If this knot was made of rope, one could actually untangle it so it becomes an obviously untangled simple loop. In 2004, it took a computer 10 minutes to do that, according to Wikipedia
The 3D printed unknot is too rigid to untangle, but there is another game you can play with every rigid unknot:
Stick a thread straight through it and connect the ends of the thread further away from the rigid unknot, so that the thread winds around at least two bits of rope of the rigid unknot and is an obvious unknot itself. Then, try to deform the thread so that it winds around just one bit of the rigid unknot, or else comes free. With the rigid knot being an unknot, this should always be possible, provided the thread is long enough. Note that the winding around the rigid unknot may be more complicated than a simple spiral, because links of two unknots are not classified by linking number alone
. I haven't tried it yet, but I assume it is a rather hard puzzle.
Try also the Thistlethwaite unknot, which is available in my shop.
This knot is available in several versions, differing in the cross section of the rope:
- Square (that's this one)
- Twisted square
- Rope with fine detail
Be warned that depending on material, size, wire thickness, detail, complexity of the knot and the mood of the guys who do the manual printability checks, Shapeways may refuse to print it. I obviously did not test this for all of my over 300 knot models. You can tell whether a knot has been printed successfully before in the chosen size and material by looking whether it says "first to try" under the material selection box.