[pianotech] Jack and Damper Spring Tension Targets

[Floyd Gadd]

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