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

[David Love]

I think I would argue that the point of finest control is not escapement but
the initiation of the key stroke.  The friction in escapement itself must be
so much greater than any capstan friction that I can't imagine how this
might make a difference.  While friction's effect might increase with speed,
speed and momentum also mitigate the effects of friction.  This is made
quite obvious when weighing off an action and having to tap the regulation
table to initiate breakaway.  As you mention, however, the difference in
measureable friction is probably so small that it's really of no
consequence.  The most efficient system, to me, would be lowest friction and
the lowest ratio at the outset of the stroke.  Thus the initiation of the
stroke would be the smoothest and as the leverage and friction increased
speed and momentum would compensate.  The increasing ratio at the end of the
stroke would, I suppose, facilitate power (though I think whatever power
you've delivered to the system is probably not influenced that late in the
key stroke) but more would facilitate soft playing by ensuring that the rate
of acceleration was still increasing.  It's all a bit theoretical though and
while you might be able to calculate differences I wonder if you can really
tell in practice.  

David Love
www.davidlovepianos.com

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of A440A at aol.com
Sent: Monday, March 16, 2009 6:46 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] capstain/wippen angle, was: key position at rest

David writes:

<< Why wouldn't you want the minimum friction to occur the slowest rising
rate
of the key, the beginning of the stroke?  The momemtum of the key will
compensate for increasing friction later in the stroke.   >>

      Two reasons: I think it best to have the least amount of friction and 
maximum ratio at the point of finest control, (escapement).  The zero
friction 
at this point assists control at ppp and the higher ratio provides maximum 
power at FFF.  Reaching the the magic line at let-off provides this.
    The difference between maximum friction occuring at the beginning of the

stroke or half way to the magic line is not measurable, but the difference
in 
ratio is.  So, why create a fall-off in the acceleration to avoid an 
immeasurable change of friction?
    I think friction's effect increases with speed, thus, placing it at the 
lowest speed in the event will minimize its effect.  At this point, the
major 
resistance is the inertia of the action parts. If the magic line is reached
at 
let-off, what we have is friction decreasing and the ratio increasing 
throughout the stroke. 
    Splitting the path on either side of the magic line creates a situation 
where friction begins to increase  and the ratio decrease as we reach
let-off. 
This can't be good. 
  
      The same concept of steadily increasing ratio can be seen in the 
original idea behind Steinway's accelerated action; with the half-round
slightly 
off-set proximally, the key ratio increased as the key was depressed, due to
the 
fulcrum effectively moving towards the performer. In later production, the 
half-rounds appear to be drilled in the middle, thus negating the effect. 
Regards,

Ed Foote RPT 
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html
 <BR><BR><BR>**************<BR>A Good Credit Score is 700 or Above. See
yours 
in just 2 easy steps! 
(http://pr.atwola.com/promoclk/100126575x1220439616x1201372437/aol?redir=htt
p:%2F%2Fwww.freecreditreport.com%2Fpm%2Fdefault.aspx%3Fsc%
3D668072%26hmpgID%3D62%26bcd%3DfebemailfooterNO62)</HTML>