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         continued from page 22             1/2 tons of extra wire to each cable to   days when metal fatigue was first be-
         length of ½ inch for each wire, this cou-  compensate. The original design factor   ing identified by scientific studies.
         pling gives about 95% of the strength of   for the cables was six-to-one. After add-  The large number of mechanical
         the wire. After the ends of the wire are   ing the extra wire, he estimated “There   splices in the main cables didn’t seem
         secured  in  the  ferrule,  the  coupling  is   is  still  left  a  margin  of  at  least  five   to bother anyone in 1883. The subject
         cleansed…dipped in molten zinc… and   times  which  I  consider  perfectly  safe,   is never mentioned today; most people
         finally painted with red lead.”    provided  nothing  further  takes  place.”   are unaware of them. On an average
           All of the wire splicing was done at   When  the bridge opened, a summary   day last year, 124,000 vehicles crossed
         a yard near the Brooklyn  anchorage.   article in Scientific American May 26,   the  toll-free  Brooklyn  Bridge.  Cur-
         In the beginning the coils of wire be-  1883 included  a casual  remark  about   rently, it is not used by heavy trucks
         ing spliced were 800 to 1000 feet long   splicing  the  wires:  “As the  bundles  of   and trains. The cables are inspected
         but with the change to larger wire they   cable wire came in comparatively short   frequently by the New York City DOT.
         were only 600 to 800 feet. This means   lengths,  joining  was  frequently  neces-  All of the steelwork of the bridge gets
         at the beginning of the cable-making,   sary”. The implication of frequent join-  repainted on a regular basis. Other
         the engineers already realized there   ing translates to an unknown number   than survival of the original hot-dip
         would  be at least three  mechanical   of  mechanical  splices  of  a type never   zinc coating from the 1870s, the pri-
         splices in every single wire between   used before.                   mary means of protecting the wires
         anchorages. In 1878, it was discovered                                and  splices  of  the  main  cables  from
         Haigh had been secretly shipping lower   Conclusion                   corrosion  has  been  simply  repaint-
         strength wire to the splicing yard. Sup-  The main cables are not rigid. They   ing them. DOT owns, operates, and
         posedly, Haigh had an understanding   are intended to flex slightly with tran-  maintains 789 bridges and tunnels
         with Anderson to reapply rejected steel   sitory loading, creating what engineers   throughout New York  City.  The  job
         to other uses. It seems the agreement   call a varying load superimposed on a   never ends. WRN
         collapsed in 1877 when the steel indus-  constant load. This is one of the basic
         try at Pittsburgh was disrupted by vio-  conditions for metal fatigue, a phenom-  Maggie Blanck helped with the research for
                                                                               this article. She has posted added factual infor-
         lent labor riots.                  enon  which  was new to metallurgists   mation on her website www.maggieblanck.com
           The trustees asked Washington Roe-  in  the  1870s. Because  the  cables  are   under  the  heading  “Industry  and  Commerce  in
         bling  to  estimate the  total effect  of   wrapped tightly with wire except at the   Red Hook and Carroll Gardens, Brooklyn in the
                                                                               mid to late 1800s”
         what had happened. In response to the   anchorages and on top of the towers,
         question “How can the cables be made   there is no way to examine the condi-  Wilhelm Hildenbrand’s book “Cable-Making for
         as good as they were originally intend-  tion  of  at least 60,000 little mechani-  Suspension Bridges with special reference to thje
                                                                               cables of the East River Bridge” is now available
         ed to be?” he replied he had added 14-  cal splices which were installed in the   on-line: purl.lib.lehigh.edu/76

         24     Wire Rope News & Sling Technology   February 2017
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