[pianotech] capstain/wippen angle, was: key position at rest

[A440A at aol.com]

MIKE writes:
   As the capstan/wippen moves thru its
> rotation the capstan moves upwards & rotates to the middle of the
> capstan & then to the rear edge. SO, as it continues thru its arc, the
> point at which the wippen is lifted moves to the rear edge of the
> capstan & closer to the wippen pin thereby accelerating the key/action
> motion. Kind of an automatic transmission affect.Things move faster
> without shifting.<
> 
      Other things being equal, the action ratio is determined by where on 
the whippen the capstan is at any moment.   It is difficult to have the same 
ratio at the beginning of the key stroke as is obtained at the end. If the 
at-rest position has the contact at the magic line, the ratio will decrease 
throughout the stroke.   If the contact reaches the magic line at the halfway point, 
the ratio will increase up to that point and then decrease during the last 
half. This is because as soon as the contact point passes the "magic line", the 
action ratio begins to decrease, since the contact point begins moving   away 
from the whippen center.   
     I find the best response is to be had when the contact point reaches the 
magic line at let-off. What is happening in this configuration is that as the 
key begins to move, the beginning ratio is at its lowest; a "first gear" if 
you will, and the point of maximum ratio occurs when the hammer is at its 
maximum acceleration, (highest gear).
     I think we want the minimum friction to occur at the moment of fastest 
motion of the key, and the rising rate produces this.   If the ratio "falls 
off" during the last half of the stroke, it is working against acceleration of 
the action by the key, which means a fall-off of acceleration relative to the 
speed of the key.   

regards, 


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



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