Ray,L can you post a photo of the gas springs you mounted on the knee? Id like to see exactly where you put them.
I have continued to work with my new AC servo on the knee. I have run it up and down very smoothly many times, but every once in a while it will hang and fault the motor going DOWN. I have also heard a bit of a growl, or chatter going down. I suspect I have a gib problem. I think it may be shifting slightly and acting as a wedge.
Eliminating the gears and driving the screw directly works very well. The crank shaft came out through the side in a bolt on casting, so I simply removed that and have a nice access hole into the knee. I was able to get the motor inside the knee casting. with a short belt to the screw. Mechanically it looks very neat, almost like it was designed that way.