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
*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
Plastic stretch cord; used for making jewelry; .8mm; about 9m
Vaseline or soap; optional; to lubricate the screws
Stain and clear-coat
Drill with 5/64" bit
Hacksaw; or other saw with a thin blade; for cutting the dowels
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