Magic Hands - Tensegrity - 3D Printed

"Ebony and Ivory" … live together in perfect harmony!

This object is not about a function that is to be fulfilled (carrying a table top or bowls etc.) but only about the principle "Tensegrity".

The thread between the two hands - besides the three threads connecting the upper and lower ring - builds the tension in this object. It's a bit magical how the physical conditions create a tension that makes this object a unit - a perfect unit. At first sight a bit confusing ... you have to look twice to understand the principle.

The printer file of this beautiful hand, obviously the hand of a woman, I found on Thingiverse or Tinkercad some years ago. Unfortunately, I can’t find out who put it there or who it belongs to.

Dimensions: Ø 114mm, H approx. 160mm

There are 3 files to print:

• Magic Hands_bottomring.stl
• Magic Hands_topring.stl
• Magic Hands_hand.stl (2x)

Print Settings

• Printer brand: Prusa
• Printer: I3 MK3S
• Supports: No
• Resolution: 0,2
• Infill: 20%
• Filament brand: Prusa; ICE
• Filament color: Galaxy Black; Wintershine White
• Filament material: PLA

After you have printed your parts ...
Remark: As all parts are designed to fit very precisely, it may happen that you have to rework one or the other part a bit with sandpaper and/or cutter due to different dimensional accuracy of the printers and the different behavior of the filaments.

• Nylon thread Ø 0,35 mm
• Superglue
• Small screwdriver
• Cutter knife
• Sandpaper
• Some patience (when creating the tension structure)

Start to insert the hand parts into the top and the socket. I inserted the black hand into the white socket. To ensure a good fit, the fitting accuracy is very tight. It may be necessary to correct the fit with a cutter knife or sandpaper. Apply superglue.

When the hand parts fits well, you can make the connection between the two hands with a short nylon thread, Ø 0,35mm. Thread or dental floss will also do the job! The length of the thread - measured between the two palms - should be a maximum of 50 mm but not much less, between the outside of the hands max. 60 mm.

Take a nylon thread of about 10cm and make a multiple not at one end. Pull it through the hole in the back of the hand of one hand, and then put it through the palm of the other. Now again make a multiple knot. While doing this, you have to try out whether the distance between the two hands is correct when setting the knot. This is a bit fiddly! It took me several tries too!

If the distance is correct, you can cut the ends of the thread.

You need 3 nylon threads of about 25-30 cm.

At the top ring the you see 3 holes. The holes - at bottom ring too - are drawn in the designer with only Ø 1,2 mm. During printing the holes can sometimes be narrower. Therefore it may be necessary to drill them out.

Take one thread and make a multiple knot at one end and then pull the thread through one hole of the top ring. Do the the same with the two other holes of the trop ring.

Now comes the most difficult part. But don't worry, you'll get there!

Place the top ring with the bottom side facing up. Hold the top ring in the right direction over the hand of the base ring.

Then feed one thread through a hole in the socket. Pay attention to the alignment of top and base! At first just clamp the string. To push the nylon thread down in the slot, use a small screwdriver. If the notch is not clean, try to open it carefully with a cutter knife.

Do the same with the other 2 threads. Now you can start with the adjustment. The distance between the two hands is already given. So when the strings are slightly tightened (do not tighten the threads too much, otherwise the hand parts could deform!), socket and top are aligned horizontally and the tension force is sufficient to ensure a stable stand, then you can secure the strings.

Hurray! You did it! … tensegrity works!