hammer crowns tearing apart (was Dolge)

[Barbara Richmond]

----- Original Message ----- 
From: "Dave Nereson" <davner@kaosol.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: Monday, May 24, 2004 2:45 AM
Subject: hammer crowns tearing apart (was Dolge)


> Tension
> >> & compression go hand in hand in the hammer pressing process.
> >>    As I stated, & piano hammer makers can tell you, that too much
> >> tension
> >> can
> >> be achieved during pressing in the outer layers of felt and it can &
> >> will rip
> >> open in the crown. This is the elastic limit of the felt.
>
>     I think this is the problem in Yamaha hammers.  As they wear, the
crown
> "blooms", i.e., spreads wider, making the hammer pear-shaped rather than
its
> original "diamond" shape.  Anytime I've filed hammers on a Yamaha, not
only
> is it difficult to find a "layer", but the crown spreads apart even worse
> from the filing than it already had been from the string cuts.  So the
inner
> part of the hammer must be compressed too much or the outer part is
> stretched too much, or both.
>     If the tone is too bright after the filing, then any voicing with
> needles near the strike point (even if it's not right ON the strike point)
> makes the crown spread apart even more.  It's very frustrating and I'm not
> sure how to handle this problem.
>     --David Nereson, RPT

Didn't Ed Foote advise needling the shoulders first on these hammers to
avoid the crown splitting?

Ed, do I have that right?

Later,

Barbara Richmond
going out to the garden now.....