Surprises

My latest strategy to tensegrify objects with a pseudo-corner linking tendons yielded some surprising results. Like mentioned in the last blog, it reduces the total amount of string required, although it might take a bit more time to prepare all components. Building models with those already joined tendons was surprisingly easy, however, precision is paramount, and especially on smaller scale tricky to achieve.

When things come together nicely, magic seems to happen. The shot shows an icosahedron with braided nylon string (not really stretchy), flattened and held together by a paper clip. I was very hesitant to push this model to the limit, yet couldn't stop once it bounced back happily. A collapsible model with non-elastic string, which makes me wonder whether I can build collapsible models of other shapes that do the same. Well, as I have a bit more building material at home I'm not too concerned about having some breakage during the experimental stage.

I want to explore the effect (and potentially integration) of UV light on my structures. The results are already very promising, much better that the photo suggests. Most of the nylon string has already a fluoro colour, spray painting the struts as well could bring some dramatic effects.

Scaling

I used up my supply of recycled struts from my geodesic dome, well, the larger length. Fuller claimed that the ratio of strut to string length remains constant independent of scale - so far, my scaling attempts had quite some errors in it.

As I was curious whether I can use eight centrally joined tendon trinities to build a six strut icosa without any support than my body and dexterity, and furniture nearby. The symmetry of this structure made it so much more elegant (at least conceptually) than most other tensegrity builds. I prepared eight corner joints with three tendons each, based on calculating the string:strut ration from a smaller and larger model.

I even got fancy and used two different colours for the tendons, I hope the different qualities of the string used won't create problems later on. After only one minor hick-up the model came together nicely, with the length I measured being precisely what I wanted according to my calculations. I can imagine that even a bit less tension would provide a stable (not disassembling) model.

The tetrahedron survived some wild storms and still hangs in its slightly hidden space, while three other outdoor installations have gone.

Next big thing

I think I got sufficiently mad during the last week to call myself an artist. I upscaled to a degree that my calculations were quite off the target, and a lot of re-adjustment was required. Three structures with 95 cm struts emerged. The first one, attached to its current destination in a stormy night before the rain hit, still survives the wild weather. The second structure didn't stay for 24 hours in the wild, the latest one still needs some painting and still blocks some of my lounge.

While the tetrahedron exposes some efficiency in the use of materials (roughly a 1:1 ratio of string and tendon), the six-strut icosahedron seems wasteful. The initial string/tendon ratio was about 2.7:1, and as I was running low on nylon strings, I wanted more bang for my bucks. I can't really prove in any fashion that in order to create a tension triangle you can equally to from the corner along its sides or to its center, and the central joints introduced another additional node in the network of strings, but in practise it works just splendidly.

The six-strut icosahedron is a strange tensegrity, connecting the 12 corners of the icosa in a neatly way highly symmetrical through its center. In a way, the minimal 3 strut tensegrity can be understood as minimal octahedron. I better test this experimentally :) Being able to reduce to string/ratio to 1.5:1 made the idea of larger icosas much more viable, and I can't stop experimenting with the result.

I hit a sweet spot with the tendon lengths. Any three struts will balance (all 20 faces), drop and squeezing tests showed a lot of robustness, and the wigglyness can be hypnotising. I won't test it to breaking strength without camera, but I love the options offered by this design in a larger scale. It's simple to suspend small scale objects in the center, some sort of generic 'picture frame' to showcase more complex models.

I wonder whether I can use a set of centrally joined tendons to build from the scratch.

Bigger things

I recycled some of the struts I used for my geodesic dome experiment. With about 90 cm strut length 6 strut models of tetrahedron and icosahedron just so fit through my front door, my ambitions certainly outgrow my available work space indoors. 23 squared still hangs in a modestly visible spot from a tree, the storms of the last few days haven't affected it.

I have no idea about the effect sunlight will produce - typical Melbourne weathers meant grey skies since I installed it. But I found a perfectly suited spot for the next installation, an icosahedron, again with some parts of the struts spray painted.

The rain seemed to have stretched the tendons, I twisted some struts to increase the overall tension. I hope my idea about visibility works out, at night it's basically invisible. Hope the sun comes back to Melbourne soon.

Do or die

2012 started suboptimal when it comes to market appearances. Without the more complex sculptures, there's less eye catchers on the table. Who cares, I'm basically trying to sell art, so can't really analyse my success in business terms.

On the other hand, the lack of sales means I can come up with new projects what to do with tiny supply of rods I still have at my disposal. The source has dried out, just after I got a better idea how to work with the slightly heavier material than usual.

However, I experimented with a different topology for the tendons in the corner. Instead of connecting the tendons between neighbouring struts, I used a little ring to join them in the center of the corner. The struts have now an individual degree of lateral movement, and the cube happily balances on each corner. I also build an octahedron and the Vector Equilibrium in star formation instead of using loops for the corner.

As I enjoyed the different movement patterns with centrally joined corners, I went a bit bigger, attempting a hanging installation for outdoors. It survived already some strong gusts in its test location, it behaves quite nicely in windy conditions. The structure tends to rotate slightly out of the wind pressure, and doesn't swing itself up easily.

Octoids

I haven't been that busy during a week with building tensegrities ever, and I enjoyed it thoroughly. I needed models I could transport without a car. It will be lots of fun to find out how practical my idea of transport will be tomorrow, unicycling with a backpack from which twenty or so tensegrity structures dangle....

Besides a set of octoids, octahedra in which colours enhance aspects of their structure, I build a number of colourful icosahedra. I hope I can source more of the material I used for the latest icosa builds, it saved me lots of work. Doing the computer related things, like preparing and uploading the slideshow turned out much less pleasurable. Nevertheless, all is prepared for an interesting market day tomorrow, including the update of the market datea for the first three month of 2012.

The next season

Many things happened since I last had a stall at the Rose Street Market, most unfortunately, my car got totalled so I now face the challenge to transport enough models either on PT or on a unicycle.

As most of my toy octahedra were gone, I prepared the components for another batch of octoids, spending lots of time on sawing, cutting and a bit of spray painting. Luckily, I didn't forget how to build tensegrities, determined to produce enough portable material for next sunday's market I got into a bit of a rush - six octahedra, one icosahedron and one cube provide the first yield of two days work.

By chance I came up with a new colour combination for square struts, which works amazingly well. I might need to prepare another batch of struts to use up all the coloured ones I have now, and getting the photo and documenting job done.

I nearly forgot the joy of bringing tensegrities to life, especially those with unique looks.