[geodesic 00622] Re: curved struts
Stephen M. Levin
smlevin at biotensegrity.com
Wed Mar 31 15:39:11 PST 2010
I thought I already sent this, but it must have gotten lost.
In an ideal tensegrity, tension and compression are separated and struts are pure compression elements. Any column under compression develops internal shear and tends to bow in the middle, re: Euler's buckling law.Theoretically, a strut would have pure compression running strait down its central core and no tensile component, a line with only one dimension, otherwise you would have shear and bending moments that are intolerable in a true tensegrity. Bows are tensed on their convex side and compressed on their concave side, tension and compression are not separated and, therefore, bows cannot be part of true tensegrities. All man made tensegrities are imperfect, as the only true tensegrities would be infinitely hierarchical. Biologic structures are infinitely hierarchical, at least at the mesoscale where they operate. To illustrate this point, Tom Flemons made a bow and a wheel using tensegrity principles http://gallery.me.com/stephenlevin1#100069, but you have to imagine that this goes on infinitely, with each compression strut a tensegrity tower, and so on ad infinitum. Fuller does discuss this hierarchy somewhere in Synergetics, but I am too lazy to research it. The use of curved struts by intent is contrary to the principles of tensegrity and you are compounding the imperfections of man, but they do look nice.
On Mar 31, 2010, at 6:58 PM, Dick Fischbeck wrote:
> Hi Phil
> All struts are bowed, right? Some bend more than others. Straight becomes meaningless.
>> Those two at the bottom are wonderful structures. There's
>> something dazzlingly simple using four bent struts to create
>> a tensional cube, and it's great having the inside and
>> outside versions next to each other.
>> Have you ever made a three-strut tensegrity with three
>> bowed struts?
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