Building an Animatronic Tail

My friend Rah and I were chatting and she happened to mention how cool it would be to have a tail. I joked that I bet someone had built one using an Arduino. A quick search showed that indeed a few people had and even a tentacle. Rah’s next question was would I built one, fast forward a couple of years and I’ve finally got around to starting. Taking a 3D printable design as my starting point.

Parts

Hardware Build

3D Printed Tail Parts

The design didn’t come with instructions, so I needed to guess how the part fit together.

Assembling the tail involved threading the Rubber cord on the vertical holes. Tieing knots at each end. The Elastic cord in the hortizontal holes. I left out the fishing cord until later.

Servo

I bolted on the servo horn, then marked out the holes in the wheel. Drilled holes with a Dremel

Servo and Wheel

Seeing how the Buckle, Arm and Brace was simple.

Assembled Mount

One thing I did wrong was gluing those three parts together before attaching the servo. Pulling them apart. Fitted the servo and glued it all back together.

Mounted Servo

Threading the fishing wire. Adding two eye hooks on ether side of the servo wheel as cable guides. A single nail at the top as an attachment point.

Assembled Tail

Electronics

Most parts are USB, so simple plug together. Battery to switch to Arduino. The servo is a little bit more work, a quick Google showed

brown or black = ground (GND, battery negative terminal)
red = servo power (Vservo, battery positive terminal)
orange, yellow, white, or blue = servo control signal line

The signal line connect to digital pin 9 on the Arduino and that was everything assembled.

Software

I started with the sample code and played around with various timing. In the end most of them didn’t look right, so I reverted the changes. The current code is on GitHub.

Things that didn’t work

My original plan was to use a pulse sensor to control the speed of the tail. I used the advanced example, reading the BPM was fine but does not vary enough to have a noticable effect.

If I was building this again. I’d look at an accelerometer to use as input to the Arduino. That would give variation required to produce more interesting movement from the tail.

Author: Zoe

A recovering games coder.

11 thoughts on “Building an Animatronic Tail”

  1. Dear Zoe,
    Thank you for this helpful article! My 13-YO daughter and I plan to build this for her cosplay.
    I have a few questions, but only if you have time:
    1. Did you NOT glue the first vertebra to the arm? Are the cords enough to hold without sagging?
    2. Whey did you use both rubber and elastic cords? Wouldn’t one or the other be sufficient?
    3. In fact, why not choose just, say, the elastic cord for the upper and lower holes, and the fishing line for the horizontal?
    4. How do you attach this entire unit to your body? (Or is this something that you use for a decoration and not cosplay?
    Thank you in advance for your advice! We are NOT trying to second-guess you, but to learn from you experiences instead!
    Cheers!
    -Mike

    1. Oops!
      She just teased me, because of my typos! “Why” not “whey” and “from your experiences” not “from you experiences”. 🙂

    2. 1. The cords and line are indeed enough to avoid sagging. So no need to glue the first vertebra
      2. I first used just the elastic but that was not enough to give the rigidity I was after. So I added the rubber.
      3. If I was building another one I would just go with the rubber. I spent most of the time playing around with the tension to the upper and lower holes to get the movement looking the (mostly) how I wanted it.
      4. You can thread a belt between the servo and the holder and secure the tail that way. The belt is also handy for the battery pack to power everything.

      Happy to help if you have any other questions or need more explanation for any of this

  2. Hi Zoe,

    Love your project. I want to try it myself.

    2 problems is there 1st. a video of the motion somewhere? And 2d is there another link to the 3D print files. Because thingiverse is down for 3 weeks already..

    Last question what do you mean with rubbers? rubberband or something more specific.

    Kindest regards!

      1. Hi thanks for your quick comment!

        The site indeed worked again!
        The link for the rubber black cord is down could you give me a similar link so I definetly have the same materials.

        You left the fishing cord out correct?

        Then I’ve read this :
        One thing I did wrong was gluing those three parts together before attaching the servo. Pulling them apart. Fitted the servo and glued it all back together.

        Why not print the whole peace as one? Or is it impossible to get the servo in? (just an idea I had to maybe print this as a whole, otherwise I would make holes and connect them with rods or something similar)

        Again thanks for the quick reaction. It means I can build it even more quicker 😀

        1. Really any 1.5mm diameter rubber cord should be fine but this is one that looks similar: https://www.ebay.co.uk/itm/Viton-Rubber-75-O-Ring-Cord-1-5MM-Diameter-From-1-Metre-Length-HIGH-TEMP/132536527479

          Why not print the whole peace as one?
          I think that is down to the size of build plate. I just went with the parts from thingiverse. If I had my own 3D printer and was building more of these that maybe the route I would take.

          3D printing and enclosure would be another nice enhancement if I was doing it all again

          1. I’ll give you the files for the new 3D print when finished via github if you want! for others in the future.

            You had enough wire with 1 m ? (fish line and rubber cord (you don’t think the elastic string is necessary correct? ) )

          2. I’m not sure I’ll build another one but it would be cool to update the post with a link to the improved parts.

            1 Metre should be enough if you get everything exact. I would get a little extra, I ended up just getting the shortest roll I could get, which I think was 5 metres or so. It was still very cheap. You are correct, I’d leave the elastic out if I was building again and just use the rubber cord and fishing line.

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