Forster upright with negative crown

[Gregor _]

here comes a trick that I was told in the piano technician class, but it´s 
18 years ago and I never tried that trick nor do I know if it is still 
taught nowadays. It´s called *Pfennigstütze* and means coin support:

drill a whole in the rim and turn a screw in direction of the backside of 
the soundboard. Take a coin and turn the screw so that it pushes the coin to 
the board. The effect should be some kind of new crown. It is necessary that 
the coin hits the backside of the long bridge. Be carefull not to apply to 
much tension.

I only would try it if everything else did not work and if there is nothing 
to loose. They told us in the piano tech school and usually they know what 
they are talking about. Hard to imagine that the soundboard can swing with 
that coin, but allegedly it works. No idea if it can work with negative 
crown. Extreme case.

Sounds like scamping and perhaps my memory strikes so that I forgot some 
important details. So: no warranty!!

Gregor


>From: "Jean-Jacques GRANAS" <lemotjuste at data.pl>
>Reply-To: Pianotech List <pianotech at ptg.org>
>To: pianotech at ptg.org
>Subject: Forster upright with negative crown
>Date: Mon, 23 Jul 2007 14:28:16 +0200
>
>Hello list,
>
>It has been a very long time since I posted here. My regards to all.
>
>Last week, I went to tune an upright Forster from the 1920’s. I was told 
>by
>the lady owner that the piano hadn't been tuned for years (sic!). The piano
>had tight pins, clean strings and was less than half a tone flat, so the
>tuning was not a problem. The lady also asked me if I could do something
>about the her piano’s muffled sound.
>
>I though driving there that the hammers were probably out of shape and I
>would likely be filing hammers. Yet the hammer heads had barely visible
>grooves. As the muffled sound was most offensive in the midrange section, I
>decided to see what the crown looked like. I removed the action and took a
>quick glance downwards behind the keybed before pulling my tack line out.
>This instrument has the worse negative crown I have ever seen. The
>measurement came to to -12 mm (around middle C).
>
>I have three questions:
>
>- I have seen references on this list to pianos designed with negative
>crown. Does anyone know if Forster made uprights with negative crown?
>- What makes a soundboard behave like this? I know string pressure will
>often flatten a soundboard with time, but -12mm??
>- What can I do to give this piano a little life, short of a ribbing/board
>replacement job. The piano isn’t worth the expense, but the customer 
>likes
>it very much nonetheless.
>
>Cheers,
>
>Jean-Jacques Granas
>Warsaw, Poland
>

_________________________________________________________________
Don't just search. Find. Check out the new MSN Search! 
http://search.msn.com/