Project 74: tensegrity trellis building with pruned branches and bamboo stakes

I’ve been in the garden a lot and building trellises using tensegrity structures for tomato plants, pole beans, sweet peas, a cucumber, a peony and even a mini basil seedling support. Now we need a bit more heat so that the plants will grow up around the structures. Tensegrity structures are ideally suited for trellising because they get stronger as they become loaded. None of the structures are attached to the ground. They stand on the ground and in a few instances are standing on pieces of wood so they have firm footing and do not sink into the garden soil. The firm contact with the ground while maintaining some freedom of movement helps to maintain the tension in the string and overall integrity of the structure.

July 6, 2019

I made this peony support last year. I put it into place after the plant had grown quite large and had to arrange the stems through the structure. I had tied the string around the ends of the bamboo poles and there was some slipping and loosening of the tension over time. I also pushed the three bamboo poles at its base into the ground a little bit.

This year, I made some improvements to the structure and to the timing of introducing the support to the plant. I used a jig saw to cut slits into the ends of the bamboo stakes to hold the string, similar to the smaller coffee stir stick models or twig models. I had finished the trellis before gardening season and put support in place just as the shoot were coming up. The trellis was not held down or pushed into the soil this time around and although it was blown over rolled to the side once. As it continues to grow, the peony and the support are mutually holding each other in place. This structure is not held down, but held in the round by the peony. It can move and jiggle around a bit, but it’s not rolling anywhere any more.

My new goal was to make something similar to the needle tower sculpture by Kenneth Snelson, Below is a video of a crew putting it up after restoration work. An interesting thing about the needle tower is that it is not attached to the ground. It is free standing on the ground.

I started small with some twigs and a tripod, or 3 strut prism shape.

Tensegrity tripod holding up some severely pinched back basil that was transplanted from a crowded pot of seedlings. They were looking a a little spindly, but seem to be growing stronger.

I like the tripod because you can have many variations on the shape depending on the way you string them up. The top triangle can be a different size than the bottom for instance. Tripods or other simple structures can also serve as a modular unit that can be joined to produce many different forms.

You can essentially stack these tripods and get the needle tower type shape as shown in these videos by Daniele-Claude Martin.

Before I had watched her videos, I was playing around with the tensegrity icosahedron (T-icosa) and changing the position of the struts on the strings, without changing the overall length of the string and found you could get a similar shape that way too. In the videos above, Daniele mentions this same relationship going from two tripods to T-icosa. In the T-icosa, all the string lengths between struts are equal. In the tower shape, you need to slide the struts around so the that every diamond shape (rhombus with all sides equal) becomes a parallelogram with two shorter sides and two longer sides. (not a kite shape) I was inspired by Mariana Barreto (on Biotensegri-tea party#8: Model Zoo), who used garden netting in her model. That video is an excellent source of inspiration for model building.

Shape shifting a Tensegrity Icosahedron into a repeating unit of the needle tower.

More tensegrity tripods

A few of these had to be redone and retuned because I had not fully secured the string at all points and after a few days some of them fell apart or loosened and fell over. Unlike the bamboo, the branches that I was using were curved and bendy, adding another variable to play with.

Two arrangements of the same sticks, below, ( because I neglected to secure all the strings the first time and it fell apart.) One of the legs of the tripod is at the level of the top of the square planter and the other two legs are on the ground. I trimmed some branches when I rebuilt it. The original is on the left and the second version is on the right. Left: exhale, Right: inhale. The tomato plant is the intended partner for this trellis.

Mini tripod with basil, Short tower with cucumber and Tall tripod with three tomatoes.

I just bought some slightly longer stakes and have a few more models to build for a couple more tomato plants and a couple cucumber plants. I may have to learn how to extend the height of the short tower and build onto the existing structure. I’m waiting for the plants to grow. So far, plants seem to be growing into the structure like the peony is, with minimal outside guidance or tying plant to structure. They are still small yet. We’ve had lots of water, but not too much heat yet. We’ve had a few storms and windy weather and they are mostly staying put, shifting slightly, but staying upright since all the strings were secured properly and stable footing provided. There was some toppling before these measures, but no plant damage thankfully.

Finally a fun little tetrahedron. I saw a computer generated drawing of this and I built this because I was wondering if this was real or just a drawing.

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