Quote: Originally Posted by SpunkyMonkey
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.