Pulleys/Cables in animatronics

Hi all, new to the forums and still relatively new with animatronics! I've run into a bit of a bump with my project, and I'm curious if anyone has any suggestions.

To put it simply, I need to rotate a servo inside of my animatronic, and have it rotate something else located a distance away from the servo at the same exact angle, 1:1 (so if the servo's shaft rotates to an angle of 45 degrees, the wheel or whatever the servo is connected to will also rotate to 45 degrees).

Basically a system like pulleys with timing belts, where you rotate one gear, and the gear it's connected via a timing belt also rotates at the same angle, and they're always in sync at the same angle. I can't approach it in that manner though because pulleys and belts generally need to remain on the same axis, but I would like one gear/servo to rotate and another gear located in a completely different part of an animatronic figure to rotate also, even if the figure is leaning or positioned so that the driven gear isn't on the same plane/axis as the driver gear (phew! Hope this all makes sense!).

I at first thought cables would be a good solution, and I'll still definitely take a look at the tentacles cable video, but it's not quite what I need. Rather than trying to convert rotary motion into linear motion, I'd just like to take rotary motion of the servo as it spins and make it rotate another gear that's positioned far away from the servo and isn't aligned on the same axis. 

Been banging my head against a wall trying to solve this for days, while I feel like I'm overlooking some really simple solution. Any advice on how to approach this, or any videos to watch, would be greatly appreciated, thanks! :)

Comments

  • Chris EllerbyChris Ellerby Los Angeles Admin
    Welcome Marc!

    You can get rotary action out of a cable by having it attach to the object you wish to rotate.  For example, your servo would pull on a cable who's housing is anchored next to your servo.  That cable housing then gets anchored near the object you wish to rotate, and the cable is attached off-center to the rotating object.  When the cable is pulled (or pushed if you use rigid metal cable), the object will rotate.

    This lesson should cover most of that for you:  https://www.stanwinstonschool.com/tutorials/animatronic-tentacle-mechanism-basics

    Our lesson on designing and 3d printing an eye mech may also help, as it shows some similar techniques with cables and servos.  https://www.stanwinstonschool.com/tutorials/how-to-make-an-eye-mechanism-design-3d-printing-assembly

    /Chris

  • Hi Chris, thanks for the suggestions! I haven't gotten around to watching that lesson yet, but I'll definitely take a look and work through it some time this week, as well as the eye mechanisms. Will report back if I'm still scratching my head, but hopefully it'll answer most of my questions, thanks again!
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