Page 10 - Wire Rope News & Sling Technology - December 2018
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         was the largest single steel wire buy in
         world history as of that moment.
           Washington Roebling was the bridge’s
         chief engineer. When he was writing the
         specification for the main cables, had no
         official  standards  to  apply  because  no
         one  had  ever  done  anything  like  this
         before. He designed the cables six times
         stronger than needed, adhering to the
         accepted design factor. He did not have
         a good  relationship  with  Kingsley;  he
         said  he  felt  “an  intolerable  aversion”
         to him. There is no indication the two
         men ever discussed the spec. Kingsley
         did not have any kind of engineering                                                                   Illustration by Jay Stringham
         background, making it seem unlikely
         he would have understood much even
         if they had talked. Steel wire had been
         used for many decades  to make  small
         items  such  as  needles,  but  this  main   A consultant’s study published by New York City DoT showed how the existing promenade
         cable application was much larger than   (top) could be widened (bottom) by adjusting the structure above the existing six lanes of
                                            automobile traffic. The feasibility of this concept requires a careful exam of the main cables,
         anything ever tried before.        The cable exam is now planned to begin in 2019.
           At the time new metallurgical meth-
         ods of making steel, such as the Bes-  call for bids. When the proposals were   the Six-to-One design factor. He wrote:
         semer-Kelly process and the Siemens-  opened, the contract went to a wire mill   “There is still left a margin of safety of
         Martin process were being introduced.   located on what is now Pioneer Street in   at least five times, which I consider to
         Roebling asked one of the assistant   the Red Hook section of Brooklyn.  be perfectly safe, provided nothing fur-
         engineers, William Paine, to run tests                                ther takes place”. Most of the trustees
         on all the steel wire  products readily   Deficient Wire              had very little technical  training and
         available in the marketplace. When in   But the Brooklyn  wire  mill didn’t   may not have understood what hap-
         1876 the megalithic stone towers were   keep up its side of the deal. They com-  pened. The public was told nothing.
         at last completed and cable making   mitted fraud when furnishing the wire.   Cablemaking began mid-year 1877
         was about to begin Roebling wrote:   McCullough’s history has several chap-  and was completed in October the fol-
           “Tests have been  going  on  at inter-  ters  explaining  what they did. Also,   lowing year. With the extra wire add-
         vals for the past six years, and con-  there was a simplistic explanation pub-  ed, each of the main cables was slightly
         stantly during the last two years …  lished by the New York Times on De-  larger than fifteen inches in diameter
         Samples were obtained from most of   cember 30, 1879. An unknown amount   when its outer wrapping was in place.
         the principal foreign as well as domes-  of wire which failed the acceptance test-  The  steel  bands  affixed  to  the  cables
         tic makers of steel wire, comprising all   ing already had been inserted into the   for attachment of the suspender ropes
         of the various grades of steel, but espe-  cables before the fraud was discovered.   were  squeezed  on  without  requiring
         cially cast steel…The principle was to   Because the diameter of the wire had   any changes.
         obtain a certain amount of strength for   been  specified  “Number  8”  (referring   All of the deficient wire is still there
         the least amount of money.”        to the gauge system commonly used in   today inside the cables. No one has a
           The focus on verifiable wire strength,   the wire  business)  Paine  realized mi-  clue which cable contains a portion of it.
         and the preference for cast steel (both   nor variations in size might be encoun-  The continuous wire wrapping prevents
         dictated by Roebling himself) marked   tered.  The  tools  for  checking  the  size   observation of the load-bearing wires
         the beginning of the big experiment. As   were  not  codified  in  scientific  terms.   everywhere except inside the anchor-
         of 1872, cast steel prices were often as   He concentrated on strength, ductility,   ages  where  they  pass  around  the  first
         high as 20 to 25 cents per pound. The   stretch, and other physical attributes.   pins of the anchor chains. If any of the
         crucible casting process limited a batch   Every one of the short lengths of wire   wire has failed internally inside a main
         of steel to the weight that could be lifted   was examined in the wire mill by an as-  cable while service since 1883, we have
         by two men working together; about 100   sistant engineer named Arthur Abbott.   absolutely no way to know about it.
         pounds. Almost seven million pounds   Erica Wagner’s  eloquent  book Chief
         of wire would be purchased. No order   Engineer explains what happened next.   Galvanized Wire
         that large had ever been placed before.   Paine and Roebling tried to estimate   New  York  City’s East River is  ac-
         The Board of Directors was aware Roe-  how much deficient wire had been put   tually a tidal strait on  the  Atlantic
         bling’s  family  business,  John  A.  Roe-  into the main cables. There was no way   seacoast.  Ordinary  carbon  steel  wire
         bling’s Sons Co., might want to become   to remove it. Roebling reported a make-  corrodes rapidly in a seacoast atmo-
         the wire supplier – they passed a motion   shift solution to the trustees. Fourteen   sphere unless the surface is protected.
         blocking this which forced Washington   tons of extra wire was to be added to   Corrosion at the surface leads to pit-
         Roebling to sell his stock in his own fam-  the four main cables, and the wire mill   ting  which  reduces  the  cross-section
         ily company. David McCullough’s book   would furnish it without charge. Roe-  of the wire, making it weaker at that
         The  Great  Bridge  describes  the  chica-  bling tried to explain this sort of un-  spot. Starting in 1837, a French scien-
         nery involved. Nine wiremakers, both   anticipated problem was  exactly the   tist named Stanislaus T. M. Sorel de-
         foreign and domestic, responded to the   reason why civil engineers employed           continued on page 12

         10     Wire Rope News & Sling Technology   December 2018
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