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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>
<A title=mjbkspal@execpc.com =
href="mailto:mjbkspal@execpc.com">Mike and Jane
Spalding</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A =
title=pianotech@ptg.org
href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> August 08, 2001 9:49 =
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Old Upright, partial =
plate,
Pitch?</DIV>
<DIV><BR></DIV>
<DIV><FONT size=2>List,</FONT></DIV>
<DIV><FONT color=#000080></FONT> </DIV>
<DIV><FONT size=2>What about this exposed pinblock - are there =
unique problems
and dangers associated with this thing? =
</FONT></DIV></BLOCKQUOTE>
<DIV dir=ltr><FONT color=#800000 size=2>Oh, this one might be =
interesting...
Since this is a subject dear to my heart, here goes the first
salvo:</FONT></DIV>
<DIV dir=ltr><FONT color=#800000 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800000 size=2>In my experience the =
so-called
three-quarter plate, exposed pinblock designs give no more trouble than =
do any
others having the more common and traditional full plate configuration. =
Try as I
might I've not been able to figure out why we regard these pianos as =
somehow
structurally deficient. </FONT></DIV>
<DIV dir=ltr><FONT color=#800000 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800000 size=2>There is really very =
little torsional
stress--relatively speaking--on the pinblocks of the traditional upright =
piano
regardless of its plate design. So, why do some of them fail? Well, =
consider how
the pinblock is glued to the back assembly. Typically there will be five =
vertical wood posts--the back posts--separated by (usually) solid =
blockers. The
grain of the posts is, of course, vertical. The grain of the =
blockers is
typically horizontal. Now to this is glued a pinblock of varied =
construction.
Some of them were multi-ply laminates much like the so-called modern =
pinblock.
Some were made of relatively thick solids much like the traditional =
Steinway
blocks. If we were building furniture we would never use a construction =
like
this because we would know it was bound to fail.</FONT></DIV>
<DIV dir=ltr><FONT color=#800000 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800000 size=2>In most cases =
pinblock/back separation
is the result of simple glue failure and is not in any way related =
to the
plate design. (I've seen a few exceptions but they are well beyond =
anything I'm
going to try to write about here.) In modern pianos pinblock/back =
separation
usually occurs because the original glue bond between the pinblock and =
the back
assembly was poorly done. Or because the horizontal blockers were left =
free to
expand and contract next to a multiply pinblock and they simply =
worked
themselves apart as changing climate conditions caused the blockers to =
expand
and contract against a relatively stable pinblock. </FONT></DIV>
<DIV dir=ltr><FONT color=#800000 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800000 size=2>The adhesives used to =
assemble the
modern piano back are typically phenol- or urea-formaldehyde =
assembly
adhesives. These adhesives dry and cure to an extremely rigid glueline. =
They
allow no glue line creep. When properly used they form extremely strong =
and
stable bonds. They require a very thin glueline for best adhesion, =
however,
becoming quite brittle and crumbly in thick section. If the glueline is =
even a
little bit on the thick side, as the blockers expand and contract =
against the
rigid and brittle glueline bond they simply work themselves =
apart.</FONT></DIV>
<DIV dir=ltr><FONT color=#800000 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800000 size=2>This is also the most =
common cause of
pinblock/back separation in the old upright--regardless of plate
configuration--except that the glue joints were commonly made with =
somewhat more
care and most of them were made using animal hide glue. Used correctly, =
animal
hide glue is a very strong and stable adhesive. But, just as with =
modern
adhesives, it was not always used correctly either. If the glue is
old--having been cooked too long--or is at the wrong =
temperature--usually too
cool--when joint closure is made the strength of the adhesive strength =
suffers.
As with phenol and urea adhesives, animal hide glue is a poor gap =
filler; if the
joint is wide hide glue will become quite brittle and crumbly. Hide glue =
also
dries to an extremely rigid glueline having no sympathy whatsoever with =
the wood
blockers need to expand and contract.</FONT></DIV>
<DIV dir=ltr><FONT color=#800000 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800000 size=2>So. Regardless of plate =
construction,
the structural integrity of the pinblock and back assembly depends =
almost
entirely on the design and assembly quality of the back =
assembly--including the
pinblock-to-back assembly fit--and on the integrity of the glue joints =
holding
them together.</FONT></DIV>
<DIV dir=ltr><FONT color=#800000 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800000 size=2>If you have reservations =
about one of
these old pianos you can always add a few lag bolts running through the =
pinblock
into the backpost. Don't bother running them into the blockers--they =
won't do
much good there.</FONT></DIV>
<DIV dir=ltr><FONT size=2></FONT> </DIV>
<DIV dir=ltr><FONT size=2></FONT> </DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000080 2px solid; MARGIN-RIGHT: 0px">
<DIV><FONT size=2>Pitch was 100 cents low, almost uniformly from top =
to bottom
(bass less, high treble more). Can I conclude from this that the =
piano
had been maintained at below 440? Can a partial plate upright be =
safely
tuned to 440 or should it be kept at, say, 435? =
</FONT></DIV></BLOCKQUOTE>
<DIV dir=ltr><FONT color=#800000 size=2>Assuming the rest of the =
piano is
structurally sound, yes. It surely was to begin with.</FONT></DIV>
<DIV dir=ltr><FONT size=2></FONT> </DIV>
<DIV dir=ltr><FONT size=2></FONT> </DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000080 2px solid; MARGIN-RIGHT: 0px">
<DIV>
<DIV dir=ltr style="MARGIN-RIGHT: 0px"><FONT size=2>Pins appear =
to be
original, or at least original size, #2 tip fits nicely, so re-pinning =
with
oversize pins looks like a possibility. Again, does the exposed =
pinblock
create any special concerns with this approach? Plate and case =
in good
condition, no sign of cracks or separation in pinblock, but most pins =
don't
have much more than the minimum amount of torque needed to stay at =
current
pitch. </FONT></DIV></DIV></BLOCKQUOTE>
<DIV dir=ltr style="MARGIN-RIGHT: 0px"><FONT color=#800000 =
size=2>No. The
exposed pinblock should not create any special concerns with repining =
with
oversize pins. Or with rebuilding properly and replacing and/or plugging =
the
pinblock. You'll find that they tune very nicely with the string coming =
off the
pin so close to the pinblock surface.</FONT></DIV>
<DIV dir=ltr style="MARGIN-RIGHT: 0px"><FONT =
size=2></FONT> </DIV>
<DIV dir=ltr style="MARGIN-RIGHT: 0px"><FONT =
size=2></FONT> </DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000080 2px solid; MARGIN-RIGHT: 0px">
<DIV dir=ltr style="MARGIN-RIGHT: 0px"><FONT size=2>And, it was =
80F and 66%RH
today.</FONT></DIV></BLOCKQUOTE>
<DIV dir=ltr style="MARGIN-RIGHT: 0px"><FONT color=#800000 =
size=2>Sorry to hear
about you're heat wave! Though it was pretty warm here yesterday as =
well--I
think it got up to 72º. We all thought about sweltering but it really =
has to get
above 75º for that to be convincing!</FONT></DIV>
<DIV dir=ltr style="MARGIN-RIGHT: 0px"><FONT color=#800000
size=2></FONT> </DIV>
<DIV dir=ltr style="MARGIN-RIGHT: 0px"><FONT color=#800000 =
size=2>--
Del</FONT></DIV></BODY></HTML>