18" 270-Strut Tensegrity Sphere - Detail
This photo diagram may help in understanding the basic pattern and connection configuration of a 270strut tensegrity sphere. The hairbands are merely added after the whole sphere was assembled, and served only to help each strut hold on to the tensional elements of the two other struts it connects to.
Each strut (270 in this particular sphere) is exactly the same size and configuration, so the first job it simply to make all the struts, with the slot cut at each end, and its tensional element (nylon string) attached.
I had made many smaller (12-strut and 30-strut) spheres prior to attempting this big one, so I would urge anyone interested in building tensegrity spheres to do the same. It will familiarize one with the basics of tensegrity construction, which will be very useful in attempting to make larger spheres.
The reason I had to experiment with the building of the 270-strut sphere was that unlike the 12-strut and 30-strut spheres, the 270-strut sphere does not have an even geometry of strut-group components around the entire sphere. When I attempted to connect the struts together in only the same six-strut components that I'd used in smaller spheres, I got a warping sheet, instead of a sphere. It was only when I realized through experimentation that the correct pattern was to intersperse 5-strut components throughout the sphere, and that these pulled the whole system into a spherical shape. In my photos, I've used yellow hairbands to highlight the five-strut components, black to highlight the six-strut components, and red for the struts between these. It simply helps to show the overall pattern.
Again, this makes much more sense (and ultimately will _only_ make sense), once one is actually physically building a sphere. That's why I suggest building some simple spheres first.
Regarding the size of the struts in relationship to the overall size of the sphere, my struts are each 4 inches long. The sphere is roughly 18 inches in diameter. So this means that for this general configuration, there's a 1:4.5 ratio of strut length to sphere diameter.