Help needed building an onager

[Robert]

Wow, that does look great! And very believable, too. The main challenge will be making the drum. I am thinking of attaching the rachet to the outside, with part of the axle protruding through the frame. Making that square and cladding in iron sheet will allow the ratchet to be slippen on and removerd with ease, also limiting wear on the axle.

You position at rest is not straight up, which will allow some pre-tensioning with the washers, too. That was a point which was bothering me, as there is no way of putting in some initial torsion if the arm is to be upright in rest.