Floating Arm Trebuchet

DocBrown · 08 Jul 2012

Thorsen said:

boohbah said:

unfortunately lordbob is no longer with us , he suffered a fatal blow to the temple from a golf ball.

That was spot on. Thanks boohbah for that....

Sure cracked me up, today

boohbah · 09 Jul 2012

best medicine...

SpunkyMonkey · 11 Jul 2012

Lordbob75 said:

I think forgot about this forum is a more accurate description of my life atm, but I have been hellishly busy.

I built that thing like 3 years ago and have since moved (it's residing in my parents garage atm), so I have no pictures of it.

It was rather small and unexciting anyways, and I never did get the wheels fixed correctly on it (never found a good axel).

Sorry about that, but good luck with your site. One of these days I might have to actually build a good one and launch flaming pumpkins with it.

Thanks for getting back. Busy sucks but I hope that busy is good too. Site is doing well. We've been able to answer a lot of questions and gotten great feedback and ideas. Mostly from students in various science/physics classes. Just as long as they don't ask me math questions.

Lordbob75 · 07 Apr 2013

SpunkyMonkey said:

Thanks for getting back. Busy sucks but I hope that busy is good too. Site is doing well. We've been able to answer a lot of questions and gotten great feedback and ideas. Mostly from students in various science/physics classes. Just as long as they don't ask me math questions.

If you are still around I can look into digging up the math on it. It's not super difficult. The entire build is really built off the ratio of weight and arm length, from there everything else is just scaled to that.

Basically you pick out what sized objects you want to throw, as well as their weight. Then you have to do some physics to figure out the arm ratio (simple lever) and weight needed. I remember reading that the counter weight needed to be about 8x heavier than the payload, but I think mine needed more weight than that.

Keep in mind as well that a FAT has weights on both sides. It also wouldn't hurt to use something that you can add or remove weight from, such as a bucket with a lid. For weight, it depends how much you need, but good choices would be water (hard to work with, but is a good weight), rocks, or steel ball bearings.

I know for the Pumpkin Chunkin someone built a FAT that used engine blocks for weights (one on each side). The FAT was like 25ft tall and threw a pretty big pumpkin.

SpunkyMonkey · 07 Apr 2013

Lordbob75 said:

If you are still around I can look into digging up the math on it. It's not super difficult. The entire build is really built off the ratio of weight and arm length, from there everything else is just scaled to that.

I'm still around... lurking. No need to look up the math, and thanks for getting back. I just figured if you had pictures and links to your site I'd put them on our trebuchet site. Our next thing on the site is putting out a cut list out there for people that want more detailed instructions or have trouble deriving material needs from the sketchup cad. We are also going to move it from the howtopool subdomain to the brightcraft.com domain. I know lots of people that do weird crap. Making chainmail, primitive blacksmithing, electronics (old school and new), etc... Like with the blacksmithing it is an old uncle of mine and he makes awesome stuff. I'd like to see this stuff documented before the people that do it are planted.

The treb has been pulled apart, measured, and put back together. Now I just need to put it in an intelligent format for another page on the site. We've gotten hundreds of emails (questions), but nobody seems to follow up with what they derived from ours. Kind of a bummer because I'd like to see what they came out with.