Can someone explain tensegrity structures to me?

[Lumpy]

I get the basic idea, but what I don’t understand is why it’s a requirement that the compression elements be “floating”- not directly connected to each other but only through intermediary tension elements.

[Isilder]

Because that makes it a special structure not simple beginner level structure…

And the benefit ?

Near the top of the wikipedia entry … " no structural member experiences a bending moment. This can produce exceptionally rigid structures for their mass and for the cross section of the components."

[Lumpy]

Thanks. I’m still trying to wrap my head around these, especially to be able to know just from it’s configuration if a structure is rigid or not.

[Quercus]

@Lumpy

I get the basic idea, but what I don’t understand is why it’s a requirement that the compression elements be “floating”- not directly connected to each other but only through intermediary tension elements.

I think one basic requirement for a pure tensegrity structure is that tension elements only be loaded in tension, and compression elements only in compression (so they must only get force pointing directly along their length).

If you connect two compression elements, then they could pull each other sideways, so the pure ‘only compression’ requirement will be lost.

[Nefario]

@Lumpy

Thanks. I’m still trying to wrap my head around these, especially to be able to know just from it’s configuration if a structure is rigid or not.

I would look at this analysis as a classic statics problem, ie, ignoring any moments imparted to the node points (because in this case here really can’t be any). Now can each node have sufficient X-Y-Z constraint to remain fixed in 3-D space? If so, the structure would be ridgid.

[DocCathode]

I LOVE Buckminster Fuller. I also collect walking sticks. I’d like to make myself a tensegrity walking stick. Can you help me?

[Nefario]

Oooh… I’m gonna think about this. Seems like you would have to have a number of vertical rigid elements or at least angled rigid elements overlapping in vertical space to support the z-axis forces. Hmmm…

[commasense]

@Lumpy

I get the basic idea, but what I don’t understand is why it’s a requirement that the compression elements be “floating”- not directly connected to each other but only through intermediary tension elements.

It seems to me that it is a “requirement” simply because that is the definition of tensegrity. If some of the compression elements are directly connected to each other, it may be a structure with a tensegrity component, but it won’t be a tensegrity structure.

I may be wrong, but IME all tensegrity structures have had some flex to them, and are never as rigid as a conventional structure.

–commasense (who built a tensegrity sphere from wire and aluminum rods in the late 1970s)

[Lumpy]

@commasense

I may be wrong, but IME all tensegrity structures have had some flex to them, and are never as rigid as a conventional structure.

–commasense (who built a tensegrity sphere from wire and aluminum rods in the late 1970s)

I certainly am no expert but I’d suspect that that’s a matter of needing to “tune” the tension elements to the same load.

ETA: plus any elasticity in the tension elements (e.g. steel wire) will allow for some flex.