My First Magnetic Tensegrity Table

Google defines tensegrity as:

"the characteristic property of a stable three-dimensional structure consisting of members under tension that are contiguous and members under compression that are not."

Sometimes it's just easier to see it than read about it so here is a photo of a popular tensegrity toy. 

A tensegrity table uses the same principles to hold two flat surfaces locked at a fixed distance from each other using only strings or some other flexible strand such as ball chain.  Some tensegrity designs are fascinating to look at as the top surface looks like it's floating in mid-air. 

I wanted something a little different.  I wanted a table surface to magnetically levitate using tensegrity principles.  How hard could it be?  Replace the strings with supermagnets and that's it right?

I started by printing a few simple surfaces to retain the flat disc neodymium magnnets that I had purchased and decided to use the attractive force but use it along the outside edges with a tensioned string in the center to tension the structure.  The attractive distance of the magnets was not as great as I expected.  The two surfaces could be no more than an inch (2.54cm) or so apart for this to work.  That would leave almost no room for the tension structure needed in the center.

So I used magnetic attraction for the center string and three fishing lines around the outside edge. It finally worked!  

I created the design to be very sturdy but to look almost wireframe. The wireframe look appeals to me as it's similar to looking at a bridge structure. 

One of the problems with working with neodymium magnets is that they are powerful.  My first attempt at this circular table used  a single arm of less than 10mm width to support each magnet.  The support arms were bent by the magnets!  Too close, and the magnets snapped together.  Too far, and there was no tension.

I like the overhead view of the structure because it reminds me of a dart board or maybe a "pop" filer that would be used on a microphone in the 1940's.

Unfortunately, I did not align the two solid magnet supports so that there was a straight on view without one of the structures overlapping. 

As a result, when someone first looks at it they assume the center is how the table is supported.  It isn't until they look more closely that they see that the bottom and top half are connected only by strings. Finally they realize that the neomagnets are keeping the table together and then they begin testing the table.

First, they always push down on it to see how strong it is and they're usually a bit surprised. After collapsing the table, they pick it up and the neomagnets snap the table back into shape.The last thing people often do is try to spin the top to see how far it'll turn.  They're sometimes a little surprised that it won't turn very far but mesmerized by the jiggling of the table as it snaps back to original position.

I think the tensegrity table looks much better after changing the hole alignments and printing a table section with better alignment.

I will be continuing to investigate other ways to use magnets in tensegrity structures.  Download the STL and 3d print your own at Printables.com.