Thanks.

Cool! Today we started building the trebuchet, but the model is definately scaled down. I have a question about the formula for mass ratio and beam ratio concerning Phssthpok's Rule ( MR = 20*BR)

Can we use that equation to determine the arm ratio for the FAKA? (1.5k/4g = 20 * BR) or is the FAKA's arm ratio fixed?

I assume you mean 1.5 kg/40g. Anyway, you are looking at a mass ratio a tiny bit higher than K'nex FAKA, and much lower than GBB's max. GBB's 1:4 arm ratio seems to work through a very wide range, 50:1 to 150:1. I would recommend something between 3:1 and 4:1. Maybe 3.7 or so, but really with an FAKA, it does not need to be too precise. I'm guessing that anywhere from about 2:1 to 5:1 would actually work well.

Can we use that equation to determine the arm ratio for the FAKA? (1.5kg/40g = 20 * BR) or is the FAKA's arm ratio fixed?

Based on the rules, I think you will have to consider the whole hanger as the CW, so take that into account. A FET is the same as an FAT without the vertical CW guides. To keep the axle from derailing, you need some rollers like on an FAKA.

Because you seem to have some experience with F-series trebs, you can probably just go straight for the FAKA.

Good luck! I'm glad my site has been of some use.

Based on the state Director's Interpretation, the arm cannot roll off of a wheel not attached to it, such as the F2k Series. This rule was added because we used an F2K design, which was totally unexpected. (Most people there had the traditional trebuchet design, therefore we were scoring way higher than they could of.) They then disqualified us on the spot and we went home sad. Determined to build a trebuchet with great efficiency, we build a FAT and took State. We now qualify for nationals, and have been searching around for a better trebuchet design.

I like your idea of an FET, but I haven't found any pictures or information on how to build it. I'm assuming that it has the basic frame that of a FAKA, and the arm contains no special moving parts but the horizontal moving wheels at the pivot. Please Correct me if I'm wrong.

Thanks again for helping us, we enjoy your site and we find it very useful. We'll be sure to advertise it at the competition and help it grow.

14. The rotating arm must include its own pivot point. External pivot points are prohibited. There mustonly be one pivot point.

Anyway, if you haven't built trebuchets before, I strongly advise you don't build an FAKA. They are one of the most complex designs, and require video analysis and extensive tuning experience to get to work to their potential. That said, if you have lots of time, an FAKA might be an ok choice. Based on the rules, a floating-arm-trebuchet-fat a great choice. I would actually go for the floating-everything-trebuchet-fet. If that goes well, you can convert it into an FAKA (well, just make an FAKA arm for it so you can use which ever works better). An FET is basically an FAKA without most of the hard parts (complex tuning, and multiple triggers), and still gives great performance. I would put a lot of emphasis on keeping the arm very light, and even more emphasis on tuning it well.

I think you should find sufficient trigger details on king-arthur-ka. Make sure to look at the large version of the images. Once you understand what the triggers need to do, the designing is up to you, but my pictures provide some examples.

We are also looking at other suggestions at trebuchets. (F2K Series disqualified)

Thanks!