Advice Needed

Okay Gang. Here's my conundrum. I'm trying to build a body for the mech in the video I'm putting on here. my problem is the wood and mechs aren't strong enough to support the body weight. Anyone have any ideas? Thanks A Ton, Kahula


  • Hi Kahula,

    To strengthen the wood you can brace it by gluing in strips that are perpendicular to the flat surfaces.  Something like a "T" in a profile view.  The strip does not need to be super tall, just enough to help prevent the wood from flexing.  That flexing also uses up energy, so making things rigid can increase the efficiency on any moving parts.

    For the servos, this is where things get a little more complicated.  There are 2 main approaches here.  One, which is never fun, is to get more powerful/larger metal gear servos.  But we all know how expensive that can be.  The other is to change how the servos are operating.   Most of these movements appear to be driven directly off the servos, meaning there is no added mechanical advantage.  If you design linkages that take advantage of leverage (or pulleys) you will be able to move heavier loads, though this comes at a cost of speed and range of motion.

    From a fine-tuning perspective there are some other things that can help.  Reducing the overall weight of the support structure could help, but it already looks pretty lightweight.  Try and find areas to remove material where possible.  Sometimes this can be as simple as drilling large holes in things.

    Also make sure no servos are supporting weight, as their ability to move will be decreased if they are already supporting a lot of weight.  For example, if there is a servo at the bottom of the character that is supporting/moving the weight of the rest of the character  This can be helped by using linkages to move things, and sometimes with counterbalancing.   The trick with counterbalancing is it can mean adding more weight, which in some cases is counterproductive.   One thing I like to do in a situation where a servo needs to lift a heavy load is to use an elastic material like latex surgical tubing or bungee cord to provide a little extra lift.

    Using bearings on anything that rotates can also help, as the bearing can support some of the load and also reduce friction.

    Beyond that making sure anything you add for the skin is as light as possible will help.

    Hope that helps!

  • Morning Chris. Thanks, it does help. My question is... is there even a way to attach a body on these mechs, as is? Thanks Karen
  • There might be, as long as the body is super light and does not need to stretch or deform (like spandex, etc.) as the body moves since that would further tax the servos.

    Since the character is a penguin you could possibly make an outer covering of feathers that would be super lightweight, but that may limit your control over the character design and desired aesthetic.  You could also use overlapping layers on the body so as it moves the material can slide without revealing what is underneath.  

    Changing the servo configuration to use linkages may also give you some strength so you can stabilize some of the moving regions (using something elastic) to counteract the wobbling that is common in animatronics.  Ramping animations can also help address wobbling.

    Great looking setup by the way.  Excited to see where it goes!

  • I'm honestly afraid it's going to end up being shipped back. I can't seem to get it to move freely with any additional weight, let alone enough to keep the movement fluent. It seems so fragile that I'm afraid to handle it normally, which only ads to the fact that that I honestly just don't think it can be done as is. Which is sad because I know the guy who built it has had dreams for it for a long time. But, we aren't miracle workers. So.... on to the next thing ;)

  • I completely understand.  Clearly a lot of work went into creating the animatronic, and it's impressive on its own.  Sometimes when it comes to mating mechanical design with art there will be bumps in the road.

  • Yup ... speed bumps
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