated model 204-M, carried a standard dipper of 30 cubic yards with optional dippers from 20 to 45 cubic yards depending on the material. Although not shipped in great numbers, the Superfront sold steadily over a 12-year period from 1976 including a large order of 10 machines shipped to Russia. Others were shipped to Australia, New Guinea and to western coal mines in the United States. A hydraulic system was introduced on some of the machines with hydraulic cylinders replacing the cable crowd arrangement, but the main hoist and dipper tilt were still cable operated.
The Marion Power Shovel Co. was acquired by Bucyrus International in 1997, and no more Superfronts have been built.
You can read more about the evolution of construction equipment in Keith Haddock's latest book release, an updated version of his fully illustrated Earthmover Encyclopedia now available in bookstores. Also, consider a membership in the Historical Construction Equipment Association, www.hcea.net
