It's sort of a trebuchet and a catapult smashed together.
The swinging counterweight. I hinged it just like the real life ones. It really works.
I kept the breakaway mechanism and the catapult bucket because I simply could not think of another angle.
I made it large and beefy and without wheels as if it had been built at the site of the seige.
So when you break the chain away the counterweight swings down like this...
The bucket comes up like this, and flings the brick considerably farther than my other catapult.
Either that or it breaks apart like so. The arms are too long and even after reinforcing it with technic pins it's still quite fragile.