Leonardo thought of it first...
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I was reading through the enormous (and enormously wonderful)
Leonardo Da Vinci: The Complete Paintings and
Drawings by Frank Zollar and Johannes Nathan. There is a large
section on fascinating catapult-like devices that would make great
ideas for the t-shirt hurling contest. In particular, the rotary
device in this picture bears a certain resemblance to the gizmo
that the Australians put together. There's nothing in the picture
that looks like a credible release mechanism. It would be awfully
hard to aim. I doubt that it was ever actually built. Maybe the
Australians can go back in time and give Leonardo some solinoids?
There was also this interesting variation on the trebuchet. Rather than having the
counterweight mounted pendulum-like on the end of the arm, it is
dangling from a wheel. The interesting effect this has is that the
force accellerating the rotation of the arm does not diminish as
the arm approaches vertical. Could be a fascinating tweak to
explore. [ a note about the movie: I copied the drawing from The
Complete Paintings and Drawings, Photoshoped it into layers, built a little model using
Lightwave ]