[pianotech] regulating S&S (ex-) reproducer actions

[David Nereson]

----- Original Message ----- 
From: <pmc033 at earthlink.net>
To: <pianotech at ptg.org>
Sent: Thursday, November 19, 2009 6:00 AM
Subject: Re: [pianotech] regulating S&S (ex-) reproducer actions


> Hi, David:
> I'm not a rebuilder, but I'll put in my $.02.  The difficulty 
> with a
> longer key lies in the geometry.  The hammers check because 
> the arc of the
> backcheck intersects the arc of the hammer tail.  The extra 
> length of the
> key makes the radius longer than a regular key, and so the 
> arcs don't come
> together until the key has moved a greater distance thru that 
> arc.  Draw a
> simple diagram with two different key lengths showing a side 
> view and
> you'll get it.
> Also, beware the spring strength.  If you have a short blow 
> distance, the
> spring doesn't "wind up" as much, so it will take a greater 
> tension to lift
> the hammer.
> FWIW.
> Paul McCloud
> San Diego


    Yes, and for this reason, I left the spring strength a bit 
on the weak side, so it wouldn't prevent checking.
    Thanks for the replies.
    --David Nereson, RPT