3D printed Möbius strips loaded with ball-bearings

I had a bit of a rummage on the Shapeways marketplace today and came up with some 3D printed gubbins that I'm intrigued by. First up is Stop4Stuff's "Twin Rail Mobius," a set of nested Möbius strips that can be loaded with ball-bearings.

A half shell and 3 rails form a bearing-like structure to encapsulate a train of 6mm balls in a mind-warping cage with a twisting, fascinating movement bringing to life the only pendent of its kind in the world.

Includes a 4mm loop for attaching to a necklace or leather cord.

See the photographs with retro-fitted 31 6mm chrome steel ball bearings... in the bottom photo, the balls have been heated until they 'blue'... check out the video to see how they move by clicking on the little icon below the camera above.

Twin Rail Mobius can-take-a-ball - Pendant

• [Noctilucent Studios]

  OK, but how did they get the balls in there to begin with!?!?!

• [42isall]

   I want one. It would go nicely with the inch tall klein bottle I am currently wearing around my neck.

  • [dmatos]

     Rather, it will go well with the inch-tall klein bottle that your neck is currently wrapped around.  Wait, what?

• [SamSam]

  The Möbius strip pendant is a cool design, and beautifully printed, but don’t go thinking that the ball bearings themselves are somehow moving along in a Möbius-like manner. The ball race just makes a very simple ring.

  That’s because the Möbius strip is interested on the surface, but not in the inner volume of the shape.

  Picture this: you have a rubber, four-sided rectangular tube. You twist it a quarter-turn and attach the ends, so it forms a Möbius shape. If you draw a line on the surface, cool! the line keeps going on all surfaces. But if you were a gnat flying within the tube itself, you wouldn’t notice anything weird — it’s just a ring.

  • [GTMoogle]

    Not at all.  The ball bearings roll along the ‘edge’, so there’s one track that loops twice. 

  • [Luke Butcher]

    Actually, you’ve kind of got it completely backwards. The Möbius strip is not the “surface” of a shape – it’s the 2-dimensional space “within” the strip. If you have a strip of paper, and you twist it and glue the ends, the Möbius strip is just the “body” of the paper strip (if it were actually infinitesimally thick, that is) – *not* the surface of the paper. To clarify: there isn’t two different points on each side of the strip, but just one point.

    What’s interesting about the Möbius strip is that it’s non-orientable, which means there’s no way to consistently define the notion of “clockwise” on it: if you move a clock along the length of the strip, you’ll find it running the opposite direction to a clock you didn’t displace. Notice that this is not the case for clocks living on the “surface” of the strip.

    This charming video actually gets it right:
    http://www.youtube.com/watch?v=4mdEsouIXGM 

    By using a transparent strip, both sides live in the same space, and the story really does take place in a genuine Möbius strip.  

    This all has little relevance to the actuall 3D object in the post, of course.

    • [SamSam]

      That’s all fine, but the fact remains that if you take an actual rectangular rubber tube (we’re talking real physical objects here), give it a quarter twist and stick the ends together, you will be left with something whose surface acts as a Möbius strip (there is just a single edge), but within which you could fit a perfectly ordinary ring.

       The metal on this object is just a single rail that loops twice, forming a Möbius strip, but the ball bearings just go around once in a regular loop.

• [gfish]

  I had one made as a present last xmas, and it’s very pleasing in the flesh. I got the 6mm synthetic ruby ball bearings from Small Parts instead, which added a nice touch of color.

• [Kimmo]

  Most groovy.

  Is there a mob who can print this for me?

  I suppose it’s a fairly trivial matter to do it half size too, eh?