Desktop Tensegrity Tower

Have you ever seen towers like the Needle Tower in Washington, D.C? It looks like it's just a trick, but it is real. This method of construction is called tension integrity, or "Tensegrity". Tensegrity is achieved when many wires or cables are stretched between poles in a repeating pattern. This pattern normally resembles a geometric shape such as a hexagon,a square or a triangle.

In this instructable I will show how to make your very own desktop "Tensegrity Tower" using only some basic hardware store materials. 

This is my entry for the Epilog Laser Contest. If you like it, please vote for me.

I credit the idea of this instructable to William Gurstelle's article in Make: Volume 6

Step 1: Materials and Tools

Materials: 

*Note that these materials are for a 4 story tower. Larger quantities of materials will be needed for larger towers.

Rubber bands; assorted sizes

#214 eye screws; 24

5/16" dowel, 96" length; other diameters will also work, just make sure the eye screw fits

Masking tape

Plastic stretch cord; used for making jewelry; .8mm; about 9m

Vaseline or soap; optional; to lubricate the screws

Stain and clear-coat


Tools:

Drill with 5/64" bit

Strong pliers

Hacksaw; or other saw with a thin blade; for cutting the dowels

CA Glue

Scissors

Sandpaper

Step 2: Prepare the Dowels

-Cut 12 8" dowels from the 96" piece.

-*Optional- Lightly sand the dowels with 150 grit sand paper to smooth out any bumps in the dowel

-Tightly wrap a layer of masking tape around the end of each dowel. This will help prevent splitting when the eye screws are inserted

-Hold the base of the eye screw with a pair of large pliers. Do not crush the threads! With another pair of pliers, gently pry the hook slightly open.

- Drill a 5/64" hole in each end of the dowels barely deeper than the threads on the eye screw.

-*Optional- Rub a little soap or vaseline on the eye screw. This will help thread it into the dowel.

-Thread the screw into the dowel.

-Unthread the eye hook.

-Apply stain and clear-coat to the dowels, following the manufacture's instructions. I made a stand for the dowels by inserting them onto nails that had been driven through a board.

Step 3: Make the Cord Loops

To make the tendules, you will first need to cut several loops of stretch cord.

The lengths of the cords given below are how long they are when they are first cut. Keep in mind that about 1" of cord is consumed in making the knot. 

Also note that the properties of your brand of your stretch cord may differ from the one used here. Adjust the lengths of the loops accordingly.

For a 4 story tower you will need:

8 15" loops

9 7.5" loops

12 10" loops

Tie each loop by making a square knot at each end and lightly covering it with CA glue.

Step 4: Make the Tendules

Mark 3" from the end of each dowel.

Make 2 right weaves and 2 left weaves by laying the dowels on top of each other at each mark so that each overlaps another.

Wrap the intersection points of the dowels with rubber bands. An equilateral triangle should be formed.

Take one of the 15" loops of stretch cord and stretch it between the 3 top points of the tendule. Wrap the cord around the eye hook to keep it from slipping off. Repeat this step for the bottom of the tendule.

Take one of the 10" loops and connect it between the 2 closest dowels, as shown in the 5th picture. Repeat this with the other corners of the triangle.

At this point you can cut off the rubber bands on the dowels. The tendule should spring up a bit and look like the last picture.

Repeat this for the other tendules.

Step 5: Construct the Tower

At this point you should have 4 completed tendules (or more if you want). There should be at least two left and two right tendules.

Lay a right tendule on top of a left tendule in an alternating pattern. You should alternate left and right tendules when erecting the rest of the tower.

Take the cord from the top of the bottom tendule and loop it around the eye hooks on the bottom of the upper tendule. This should form a hexagon as shown in the picture below.

Loop the 7.5" cord around the bottom hook of the upper tendule and the parallel dowel on the tendule below it. Refer to the second picture for a diagram.

Repeat these steps for all of your tendules. Remember to alternate left and right tendules

Step 6: Improvements

I thought that this tower turned out quite well, but here are my thoughts on improving it:

-Trying it with metal rods

-The tendules seemed to be a bit clumped; A future version may include dowels that are spaced farther apart like the Needle Tower

Comments

[ArthurO1]

Most of the 15" plastic stretch cord loops ultimately follow a hexagonal shape. But the two loops at the very bottom and top of the structure follow a triangular shape, and are exceptional. I wonder if the finished structure would be improved by making these two loops somewhat smaller than 15"?

[Data643]

I just assumed that mine were stretching loose, but that would definitely explain why the top loops tend to be very loose. I'll play around with different widths and try to update this Instructable at some point.

[safa salkhi]

well done.AMAZING....
I am going to try this with my students in our architecture modeling atelier
I wander if I try your advise about not looking clumped, I should change the position of plastic bands while tying ?If so, dose the size of cords changed a lot?How should I calculate the new?

[dombeef]

How doesn't the needle tower fall down?

[bwelkin]

It doesn't fall down because it has "tensional integrity" a phrase used by R. "Bucky" Fuller to describe a structure that used tension and compression forces in equilibrium. The wires are under tension and the dowels under compression.

Bucky Fuller was beyond genius. If you read, understand and retain any of his books you are already a genius. But even if you just READ one it will push you a giant step to being one. Try "Spaceship Earth" - you want to travel on a large life sustaining space ship through the Cosmos? Voila - you're there now!

[dzurn]

It doesn't fall down because R. Buckminster Fuller says it can't

;)

[St Jimmy]

I think it's that the wires pull inwards on the supports, forcing them downwards, and stopping the tower from falling. It looks awesome though, doesn't it?

[dombeef]

Yeah, very cool!

[defec]

interesante!!

[Wasagi]

I love the needle tower!! It's even cooler in person! And this is fantastic I have got to try this!

[JamesRPatrick]

Do you live by D.C. as well?

[Wasagi]

In Arlington, less than two miles away.

[JamesRPatrick]

Sweet! I'm in Northern Virginia.

[Wasagi]

Woah!

[Treknology]

WARNING: You need a very good understanding of "tensegrity" if you dare to open and service an IBM golf-ball typewriter!!!

[CameronSS]

Very nice! I've always wanted to try building one of these so I can explain to myself exactly how they work. I think you left out a step, though... Somewhere between steps 1 and 2 you apparently cut the 96" dowel into 12 8" sections, but never mentioned it.

[scubabeaver]

It says about cutting the dowel on the first ine of step 2

[CameronSS]

It didn't when I posted that comment, hence Data643's "Thanks for the catch." It's since been fixed.

[Data643]

Thanks for the catch : )

[floatingbones]

Excellent little project!

I'd never heard of making square knots and then super-gluing the knot. Interesting. An alternate technique to loop the cord is to use beadalon crimp bands bands and the appropriate crimping pliers.

For tensegrity newbies, an easier project can be found at http://mew.cx/mf2007tx/ (with a Bre Pettis video of the same at http://www.youtube.com/watch?v=96kz98yEO1w ).

One artist at tensiondesigns.com makes and sells tensegrity towers. I have a friend who has his 8-foot model. Amazing!