Trebuchet of the large variety (a work in progress), 4.28.07 update

Step 7 Current questions

A list of things that need to be resolved (I'd love to hear your thoughts!):

(1) The main support pieces need to have an axle hole drilled clean through them. I'm not sure how to do this precisely enough such that the axle is level when in it's in place. The difficult comes from the fact that pieces are bolted together and have a little bit of give. The wobbling of the pieces is very slight and may be insignificant...I'm really not sure.

(2) A good counterweight material is needed. High density is a must but something that comes in manageable pieces is also important. I've done concrete blocks before and it worked alright--would adding metal to the concrete mix be beneficial?

(3) Wheels, how do I get strong removable ones? I'd rather not purchase them because I bet they'd be expensive. A trip to the scrapyard is probably in order. Other ideas?

(4) Arm ratios!? (This is the ratio of the throwing arms long end to it's short end; the ends are split by the axle's position). What's the advantage of a large ratio (5.5:1) vs a small one (2.5:1)?

Comments

[spaten0]

Um what is a good counter wieght if ur in the woods find a downed tree and cut it up the logs will be heavy lol

[ace117]

the longer the arm with the counterweight is the slower the trebuchet will swing, for adjustable range I would make several attachment holes and then test it to see what the range is, the further from the fulcrum you go, the less range you get in the end. if you don't understand this tell me and I will explain in further detail.

[aalva93]

id like to know how this goes im doing a physics project with some friends and this would help alot

[willy_Nilly]

Found this and played with it a little. Looks cool. I suppose it's accurate. I hope this helps. Keep up the good work!!!

http://www.algobeautytreb.com/

[surfreak]

I haven't built anything huge (mostly small, efficient ones for competition), but these sites have a LOT of good info:

http://www.ripcord.ws/
http://www.siege-engine.com/Chapter.Engineering.shtml
http://www.siege-engine.com/Chapter.EnginesOfWar.shtml

Metal to concrete blocks could work, as long as the metal is denser than the concrete (which shouln't be hard). Old lead tire weights from a tire shop should be free and work well. You might be able to get away with old tires for the wheels if you built a support for the inside. Wood circles or large oil drums/cans to support the rubber? Just throwing out ideas here.

On the axle, it doesn't have to be perfect. The looser it is the farther it'll throw (less friction). But the tighter it is, the more precise the machine will be (read: accurate). If the axle is a litle crooked it won't really affect it. You can compensate by angling the throwing arm hole if it gets to be an issue.

But I'd definitely say that a massive Floating Arm Trebuchet is in order. Those things rule. I built one for competition that used 1/2 the cw and was 3/4 the size of an older, "standard" treb, and it threw twice as far. Definitely check out the ripcord site, though. Ridiculous amount of information and treb theory.