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side view of stake and nylon twine arch against a red fence

On November 14, 2003, I finished assembling my first tensegrity arch. It turned out well. It didn't need staking, though in that day's high wind I laid it on its side before leaving since the wind had managed to blow down all the other tensegrity structures I had around. Maxim Schrogin was the main inspiration for this project. I was much impressed by a tensegrity arch he built that he was good enough to give me pictures of a year ago. A few years before that, I had also heard from a fellow named Tom Longtin who had computer-generated diagrams of an arch on his website. I wasn't really sure whether his stuff was a fantasy or could actually be fabricated. I'm glad I finally got around to this. It is a very interesting structure and well worth assembling.

I used a zig-zag geometry with extra tendons to triangulate the two bases and additional tendons to connect adjacent struts in each stage of the arch. The latter tendons are necessary to keep linear realizations of zig-zag or diamond topologies from extending absurdly until the structure looks like a long thin tube.

All the struts are equal length and the curvature derives completely from varying tendon lengths. I had trepidations about assembling such a totally asymmetric structure. It turned out the three-fold symmetry of the topology and the symmetry of the topology of the successive stages were a great help.

For the papers I worked from to assemble the structure, see the datasheet which also includes some computer-generated views of the structure. This structure is also available for viewing in all the tensegrity viewers as "8-Stage Zig-Zag Arch".


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