Main Cable Painting

Main Cable Photo Gallery - Original Construction and Contemporary Photos

February 23, 2011: The painting of the two main cables of the Golden Gate Bridge began with the delivery of 400 feet of scaffolding. Before paint operations could begin at midspan, scaffolding was installed along the 400-foot-long portion of the west side main cable running south from midspan.

Main Cable Painting Project - Scaffolding is Delivered - February 22-23, 2011

Main Cable Painting Project - Scaffolding Assembly Begins - February 23, 2011

April 2011 to September 2011: Painting of the first 400-foot-long section of the west side main cable was completed.

October 10, 2011: Disassembly of the scaffolding began. The scaffolding was moved to the portion of the west side main cable extending 400 feet north from midspan.

November 23, 2011: The reassembly and additional pre-painting preparations on were completed.

December 2011: Painting along the west side main cable section running north from mid-span began.

December 2011: Installation of scaffolding was completed on the east side main cable at midspan and paint operations began.

April 2012: Painting is completed on the west side main cable section running 400 feet north from midspan.

May 2012: Scaffolding is removed from the east side main cable in preparation for 75th anniversary on May 27, 2012.

July 2012: Scaffolding is re-install on east side main cable.

August 2012: Painting of the east side main cable resumes.

November 2012: Completed the east main cable sections - both 400 feet north and 400 feet south of midspan.

Main Cable Construction - 1935/1936

The Golden Gate Bridge has two massive main cables which pass over the tops of the 746-foot tall towers. The main cables serve as the “hanger” for the vertical suspender ropes which, in turn, hold the Bridge’s roadway. The diameter of each of the main cable, including their exterior wire wrapping, is 36 and 3/8 inches and each main cable is 7,650 feet long. The total length of wire used in both main cables is 80,000 miles. Each of the main cables contains 27,572 galvanized wires which are bundled into 61 strands that contain 454 wires each. The combined weight of the main cables, vertical suspender cables and accessories is 24,500 tons.

Before the main cables could be constructed, for added safety and maneuverability, the workers built work platforms which hung under the area where the main cables would then be spun (pictured below left).

The wire used to build the main cables was laid by a loom-type shuttle that moved back and forth as it laid the wire in place that formed the cables. The spinning of the main cable wires was completed in six months and nine days.

The cable stringing operation was accomplished using 4 spinning carriages, two working from each anchorage. As one carriage left its anchorage base and went up and over the main tower, down to midspan, where it was then met by another carriage bringing the wire form the opposite anchorage. The wire bights were exchanged and each carriage returned to its starting point.

Cable formers used vertical separators, in a frame, to keep each of the 61 strands in proper relation with one another—in vertical rows (pictured below middle).

Compacting machines were used to “squeeze” the cables into their circular shape. Each consisted of a frame which surrounded the cable with 12 hydraulic jacks around the circle (pictured below right).

Cable bands are attached to the main cable with large bolts at the point of attachment of each the 250 pair of vertical suspender ropes. Occasional re-tensioning of main cable band bolts becomes necessary because constant temperature and load changes in the main cable produce minute changes in the cable diameter, and those changes in cable diameter, together with temperature effects on the cable band itself, cause tension in the bolts to relax. In 1954, the cable band bolts were retightened for the first time since original construction.

 

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All photos are from the archives of the Golden Gate Bridge

and may not be used without permission.