Building a Trebuchet

[jenarelJAM]

So, at my college we've got this amazing day in the spring where we beat each other over the head with noodles. It's called the Epic Quad Battle.
See here: http://www.youtube.com/watch?v=K3Hpnqqowj8
<object width="425" height="355"><param name="movie" value="http://www.youtube.com/v/K3Hpnqqowj8&hl=en"></param><param name="wmode" value="transparent"></param><embed src="http://www.youtube.com/v/K3Hpnqqowj8&hl=en" type="application/x-shockwave-flash" wmode="transparent" width="425" height="355"></embed></object>

So, my friends and I have a mere 2 1/2 months to get ready. Supposedly we're allowed any water weapon but a super-soaker, so for this year's Epic Quad Battle, we want to build a trebuchet and shoot... water. Not water balloons. That's the problem. We're planning on building this to shoot objects a couple hundred feet (depending on the weight used, which will be variable). To throw it that far, we'd need to put a lot of energy into throwing it, energy that would then be transfered into whoever it hit in the form of pain. Ouch

So that's not our goal. I come to the amazing collective mind of AO to think of an alternate source of ammunition. The goal is to get people wet, without hurting them. We haven't built the trebuchet yet (in the design phase right now), so other ideas are possible (for instance, shooting a lot of tiny water-filled projectiles at once, covering a broader area).
No, we're not going to use paintballs...


Here's where we are so far. Cross bracing will be added when we calculate the lengths of the weight arm and sling arm so we can account for clearances. As of now, the trebuchet stands 3'1" tall (1" for the plywood), 4' long, and we're thinking the sling arm will extend about 4' back from the hinge. It will be made from 2x4, plywood, and screws. We're looking into a metal bar for the hinge itself.

<a href="http://s43.photobucket.com/albums/e383/jenarelJAM/?action=view&current=Trebuchetpic.jpg" target="_blank"><img width=33% src="http://i43.photobucket.com/albums/e383/jenarelJAM/Trebuchetpic.jpg" border="0" alt="Photobucket"></a>

Oh, and I can get my hands on almost any tool I will need (chop saw, table saw, power drill, roto-hammer, mill, lathe, etc), so figure we can build almost anything.

So, any advice on what we can use to effectively bomb the masses at this year's Epic Quad Battle?

[Indignant]

the epic quad battle is so great. my friend's brother goes to davis and showed us some of his stuff

[jenarelJAM]

I should add that we're planning on putting up to 160 lbs of weights on it, which means we can throw up to ~16 lbs of projectiles. At another time (not the EQB), we'll probably test it with a bowling ball

[ahellers]

condoms?

t

[jenarelJAM]

We thought of it, but more as a prank than anything else. After all, condoms are designed *not* to break

An update on the design:

<a href="http://s43.photobucket.com/albums/e383/jenarelJAM/?action=view&current=trebuchet.jpg" target="_blank"><img width=50% src="http://i43.photobucket.com/albums/e383/jenarelJAM/trebuchet.jpg" border="0" alt="Photobucket"></a>

[zondo]

Sponges? Easy to cut into small chunks if they're dry... although, aerodynamics may suck and they won't go too far. At the same time, that would dissipate the initial shock of energy to launch them.

Man, and to think all we did in the spring was run naked through the diag on the last day of exams...

[paintball72]

gelatin

some sort of gelatin could work. one big glob hucked into the air, it might break apart but id think that it would fly better than sponges. I've done it with my trebuchet and had a bowling ball sized globe of gelatin and it flew across a corn field and into a crowd (they all knew it was coming and were fine with it) it stayed together and splattered 15 or so people. a little more that half of the time it does break apart. but it usually still sprays them :rofl: fun stuff

[teufelhunden]

I don't know if you're going to be able to throw -anything- a couple hundred feet into a crowd of people while minimizing the risk of injury.

[jenarelJAM]

Well, for the event, we're probably going to be about 50 feet away. The trebuchet is also a project that we've been talking about for awhile, and we want to make it versatile.

[pmstc]

sodium polyacrylate.
its the stuff they use in diapers and it can absorb up to 1000 times its weight in water. im sure you can get some off ebay or something. or maybe from your chem lab.
it turns in to a sort of gel substance, depending on the ratio of water to sodium polyacrylate. I'm sure you can get it just solid enough to fling but liquid enough to splatter and get everyone wet.

[zondo]

...although with the jello it will just wash away with water instead of possibly resulting in a littering fine. You could double the amount of gelatin to make the mass more stable. This would require field testing . Also, you'd have to watch out for the bees and yellow jackets that come with every picnic.

[BiNumber3]

wet sponges can actually fly pretty far, not incredibly far but with a trebuchet perhaps far enough.

also do u plan on using a sling on it? ive build em with and without, the sling really helps if made right. (mine were of small scales tho:P)

[jenarelJAM]

Yes. The majority of the momentum for the projectile comes from the secondary arc created by the sling on the end. I haven't added it to the model because I don't know how to do rope, and we're still determining how the sling will be built.

I'll take a look at sodium polyacrylate. Does it smell? If it smells like diapers, people might get ticked...

Yeah, one of the problems with sponges is the mess. We'd have to pick them all up afterwards.

I wouldn't want to throw jello-brand jello, or anything with sugar in it. Basically "water" is allowed, but mixing it with anything might be iffy. The event will be watched and rules will be enforced.

Does anyone know where we could find something more along the lines of really really small water balloons? We're thinking of taking balloon animal balloons, filling them say, 2 inches, then squeezing it to the end, tying off the end, and cutting it off. Then we'd tie a knot in the end of the remaining balloon and repeat until the balloon has been cut into a bunch of small water balloons.

[zondo]

You could probably fill the whole thing and twist up little segments... like sausages.

[ahellers]

We thought of it, but more as a prank than anything else. After all, condoms are designed *not* to break

not if you get the ones from the mechine in the gas station bathroom... they come in colors too!

t