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Floating Arm Trebuchet Plans Download

Don't forget to download the free plans for use in Google SketchUp. All comments are welcome!
Click to Download Trebuchet Plans
6 Foot Floating Arm Trebuchet Plans If you don't have Sketchup get it here Sketchup
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Some news for you!
The parts list has now been added in Page 5. General construction steps coming soon. Please contact us with questions or corrections!
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Build Your Own Floating Arm Trebuchet

Here are the basic plans for a floating arm trebuchet featured on YouTube. (6 Foot Floating Arm Trebuchet) It has been fired with 20 and 50 pounds of counterweight but it could easily handle more. The projectile was around 9 ounces. At 20 pounds we would hit around 70 meters. At 50 pounds we were just short of 200 meters. The pictures and general measurements should be enough for most people, but we highly recommend you download the sketchup plans above. The file can be viewed with the free google sketchup program and you can use the measuring tape to get any details you need.

The Basics

Everything wood was made out of 2x4's for most construction but we used 2x6's for the wheels. Top wheels are 4" and the bottom wheel is 4 3/4". For the bottom trough for the projectile we just used some old thin plywood for that. The ones that look like 2x2's (The vertical pieces and 45 degree support pieces) are just 2x4's cut in half rip-wise. Obviously you loose some material ripping so they aren't true 2x2's but you can adjust for whatever you have.
The wooden wheels are not really necessary and you can substitute something else. We wanted it to be more primitive so we made a jig on the tablesaw that clamped onto the mitre gauge so the wheels could be cut. On the bottom wheel we cut a groove in it on the router table so the launching arm could follow it and made a complimentary cut on the launching arm to guide it. Again, this probably isn't necessary. We could have went to the hardware store and got 3 replacement lawnmower wheels or used skateboard wheels or whatever. But if you don't have the groove on the bottom wheel and use something else I would suggest extending the 2x4 out far enough to keep the travel of the launching arm from moving too far left or right. Also, if you use skateboard wheels you might want to consider using a much narrower bar to hold the weights so the wheels can jump a narrower gap. That is why we went with 4 inch wood wheels.
You will also notice the bracing supports that are at a 45 degree angle and the 2x4 guides. The guides probably aren't necessary either but we were extra cautious. But I'm sure if you keep your weights clamped down so the launching bar is in the center and you have something on the bottom wheel to keep it from skewing too much there should be no problem.
The cylindrical axels for the wheels was 5/8 " steel rod and we cut grooves in it with a sawsall to hold the spring clips. But it could have easily been done by drilling a hole and using cotter pins. The wheels and the shaft for holding the weights all had metal washers for spacing and friction reduction. We also made wooden washers as spacers for the bottom wheel. Regular grease was used to lubricate any areas where it made sense. For high stress areas like the top of the arm we cut steel reinforcement plates. With counterweight over 50 pounds it might be a good idea to put plates near the center wheels too. UPDATE! Yes... If you do increase the weight to massive amounts it IS a good idea to have reinforcement plates near the center wheels and use a beefier arm. We recently loaded about 100 pounds and broke the arm. The new one will be a full 2x4. The old one was from left over scrap and was only 1 1/2 x 2 1/8 (In the plans it shows 1 1/2 x 2 1/2). But it split horizonally right down the middle.
We noticed that for heavier weight it was crucial to bend the release nail at a different angle than lower weight otherwise it would do line-drives. Testing for the best trajectory is important.

Other Trebuchets and Links

You must go to The Hurl A great set of forums frequented by the masters of siege weaponry. If you have a question or want to throw out some ideas to be blessed or pummeled this is the place to be.

Andy's Trebuchets, both big and small page is a great resource. He has 7 different trebuchets, a size calculator, plans, and also help with slings.

We've been contacted or had comments from some people on the youtube video. If you are building a trebuchet and ours helped with inspiration we would love to post links to your vids, pictures, etc... We can also put pictures up if you'd like.

IrishSnipez built a treb similar to this design. It is at Floating arm trebuchet, 6 foot and it really makes the projectile fly.

Credits

First, and most importantly, The Floating Arm Trebuchet, invented by Ron Toms Without his vision none of this would be possible. Visit his pages to see an incredible selection of kits ranging from hurling machines to DaVinci inspired works.

Also thanks to YouTuber hfagerhaug. His video at Haralds Floating Arm Trebuchet 2 was used to get some general ratios. My son did a screen cap of one of the frames, printed it out, and guesstimated the ratios in millimeters and redesigned based on 6 feet in height.

Tools Used and Special Notes

We used a tablesaw, router, grinder, sander, sawsall, drill, and a drill press in addition to small hand tools. Screws were 3 inch and 2 1/2 inch depending on where they were used. The bar for the weights was just some left over black pipe that was cut to size. For this trebuchet all we cared about was distance so it uses round free weights. The nice thing about the free weights is that you can move them close to the vertical drop arms. That keeps everything centered. On your trebuchet you might have to design for accuracy and use a basket system filled with sand or rocks or whatever. In that case you will need to have something else that keeps the bar centered and/or have the baskets balanced far enough out on the bar so the bottom inside of each basket doesn't exert force on the drop arms.

Questions and Contact Info

The measuring tape tool in sketchup works wonders. We get a lot of questions about the trebuchet and we do our best to answer them all. If you email please include a subject otherwise it will usually get kicked to the spam curb by our mail server. Most of the questions are already covered on this page or in the downloadable plans but there are also some really good ones that we try to reflect in the page content. We will soon be expanding the site to include a FAQ and forum to cover questions we see repeated often and put it in a CMS instead of this awful looking hand-coded HTML.
If you have questions you can email us at: Again, we do try to answer every email and also update the site information based on your feedback.
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