1/2 punching

[David Ilvedson]

And very low friction...wippen cushions showing little wear

David Ilvedson, RPT
Pacifica, CA  94044


----- Original message ----------------------------------------
From: "David C. Stanwood" <stanwood at tiac.net>
To: pianotech at ptg.org
Received: 8/6/2006 3:53:08 AM
Subject: Re: 1/2 punching


>Ric Wrote:

>>Since all this is up, I might as well reveal (since I am an open source
>>kind of guy) that I'm working on a scheme useing center pin wire along
>>these lines to cause a clear and distinct dual ratio characteristic to
>>key travel.  Since the initial part of the key stroke benifits greatly
>>by reductions in dynamic weight, yet the last 3 mm of key travel could
>>well benifit by an increase in stack action travel for key travel, if
>>the key could be made to act as a low ratio key for the first half of
>>its travel and then act as a higher ratio key for the last half of
>>travel then both these benifits are served.

>Another blast from the historic past: Chris Robinson has a set of slides 
>showing the capstan position with the magic line overlaid on the image at 
>rest, half, and full stroke with a long ago Steinway factory installed 22 
>degree angled capstan and angled heel for what he calls the Involute gear 
>effect.  With this set up the capstan/heel contact point stays on the line 
>rather than moving up through it as with the capstan at present day 90 
>degrees with straight heels.   What's interesting in relation to the 
>present discussion is that the point of contact, while staying on the magic 
>line, actually moves front to back along the magic line.  So the ratio is 
>low to start with and higher to end with giving a sort of "wip" effect.  I 
>was very impressed when I saw this in his class.

>David Stanwood