Thursday, 3 March 2011

Triple Y

I used wide bamboo struts as basis for a large tetrahedron, which fills nearly a cubic metre in total. The build posed a variety of challenges, with some set-backs on the way. I diverted from my initial plan to build a tetrahedron with 3 clockwise and 1 anti-clockwise corner, although I know think the way I finished the build could work for this 'deviant' tetra as well.

I drilled three holes at either end of the base struts. The holes are less equidistant than I hoped for, if I reuse the method I need find an easy and precise marking method. The variety in diameter meant as well that pre-calculating tendon lengths made little sense, especially as I used 25% shorter struts for the 'floating struts'.

I knew from my first build using holes for the tendon attachment often ends up very difficult. I need to pull the tendon out for some length to tie a knot, it's no fun to do this when the structure is nearly ready. As I planned to use grooves to attach the smaller struts, I just need to find a way to attach the tendons while minimising the amount of 'final tendons'.

By analysing other tetra models I noticed a way to build first a (very slack) 3-strut tensegrity, and then thread the remaining struts first in upper triangle, then in the vertical tendons. In theory, this works well, yet only the base triangle kept its initial length. The failed build attempts convinced me of the feasibility of this approach, and with another intuitive shortening of most tendons I ended up with a stable structure.

The colours join base triangle and top hexagon, the more vertical tendons shape the letter 'y', hence the name Triple Y. It balances on all corners, yet the design favours the biggest triangle as base. Plucking the tendons produces a range of sounds, and quite unpredictable patterns of movement. The sculpture fills about a cubic metre of space with a triangle, a hexagon, three 'y's and six uniquely shaped bamboo struts.

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