Old Upright, partial plate, Pitch?

[Mike and Jane Spalding]

Tom & Del,

thanks for your posts.

I did look for recently replaced strings, but all were uniformly coated in
decades of dirt.  Also, the top shows no signs of delamination, block is
well secured to the posts with a healthy glue joint and with some large lag
bolts which appear to be very old, if not original:  hex heads with fancy
pressed brass washers on the pin block face.  Pin angles are pretty much
where they belong, a few are straight but none tipped towards the plate, and
the straight ones are no looser than the others.  With your encouragement,
I'll be recommending re-scaling/re-stringing with oversized pins, along with
the action and rib/soundboard repairs, and tuning to 440.

One curiosity I didn't mention was the soundboard/rib separations.  The
soundboard has a ripple running from corner to corner along the grain, that
bows away from the ribs, creating a 3 to 4 mm gap between the ribs and the
soundboard.  There is not a single crack showing in the soundboard.  I'm
wondering if next winter, when the humidity drops to 30% or so, if the the
ripple will flatten out and the cracks will open up.  Anyone seen this
before?

thanks,

Mike Spalding


----- Original Message -----
From: Delwin D Fandrich
To: pianotech@ptg.org
Sent: Wednesday, August 08, 2001 1:04 PM
Subject: Re: Old Upright, partial plate, Pitch?

List,

What about this exposed pinblock - are there unique problems and dangers
associated with this thing?
Oh, this one might be interesting... Since this is a subject dear to my
heart, here goes the first salvo:

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.

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.

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.

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.

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.

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.

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.


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?
Assuming the rest of the piano is structurally sound, yes. It surely was to
begin with.


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.
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.


And, it was 80F and 66%RH today.
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!

-- Del

----- Original Message -----
From: Tom Cole <tcole@cruzio.com>
To: <pianotech@ptg.org>
Sent: Wednesday, August 08, 2001 3:19 PM
Subject: Re: Old Upright, partial plate, Pitch?


> I would assume that the piano has been tuned at -100 cents to avoid
> string breakage. Look for any strings shinier than the rest as evidence
> that this was a necessary measure.
>
> If you haven't already, it would be good to remove the top to see how
> well the pinblock is glued to the frame of the piano, as well as to give
> you a good look at the laminations. I always get a look at the angle of
> the tuning pins from the side. If they are beginning to dip toward the
> floor, you most likely would need to replace the block. Andre Bolduc has
> a great method of replacing upright pinblocks.
>
> If all looks normal, though, you should be able to restring with 3/0 (or
> 4/0) pins and tune to pitch. I recommend rescaling.
>
> Tom Cole
>
> > Mike and Jane Spalding wrote:
> >
> > List,
> >
> > Today I inspected a Harrison upright with a 3/4 plate (pinblick
> > totally exposed)...
>
>