30 Foot Trebuchet

30 Foot Trebuchet

Ryan Bavetta
aka Bavetta
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By bavetta, torpex, rubix, rustaman, damonv

4 ratings

- Video 1 - - Video 2 - - Video 3 -

We built a 15 foot tall (30 foot extended) trebuchet and fired water balloons and other similar projectiles.

The hall we live on at our dorm (Tetazoo) voted to spend the money garnered from having Laura Stewart as a faculty fellow to hold the 1st "Laura Stewart/Tetazoo build day". We went to Home Depot and bought supplies in order to build 2 to 3 smaller trebuchets. When the day came around, not many people were immediately interested in building them, so it was decided to build one large one instead.

There is not a lot to say about the construction, you can pretty much get it all from looking at the pictures. There are ratios that many trebuchet webpages say are good to have - length ratios, weight ratios, etc. We thought about them in the design phase, but ignored them during construction.

We made a frame out of 2x4s, decided that it was too weak, then kept adding 2x4 supports and cross-braces until the frame felt more sturdy.

The axle was made from a 1.5" black pipe sliding around a 5/8 steel rod. It worked really smoothly, at the end we noticed that it had bent slightly from the large weight, but it still seemed to work without much friction.

The weights were concrete that we cast a few days earlier: three 60lb weights and one supa-mother 300-400 pound monster. We put U-bolts in the concrete before they set so that we could attach them to the arm.

Here were the results of one day of testing [in ft]:
22, -5, 3, -33, -38, -30, -6, 0, [change to large weight] 0, 0, 28, 204, 126, 232

Just when we started getting the hang of it the big weight fell off of the arm (see the last photo) and we called it a day. We are apparently going to try a second run this next weekend. We'll update the results after it happens.

By trebuchet03	2006-05-09 22:09:11
This puts a smile on my face :P How much did it cost... approximately?

By bavetta	2006-05-10 19:56:08
We spent a little over $200, but we also bought a lot more hardware than we needed, since we originally were going to make 3 of them.

By rubix	2006-05-12 09:10:24
More specifically, three (much) smaller ones. =P

By www

2006-05-11 13:36:58

Ok I was wondering if you had any blue prints for this trebuchet. i was also wondering if you had a list of materials with costs. i am really interested in what you guys have done here. i need this infomation for a school project. it would REALLLLY help if you could send me this information Via e-mail. My email address is: sk8erbrendon222@aol.com
Thank you!!!!!!!!!!
Also reply on this site. If you want.

By trebuchet03

2006-05-11 13:54:25

I don't have prints for the ones I've built -- that was more of get some wood and see where it goes... iono if Ryan has something though :P

The design is fairly simple though - two A-frames (main supporting legs) connected to each other (make a bit of a square pyramid) - then the boom/arm (strong enough to hold the weight) and the axle (strong enough to hold the boom/arm and weights). Looks like this design has two vertical A frames with buttresses on either side.

The further away the weight is from the axle - the bigger the moment you'll get... but that requires the trebuchet to be taller to allow it to swing. Likewise, the further the arm is from the axle, bigger moment - but it needs to be taller to allow the weight to get a full swing.

Do some reading on the internet on how they work... once you understand, you should be able to come up with a design of your own to meet your 'needs' -- another source of weight is jugs of water. Not to expensive, but not as dense as concrete...

By rubix

2006-05-11 14:06:41

trebuchet03 pretty much has it down. We didn't have plans as we started building this thing, but we had a general idea. The materials were basically wood 2x4s, lots of 2.5" screws (to attach the wood through 2x4s), some rope, some eyebolts for tying rope and attaching weights, and a big fat metal rod for the main axle.

A couple good trebuchet resources are:

http://www.ripcord.ws/ Very good and clear explanations of how trebuchets work.

http://www.trebuchet.com/ Commercial website, but lots of different models you can check out.

http://www.siege-engine.com/Chapter.EnginesOfWar.shtml A gallery with lots of pictures.

You might also want to start off building something smaller, since the bigger it is, the trickier it gets (also much more dangerous swinging 500 pounds around). I've built smaller ones out of scrap wood & metal, so they really don't cost that much. Good luck!

By www	2006-05-11 20:16:40
HEY THANKS FOR THE REPLY'S. ITS VERY HELPFUL. YOU GUYS ARE AUSOME! BUT I WAS JUST WONDERING IF YOU HAD ANY MEASUREMENTS OF THE LENGTHS OF THE 2 X 4' S' AND I DON'T HAVE TO BUILD ONE FOR THE ASSIGNMENT BUT I WOULD LIKE TO IN THE FUTURE. ALL I NEED TO DO IS DRAW A SCALE DRAWING AND A LIST OF MATERIALS WITH PRICES. THANKS FOR EVERYTHING. FURTHER HELP WOULD BE APPRECIATED. ps nice site.....

By rubix

2006-05-12 09:09:39

All of the 2x4s were 8 feet long. To create the long-legs of the A-frame, we joined two 8-foot 2x4s end to end, and attached them together with 2 foot 2x4s screwed in on both sides. Kinda like this: (side view)
|------------|
-----------------| |----------------
|------------|

The bottom of the legs of the A-frame were spaced 10 feet apart. We used two more end-to-end 2x4s to make the bottom, so we had 3 feet leftover on either side.

The width in between the two A-frames was somewhere around 3 feet, but that was entirely dependent on the width of the counterweight we used.

Pretty much everything can be bought at any hardware store, so go check out your local one to see for prices. We used about 50 2x4s.

By rubix	2006-05-15 13:05:45
Sorry that ASCII art totally didn't work. It was just two smaller pieces sandwiching the ends of two larger pieces at the middle.

By Tweetybird	2007-05-21 15:54:41
Nice Job. Excellent concept!