![]() ![]() Now you have a seriously strong bond which is just as strong as the rope. Then pour in epoxy or glue and let it set. So anyway, think of the sockets like taking a funnel and sticking a ten strand (really, it’s many more!) rope into the narrow end and then unravelling the rope so you have all the various strands and yarn fibers spread out in the bushy mass filling the vee of the funnel. ![]() ![]() Some are better, but I don’t know the numbers offhand, but if you’re rope can hold 10 tons and you tie a knot, suddenly it’s only good for 5 tons max. You also don’t do knots because a knot on it’s own reduces the strength rating by around 50%. You don’t tied knots into steel (or metal) cables because it causes too much bending which seriously reduces the strength of the cable. The harder you pull on the cable, the tighter it seats into the socket. Basically, doing sockets is a good thing, because it puts the tensile loads into compression. Posted in Engineering, News Tagged Arecibo, cable, collapse, failure, finite element analysis, forensic, neutron imaging, Radio Telescope, socket, spelter, zinc Post navigationīecause welding kills the strength of the cable, which is not something you want to do. It’s cold comfort to astronomers and Arecibo staff, perhaps, but at least it’s a lesson that might prevent future failures of cable-supported structures. But being able to pin the bulk of the failure on a single, easily understood - and easily addressed - defect is comforting, in a way. The resulting shear stress caused the zinc to slowly flow around the cable strands, letting them slip out of the surrounding steel socket and - well, you can watch the rest below for yourself.Īs is usually the case with such failures, there are multiple causes, all of which are covered in the 300+ page report. The full report (PDF) reveals five proximate causes for the collapse, chief of which is “he manual and inconsistent splay of the wires during cable socketing,” which we take to mean that the individual strands of the cables were not spread out correctly before the molten zinc “spelter socket” was molded around them. They enlisted the help of the Columbia University Strength of Materials lab, which sent pieces of the failed cable to the Oak Ridge National Laboratory’s High Flux Isotope reactor for neutron imaging, which is like an X-ray study but uses streams of neutrons that interact with the material’s nuclei rather than their electrons. But one always wants to know the fine-scale details of such failures, a task which fell to forensic investigation firm Thornton Tomasetti. So there was no real mystery as to what happened, at least from a big-picture perspective. The long run-up to the telescope’s final act had a silver lining in that it provided engineers and scientists with a chance to carefully observe the failure in real-time. ![]() The inevitable finally happened on December 1, when over-stressed cables on support tower four finally gave way, sending the platform on a graceful swing into the side of the natural depression that cradled the reflector, damaging the telescope beyond all hope of repair. From the first sign of problems in August, when the first broken cable smashed a hole in the reflector, to the failure of a second cable in November, it surely seemed like Arecibo’s days were numbered, and that it would fall victim to all the other bad luck we seemed to be rapidly accruing in that fateful year. In case you somehow missed it, back in 2020 we started getting ominous reports that the cables supporting the 900-ton instrument platform above the 300-meter primary reflector of what was at the time the world’s largest radio telescope were slowly coming undone. Nearly three years after the rapid unplanned disassembly of the Arecibo radio telescope, we finally have a culprit in the collapse: bad sockets. ![]()
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