Yes, friction is a very important and very fussed-over detail when regulating or rebuilding actions, and for the very reasons you state; there is indeed a sweet spot.
In this specific case, I don't think variations in weight added to the key would change friction much as the majority of the...
They are all standard. I do a lot of piano rebuilding and wind up re-weighting of keys. Its a pretty standard model.... weight at one end, finger presses at the other, lead weights installed somewhere between where the finger presses and the fulcrum. In the bass section this always means...
Moving the mass towards the fulcrum means adding more mass to achieve the same force to move the key. Does this not balance out the increased MOI of 'less weight further from the fulcrum'?
I am trying to determine tradeoffs in how piano keys are weighted. Piano hammer weight and the behavior of the mechanical parts in a piano action yields a spread of roughly 5:1 in leverage - every gram of weight added to the hammer adds roughly five grams at the key. Piano keys (the wooden...