Hello David,
I would suggest that it is a good idea to shim this gap in the
flange/block fit whether the piano is brought up to pitch or not and whether or
not the gap contributes to the crack you describe in the plate.
In my opinion the crack that occurs next to the strut in the tenor is a
good indication of the ability of the hole for the screw to be a stress
raiser. I have seen several of these cracks on 88 note B's and none, although
perhaps some contributor here will report otherwise, on the 85 note B's. The
difference between the two pianos is that the hole for the screw on the 85 note
piano, that is, the original design, was about two and half inches or so from
the plate strut.. The stress raising effect of this hole was then distributed
into a region of lesser stress keeping it below the critical level of forming a
crack. When the piano was enlarged, apparently without consideration of the
effect of this hole as a stress raiser, it was moved much closer to the strut
which then placed it into a region of, apparently, higher and more complicated
stress, resulting in a propensity to crack if other factors militated in such
a direction. Interestingly, I have seen this on pianos from as far back as the
turn of the 19th century and as recently as B's produced in the late 80's.
You would think, in a hundred years, the factory would have detected this
and corrected it.
All but one of these cracks that I have seen over the years come out of
the screw hole and proceed roughly parallel to and close in in a slightly
angled fashion to the strut. These kinds of cracks seem to have very little
effect on the stability of the piano and I have two that I see from time to
time that are at pitch.
There is another kind of crack, much more dangerous, which I have only
seen once and not on a B, which proceeds along the plate parallel to the
stretcher for four, five or even six or seven inches. The only one I have ever
seen was, I think, on an M. I have had one decribed to me recently which was
on a B and was informed that the piano was 'extremely unstable" by a very
reliable tuner, as was the M. These kinds of cracks I would take an entirely
different approach to and not raise the pitch were it low.
I would suggest that a possible source of these cracks, at least as they
occur on B's, and probably the other models to a point, arises in the
complexities of the stress distribution created by the interaction of the horn
wedge and the detachable strut on the plate with a possible complication
arising from poor fitting of the top of the block to the plate webbing and the
stress raising effect of the screw hole along with its placement too close to
the strut. Obviously complexities attaching to the removable strut should be
discounted in the models without one. The fitting of the block to the flange,
except as an indicator of general sloppiness, is probably secondary. This
interaction may also account, although this is somewhat speculative, for the
orientation of the crack whether parallel to the stretcher or parallel to the
strut. All of the pianos that I am aware of with these problems have been
restrung: I suspect that subsequent installation of the wedge and strut may
have contributed to these problems by increasing stress in the region adjacent
to the strut.
In my opinion, although anyone with any experience in removing Steinway
plates is readily aware that they may be flexed down somewhat during
installation at the factory, it is more important to set the plate properly
with a minimum of flexing on B's.
Even if flexed slightly though as one frequently encounters, which may be
actually innocuous, it is very important, in my opinion to install the wedge
under the horn before stringing, securing it so that it neither forces the
plate to be bowed back toward the stretcher or allows it to flex forward to
close a small gap between wedge and horn. Then the removable strut can be
reinstalled and should be ground or shimmed to function similarly to the wedge;
that is to allow no motion. Waiting until after stringing is completed is
highly problematic as a technique in my opinion, although the piano may be long
gone before such a problem becomes evident in the form of a crack. Both the
strut and the wedge are functionally, similar to nosebolts as they should
merely restrain the plate, or motion in it, and not force it somewhere.
Although I know sometimes the removable strut may even be removed when the
piano is strung and up to pitch, even stringing the piano and leaving the wire
slack may bring enough strain into the system to render inadvisable installing
the wedge after stringing. The complications of the two when installed
otherwise, may, along with the stress raising effect of moving the hole closer
to the strut allow the strain to exceed the yield point and, over time, allow
stress relief to manifest itself in the form of a crack.
Finally, I would guess, although again I have nothing but incidental
observation to back this up, that the orientation of the crack itself suggests
some things about the interaction of the two as contributors to these cracks.
These are mere speculations but it maybe that where the crack is parallel to
the strut, as most I have seen are, a reasonable suspicion can attach to the
installation of the strut: either independently or in conjunction with the
wedge, it may be actually forcing the horn back and to the left resulting in a
crack emanating from the screw hole and proceeding parallel to the strut.
Where the crack is parallel to the stretcher perhaps the wedge has been
installed either too tightly prior to or subsequent to stringing causing the
horn to be rotated upwards and towards the stretcher with the result of stress
relief now appearing as a crack proceeding parallel to the stretcher and
somewhere in the neighborhood of the flange.
A third possibility is that the wedge is either installed too tightly and
too much to the right - again creating a tendency for the horn or rotate,
increasing stress in the vulnerable region and forcing, again, a crack.
There are, no doubt, combinations of these effects. In general, I think
all of it is more likely to be avoided when the procedure I have outlined above
is followed.
Regards, Robin Hufford
David Skolnik wrote:
> Dear List -
> I have a beautiful Rosewood B which sounds great, but has the classic crack
> in the plate, emanating from one of the plate / Pinblock screws, right at
> the treble side of the tenor brreak, ie. just before the bass. The
> probable cause was the poor fitting of the replaced block. A gap of at
> least 1/32" is detectable between the block and flange, running for about 8
> or 9 inches.
> The question: If the customer determines he wishes to take the risk in
> pulling the pitch (eventually) to 440, and is aware that he might,
> ultimately need to replace the plate. Is it advisable to, first, drop pitch
> and shim the gap? I'm having trouble visualizing how the crack alters the
> stress patterns on the plate in that area.
>
> Many thanks.
>
> David Skolnik
>
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