Let's call this a prototype. I've wanted to make myself a catapult or more precisely a trebuchet since I watched a show on PBS when I was a kid. The idea that an elevated weight could be used to propel large stones at a castle was incredibly intriguing. I got even more interested when I found out that there is an annual pumpkin tossing competition that has a trebuchet category. The opportunity arose for me to make one myself when my son decided he wanted to do a medieval themed birthday party. We had also just recently painted our fence and taken down an old playhouse in the back yard. I had everything I needed. I won't go into the details of angles and dimensions as there are plenty of more detailed resources online. I effectively started with the length of the arm and all dimensions were ratios from there. When I started I was too impatient to figure out the exact ratios so I made it 'adjustable'. I learned later on in the process that the ideal dimensions are fairly consistent as you scale up and down so I didn't really experiment with any of the other settings.
Since I only had three days to put this together and the goal was to use it in a party game it's far from perfectly tuned. I managed to get it to toss a tennis ball about 100 feet. With a larger weight I think I could have tuned it to a distance closer to a soccer field. The only real trouble I had with it was figuring out how to 'release' at the right time. This is the only adjustable piece that I did take advantage of. I put a ring on the end of the string and hooked it on a nail. I adjusted the angle of the nail until it released perfectly. The other not so obvious piece was how to arm the ball in the sling. I started with the leather pouch horizontal but quickly realized vertical was the right way to go because it would release and get out of the way.
This was a fun project. Now I'm ready to build a pumpkin tossing version.
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