jack hitting h.flange

Jon Page jonpage@attbi.com
Tue Aug 20 08:23 MDT 2002


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At 08:33 AM 8/20/2002 -0500, you wrote:
>List,
>
>One solution for this is to install thicker jack stop felt in the 
>repetition window.
>
>I discussed this problem with Eric Schandel from Steinway, and this was a 
>suggestion he offered. He had no explanation why some clicked and others 
>didn t.
>
>We were able to do this and had success with it.
>
>Sincerely,
>Gary Mushlin, RPT

Ultimately, the reason for this is that the key is driving the wippen 
through too great a distance.
Knuckle radius has a very minor affect on this, Key Ration is the 
culprit.  You need to move the
capstans forwards to have the action regulate optimally. What you have is 
too much after touch.

You can fudge the faults to attenuate the symptoms by increasing hammer 
blow and/or decreasing dip.
But for a given set of parameters (Key Height, Dip, knuckle radius, Hammer 
blow, hammer length), there is an optimal KR
which produces minimal after touch, that is for the jack to just clear the 
knuckle at full dip. Sometimes the wippen heel needs
to be relocated as well to maintain the cushion over the relocated capstan.

Jon Page
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