[pianotech] capstain/wippen angle

[David Ilvedson]

Which piano has the rolling knuckle?

David Ilvedson, RPT
Pacifica, CA  94044

----- Original message ----------------------------------------
From: "Richard Brekne" <ricb at pianostemmer.no>
To: pianotech at ptg.org
Received: 3/16/2009 10:45:50 AM
Subject: Re: [pianotech] capstain/wippen angle


>Hi Mike !

>THIS was the clue I needed...  Yes I understand the roller capstan then 
>would move closer to the whippen center if it started below the magic 
>line, then get farther away as it passes. Now I just have to think a bit 
>on how the whippen heel is moving through this.  Any given point on the 
>heel is not going to change distance from the whippen center through the 
>key stroke. So as the key raises towards the magic line, the roller 
>capstan would roll towards the whippen center as its distance from the 
>center decreased. Then at the magic line it would cease rolling and be 
>as close to the whippen center as possible, continuing upwards it would 
>reverse direction and begin to roll the opposite direction... away from 
>the whippen center... Almost like a pendulum motion if the starting 
>point was just as below the magic line as the ending point is above. 

>So..... how does an angled capstan that does'nt roll at all counter this 
>tendency... I can see I am going to have to re-read these posts and do 
>some thinking on it :)

>Sorry bout the misquote... I'm sure Dale is ok with it.
>Cheers and Thanks
>RicB


>    Ric,
>    I wish I had reasoned out the quote you attribute to me - but it
>    belongs  to Dale Erwin.  I hope he won't mind if I attempt to answer
>    your  question.  Whether it ends up closer or further away depends
>    on where,  in relation to the magic line, the motion occurs.  For
>    example, if you start below the magic line and end an equal distance
>    above it, the roller will move towards the wippen center until you
>    reach the magic line, then move away, ending up right where it
>    started.  The "best a tilted capstain could achieve" would depend on
>    how wide the capstain is.

>    Mike

>        Richard Brekne wrote:
>        Been trying to visualize this a bit and have the following to
>        ask you  all about.

>        Consider a capstan that was a brass roller instead of what we
>        have  today. So that as the key move and the capstan raises the
>        whippen this  brass roller simply rolls along the underside of
>        the heal.  Wouldn't  this result in the roller-capstan starting
>        off further back on the  heal (closer to the whippen flange)
>        then it ends up ? I.e. the  opposite of this increasing leverage
>        concept ?  And if that is the  case.... then wouldn't it be more
>        likely that the best a tilted  standard capstan could achieve is
>        to more or less compensate for that ?
>        Cheers
>         RicB