I built this catapult (actually a trebuchet) based on an article in Make Magazine by William Gurstelle.  It worked extremely well!  Was able to launch basketballs 80 - 90 feet, and small pie pumpkins over 100 feet.  I think fine tuning of the sling release could further enhance the performance.

It is made of plywood, a few 2 x 6's, and a lot of plumbing parts.  The folding design is great for storage, and in my case, the catapult actually went up on the roof of a church for the main launching event.  It fit up a ladder through a roof hatch with no trouble.  (Well, other than the fact that it is bulky and heavy).

The counterweight is two 60 pound bags of concrete, which gave about a 100:1 ratio for the pie pumpkins and basketballs.  After the pictures were taken I also added several bungee cords (2 x 18" and 2 x 24") to assist with pulling the weight down, and it added another 20 feet or so to overall distance.

Just something fun about catapults!

Step 1: Building the platform

The base is made of 3/4" plywood.  It uses about a full 4 x 8 sheet, which I cut up into four 2 x 4 sections to make it easy to work with.  The uprights are two 28" long pieces of 2 x 6 lumber glued and screwed together.

When you cut the plywood sections to size there are three pieces of wood per section.  The platform piece itself, and then two narrow reinforcing pieces that go along the edges.

Cut the plywood and 2 x 6s to size, and glue and screw together.
<p>what is that on the back of it</p>
<p>Really great design!! Built it with 4 adults and 4 high school kids in about 5 hours. Cost somewhere in the neighborhood of $300. You could save money by finding a plumbing supply house vs a &quot;big box&quot; home center. Also we are going to replace the concrete with free weights. If you use the concrete, you can soak the bags in water and make them &quot;solid&quot; blocks. First shots were last night. 1 lb spaghetti squash, 125 feet :-) Oh, and after building this. You can not help but smile.</p>
Build went good but not getting any distance at all. Mot stalling but seems to rotate slowly. Played with sling length and relase pin angle to no avail. Lithium grease seems really thick. Not sure how far to tighten pipes and still allow for quick rotation but still remain safe. Also 2 bags of cement will not fit on counter weight union so I used 11 inch pipe uprights instead would this slow it down and reduce power? Thanks.
Mine took a lot of fine tuning. It threw best with small pie pumpkins or footballs and basketballs. I didn't have a problem with bags of concrete, so not sure how changing the pipe length would affect things. The unions need to be able to spin freely.<br><br>I also added some bungee cords to hooks on the bottom of the counterweight to make it pull down faster. That helped with distance.
<p>that's really nice instructable!</p><p>I have difficulties with watching the video, could you please upload it in youtube?</p>
Hello this is a great pumpkin launcher. We're looking to build it for a physics project. We have a question: what makes the pumpkin actually launch? Do you cut a string? Please let us know, thank you!!!
Look at step 8. It uses an equestrian panic snap that hooks on to a ring on the catapult arm. Cord is lashed around the panic snap body and pulling that cord causes the snap to open and release the ring. Hopefully that makes sense!
I built this, it works well. couple of tips/suggestions. <br>- make the middle plywood section wide enough to allow for sling slide without hitting hinges <br>- offset the the two posts on the side plywood base so that folding is easier/tighter. It wont look centered but travels easier. <br>- cut handle holes in outside of plywood <br>- use a stainless anchor shackel for the trigger, add a safety chain you pull just before firing <br>- If you make the posts taller say 36 instead of 28, you can extend the weight a bit farther and add some yardage <br> <br>Great design though. Kids love the thing.
I noticed in your photos you didn't include wheels. Think the MAKE instructions recommended castors. I found a reference to a PBS/Nova article about adding wheels to a trebuchet will increases distance. Here's the reference. <br> <br>http://www.pbs.org/wgbh/nova/lostempires/trebuchet/wheels.html
I think I have about $200 or so in lumber, fittings, pipe, etc. It was a fun build!
How much did it cost to build this?
2 questions: <br>How well would this work with a bunch of snowballs? <br>Could you make a video showing it in action?
Should work fine for snowballs. You may need to adjust sling length and release. Sweet spot for this is about 1.5 - 2.5 pounds. <br> <br>No more video! It's folded up in the garage for now. I'll shoot some vid the next time I set it up.
I meant in the ible.
Actually that is a Trebuchet
That looks very nice (I didn't know you could buy branded pumpkins?). <br> <br>It would be nice to see a video of it in action?
Pie pumpkins are a type of small, sweet pumpkin, usually used for making pies. They generally weigh between 1 - 2 lbs. which makes them the perfect size for this catapult. <br> <br>I have a short video of a test launch that I'll post soon.
Short video of a test launch during tuning phase. Throwing a football, which hits a tree! <br> <br>http://flic.kr/p/doYTba <br>
Nice shot!
If you build a proper chute for the projectile to run down you can fine tune your accuracy for left and right... just like they did during historical sieges.
Awesome design. I love that it is collapsible for easy transport/storage. <br>All your steps are well documented and easy to follow. <br>5 stars!
Very cool. Though this is technically a trebuchet, which, IMO, are more awesome than catapults. http://en.wikipedia.org/wiki/Trebuchet

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