The advantage of servos is that they can provide constant torque preloading, allowing the preload to be kept low (otherwise, the servo will overheat) but still sufficient.
A spring might also be an option if designed properly. I’ll probably give it a try in July.
You can use a spring with long travel and low K (like a very soft torsional spring, preloaded several turns, or a spring connected by a wire to a drum on the joint) to reduce the change in torque across the range, if that helps?
A spring might also be an option if designed properly. I’ll probably give it a try in July.