Articulated Arm Prototype

Here is a little prototype that I am working on to learn about the shop that I will be building my installation in. I used a few pieces of scrap wood and some wire to attempt to make an articulating tower. I think that if I revisit this concept, I will need to find some uninsulated wire so that it doesn’t get bound up in the wood so easily, and I will need to play with the sizes of the components to achieve a better motion profile.

Oh, I know there are some toys/other things that use this concept, but I can’t think of what they are called. If you know of some, I would appreciate some leads.

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12 Responses to Articulated Arm Prototype

  1. Rich Davies says:

    Have a look at the above website ( similar concept.



  2. Tim Deagan says:

    A few years back I built some ‘robotic dreadlocks’ using this concept. The device is a helmet with 4 rows by 4 columns of these stacks (I used buttons with fishing line). The lines were controlled by 8 RC servos. Each servo controlled a row or a column, so that each stack had an X axis controlled with 3 other stacks in its row and the Y axis controlled by 3 other stacks in its column. This allowed the dreadlocks to ‘dance’ at the behest of a PWN servo control run by a Basic Stamp microcontroller.

    I stole this idea from those toys which allow you to push in the spring-loaded bottom and they ‘sag’ in response (or dance if your imagination is up to it.) I experimented with a straight stack and having beads between the levels. I eventually settled on a straight stack.

    I have done some experimentation (not very encouraging yet) where each level in the stack has 4 electromagnets and motion occurs by repulsion/attraction. This is a very noisy device in the electrical sense.

    I am currently modifying the ‘dreadlock’ hat into a pair of tentacles controlled by biofeedback, a prosthetic set of working ‘antennae’.

    This approach has fantastic potential in my opinion. Good Luck!!

  3. Mike says:

    There used to be toys that were about 4 inch tall figures standing on a 3/4 in tall base. The base has a spring, that kept an internal plunger expanded. The plunger was attached to strings that ran through the joints of the figure. If you left it alone, it stood there. If you pushed the plunger in the base, the figure would droop or fall. A rapid series of pushes would vaguely simulate dancing.

  4. Mike says:

    Rock’em Sockem Robots may work via a similar method, but I’ve never taken them apart.

  5. phil says:

    Some endoscopes use a similar principle to this. You can use a multi-lumen catheter with control wires up the outer cores – or more easy to construct yourself and fun to play with: two springs one inside the other, the inner one should be a tension spring ie cannot be compressed any more than it already is, 4ish control wires run up between the ID of the inner and OD of the outer, put flexible packing strips up between the control wires to keep them evenly separated. Fix the control wires at one end and pull the other end. You can then stick what ever you want up the centre as like wires to an LED. I think there’s a patent on it somewhere and maybe even a website promoting the concept.

  6. mahto says:

    Thanks everyone!

    @Rick: Thanks for sharing, it must be quite a feat to get the snake arms to be that stable, and to be able to apply any useful force at their tip.

    @Tim: Those sound way cool, do you have photos of them online? I was actually thinking about making some beaded ‘lampshades’ that danced to music or something.

    @Mike: Thanks for the links! The push puppet toy site brings back some fond memories :-).

    @Phil: Aha, using springs would allow you to miniaturize the whole assembly, which would make sense for endoscopes… I could see some cool applications, such as a proboscis for a mechanical mosquito…

  7. jay says:

    Have you seen the work done at this place?

    The triangular “fingers” seem pretty similar (and a little more forgiving than wood).

  8. Sean Ragan says:

    That’s really cool man. Somebody has probably already mentioned, or you have already figured out, the idea that the smaller spacing blocks should be circular to allow unbiased omnidirectional articulation. Try using the 1/4″ plywood cutouts from a 1.5″ hole saw!

    • mahto says:

      Hi Sean! Ahh, cutouts sound like an excellent source for round spacing blocks. My father suggested using marbles, so that was what I planned to try today.

  9. John says:


    I saw this application used to articulate Jabba the Hutt’s tail in Return of the Jedi.

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