Yet another experimental key, I'm trying another key with open ended moving weights, this time the energy stored in two small flywheels attached to the axle of a pivot bearing,  the bearing holders are slotted into a stand and the flywheels also act as bearing tighteners , the main arm is now fitted and the contact post, I have used Neo disk magnets in repulsion mode as a tensioner with a spring loaded adjuster which is nice and smooth just the contacts to fit and a clean and polish and its done, it has an exceptional feel to the action very precise yet not to hard as I'd hoped by using the thinner leaf knob mounting, the flywheels seem to give a big key feel to a short stubby key, its turning out to be a real one of YUH special :)))