Eight Level Dowel Tower
This sculpture is perplexing. It is stiff without being rigid, and it has weight without being heavy, it has depth while appearing flat (if you squint).
Each unit is a repeated module, like from a stamp, or from a brick wall. Each new layer is offset from the previous.
The whole thing is uniquely bouncy and springy and jiggly. In your hands, it is wild and alive. Maybe it can be compared to a molecule.
I'm proud to have been able to translate theory (see here for some learning resources) into practice. I went through a lot of trial and error in fabrication and assembly before the structure came together. But when it did, what a delight!
When the components and connections are just right, limp twine and loose sticks can hold together in space. For me, this piece is proof that tensegrity really works.
I cut equal lengths of dowel and carefully pre-drilled the ends. This was a clumsy process with a hand-drill and bench vise. I did have to sacrifice many pieces where the drill hole was off-center, crooked, or the wood split. Though, I was able to get a rod with two satisfactory holes in the ends more often than not.
I added screw eyes to the ends. Knowing that the tendons could be pulling in all kinds of directions, having a versatile hitching post was important.
The struts complete, the next task was to find the right tendon lengths. Tendons play three roles in a structure like this: edge, draw or sling (as specified by Kenneth Snelson here). For simplicity I wanted the edge and draw tendons to be of equal length. So this means fabricating my tendons in two lengths.
Each tendon is a length of twine with each end melted to form a stopper. The cut end of nylon line melts easily with a candle or a lighter and contracts, melding into a nice strong glob (which has the added benefit of preventing fraying). I would cut a new piece, melt one end, then measure the prescribed distance, make a mark, cut again a bit beyond the mark, and then melt this end until the glob reaches the mark. This process yields tendons which are nice and uniform in length.
The method of hitching each tendon to each screw eye is an overhand knot, tied around the post, where the stopper sets the knot so it won't pull out. Kind of like a grappling hook.
Then, finding the right length values is a matter of trial and error. I would fabricate a batch of tendons and assemble the first level. Too long and the rigging is slack, and the knots can come undone. Too short and the final piece doesn't reach, or you have to pull so hard that a strut snaps and the whole thing flies apart. (Safety glasses are recommended). Then I'd disassemble, throw that batch of tendons away and make a new batch of a new length, and try again.
It's the last tendon, the one to complete each module, which is the most difficult to attach. You have to pull hard and manage to the the knot with minimal slack. I used a locking forceps to help with the pulling, and tweezers to help with the tying.
Soon I found the right length values and the structure came together just right: tight and stiff, but not so much so that it was impossible to assemble.
In his reference (linked above) Kenneth Snelson specifies six draw tendons per level. But I found you can get away with only three, and this makes the sculpture much more bouncy and lively. I think the way it moves is the best part.