catapults
 

has any one attempted or successfully made a good catapult? Care to share a brief description ?

Never have but I bet you could get A LOT of informatin on how to make one on google.

SCA websites would be VERY useful for this sort of thing also. I'm assuming you mean one of the giant boulder-hurling types, usually called either a trebuchet, ballista, or onager. Catapault usually means a smaller machine that projects rocks or arrows.

try:
trebuchet.com, http://www.tbullock.com/trebuchet.html, http://www.howstuffworks.com/question127.htm

I have built a table-top Trebuchet. It measures about 20"x20"x16".
I made it out of 1"x2" pine. Used a transformer from an old cash register for the ballast. The sling was cut from an old pair of denim jeans.
While it's not a boulder hurling beast it will launch a marble over 50 feet. I will post pictures if you want.
Currently the welding professor has it to draw up plans to construct one entirely of steel. Tried to explain some weight/stress problems he will run into but he just wants to have a project for the students to work on other than just running beads on blocks.

I built a 6 to 8 foot trebuchet in my high school physics class. IT was very cool! We used all wood, except for the bar the arm spins on. It worked really well, and I still have parts of it in my dad's shed. I wish I could tell you more details on how to build it, but it's been a few years since then.

I've built a couple trebuchets, as well as an onager.

For those looking for an explanation, a trebuchet is basically an arm with a counterweight on one end and a sling on the other. An onager is a machine powered by twisted ropes that swing the arm around, connected to a sling.

For extreme power, look to onagers. www.onager.net has a good one, built by I believe Bob Carbo. These machines probably get the most power for their size out of all catapults.

For accuracy and efficiency trebuchets can't be beat; this assuming you take into account the more modern FAT (Falling arm trebuchet) and F2K models.

All this and more on www.trebuchet.com , which has it's own msg boards.

The only advice I can offer is:
Do not build the main shaft from soft wood like pine. We built one once on a movie set and the main shaft snapped when it hit the crossbar. It flew in the opposite direction of our waterballon basket, narrowly missing some spectators.

There is a great programme called Scrapheap Challenge / Junkyard Wars, in one eposode they built a trebuchet out of junk. Very interesting to see how these things work, and in one case didn't work and just fell apart.

Here's some simulators that I used.

http://www.ripcord.ws/simulators.html

WinTreb is the best one.

There's also the Punkin' Chuckin' contest (pumpkin hurling), which I saw a special on. Downright frightening.

Sorry to bring this thread back from the dead. I was going to start my own trebuchet thread when I found this one.

NOVA did a special on trebuchets, where about 100 people built two original size trebuchets from scratch. They used no modern technology. Each were about 3 or 4 stories tall, and they launched huge boulders at a castle wall they built. I have it on VHS.

I've built about 6 trebuchets, ranging in size, and 2 mangonels.
My biggest trebuchet was 6 feet to the axle, and 14 to the tip of the arm. A few friends and I built it about a year ago. We were disappointed on launch day, though. It didn't work as well as we had hoped for. About 150 feet. Not much for a catapult that size, but not bad I guess. We were going to tweak it and improve it, but we lost interest after a while and eventually it got dismantled. I think our problem was that we only had 150 lbs of counterweight, and our arm alone was about 50 pounds. We probably needed about 300 lbs or so.
http://www.toddfx.com/pics/trebuchet.jpg

I also had one about 6 feet to the tip of the arm, which launched soda cans pretty far. That was actually the first one I built, and I don't have any pictures of it. It was dismantled long ago.

My third biggest one is about 3 feet to the tip of the arm, and launches rocks and large marbles. It's been a while, so I forgot the distance it launches. I still have it and it's in perfect condition. Actually these pics are of it right now. I hauled it out to take these. I think I could get about 50 feet out of this if I added more counter weight. I just never got around to finding something heavy tnough.
http://www.toddfx.com/pics/trebuchet2.JPG
http://www.toddfx.com/pics/trebuchet3.JPG
http://www.toddfx.com/pics/trebuchet4.JPG

I also built 2 popsicle stick trebuchets, and one "floating arm" trebuchet. I can't find them though. They both worked pretty well.
My smallest one was this one made out of toothpicks. I don't know where the arm for it is. It's about 2 inches to the axle, so it'd probably be about 4 inches to tip of arm. It launches fishing weights and small nuts about 10 feet or so. I think I used some heavy duty bolts and nuts for the counterweight.
http://www.toddfx.com/pics/trebuchet5.JPG

I also built this Mangonel a while back. It doesn't work too well though, it's only been launched a few times. This was the last thing I built right before I lost interest in siege weapons. It's torsion powered, but it's loosened in this picture. You wind it up by spinning the handles on either side in opposite directions. I'm not strong enough to tighten it to what it needs to be to get maximum performance, so it was probably a bad idea to make it torsion powered. It launches about 15 feet :hmm:
http://www.toddfx.com/pics/mangonel.JPG

I'll try to find my popsicle models, especially the floating arm version. It works better than the normal trebuchet, actually.
Heres a picture of what a floating arm trebuchet (FAT) looks like, for those unfamiliar:
(not mine)
http://www.trebuchet.com/fat/t1.jpg

Holy crap :eek: I want one!

That is pretty damn cool.