You don't want to be on the business end of this thing.
Problem: We have tennis balls and ice balls just sitting here.
Tools: Research, trial and error, wood, bricks, vinyl.
This was a post grad school project.
I promised myself that if I finished grad school, I was going to build a trebuchet. This ended up being a really nice quarantine project for my son and me. It's powered by four bricks (I started with two bricks, but that wasn't nearly enough power).
It's not really a UX project, although it did require a fair amount of research and planning. It took some trial and error to get it right:
Gotta get more bricks.
The angle of the nail is key to getting the sling to release at the top of the the swing.
Poly-blend cloth is too floppy for the sling - vinyl gets a nice smooth release (I still want to try denim).
Gourds are too heavy, at least for four bricks. Tennis balls are ideal.
Ice balls are too slippery for the sling, so you have to wrap them in a paper towel or something to get some friction.