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bigbangtheory wrote:Ok, I've read the Wiki article about this and it didn't clarify this..? I get the difference between a FAT and a hinged counter weight but everyone seems to favor a the FAT, what makes it the more favored trebuchet? Is it more accurate? I' m debating between the two for the event and don't know which one would work better.

Having built both a FAT and a traditional treb with a propped counterweight I can say a properly built FAT will come out the winner.
The FAT allows the weight to drop vertically and converts more of it's energy into moving the arm.
Now, the key is building the best possible machine. (by minimizing weight, choosing the correct arm and sling lengths, and finding the best settings though practice and trials).

Just to follow up on what wlsguy said, FAT definitely are favored for a reason. When built properly, FATs will achieve farther distances than other designs. Speaking from my experiences, even a somewhat poorly built FAT will rank higher than a hinged CW treb built than I higher quality hinged treb (at least at my regional). Another thing from my experience, here were something like 6 FATs at Indiana state last year and from what I know those six were ranked 1-6. No doubt there were some desently built hinged counterweights that day that even the worst FAT outperformed.

Thanks, that's really helpful.

bigbangtheory wrote:Thanks, that's really helpful.

If you weren't already convinced;

I ran some simulations of a traditional treb with a propped counterweight. This issue becomes the length. When the cw is propped, it maked the entire machine longer by 15cm.
This directly affects the length of the long and short arms and reduces them accordingly to stay within the 65cm limit. This arm reduction reduces the throwing distance by more than the prop adds.

The FAT does not have this issue.

bigbangtheory wrote:So, I'm looking at the rules and it says my counterwieght must be contained in a 15cm BOX. I was going to use like a little pouch made out of leather, why does it have to be a box? Frustrations....

The 15cm box is the max size of the Counterweight. This is to give you the needed information for planning your design (so it doesn't hit the bottom when the arm goes through a launch motion). You need to plan for a counterweight with a hook and attach some sort of ring, hole, etc to attach the counterweight.

Wheels might make it easier to move but also provide for unintended variation. It's only a 65cm cube. just build it heavy enough to stay put but light enough to pick up. We have used drawer liner (the stuff that keeps silverware from moving around in your kitchen) glued to the bottom to provide a surface that doesn't move on gym floors.

Finally, the pouch string length is dependant upon each trebuchet. A little change (25mm) makes a big difference. Start by making it the same as the long side of your arm and adjust from there.

Thank you! This event is a whole lot more complicated then it sounds at first.

ok i was wondering, when you launch the projectile, do you have to get it to stay in the box or can it bounce out???