American Machinist

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TODAY'S GLEAMING new subways, the English Channel tunnel (otherwise known as the Chunnel), big-city sewers all have something in common: 30- to 40-ft dia shafts far beneath the surface of the earth. Far from sight, these impressive tunnels are bored through rock by some of the biggest pieces of machinery capable of independent movement which are appropriately named tunnel-boring machines (TBM).

Building TBMs requires a lot of impressive engineering and fabricating expertise. Manitowoc Inc builds the machines under contract from Robbins Co (Kent, Wash). Robbins perfected tunnel boring and sells its machines to tunneling contractors worldwide.

All of the manufacturing-engineering and fabrication skills of Manitowoc are called into play by the Robbins' work-and those skill are considerable. Manitowoc Engrg, a unit of The Manitowoc Co, is one of the world's leading manufacturers of crawler cranes. Its line of products includes 50-ton to 1000-ton capacity cranes with booms up to 640-ft long.

Tunneling machines bore through the earth, crushing and fracturing rock and "mucking" it out on conveyors. They are big, heavy, tough, and precise. A tunnel borer is 60- to 70-ft long and weighs about 500 tons. The cutting faces of the Robbins machines built at Manitowoc are 27-to 35-ft in dia. Each machine is fabricated, machined, and assembled in Manitowoc-tens of thousands of man-hours of work. …

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