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Desktop Trebuchet

by jam4ar, published

Desktop Trebuchet by jam4ar Sep 27, 2011
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Summary

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

Instructions

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:
http://members.localnet.com/~lorilee35/tuning.html
http://thehurl.wikidot.com/tuning

Have fun and don't put your eye out.

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File Support1.stl does not slice through Slic3r. Comes out all messed up. shows working/ok in Netfabb, no repairs required. every time I try to slice that part, the gcode shows just the bottom perimeter, then kinda sillystrings off into +Z. No problems with any of the other parts and had another user confirm this problem with his Repetier-Host + Slic3r. To get around the problem, I had to set Support2.stl to -1 xyz scale to mirror it.

Maybe it is the new version of Slic3r, but I just finished mine and it worked fine using Slic3r. Cheers!

Boy this seems perfect for launching 20mm test cubes...

Someone should get on designing the perfect companion for this...printable rocks...

Any chance of getting a .zip or .tgz of all the parts ?

Ask and ye shall receive.

Thanks - that's my weekend printing ahead for ;-). Friends were just saying how cool it would be to make a Trebuchet - now I can

cheers

Great! Make sure you upload a picture of yours. This is the first thing I've ever designed so I'm really interested to see how it prints on other people's machines.

I added a couple of links describing how to adjust things for optimum performance be sure to give those a read.

Love it! I was working on a trebuchet as well (adapting from a design found on instructables) but I was having trouble making the moving parts, you know, move properly). Looks like you nailed this. Thanks!!!

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