Arny Krueger wrote:

Nonlinearity is inherent in the action of a lever arm that pivots on the
bar and accepts a vertical force.

Ah, thank you! I was wondering how you could make the torsion bar
non-linear (I don't think you can, realistically), but of course it's
simple to build it into the linkage in the way you describe.

Thanks, Arny.

--
SteveT