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Trebuchet range?

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Trebuchet range?

Unread postAuthor: paaiyan » Thu Dec 20, 2007 10:30 am

SO I'm going to try my hardest to actually work on and finish my trebuchet over Christmas break. It's going to be about 16 feet high with the arm up, 12 foot throwing arm. The arm is going to have a 3:1 ratio, which is what my research tells me is most optimum. Hinged counterweight, no less than 500 pounds. I'm probably going to throw objects between 5 and 15 pounds. The sling will also be about 9 feet long as I've read that you want the sling to be directly under the axle when loaded. I'm going to tune the release peg for a 45 degree release angle.

What I need to know is, does anyone here know enough about trecuchets, or enough about physics to be able to tell me what my range might be?

For now my friend and I are dubbing it Shenanigans, but if it exceeds our expectations by a lot and shoots past a predetermined distance, we're painting it pink and calling it the Fairy Flyer. I'll be sure to post pictures when it's done.
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Unread postAuthor: Ragnarok » Thu Dec 20, 2007 10:41 am

An estimate can almost be made from those numbers, but the initial angle of the arm before triggering also needs to be known, as well as the weight of the arm - assuming it's of constant sectional mass. If it's not, that complicated things and adds more variables.

I'd recommend a slightly lower release angle. It'll launch slightly faster, and with drag, the ideal launcher angle drops slightly under 45<sup>o</sup>. Actually, that can be calculated too if you want.
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Unread postAuthor: paaiyan » Thu Dec 20, 2007 11:05 am

Well I don't really know the initial angle honestly. But I did just discover a program that estimates my range. It's telling me that if I use a propped counterweight, I can pull around 1000 feet, which friggin rocks. But I may have to modify my plans to account for that prop.
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Unread postAuthor: MaxuS » Thu Dec 20, 2007 12:46 pm

What are you planning on making all of this from?
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Unread postAuthor: jackssmirkingrevenge » Thu Dec 20, 2007 12:54 pm

Hinged counterweight, no less than 500 pounds.


That's heavier than a 55 gallon drum full of water, I can understand MaxuS' query above.
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Unread postAuthor: paaiyan » Thu Dec 20, 2007 5:41 pm

Most of the frame is 4x4's, and the throwing arm is a 6x4 if I remember correctly. I'm still unsure about the axle. I have some 2" square steel tubing that I don't know if I can use. I know how to rig it to use as the axle, but I don't know if it can hold the weight.

EDIT: And for the actual hinge, I've got a half inch bolt that's going to go through to 4x6 and be supported on either side by steel plates screwed into the 4x6, it'll be sturdy.
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Unread postAuthor: rna_duelers » Thu Dec 20, 2007 6:09 pm

Use some wheels to counter the shock,other wise the whole thing could flip or destroy itself after a few shots.

And are those sizes of timber going to be pine?You should steer towards a hardwood.
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Unread postAuthor: paaiyan » Thu Dec 20, 2007 6:57 pm

I don't really know what the timber is. And wheels aren't an option.
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Unread postAuthor: rna_duelers » Thu Dec 20, 2007 7:06 pm

Then how do you plan to move it?I had a small trebuchet that way maybe about a meter high or so and it would every now and then shoot out the back,so look out which way you have it facing in both directions.
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Unread postAuthor: paaiyan » Thu Dec 20, 2007 7:46 pm

I'm building it that it can be disassembled for storage. I live in the burbs, and a 16 foot trebuchet in my backyard might draw unwanted attention. Everything will be securely bolted together on-site.

EDIT: As for having a smaller trebuchet, go big or go home.
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Unread postAuthor: boilingleadbath » Thu Dec 20, 2007 8:03 pm

You realize that a trebuchet of that size will have peak axle loads of a few tons, correct?

As far as all the rest of your figuring goes, check out <a href="http://www.ripcord.ws/atreb/atreb.html"><b>atreb</b></a>.
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Unread postAuthor: paaiyan » Thu Dec 20, 2007 8:16 pm

What do you mean peak axle load? The greatest force exerted on it at some point, or the most weght I can use?

EDIT: The counterweight limit on the free version of A-Treb is 40 pounds, considerably less than what I'm using. And it costs 20 bucks to buy.
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Unread postAuthor: Tom Hogan » Thu Dec 20, 2007 9:26 pm

I built a floating arm trebuchet last year for a competition. It had top fit in a 60cm by 100cm box. With a 3km counter weight it could throw a golf ball 33 meters with 1ft by 1ft accuracy. I may be able to post pics sometime.
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Unread postAuthor: paaiyan » Thu Dec 20, 2007 9:56 pm

Tom Hogan wrote:With a 3km counter weight it could throw a golf ball 33 meters with 1ft by 1ft accuracy.


Wow, that's a long counterweight.
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Unread postAuthor: DYI » Thu Dec 20, 2007 10:06 pm

I think he meant 3kg... :lol:
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