Spider Fangs! Mechanism C&C please?

Hey everyone,

Figured I'd share what I've done so far and see if anyone has done any similar mechanisms in the past (not necessarily for a spider) or else has any suggestions for me, before I start spending money.

I'm prototyping a spider-head puppet, roughly the same size as a human head.  I'm trying to wrap my brain around how to accomplish two articulations:

1) Spread its chelicera (ideally, *pivot* each chelicera, outward to a 45 degree angle or so)
2) Extend / withdraw its fangs like a jackknife (ideally synchronized and spring-loaded for smooth performance)

I expect the puppeteer's hand will need to go inside the head or else behind the head. But it could also be operated via brake cables, etc.

Here's a pic of my second iteration of the fang extension mechanism. I just cobbled it together with some cardboard, tubing, pens etc.

It's a start, but it isn't great. I'm sure a better, simpler design approach is out there somewhere.  Like, for example, the swivel of the fangs could occur without a big, visible spring attached to the back of the fang itself--and there's gotta be a way to do this where there's only a small hole in the chelicera, where the base of the fang attaches, rather than a huge slit that unnaturally accommodates half of the fang. 

As for the chelicera-spreader (are you as grossed out as I am by that term?), I had an idea involving one of those "grabber" poles:

I thought about breaking down the pole to try and orient the pincers at a perpendicular angle to the handle. It'd require a new style of mechanism to link the pincers to the trigger--the existing wire wouldn't work. Before I go breaking anything, figured I'd see if anyone could recommend another approach.

I'm super excited to share progress on this fella. If anyone has any suggestions, I'd love to to hear from you! 


  • Hi Dan,

    Your mech for the fangs looks pretty good.  You might be able to get it to work without having a spring visible by using a rod (rather than cable) and having the spring inside the head on the rod.  Or using a more rigid cable that can push as well as pull.

    For the chelicera movement, the device you found is a good reference for how to achieve that result.  I would try making your parts based on it rather than using the existing product if you can get away with it.  Might be cheaper or a better fit for your design, unless the off the shelf product ends up being the right size/budget.

    This sounds like a cool project, I hope you can share more with us as you build it!

  • Thanks for the feedback Chris, I appreciate it!
  • I'm hoping someone familiar with mechanical engineering terminology could review the diagram below and suggest any ME terms or keywords which could help me refine my web searches. (My searches thus far are either too vague or inaccurate, and I have yet to find relevant terminology through online research). 

    The model I proposed last year didn't quite pan out. We had trouble backwards-engineering the pincer mechanism and incorporating a handgun-like handle / trigger. Even if we were to keep the pincer's full-length rod handle, simply having the chelicerae spread apart doesn't feel "organic". As a result, I would also like the fangs to extend / retract--ideally with a single shared mechanical trigger. I've put many, many hours into researching this, even trying to find constituent mechanisms for the chelicera / fang / trigger, but no solid results so far.

    Know of any  monster movies where a giant bug puppets have "multi-jointed" mandibles like this? Every giant spider movie I've checked out features "simplified" fangs, where the fang and chelicera are combined, forming a single rigid digit that hinges where it connects to the head. More like a stag beetle's mandible than a spider's actual mouth parts.

    The closest I could find--a mandible with two joints--is the male Judas in *Mimic*; the bug is just about to charge at Mira Sorvino, and sort of roars at her. Presumably the triggering mechanism is much more sophisticated (ie expensive) but maybe the general principle of its design could be applied to a hand-triggered model.

    Any advice or insight would be greatly appreciated!  

  • You could use some springs, spring steel, elastic, or flexible plastic to keep the assembly in the "closed" position when no tension is applied, then you could have a cable or other linkage pull the mandible segment into place.   For moving the fang segment you could have a cable inside it that attaches to part of the pivot point on the mandible section so as the mandible moves tension will be applied to the fang, forcing it to fold outward.   This is similar to how many finger mechanisms work.

    Heres a good starting point:

    You could potentially do the entire mandible/fang assembly as a 2 segment finger/tentacle mech.


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