Zheng3 Penny Ballista
by zheng3, published
This nefarious device can easily launch a U.S. penny across a room when printed at 1:1 scale.
It's the first upgrade many Seej players seek when they need a little more oomph than the Zheng3 Penny Catapult can provide.
Seej is an open-source tabletop wargame based around 3D printing. Rules for Seej are at s33j.net
Do you need this in your arsenal? Yes. Yes you do.
Penny not included!
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Construction is really simple! Needlenose pliers are recommended, but not strictly necessary.
You'll need two elastic bands to complete this ballista. Tie a single band through the bore on one of the two D-shaped locking keys. Repeat the process with the other locking key.
Feed the end of one band through the rectangular bore on the ballista's left post. Insert the tenons of the locking key into the square mortises on the post to lock the band in place. You'll be tempted to repeat the process with the other side, but don't give in. It will save you precious minutes of frustration.
Unlike the Zheng3 Penny Catapult, these locking keys should be a snug fit. If some settling of the plastic during printing has made the mortises too small, trim the tenons a bit with your blade of choice.
Center the nock on the knot that connects the two rubber bands. Make sure that the penny's cradle is facing forward.
Feed the end of the band that's been locked down through the rectangular bore on the nock. Tie the free end of the band to the second band. Now feed the free end of the second band through the outside of the rectangular bore on the right post and loop it through the second locking key.
The nock has a wee nub on its underside. Slide this nub into the ballista's firing groove; it will improve accuracy.
Load a penny into the nock, pull it back, and fire away. Be safe!
Seej is a tabletop wargame based around 3D printing. Check out http://www.s33j.net for rules and more information.
Or just jump right in and download the Seej Starter Set: http://www.thingiverse.com/thing:24013
You can also search Thingiverse for Things with the seej tag.
Be sure to check Zheng3.com for updates. If twitter's more your thing than follow Zheng3 at https://twitter.com/Zheng3_Jim
Flagrant stagecraft alert: There's a piece of hookup wire holding the nock in firing position for dramatic flair.
Thing-O-Matic users may want to check out the Zheng3 Short Stock Penny Ballista, which will fit on a 120x120mm build platform: http://www.thingiverse.com/thing:23545/
EDIT 6/1/12: There's a new STL that fixes some flipped normals and weird N-gons on the locking keys. If you're having problems printing the previous version, try the clean model. ReplicatorG is pretty forgiving, but other slicing software may be less so. Good luck. We're all counting on you.