Flag poling Petrof pins?

[Delwin D Fandrich]

----- Original Message -----
From: "Robert Goodale" <rrg@unlv.edu>
To: <pianotech@ptg.org>
Sent: August 14, 2002 9:27 PM
Subject: Re: Flag poling Petrof pins?


> Ron Nossaman wrote:
>
> > I wasn't aware that open face meant the pins stand upright instead of
> > leaning back, but there are a lot of things I don't know and that
> > isn't the problem in any case.
>
>
> On most pianos with exposed blocks, the block itself will lean forward 6
> or 7 degrees instead of the pin leaning back 6 or 7 degrees.  Kind of a
> neat idea actually.

Not so.... I've replaced about as many flat open-face blocks as I have
angled open-face blocks. Indeed the one I'm doing right now (an 1889 Decker)
is flat. The last open-face Knabe we did was flat, as was--I think--the last
Bosendorfer we did. And the next one coming up is also flat.

The practice of leaning the pin back by 6º or 7º was introduced to enable
the pin to rest against lower edge of the plate without appearing to do so
from the top of the plate. It was never good string/pin geometry but the
practice did help to prevent the destruction of many an old three-ply
pinblock. There is no need to continue the practice today.

None of which helps you with your problem. Assuming more-or-less standard
string geometry for this type of block the string should intersect the pin
about 5 or 6 mm (that's a proud 3/16" to about 7/32") above the block
surface. And they should be consistent. If this is the case--and if the pins
are reasonably tight--it is unlikely that the pins or the pinblock is the
cause of the instability you're encountering.

How do the strings render through the various bearing points? Do they pass
over acres of felt on their way to the agraffes? What are the string angles
like?

Del