You have all seen the "Spider in the Box" joke box. Does anyone know where
to get the plans for one? Maybe, I should say, does anyone know how the
mechanism works. The box is a piece of cake, but its getting the spider to
pop out that might be "interesting."
Never seen it, but I do make similar automata.
I think it's just a box, with the spider on a wire spring. Don't
think of it as a "box with a spider that jumps out", think of it as "a
spider on a wire above the box, that folds up when you close it".
The wire is C shaped, with a few coils wrapped in at one end to
provide a bit more oomph in a small space. A couple of flat loops
right at the end allow it to be screwed down (actually they're easier
if they're almost-loops that don't cross, not full loops).
The spring is mounted on to the top of a block inside, against the
nearside end, about 3/4 of the inner height. This allows the spider to
be pushed down below its spring mount when closed.
The spring is pushed down by a shaped (smoothed off) cam block glued
mid-way under the lid. The cam block rides on the length of wire below
the spider, rather than the lid hitting the spider itself.
To design it, draw it out full size in side view on a piece of scrap
plywood (just draw the spring mount first). Now hold a first-try wire
loosely against it and try pushing it down with a cam-block, moving by
about half a lid-length. Allow the wire to pivot loosely in your
fingers. You might even want the rubber spider in place too, to give
the real look of it.
When you're happy, then make a wire with a coil torsion spring in it,
about where you'd been allowing it to pivot. fasten this to your
board. Firm up the cam block design.
Draw in a box around your works.
Make a real one to match. I suggest making the base screw-on, possibly
even making the first lid with screws in it for the cam block. Don't
glue automata together until you've got a happy mechanism running on
your screwed trial piece.
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