Any suggestions for the best mechanism to make my luggage smile?

[TheoJones]

I am building a small (but functional) model of Terry Pratchett's Luggage as a gift. The case is a fairly simply wooden box, flame treated and varnished -

My vision is to have the luggage able to do two key things; I want the lid "mouth" to be able to open, "smile", chomp at something placed in it, and then close down.. so it has teeth:

The idea is that the teeth are concealed inside the lid and base when the lid is closed - the lid being opened by an arduino/stepper motor combo using a simple lever arm. with that in mind, there's a support structure around the lip;

part of the support is not in place for clarity here.

I had intended to drill some holes in the "jaws" and put compression springs inside - problem 1, these are insanely too strong - the weakest springs I can find pop the teeth "up"and the weight of the closed lid is not enough to compress them. I really don't want the stepper motor to have to force the lid closed... (my plan to prevent someone causing damage by pulling the lid open is to make opening the lid essentially a disconnected action - the motor lifts the lid far enough to animate it, but the owner could simply lift the lid - it's not connected.

My first question - what would you use for this lift mechanism? 3D printed flexure? a very light spring steel leaf?

Once I have solved the teeth problem, I move to the feet, and am currently thinking a 3D printed scissor lift to allow the box to move between two positions - "sitting", where the box is on the ground and the feet are hidden, or "standing" where the box is supported by a ring of feet;

I think that's a safer proposition, as there are a good set of scissor lift platforms on thingiverse.

I am hoping that this is the correct forum.

Comments and Suggestions welcome

 

[smithjohnj]

I understand you plan to use a motor tolift the box lid. The upper jaw is fixed to the inside of the lid. I would make the U-shaped lower jaw more ridge, which sits on the angled ledge at the upper edge of the box bottom as in your photo. The lower jaw is then pinned with a pivot point on each side at the rear of the box. This will allow the lower jaw to hinge up and down to expose the teeth and gums in the front, tapering down on the sides. You can place limits to restrict how high you want the teeth to rise. To hold the lower jaw up when the lid is open I would use ball and detent catches which will lightly lock the lower jaw in place when it rises to the “correct height”. Perhaps putting the catches at the front corners for the best support since the rear will be supported by the pivots. The lid “attaches” to the lower jaw,toward the front, with magnets or a weak mechanical latch which will easily detach when he lid raises “too high” and the catches engage. The catches hold the lower jaw and continuing to raise the lid breaks the magnetic field or pulls apart the mechanical latch so the lid can open. When the lid lowers the weight of the lid frees the catches and pivots the lower jaw back into place. This approach would be consistent with your “disconnected” lid idea.

 

[TheoJones]

I understand you plan to use a motor tolift the box lid. The upper jaw is fixed to the inside of the lid. I would make the U-shaped lower jaw more ridge, which sits on the angled ledge at the upper edge of the box bottom as in your photo. The lower jaw is then pinned with a pivot point on each side at the rear of the box. This will allow the lower jaw to hinge up and down to expose the teeth and gums in the front, tapering down on the sides. You can place limits to restrict how high you want the teeth to rise. To hold the lower jaw up when the lid is open I would use ball and detent catches which will lightly lock the lower jaw in place when it rises to the “correct height”. Perhaps putting the catches at the front corners for the best support since the rear will be supported by the pivots. The lid “attaches” to the lower jaw,toward the front, with magnets or a weak mechanical latch which will easily detach when he lid raises “too high” and the catches engage. The catches hold the lower jaw and continuing to raise the lid breaks the magnetic field or pulls apart the mechanical latch so the lid can open. When the lid lowers the weight of the lid frees the catches and pivots the lower jaw back into place. This approach would be consistent with your “disconnected” lid idea.

I like this approach; I think it has a lot of mileage.

Off to tinker!