[NicknamedBob]

"Someday I need to dig into the reason why the counterweight is hinged..."

The counterweight is hinged because it's a bucket. Fill the bucket with rocks and you are ready to go.

With any other configuration, the rocks would spill out.

In case it hasn't been noticed, the round stone to the left in the picture is the ammunition.

[sionnsar]

Well, that much is obvious but it would probably be easier to design a fixed enclosed container that would give the trebuchet rather more leverage, especially at the beginning of the launch.

[ASA Vet]

That model has a 300 lb throw weight. More than enough to provide flight flights home to most illegal invaders.

[rottndog]

There’s another reason the counterweight is hinged...this helps to better transfer the potential energy in the weight to the kinetic energy of the projectile. Also, a proper trebuchet is mounted on wheels, as the rolling motion during the swing action of the arm also better transfers energy to the projectile.

I’m not an expert...I just saw a show on PBS, where they actually built one to a medieval drawing, and gradually figured out what worked best.