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Zheng3 Penny Catapult

by zheng3, published

Zheng3 Penny Catapult by zheng3 May 15, 2012

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28605Views 5825Downloads Found in Mechanical Toys
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Summary


Oye! Oye!

Brenda the articulated battle tardigrade has been released into the wilds of 3D printing!

Join the Horde to be among the first humanoids to learn about the next epic project from Zheng Labs!

We now return you to your regular model description.


http://www.zheng3.com/2012/05/15/the-penny-catapult/

Here's a basic torsion catapult. It uses one or more elastic bands to launch a U.S. penny if you print it at 1:1 scale. You probably won't get enough torque to be impressive with fewer than 3 bands.

Penny not included!


Instructions

Construction is snap-together!

Feed an elastic band through each of the bores on the side braces. Tie it through the bore on each winding key. Slip the end of the throwing arm through the rubber bands. Repeat with as many rubber bands as will fit through the holes. Needlenose pliers will help here.

Twist each key 10 times and then lock it in place by inserting the locking tenons into the square holes on the side braces. The more twists, the more launching power you'll have. Careful, pennies can sting, especially if you take an Abe to the forehead.

Flagrant stagecraft alert: the clever-eyed among you will note the use of black electrical tape to keep the throwing arm cocked for the photo.

If you need a target, try the Seej basic bloxen: http://www.thingiverse.com/thing:23620

UPDATE 6/2/12! Thanks to Thingiverse user Wauter for pointing out some geometry problems in the winding key and side braces. These have been addressed in zheng3_catapult_clean.zip

Seej is a tabletop wargame based around 3D printing. Check out http://www.s33j.net for rules and more information.

You can change the payload's arc by raising the front of the catapult. Have fun storming the castle!

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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
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a href="http://www.amazon.com/gp/product/1556525265/ref=as_li_ss_tl?ie=UTF8http://www.amazon.com/gp/produ...
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amp;tag=zheng3-20
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amp;linkCode=as2
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amp;camp=1789
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amp;creativeASIN=1556525265"
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The Art of the Catapult
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, 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.

http://www.thingiverse.com/thing:23200http://www.thingiverse.com/thi...

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."

"http://www.thingiverse.com/thing:23200http://www.thingiverse.com/thi"

Should be

"http://www.thingiverse.com/thing:23200"

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
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