Science Buddies: "Ask an Expert"

Hi. I have to make a catapult (large and creative one) that can hurl things up to 70 yards away. I already have the materials and general size (1m wide, 6m length, arm 2.5m-6m...).

I was wondering if anyone had advice. I most desperately need links to websites that offer free help. I know the basic catapult structure, but I also know that it is the little things in engineering that makes something the best. I was going to build the "typical catapult," but I'd rather do something more creative that can hurl something farther, but I haven't been able to think of anything.

Any tips?[/u]

Does it have to be a catapult, or can it be a trebuchet. You will get more reliable performance, and greater distance with a trebuchet (although adjusting the length of the rope/chain can be a little tricky with a trebuchet. They have been built powerful enough to throw pianos and cars. And, after all, medieval siege engines dealt the death knoll to castles and changed history.

A man named Ron Toms runs a website dedicated to trebuchets and catapults. It is:

http://www.trebuchet.com/story.php/fat.html

There are sites on the internet that have programs that can calculate trajectory and distance to be expected depending upon design. So research will be very rewarding. Start googling. Here is a starting point:

http://members.iinet.com.au/~rmine/tsims.html

BTW, this does make a good science fair project. My son won the county science fair by building one (though his was only about 12" tall, it could throw a boulder 20 feet)

Once you get your research done and get underway, feel free to ask specific questions regarding design. I can probably provide a lot of hints (you have to do the groundwork first).

A couple of other interesting sites:
http://www.rlt.com/sendpagebyemail.php? ... rfats.html

http://members.iinet.com.au/~rmine/gctrebs.html

If it has to be a catapult, not a trebuchet, there are similar sites out there. Some good search terms will be "medieval siege engine", catapult, trebuchet. etc.