by jam4ar, published
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I noticed a startling lack of small projectiles in my office. I also noticed an abundance of 20mm calibration cubes. Solution: Desktop Tebuchet.
Video Demo: http://www.youtube.com/watch?v=kW5KLmR86kk
Print sled.stl and frame3.stl twice. Don't print trebuchetassembled.stl. Print 1 of everything else.
Assembly is pretty easy, if you need help download the assembled sketchup file. The supports will have to be glued into the bases. That's the only place where my print required glue.
The 45mm x 3mm bolt is the axle for the counterweight basket.
You'll also have to make a sling. I used duct tape and some cotton string (see image.)
When the sling is hanging from the arm, the bottom of the sling should be at the main axle.
Use a drill to add a small hole (I used 1/16") to the top of the throw arm, go through the hole for attaching the sling and into the other side a bit. About 1/4".
Cut a straight section of a paperclip and insert it into the hole, bend it back (away from the pieces printed in frame2.stl) to about a 45 degree angle. This pin controls when your sling will let the projectile loose, straighten it up a bit if it's releasing too late, bend it more if too soon.
Add counterweight to the basket, the ratio of counterweight to projectile mentioned on sites that know about such things is between 75:1 and 100:1. I use a bunch of brass keys.
It's all really "fiddly" for a bit, but once you get your weights, sling, and pin adjusted properly it works pretty well.
For more info on making adjustments see:
Have fun and don't put your eye out.
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Desktop Trebuchet by jam4ar is licensed under the Creative Commons - Attribution - Share Alike license.
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