Zheng3 Penny Catapult

by zheng3 May 15, 2012
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Mine seems to be launching downwards, any solutions?

Printed, and it's terrific! However, I notice the bottom of the arm hits the floor/table/flat surface when using it. I noticed in several pictures people had these little feet printed to lift it up slightly. Where in the world did you people get the feet?

I don't understand what keeps the two side braces from collapsing in on each other.

This works a lot better if you use string instead of elastic bands, loop it backwards and forwards a few times, then tighten (fiddly). Pennies go quite a few metres then :)

It's all about the torsion.

Sooner or later somebody's going to use a guitar string or some piano wire. I'd love to see how that works.

Seej is an awesome idea! It reminds me of my favorite childhood boardgame called Crossbows and Catapults! http://boardgamegeek.com/boardgame/2129/crossbows-and-catapultshttp://boardgamegeek.com/board...

Awesome! Could you separate out the parts at some point? I tried a couple of times to print one for my kids, but a couple of the crossbeams keep curling up, and so I need to cancel the whole thing. :/ If the parts are broken out, I could deal with those problem parts separately.

Just updated this Thing with a .zip file containing one copy of each of the parts. Hope the kids enjoy the new catapult!

very cool, the beams on mine are a very loose fit though, so needed glue, is that normal? how much allowance did you make on the dimensions?

I'm printing on a MakerBot replicator and the bores are quite snug when I print with black ABS.

Here's a pic of the bore and crossbeam in orthographic view so you can see the (fairly lax) tolerance.

You might have better results if you scale the crossbeams up in X and Y just a bit.

The winding keys on the sides should be very loose so that you can take them in and out easily.

 I had the same issue. The cross beams are all loose enough that with tension, the whole thing collapses into a very narrow catapult.

Yes! garyacrowellsr is correct!

"Catapult" is a catch-all term for siege engines like this. I think this is somewhere between a mangonel and an onager. Call it what you like, as long as you have fun with it.

The design for this catapult/mangonel/onager is loosely based on one from
a href="http://www.amazon.com/gp/product/1556525265/ref=as_li_ss_tl?ie=UTF8http://www.amazon.com/gp/produ...
The Art of the Catapult
, specifically pages 127-136.

Could you possibly make the arm a separate file, or even a SCAD, for us non-americans? :) Otherwise, excellent stuff looks great :D

Zheng3 Penny Catapult Base
by zheng3

Wait, there's an internet OUTSIDE of the US? Weird.

Here's the throwing arm.


Zheng3 Catapult Arm
by zheng3

The above URLs are repeated and take you to a beautifully animated 404 page saying "There is nothing here, YET."


Should be


OIC, The link is correct on the little box with the picture in it, silly me for clicking on the blue text....

Zheng3 Catapult Arm
by zheng3