Page 22 - Wire Rope News & Sling Technology
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continued from page 20
         ing station at the mill in Red Hook.
           Abbott cut  60 feet of  wire  from ev-
         ery 40th coil. He employed  a Fair-
         banks  testing  device  to  apply steady
         strain, recording how much the wire   James Brady operated a small machine shop near the site of the Brooklyn tower. He produced
         stretched. The load was then increased   this clever coupling ferrule for splicing the main cable wires. Somewhere between 60,000 and
                                            200,000 of these are inside the Brooklyn Bridge main cables.
         to the breaking point. The same test
         was applied to a 6 foot length from ev-  The procedure for making the main   about 70 pounds which he bought from
         ery 5th coil, and to a 16-inch piece from   cables began with a single “guide   a steelmaker in Pittsburgh named
         every coil. He also did a severe bending   wire”  hung  with  a  precise  curve  be-  Anderson. Drawing a larger wire size
         test on a one foot piece from every coil,   tween  anchorages.  Using  a  traveling   also meant a shorter length would be
         wrapping it tightly around a half inch   wheel to convey a doubled length of   drawn from the same rods, which,  in
         diameter. The aim was to employ wire   wire across the river, more wires were   turn, meant more splices in each cable.
         of consistent quality and strength.   added until a group of more than 300   Washington Roebling decided to aban-
           Washington Roebling explained to   were strapped together as a strand.   don the wire  splicing  method his  fa-
         the bridge trustees: “If a weak wire is   Each main cable was made of 19 such   ther had used for wire ropes since the
         spliced  to  a  strong  one  and  stretched   parallel-wire strands. When cable-  1840s. Tests showed  it wasn’t strong
         from tower to tower, the strength of the   making began, the wire furnished by   enough for steel wire.
         weak wire is the measure of the whole   Haigh exceeded the spec. Hildenbrand   After many experiments,  he  and
         length”. Erica Wagner, who has writ-  said the average strength was 172,000   Hildenbrand contrived a novel me-
         ten  the  first-ever  full-scale  biography   psi.  This  initiated  a  major  change:   chanical connector. The technique they
         of the Chief Engineer, sees an anal-  “After  two  strands  were  completed…  chose doesn’t have a name because the
         ogy. She says: “When I’m buying yarn   it was concluded to increase the size of   East River project was the only time it
         for  knitting,  I  observe  the  batch  num-  the wire…” Only 282 wires then were   ever was used to form bridge cables.
         bers on each skein – if you are buying   needed to make the other strands   Hildenbrand explained:
         more  than  one  skein  of  a  colour,  you   which saved a lot of time.   “Experiments  made  with  different
         have to make sure you have skeins with                                kinds of splicing gave the preference to
         the same batch number, because there   Splicing the Wire              a screw-coupling…tapering the ends of
         can be slight variations in the dye. So   During the Civil War, Pittsburgh, PA   the  wires  a little and  turning  a cylin-
         each skein of wire in a cable should be   had become the steelmaking center of   drical  screw  on this  cone.  By a screw
         matched in the same way.”          the nation. Haigh used rods weighing                continued on page 24

         22     Wire Rope News & Sling Technology   February 2017
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