What matters most ?

[A440A@aol.com]

Greetings, 

Richard asks: 
<< Whats is more important to the <<heaviness>> of the action, the inertia
of the hammer and top action, or that of the key. Or if there exists a
kind of border condition where one becomes more important then the other
and vice versa.... what is that condition ? >>
>Or if there exists a
>kind of border condition where one becomes more important then the other
>and vice versa.... what is that condition ? 

Bill answers (in part): 
The only reason to adjust key 
inertia would be in meeting the requirements of top action inertia. 
So from a design standpoint, I'd say that top action inertia is the 
one to pay attention to. Key inertia is the tail on the dog which 
wags when its's happy with the weight of the rest of the dog.

   Well, this isn't a simple subject for several reasons. The main one is 
that the final judgement is to be made by pianists, so a fluid and subjective 
slant is the foundation for all that follows.  The best we can hope for is 
generalities that apply to most. Softer hammers will be felt as "heavier" than hard 
ones, all other things being equal).  
   There are limits to how much FW can be used before the action becomes 
recalcitrant.  Excessive FW  presents inertial problems of its own, regardless of 
the BW or top action inertia.  Accelerating 50 grams of weight is a chore when 
attempting to play fast, so we can't just disregard key weight.  
   Leverage can really change the perception of heaviness, but not for both 
ppp and FFF playing.  A heavy FW might feel smooth and light when played 
slowly, but its inertial resistance goes up with the square of velocity,(I think), 
so that smooth,controllable action begins to fight back when you try to play it 
fast and loud.  
  Soooo,  the more influential component in the action might depend on the 
dynamic level under consideration.  There is a golden mean in all of this, where 
the relative weights and leverages are in an optimum relationship.  I don't 
know exactly how to define it, but like porn, I know it when I see it.  
Regards, 
Ed Foote RPT 

(Ps,  Am I the only one that thinks the best feeling action has the 
capstan/heel contact point exactly on the centerline twixt whippen flange pin and 
balance rail pin when escapement begins???????  That is sort of a troll).