[pianotech] Jack and Damper Spring Tension Targets

[David Ilvedson]

You are actually reading the jack spring tension and then repinning for correct tension?   

David Ilvedson, RPT
Pacifica, CA  94044

----- Original message ----------------------------------------
From: "Floyd Gadd" <fg at floydgadd.com>
To: pianotech at ptg.org
Received: 7/28/2009 8:47:04 PM
Subject: [pianotech] Jack and Damper Spring Tension Targets


>List,

>I'm still exploring the regulation of my 1966 Heintzman console.  The jack
>return is REALLY snappy.  I'm trying to identify an appropriate target for
>the jack spring tension.

>In a posting dated Oct 15, 2007, Ted Sambell reports that Shimmel recommends
>a jack spring tension of not more than 30 grams in a vertical piano,
>measured at the jack heel with the jack being moved forward by the pressure.
>Optimum damper pressure is indicated at 40 grams, measured at the felt, at
>the position of normal damper lift.

>In a posting dated January 2007, Don Maninno distinguishes between the
>European design (Schwander?) where the jack springs must be strong, and the
>hammer springs relatively weak, and the American (Pratt Read?) where the
>hammer spring is relatively strong, the jack springs relatively weak, and
>the damper spring does not affect the touch very much.

>So the numerical targets quoted by Ted are presumably for the European
>design.  Does anyone have numberical targets for the American design?

>Thanks for any help you can give me.

>Floyd Gadd
>Manitoba Chapter