“No ropes so long as would be required to support these walks had ever been built for such exacting service.” - Engineering News-Record, 1930


John A. Roebling (Fig. 4) was born in Prussia in 1806, studied bridge engineering at the


Royal Building Academy in Berlin, immigrated to America in 1831, and co-founded the town of Saxonburg in Butler County, 35 miles north of Pittsburgh. Roebling’s familiarity with the early efforts to make ropes out of wire led him to experiment with making a wire rope for the Allegheny Portage Railroad, which used costly hemp ropes to haul canal boats over the mountains (www.nps.gov/alpo/index.htm). Tough he had no experience with making rope, he built a ropewalk on his farm and soon grasped the fundamental principles. As he wrote in 1843 in the American Railroad Journal, the Wired magazine of its day, “Te novelty of my process chiefly consists in the spiral laying of the wires around a common axis without twisting the fibers; and secondly, in subjecting the individual wires while thus laying to a uniform and forcible tension under all circumstances. By this method, the greatest strength is obtained by the least amount of material, and, at the same time, a high degree of pliability.” Besides being an innovative engineer, Roebling was also an astute businessman. He installed his 7 x 19 wire rope (Fig. 5) on the Portage Railroad at his own expense, and with its success he began marketing his wire ropes for canals and for ships’ tillers and rigging. Roebling built his first suspension bridge, a canal aqueduct, in Pittsburgh in 1845, and he


Fig. 4: John A. Roebling, the pre-eminent suspension bridge engineer in the 19th century, founded a wire rope business that


prospered for over 130 years. Rutgers University Special Collections


20 MAY-JUNE 2012


immediately patented the traveling wheel method he devised to lay individual wires into the aqueduct’s 7- inch cables (Fig. 6). In 1849 he moved his wire rope business to Trenton, N.J., to be closer to his customers in the East. In the early 1850s he won fame as the world’s pre-eminent suspension engineer by building the Niagara Falls Suspension Bridge with four 101⁄2-inch cables


WIRE ROPE EXCHANGE


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