Curing a RoboRaptor's LockJaw

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MrScott's picture
Curing a RoboRaptor's LockJaw

I picked up an orphaned RoboRaptor last spring. One of its faults is that its mouth never opens during the left head turn. The poor little guy suffers from lockjaw.

At least he did, until tonight.

It now snaps those jaws like a good raptor should.

Here's a little video and stills montage detailing what I did.

Nocturnal's picture

Not bad, though I wonder how long it will take before the mounting clip bends back.

Tell me, did you consider tying a few knots in the cable to reduce its lenght?

MrScott's picture

I did consider knots, but two things caused me to try this first.

1- Knots cut tensile strength by as much as 50% and I know some robots have suffered snapped cables. If the cable is marginally strong enough as designed, weakening it isn't a good idea.

2- Knots would require much more dissasembly to take off the other body half, remove the upper electronics tray, and free the cable end to make the knot. This fix required removing one leg, and one body half. No internal disassembly was needed. I used needle nose pliers to reach in and bend the clip.

As I mentioned in a nearby thread about snooty quads, this is not an elegant fix, but it is an easy one.

The metal clip may or may not straighten again. If it does, I've lost nothing but my time. The raptor will be back to how it was when I got it.

I say that the clip may not straighten again, because not much force is needed to move the jaw. Before deciding on this fix I confirmed everything was connected properly by pushing on the lever with the tip of a screw driver. Very little force was needed.  

If the clip does bend back, or break, I will do the more elaborate fix of freeing the cable end and adjusting its tension.

Another fix would be to put a small set screw in the lever so that the cam pushes against the screw tip. That would allow fine tuning the cable tension by adjusting the screw. 

newnhamrs4's picture

very good, i will adjust mine. well done.

MrScott's picture

If you haven't done the RoboRaptor tear down before, here's the steps I went through (again) last night.

  1. remove battery door (left my batteries in for tests of exposed mechanisms)
  2. lie the raptor on his right side, with his left side ready to be worked on
  3. remove the left leg outer half screws and lift the outer leg half free (set aside with screws in place)
  4. remove the screws attaching the clear leg struts to the leg mount plate
  5. I found the sectioned interior of the battery door was ideal for storing sorted screw types
  6. pop the pin on the leg assembly from the underside of the leg mount plate as you simultaneously pull the clear leg struts from the top of the leg mount plate
  7. slide the leg assembly to the side and up,so that it clears the leg mount plate (set aside)
  8. remove the screws from the left body half (including the little one hiding behind the left arm)
  9. remove left body half and set aside (with screws in place)
  10. don't lose the power button that just fell out of the raptors butt
  11. locate the motor at the base of the neck between the shoulders
  12. locate the cable attached to the lever just to the rear of the motor
  13. push the lever rearward to confirm the cable movement causes jaw movement
  14. holding the raptor in your hands, power it up and note the neck motor cam as the head turns to the left
  15. the cam should be moving the neck cable lever
  16. power off raptor while neck cable lever is pushed as far as the cam will push it
  17. determine how much further the cable must travel to open the mouth
  18. if the slack is slight, bend the metal cable attachment clip to take up the slack

There you have it. Your mileage may vary.

  1. reverse steps to reassemble
GWJax's picture

Very Nice Mr. Scott, But I do like the set screw idea better! And you are right about the tie knot. Don't do it unless you put in a stronger cable. GWJax

MrScott's picture

My knot knowledge goes back to equal parts scouts, rock climbing, and rocket recovery harness assembly.

Most knots are death to tensile strength. Some knots only mortally wound it. Having strands cutting across other strands generates a lot of stress.

Terribuddha's picture

Your video is unavailable. :(

MrScott's picture

Looks visible and public to me.

RoboRaptor Cured of LockJaw

Added: January 07, 2008, 11:05 PM
Time: 02:12
Views: 164
Rating: 5.0
Comments: 1
Responses: 0
Broadcast: Public

idrum289's picture

I just viewed it too with out a problem

Terribuddha's picture

You know, I just clicked it again, and it worked this time...
Must be my stupid comp.... Ugg. I hate it when it 'hickups'

CraigB's picture

Mr. Scott, do you have any advice on removing roboraptor battery compartment and adding a rechargable battery pack?

MrScott's picture

I haven't done it myself, but I don't see why you couldn't. You might need to match the weight of the current battery option, as the WowWee walkers tend to rely on a finicky balance to waddle around.