Plugging Pinblocks/Del

[Delwin D Fandrich]

----- Original Message ----- 
From: "Joseph Garrett" <joegarrett@earthlink.net>
To: <pianotech@ptg.org>
Sent: November 15, 2003 8:43 PM
Subject: Re: Plugging Pinblocks/Del


> Del said: "And have you looked at any of these plugged blocks ten years
> after twenty years? I have. That's why I still duplicate the original.
With a =
> little practice it's not really all that big a deal.
>
> Del
>
> Del,
> ...I suspect the ones you've seen were poorly/improperly done and were an
> accident waiting to happen. With the right fixture(s), it's a viable
> alternative. Yes, it is time consuming, but think of that 8' Chickering
we
> did, lo those many years ago. Remember the hassle of putting the darned
case
> back together!???? That weren't a fun gig, as I remember!<G>

Since this question has come up several times I've given some thought to
why some of these repairs fail. Now, obviously, I'm only going to get the
failures in here for new blocks -- I'll never see most of the successes. So
I have no way of knowing how many plugged pinblocks are out there relative
to the couple I've seen that have failed.

This goes beyond the quality of work, I think. Although this could
obviously be a factor. Those I've replaced seemed to have been reasonably
well done. I doubt I'd have done any better. I suspect success or failure
depends more on how the original pinblock is used as a structural member
and on how the original block responds to changes in moisture content. In
those plugged blocks I've encountered that have failed (and I'm going by an
increasingly failing memory here) the mass of plugs was pulling away from
the front (i.e. toward the front of the piano) of the block. There were
also numerous small cracks opening up around the plugs throughout. I did
not consider these to be structurally significant, just visually annoying.
Veneering over the top of the mass of plugs may have rendered these
invisible and I don't know that they were significant enough to have
telegraphed through the veneer and become visible.

I can think of several reasons for this failure. Most obviously the tension
on the strings, hence the pins, may simply exceed the structural
capabilities of the pinblock design and assembly. Since one of these pianos
was a Chickering similar to the one you refer to I suspect there may have
been quite a lot of rotational stress on the mass of plugs. This may not be
a factor in a pinblock designed to keep the line of stress more directly in
line with the strings.

The other problem I see with this technique is with the aforementioned
physical changes that might be taking place in the original material due to
varying levels of moisture content. One of the plug failures was in an
original block made almost entirely of one single piece of maple. The mass
of plugs, along with its requisite bath of epoxy, is going to be relatively
stable regardless of changes in relative humidity. The original block,
however, is going to continue swelling and shrinking just as it has for the
past 137 years. And no adhesive known to mankind is going to prevent the
two from separating.

(To diverge down the bunny trail a bit:  And we wonder why all these
upright pinblocks separate from their back assemblies! That's another
system designed to fail. And, as long as we're off the main trail, all of
this also applies to the practice of installing pinblock inserts in
original vertical piano pinblock panels. I've also replaced one of those.
In an upright that came in many years back for bridge caps I was surprised
to see an insert in the original pinblock. The piano had been restrung
about five years earlier but no bridge work had been done. The insert had
been fitted at that time. It had been reasonably well fitted and was bedded
in epoxy but it had come loose and was rotating out of the pocket that had
been routed for it. Now, I still install inserts in upright blocks, but I
make sure they are also mechanically well fastened as well as epoxied in
place.)

You mention the challenge of replacing the pinblock in that 8' flat-strung
Chickering. Yes, it was an 'interesting' project. But, remember, it had
only been a few years before that when my shop did the first Steinway
pinblock installation ever in the Portland area. At the time pinblock
installation generally was about as common as soundboard installation is
today. There were still 'rebuilders' who claimed replacing the pinblock
detracted from the authenticity and value of the piano.

Since then I've done quite a few pinblock installations in these old
pianos. Some are even more challenging than that old Chickering. I am now
contemplating my old tri-level Knabe. Not only does it have an open block
that is structurally integral to the design, it is showing signs of
catastrophic failure. Along the outside of the rim on the bass side the
veneer has buckled, indicating that the pinblock has shifted within the
mortise. It's going to be another 'interesting' project. But, like most
procedures it gets easier and faster with experience. And it is work like
this that keeps this profession from becoming overly boring and I look
forward to them.

Del