Define Tensegrity Sphere to a Child

August 18, 2009 5:44 PM

How to best describe a tensegrity sphere in a way everyone can understand

I am using an image of a tensegrity sphere as a logo for my yoga studio. When people go to my website, I know they'll be interested in know more about it. How would I best describe it holistically in a way that a child can understand? And what natural phenomena does it best model?

posted by goalyeehah to science & nature (10 comments total)

A suspension bridge with no end-points.
posted by orthogonality at 6:03 PM on August 18

here's my start:


imagine the frame of a box made from steel beams.

You can push or pull on the box and it will keep its shape.
Steel beams are strong under compression (pushing) and tension (pulling)


Now imagine the same frame made from lego blocks.
If you push down on the blocks they keep their shape, but if you pull on the blocks they come apart
Lego is strong under compression(pushing), but weak under tension(pulling).

what if you made the same frame out of string?
If you pull evenly on all eight corners the frame will keep its shape, if you push it falls apart
string is strong under tension(pulling), but has no strength under compression(pushing) - you can push on a rope, but you can't push on a rope.

What if you made a frame out of string and lego?
You could tie the bricks together with string, the lego could provide compression strength and the string could provide tension strength.

It turns out that structures don't always need to have tension and compression strength in the same place.
You can design structures which have steel cable where you need tension (pulling) strength and wooden beams where you need compression (pushing)strength.
Wood is very strong under compression (pushing), and not as strong under tension (pulling)
Steel cable is very strong under tension (pulling) and has no strength at all under pushing.

The designer Buckminster Fuller, designed structures made from beams and cable using a principle he called Tensegrity, in which the beams only have pushing forces placed on them, and the cables only have pulling forces places on them
posted by compound eye at 6:10 PM on August 18 [4 favorites]

...A human body is a bit like this, we can stand upright and walk around because our bones provide strong compression strength and our bones are held in place by out muscles and tendons, which are like cables with tension strength and keep everything together. These two strengths, the compression strength in our bones and the tension strength in our muscles and tendons work together to make our bodies stable and strong...
posted by compound eye at 6:16 PM on August 18

Bucky felt it was a good model of Universe and all dynamic systems. I've built one for myself. It does not take shape until the last strut is wired into place. One thing Bucky set out to prove was that weight does not imply strength in a structure. Once dropped the sphere bounces, the shock is absorbed and nothing breaks.
posted by goalyeehah at 6:20 PM on August 18

I've got that, compound eye. Thanks.
posted by goalyeehah at 6:22 PM on August 18

Tensegrity is a building system that does not depend on gravity because the forces are directed in a way that it holds together "internally".
posted by DU at 6:28 PM on August 18

You really need a model. An actual physical one to use in class, and some pretty 3d rotating one for your website.

This might be one of the few actual good uses for 3d spinning stuff on the web, right here.
posted by rokusan at 6:28 PM on August 18

A striking example of tensegrity is Snelson's Needle Tower sculpture. If the cable were loosened, the struts would lie in a pile. But tighten the cable and the tower is erected. I think it's amazing and counterintuitive that one could raise a structure many tens of feet with no overhanging mechanism, simply by pulling a cable. It's also quite appropriate for a yoga studio logo to evoke the idea of creating and releasing tension in unexpected and elegant ways.

Also, tensegrity models have even been applied (intensely by one particular research group) to the mechanics of individual tissue cells, though this approach is extremely controversial among cell biologists studying the cytoskeleton. Just Google "Ingber tensegrity."
posted by Mapes at 7:39 PM on August 18 [2 favorites]

whoops I meant you can PULL on a rope, you cant push on a rope
posted by compound eye at 8:25 PM on August 18

Rokusan, I will have a model for classes. The 3d image on website will be coming in the future.
posted by goalyeehah at 8:39 PM on August 18