Roebling’s Cable

Roebling’s Cable. Upper Delaware Scenic and Recreational River. John A. Roebling’s legacy is based on his use of suspension cables to hold up bridges and aqueducts. He devised the techniques of air spinning, which is still used today to build much larger spans. This former aqueduct is the nation’s oldest existing wire cable suspension structure and the earliest of Roebling’s works still standing. Though much of the aqueduct has been reconstructed, the cables and almost all the ironwork in the suspension system are original., Air Spinning – making the endless wire cable , Two at a time, 36-inch-thick wrought iron wires were shuttled across the river over the stone piers, looped over anchor chain shoes, then shuttled back to loop over the opposite set of anchor chain shoes. The end of one roll of wire was spliced to the beginning of the next roll of wire. Back and forth they went, splicing wires together as needed, until a bundle was created. Seven of these bundles made up a single cable., Each of the two 8.5-inch thick cables has 2,150 individual parallel wires. The wires are oiled, wrapped, and painted to protect the cable from the weather. Each cable is 576 feet (176 m) long. Together they support the weight of almost 2,000 of water., Iron rods hang – or suspend – from the cables to hold up the trusses supporting the aqueduct. Between the masonry piers, the wrapping wire compresses the wrought iron wires to form the cables. Cable wires are separated and bundled into their seven strands as each loops over an anchor chain shoe. Anchor chain shoes and pins connect the seven bundles of wire to the anchorage. Shoes are pin-connected to the chains of the anchorage. The cable anchorage system is encased in cement and stone, and buried almost 20 feet (6 m) below the surface, excluding air and moisture to prevent rust and decay. Look closely to your left and you may discover one of the hundreds of splices required to create each of the seven continuous strands of wire into this cable.