(picture of tensegrity icosahedron) This Tensegitoy kit contains thirty slotted and drilled wooden dowels, thirty brass tipped elastics, and sixty-four caps. It can be used to make an assortment of different polyhedrons and other shapes, according to the principles of tensegrity, with the sticks serving as compression elements, while the elastics provide the tension. For those who yearn to do more than this kit allows, there are extender and bulk kits, containing 60 and 180 sticks, respectively. The cost is rather high, at nearly a dollar per dowel. On the other hand, the kit's clearly-written and carefully illustrated instructions are invaluable, and making your own requires more initiative than most of us have. (George Hart has an easier tensegrity structure project using soda straws.) At the least, using the kit first gives you a better feel for how to work with tensegrity.

(picture of five-pointed tensegrity star)(picture of cat with tensegritoy tetrahedron)

The simplest model we made was an approximation of a simple tetrahedron, or perhaps we should say truncated tetrahedron, since the ends of the struts do not quite meet, but instead form triangles. The model pictured at the top is the tensegrity version of an icosahedron, with pentagonal spaces at the vertices.

snapshot of family members under Tensegrity Tower at the Hirshhorn
Tensegrity models are more difficult to construct than most designs from the geometrical modeling kits reviewed in this weblog. This kit is marked for ages ten through adult, but might be questionable for the lower end of that range.

Check out this link to the Needle Tower, which is a wonderful example (shown only partially in the family snapshot on the right) of a tensegrity tower at the Hirshhorn museum in Washington, DC. It looks as though about 36 enormous aluminum sticks of gradually decreasing size were required to build it. It is wonderful to stand under the tower and look up at the regularities of the structure. This sculpture was created by Kenneth Snelson, who first invented tensegrity structures in 1948. (The word tensegrity was coined by Buckminster Fuller.) The nature of elastic means that our toy will age and lose its stretch within a few years, but the stainless steel cables used by Snelson last far longer.

Posted: Mon - January 3, 2005 at 08:19 PM