Key return speed

[A440A@aol.com]

Stephen writes:

<< I'm clearly convinced that the return speed of the key is one of the most 
important features for control and repetition, but I wouldn't know how to 
improve that speed in an action otherwise well regulated.

Any thoughts ? >>

         Repetition is determined by the speed of key return, and how far it 
has to go before the jack resets under the knuckle.  The latter is determined 
by back check height.  The former is a combination of spring strength, (which 
needs not be stronger than what it takes to raise the hammer just slower than 
what you can feel in the key), how much weight there is in the key, and what 
the leverage ratio is between the whippen and key.  
    It is this last that can make a huge difference!  We cannot 
indiscriminately change the action ratio by moving the capstan closer to the balance rail 
pin without slowing the action up.  There is a maximum ratio limit before the 
inertia of the key becomes the controlling factor in its return speed. 
   A tighter balancier pinning will allow more spring strength, but if you 
get over 9 grams, it may also slow things up.  The more aftertouch there is, the 
farther the key has to go to reset, also.  
regards,  

Ed Foote RPT 
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html