I fulfilled a childhood fantasy this week. Over Christmas, my brothers and sister and I built a catapult, a trebuchet to be exact. I have dreamt of doing this since I was a little kid, and I have to say watching it launch a baseball 160 feet was…well, pretty damn cool Heh, I still can not believe it actually worked.
How it performed——
It threw tennis balls about 140’, and baseballs about 160’. We did try to throw a big rock, but it fell out of the sling, need to fix that… It was amazingly consistent for a given projectile and counterweight, and a given ball landed within about 5’ on consecutive throws.
You can see most of the throws at .
My favorite video clip is http://onemanswalk.com/img/2003/12-December/Building%20a%20Trebuchet/MVI_2059.avi, it was the last throw we did before I had to leave to go to the airport, and also the farthest. Connection is kinda slow, but this video clip is well worth it.
As we added mass to the counterweight, the projectiles just kept going farther, so there’s still some experimentation to be done to see how far we can actually throw something. I have a feeling there will be some mini-boulders getting launched off of my parents’ roof sometime soon.
How we built it——
There are tons of really good sites online that talk about how to build trebuchets. We used ripcord’s at http://www.ripcord.ws/. The actual pdf w/ the instructions that we used is at http://www.ripcord.ws/plans/RipcordTBT.pdf .
We DID make some changes of course
- First of all, ripcord’s was way too small, and built to throw tennis balls 40 yards (if I remember correctly). So we doubled all the measurements.
- To support the greater weight and size, we used 1/2” rods instead of 3/8” rods for the axles.
- We used 1×2 wood for everything except the arm which was 2×2.
- We used nuts and bolts to hold everything together instead of wood glue. This had the added benefit of making our trebuchet portable, it actually fit in a ‘89 chevy nova – including the 8’ arm, hehe.
- Instead of a coffee can for a counter weight, we used 1 full can of paint, and one empty one that instead contained a brick and some huge iron tools. Though I’m terrible estimating things like weight, I’d guess it was ~ 70 pounds. We attached this to the arm w/ a piece of wire. Simplest thing that could possibly work, right?
That’s what we did intentionally, but we also ran out of time before I had to leave to go to the airport, so:
- We didn’t have time to attach the outriggers. In ripcord’s design, they provide a lot of stability, and our catapult waivered a bit more than it probably should have. But, it seemed to work just fine supporting a ton of weight. I wonder if switching to bolts over wood glue made up for it.
Getting buy-in from “volunteers”——
Yeah…should have done that.
So I had this great project, and I was sure that everyone was not only going to agree that it’s a great project, but also want to help out with it and participate. Turns out it would have been a good idea to spend some time getting buy-in. To change it from them helping me with my project to us all working together on a project that we all take ownership for.
At the very least, trying to get buy-in early out and failing would have set expectations of everyone involved. As it was, this project that I was hoping was going to bring my siblings together, actually added to the holiday stress. Not to worry, once it was done, all was forgiven, and everyone enjoyed watching it launch its missiles into the air, but there are lessons to learn from its construction.
The 3 reactions of my 3 siblings were very interesting.
Nathan (21) was totally cool and supportive. He’s the closest to me in age, and has seen me do these projects before. More than that, he was almost as excited as I was by the idea of a catapult. However, he had a project of his own that he had to work on during the middle of our building, it took precedence. That project was a suprise, but we were totally on the same wavelength through out this.
Ceci (16) was also excited, but she likes her sleep, and she liked the playstation game she got for Christmas. She helped when she didn’t have something that she thought was more important, which should have been fine. However my expectation was that she would help out unless she was doing something else. The difference in our expectations frustrated us both a bit. Should have sat her down and gotten her to agree on some kind of committment.
Javi (13) was actually not excited at all. It never really occured to me that someone wouldn’t naturally WANT to build a catapult. It should have. Again, he actually ended up helping but only for very specific tasks when we needed an extra hand, and he was usually grumpy about it, because I was upset that he wasn’t helping more, and he thought was going out of his way to help at all. Javi and I really needed to have had that talk.
Funny thing about Javi, as soon as it worked, then he got excited. What can I say, kids.
Dunno, maybe nothing, maybe mods on this one. Ceci want’s to give it wheels, I’d like to see how much and how far it could throw. We could always build a 20’ trebuchet out of 2×4 or something big enough to throw a cow…