Eye Lichen from The Labrynth

Josh B
Josh B ✭
in Animatronics

I am looking for mechanical help, or help with motion transfer, for a project that I am working on.

The project is to recreate the Eye Lichen from the movie The Labrynth, moving 10 to 12, animatronic tentacles. An example of these tentacles can be seen on this site under "Cable Mechanism Basics - Tentacles". Mine will only move in two directions, left and right, and will not be very long. The longest tentacle will be about 10-inches and there will be about 10 to 12 of them. I also want them to move using a motor or servo, not "human controlled" like a puppeteer.

The tentacles will be laid out in a random pattern in a box that is about 18" x 18" x 2" (Example). Because of the limited thickness of the box (2-inches) I do not have much room. The two dots, one red and one black, indicate the holes that the cables will be running through. The dashed line is there to indicate that they are paired with each other.

To move the tentacles left or right, I need to pull on either one of the two cables that protrude from the tentacle and out the back of the box. So, when one side is pulled on, the other side needs to loosen up. I have created a prototype that uses small servos to pull on them (Example) but I want to add more tentacles and fewer servos.

A couple of things I have thought about using are:

  • Rack and pinion type setup, but that would require me to change the direction of the pull, from forward/back to left/right.
  • Some type of spinning rod that would wind-up/un-wind the cable.

My Questions

  1. How do I get all of these tentacles, which are not lined up, to move at the same time? I have see a documentary on the making of The Labrynth and Ross Hill, the puppeteer, seems to have 5 levers to move like 30 eyes. How?
  2. What would be a good way to wind-up/un-wind these cables besides using one servo for each tentacle?
Anybody have any experience with something like this that they are willing to share?

Thank you!



Comments

  • Chris Ellerby
    Chris Ellerby Admin
    Hi Josh,

    If you want to use servos you should be able to route the cables from multiple tentacle mechs to a single servo using something like pulleys.  The challenge there is the strength of your servo.   You could also route your cables inside of housings (tubes) to allow them to be redirected.

    A cam or crank mechanism could work here as well.  If you look up "crank ghost" on YouTube you will find examples of a mechanism used a lot in the Halloween & Haunted Attraction industry.  Basically you have a single slowly rotating shaft with one or more arms attached to it.  Then your cables can attach to different points on different arms to move in a repeating pattern with some variation.   The challenge there is if the movement/performance you want to get of your character is possible with this type of setup.

    For Labyrinth, they likely had the tentacles grouped up and connected to multiple levers as you mentioned.  If you have 5 levers to move them you would want to try and spread out the tentacles connected to each lever so they are not right next to each other so you have a somewhat random distribution of movement to make them feel individual.  There's no limit to how many cables a lever can pull, the only real limit is the strength of the person pulling the lever.  With servos and motors you have to be a bit more calculated.  In both cases it's a matter of getting mechanical advantage where possible using leverage, pulleys, gearboxes, etc to provide the force needed.   But there is always a tradeoff between power, speed, and distance traveled.

    Making your tentacles as light as possible and as easy to move as possible is the first step.  Then it's a matter of routing your cables so there is as little friction as possible and connecting them to your source of movement.

    Best of luck!

    /Chris
  • Josh B
    Josh B ✭
    Thank you for your help Chris. I ended up going with pulleys on rods. I haven't received the parts yet so I don't know if it is all going to work but my fingers are crossed. I will have 3 rods with 3-4 pulleys on each rod connected to 1 high torque servo through gears. I might need to tweak some things here and there but I was told that the servo had enough toque to do the job. I am taking your advice and making the tentacles as light and easy to move as possible. I have also used bearing on the rods to make that turn nicely w/o much friction.
    Once I get the parts, and get it together, I'll post an update.

    Josh

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