Magnet tensegrity sculpture

Introduction

I've always been fascinated by tensegrity structures and when a magnet design flash contest was announced I thought it was a good opportunity to explore this fascinating concept further.

The model I came up with is a simple two arc structure with a gear like plate floating in between them, held in place by fishing line and strong magnets.

This is not a tensegrity table. The construction with magnets is not strong enough to hold much weight at all… It is simply pretty to look at. It is stable enough to give the gear a spin though, and that can look pretty cool.

Printing instructions

The frames

Print the frames strong, with many perimeters, to make sure they don't flex too much. They will need supports, and here I strongly suggest using organic style support. Here's how I printed them (using PrusaSlicer):

• Nozzle - 0.4 mm
• Layer height - 0.3 mm
• Perimeters - 6
• Top and bottom layers - 4
• Infill - 20%, Adaptive cubic
• Support material (build plate only) - Organic

The gear

This needs to be printed fairly light, to help with the floating effect. This also means it will be fairly brittle, so be careful to not over-tighten when assembling. The gear is printed in two halves and is then designed to be glued together with the help of four guide pegs (which will need a brim when printing). My print settings (using PrusaSlicer):

• Nozzle - 0.4 mm
• Layer height - 0.2 mm
• Perimeters - 2
• Top and bottom layers - 3
• Infill - 15%, Lightning
• Support material - None

Assembly

Parts

Apart from the printed parts you will also need:

• 1 M4 countersunk screw, 15 mm
• 1 M4 lock nut
• 1 2.5 mm wood screw, 10-15 mm
• 2 15-20 mm neodymium magnets, 5-7 mm thick, about 10 kg of lifting force, with hole for screw
• Fishing line, about 1.5-2 m

Putting everything together

The gear

Use the 4 guide pegs and glue to assemble the gear. Use the 2.5 mm wood screw to attach one of the magnets to the gear.

Here comes the fiddly part… It might help to use the photo of the sculpture as a reference.

Threading the line

Make a knot on one end of the fishing line and thread it through one of the 4 holes (one at each spoke) on the magnet frame, from the bottom and up. Then thread it through the corresponding hole of the line frame. In the round part of the frame there is a channel where the line is meant to run. Thread it through this to the next hole (using a small screwdriver to block the channel can help with getting hold of the line again) and then down through that hole and then again through the corresponding hole of the magnet frame. Continue in the same manner until you've threaded the line through all 8 holes and have what looks like 4 lines holding the two frames together. Do not tie off the end of the line just yet.

Sounds way more complicated when describing it than what it actually is, but doing it this way, one long line rather than using 4 separate lines, makes it easier to adjust everything later…

Take a smaller piece of line (maybe 20 cm, just to make it easy to work with) and tie a knot on one end. Thread it through the gear bolt, from the thread end. You'll see that there's a larger pocket there to hold the knot. Thread the loose end through the small hole on the “cone” part of the line frame, going in from the flat part. Tie a knot, and adjust it so that the length of line between the frame and the gear nut is about 10 mm. You'll find that there's a pocket to hold the knot on the frame as well. Finish by attaching the bolt into the gear.

Adjusting the line

This part can greatly benefit from having an extra pair of hands available.

Make sure that the magnet frame is standing stead on a flat surface. Either have someone holding it down or use something to keep it in place. Hold the line frame “upside-down” above it and make sure the lines aren't tangled and held tight. Use the free end of the fishing line to adjust the height of the line frame.

Either have someone hold the gear up or just make adjustments in-between holding it up to test if the distances are correct.

You'll want the distance between the magnets be about 10 mm, which means the length of line visible between the frames should be about 100-120 mm. This all depends on the strength of your magnets though. Once you've found an equilibrium where the magnet in the frame can hold up both the gear and the line frame, tie a knot on the free end of the fishing line and cut it to length.

Final instructions

Enjoy.