Fig. 8: Roebling bridgemen compacting the main cables on the GWB, 1931. The 2 7/8 inch footbridge ropes are visible in clusters on each side of the cables supporting the footbridge on the New York side span. PANYNJ.


Fig. 9: With a “ROEBLING CABLES” sign on top of the New Jersey tower,


workers hang the bridge deck from the 2 7/8 inch suspender ropes, 1931. PANYNJ


“The configuration of the 37-wire strands around the center rope provides high capacity resistance to erosion and fatigue…. This design is inherently very appropriate, and we will use the same


configuration for the replacement ropes.” - Bernard Yostpille, PANYNJ’s Chief Structural Engineer


For the Hudson River Bridge’s 2 7/8 inch suspender ropes,


Sunderland specified a 6 x 37 rope with strands similar to Charles Roebling’s patent, and a 6 x 7 independent wire rope center composed with two wire sizes in the outer strands and a 19- wire center strand with three wire sizes (Fig. 5). At the Roebling Company’s Kinkora Works steel and wire plant in Roebling, N.J., ten miles south of Trenton, steel workers used scrap steel and pig iron to make the wire for the suspender ropes and for the bridge cables, and wire drawers drew it into the 11 different sizes needed for the strands, the rope center, and the bridge wire. Rope shop workers at the Company’s main plant in


Trenton made the strands and closed them into 7,200-ft. long, 2 7/8 inch ropes with a 25 inch lay on the 80-Ton Wire Rope Machine, which Charles Roebling built in 1893 to make 30,000-ft. long, 1 ¼ inch ropes for cable cars (Fig. 6). Te Company transported the GWB ropes back to the Kinkora


28 JULY-AUGUST 2012 WIRE ROPE EXCHANGE


Works, where workers cut them into prescribed lengths, prestressed them with 200,000 lbs of tension on the unique Prestretcher there, and shipped them to the bridge site in 760 to 3,500-ft. lengths (Fig. 7). As described in the first article, Charles Sunderland


developed the Prestretcher to enable the Company to use the ropes initially to support the footbridges for building the main cables (Fig. 8). When the Roebling bridgemen completed the cables, they cut the ropes into the required suspender rope lengths, socketed them on site, and installed them to support the bridge deck (Figs. 9 & 10). After more than eight decades of service, tests on the


ropes removed in 1999 and on ropes still in place indicate that the Roebling suspender ropes retain much of their original load bearing capacity (Fig. 11). According to Bernard Yostpille, “Corrosion is the basic problem with suspender


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