1/2 punching

[David Ilvedson]

Ric,

I'm looking for the Bechstein action spread...Renner action, 9fter

David Ilvedson, RPT
Pacifica, CA  94044


----- Original message ----------------------------------------
From: "Ric Brekne" <ricbrek at broadpark.no>
To: pianotech at ptg.org
Received: 8/5/2006 3:41:23 PM
Subject: 1/2 punching


>I'll tell you what I'd try there David.  Instead of starting right off 
>by repositioning capstans,  I'd simply take strips of flange paper, say 
>0.2 to 0.3 mm thick and place them under all punchings tight up to the 
>back side of the balance rail pins. One strip should be good for most of 
>each section on a grand.  See if this does it for you. Essentially its 
>the same thing as what David Stanwood describes with his <<ratio shim>> 
>except that you are simply installing for the entire piano.  Should drop 
>the Balance Weight Ratio... or Strike Weight ratio if you prefer by 
>around 0.5 +/- a hair.  As David states, the problem of chucking doesnt 
>turn up.

>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.  Looks quite doable really.  
>The standard punching actually does this to some degree... tho key to 
>key variance in this performance is quite large.  Defining front and 
>back fulcrum points more precisely lets you have all the weight 
>advantage benifits of the back half punchings and at the same time all 
>the travel (distance) benifits of front half punchings.

>Cheers
>RicB
>------------
>Well, that's what I have on this Bechstein E...strikeweight of 6.0...the 
>veneer shim sounds better...so the problem is the key leverage?   The KR 
>averages .52...I would have to move the capstans to improve it otherwise?

>David Ilvedson, RPT
>Pacifica, CA  94044