Tensegrity Stand/Sculpture

This was an idea I had been wanting to try out for some time. I wanted to experiment with more fluid shapes in 3D CAD, and also see if I could apply a spiral shape to a tensegrity assemblage.

In addition to the prints provided here, this requires monofilament fishing line (I used "30 lb test" - diameter 0.55mm/0.022in).

Fitting all of the pieces together is very finicky. Start by cutting four pieces of monofilament about 25mm/10in long - these are much longer than the final length, but the extra length is needed to provide "handles" for assembly.

The line is held in place with tapered plugs; each plug is in two halves, and is designed to wedge the line in place in the tapered holes in the main top and bottom pieces. I provided print files which will print more plugs than needed, as you are likely lose some during assembly. An additional note: In my prints one of the central holes in one of the main pieces turned out a bit larger, so I printed additional plugs scaled up 120% to fit the larger hole. All of the other holes use the "standard" plug.

A tip on inserting the plugs and line (see photo on this): Hold the two plug halves between thumb and finer with a small gap between them. Insert the line into the hole, and from the large side of the hole slide the plug halves over the line and into the hole. Allow the plug halves to clamp the line firmly, but do not insert the plug fully; first make sure the line is centered in the plug. A hemostat/forceps is a good tool for working with the monofilament. See assembly instructions for more details.

Assembly instructions:

Step 1 : Start by inserting the line and plug in one of the center holes in the spiral. Insert the plug firmly initially, and once you are sure it is correct, push it all the way in using your two thumbnails to both push the plug halves and keep the line centered.

Insert the line and plug halves into the second center hole - use the long line to give yourself room to work, and insert the second plug firmly but not completely. This grips the line, but still allows it to slide through the plug. Pull the line through the second firm-but-not-tight plug until there are about 25mm/1in between the two spirals - basically just adjust the length for the separation you want. When you have the desired length, push the second plug all the way in. Trim off the excess line on both ends with a razor knife.

Step 2 : Insert the other three lines and plugs into one of the two main pieces. Push the plugs all of the way in, but do not yet trim the lines.

Step 3 : Insert the other ends of the three lines into the holes in the opposite piece firmly-but-not-fully. Make sure the right holes are lined up (the bases of the two spirals should be opposite each other).

Step 4 : Adjust the line lengths between thw two pieces by pulling the line between the firm-but-not-fully-inserted plugs until all three lines are tight and of equal between-top-and-bottom length.

Step 5 : When you are sure all adjustments are satisfactory, push in the last three plugs fully and trim all excess line lengths with a razor knife. Done!

The OnShape 3D CAD files for this are available here:

https://cad.onshape.com/documents/23a3eb2dd3e72d741a28ded9/w/002547f76bcda45279692c80/e/5a960ea5892804618101af92

Print instructions

Use the 3mf files and print in PLA; otherwise :

Print the top and bottom halves flat side down, 20% rectilinear infill, concentric top and bottom; perimeters = 4. No supports are needed.

Print the plug halves flat side down, no brim required.

Note that a "test block" is included for testing the hole size plug fit. Also useful for practicing plug insertion.