Need advice : Building a Catapult

[teh1337tim]

Hello my dearest europa barbarorum history geeks and gamers...

I have long played EB and other historical games and have now came to you geniuses to help me in a school project.
We're tasked to build a catapult style weapon that can launch objects 10m - 50m
Restrictions are a 75cm in height and width (to get in classrooms and past doors)

We of course have to build it ourselves and as such, I'm here asking if any of you can point me to any sources that can assist me.
Of course this must not be over complex as my two partners are females... (basically im doing all the work lol).

I've looked up at designs from the Warring States period, Han, Tang and others eras in china and Medieval Trebuchets and onagers.

Any help is much appreciated... oh and I'll post pics once this project is complete.

Tim!

:')

[FriendlyFire]

If you can afford $20, I'd buy a catapult or trebuchet kit (e.g. this one from ThinkGeek, you could probably also find it in a good toy/puzzle store), build it, figure out how it works, and then scale it up.

[Brennus]

FriendlyFire's suggestion is probably the easiest way to go about it. I would personally recommend a trebuchet type system as a counter-weight means of proppelling projectiles is easier to construct than a torsion relaint system like a catapult or onager. When I was about 7 i constructed a trebuchet out of cereal boxes, it was only about 30cm high but I could launch projectiles about half a metre with it.

Are there limitations on what materials you are allowed to use?

[teh1337tim]

No restrictions on materials other than no kits...

Good suggestion. Ill think about that ... thanks

[-42-]

I was forced to build a cardboard trebuchet last year as a physics assignment (It ended up throwing about 10 meters). I would recommend a trebuchet of some sort (torsion based is a pain to do) and make sure that you have a free hanging weight, sling, and wheels, all of which improve range. I would recommend plywood of some sort, just be sure to reinforce as needed.

[Conradus]

A friend of mine built a catapult about 10 years ago, when he was just in high school.
It looked fairly much like a trebuchet, but in stead of counterweight he just used a elastic (like the one you use to bind things on your bike) to shoot. So you pulled back the arm, put an acorn of whatever in it and released. It managed 10 m for sure.

[Tanit]

Could always build a Gatrophetes, that could fit the size requirement and still be life sized. And it was a siege weapon.

[vartan]

Of course this must not be over complex as my two partners are females... (basically im doing all the work lol).

Unacceptable.

On a more lighter note, will you possibly be making any video(s) of the device in action?

[Maeran]

found this

http://hila.webcentre.ca/projects/trebuchet/index.htm

Or an onager using bungee cord (as suggested by Conradus) would be good. I found the trebuchet when I was looking for videos from Scrapheap Challenge, when one team went for a trebuchet and the other made an onager. The onager won on range because the trebuchet team had reliability problems with their build.

Yes, a gastraphetes would be great, but I imagine there would be problems getting the tension. Plus the teachers might not believe it's not just a crossbow.

[Cute Wolf]

[vartan]

Might want to provide a source Cute Wolf.

[Ca Putt]

In Highschool I once built a small catapult(about one Span in length 25 span range :) ) tho I cheated, as it was not torsion propelled but relied on a elasticstrap(similar the aforementioned bike thingies but just 3 mm in diameter). lucky me that it actually wasn't a history assignment but a voluntary project for arts and crafts otherwise I'd have to "make it torsion".
from my experience the basics of an onager are WAY more simple and easy to produce than those of a tribuchet but you got the problem with the twisted ropes, the trebuchet needs some weight and angle callibration which is about as annoying(judging from building dozens of LEGO trebuchets :D )

[bovi]

If ThinkGeek's offering is not to your taste, there is also Catapult Kits.

Edit: Oops, saw now no kits, sorry.

[Rhilanth]

I had to build one once for a physics class. I wouldn't recommend what my partner and I did though, but it was definitely fun. We obtained a large drum that was used to block off parts of the road from a junkyard and cut it in half to fill it with water. We took a gift certificate to menards and got a few strong metal pipes and some boards, and then, proudly refusing to use math or calculations whatsoever we created a 7.5 foot trebuchet that could launch things almost a football field away. We usually fired pop cans, as a tennis ball would just get caught in the winds.

We hauled it to school on the back of a boat trailer and set it up. We fired a pop can, but it flew off the trebuchet backwards and landed on top of the 3 story school. It was probably one of the most fun creations we've ever made. We also did it without spending any money.

However, we got a C, because the assignment was very similar to yours. We just wanted to build a massive one for the hell of it. Nonetheless it was pretty impressive as it did shoot forward a few times as well, though using a tennis ball it only ended up flying up into the air at a high arc, getting caught by the wind, and then flying back into the teacher's parking lot.

Nontheless, it was great fun and I still remember making it, unlike many other things from physics.

[Ca Putt]

@Rhilanth: that really makes me want to have closer connections to Metalworkers and Junkjard owners (I actually don't even know where "our" Junkyard is :D )

[teh1337tim]

i've assembled the needed wood and rope and metal pieces... now only to get the calculations in order to proportionally size everything...

Its not due till jan 3 but im planning to begin building this thanksgiving weekend after we size everything proportionally...

Then lots of calculations regarding whatever is applicable.

Fun times.