AB Chase Concert Grand

[Farrell]

Maybe another way to look at this is, instead of addressing what supports
string tension, is to ask what do the wooden beams/braces under the
soundboard do?

I'll stick my neck out and try to answer that question. Del, et. al., please
correct me if I am off-base on any/all of this.

I think the braces are mostly there for stiffening soundboard termination
components - the rim and bellyrail. (Actually, I think many are there for
marketing purposes.) Most rims, where they are curved, are relatively stiff.
But the flat bass side of bigger pianos and the belly rail of any piano will
commonly benefit from the installation of braces to stiffen these
components. The rim and belly rail need to be stiff (and massive) to
minimize soundboard dampening.

Better pianos will often have more, and more massive, bracing for the rim
and belly rail. Cheap little microgrands often do not have any braces. Now
these two pianos will have similar string tension (do you think the cheap
little microgrand has a stronger plate to support the string load all by
itself without being equipped with any braces?). Obviously you don't need
braces to support the string load. But one piano sounds better than the
other - perhaps, in part, because the better piano has a rim and belly rail
that is stiffened with braces.

On some pianos that are equipped with a horn, like the Steinway and Bear
Bros. (two horns!), the beams can also support a portion of the string load,
as Del pointed out.

Running For Cover,

Terry Farrell

----- Original Message ----- 
From: "Dean May" <DeanMay@PianoRebuilders.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: Tuesday, April 06, 2004 9:18 AM
Subject: RE: AB Chase Concert Grand


> Del wrote: It's the plate. Unless there is some kind of horn or other
> coupling
> mechanism.
>
> Could you elaborate on why a horn would couple load but you don't feel the
> nose bolts do? I don't see the functional difference. Maybe we are talking
> about different things. Are you talking about the horn inside the action
> cavity under the pin block at the bass break? Or the contraption bolted to
> the rim on the picture in a previous post?
>
> Also on the screws and compression set, that is a good point you make. It
is
> why it is important to check plate screws for tightness. But I would think
> the amount of compression would diminish exponentially to a maximum.
Perhaps
> the compression nearing its maximum is one of the factors affecting when a
> piano reaches tuning stability.
>
> Del wrote: Not exactly. I have, however, watched factory workers remove
the
> screws
> holding the plate/pinblock to the inner rim and install or remove shims to
> raise or lower the front of the plate assembly without dropping tension. I
> wonder what it was that was supporting all that string load while the
plate
> assembly was being adjusted for height? Certainly not the rim assembly.
>
> This is an interesting observation. I've often wondered what that plate
was
> capable of. But you've got to admit that the front of the plate with all
of
> those wide flanges is considerably more rigid than the back part that goes
> around the rim. I'd be curious to know what that did to the tuning of the
> piano.
>
> I am not arguing that the plate is incapable of carrying all of the load
by
> itself- especially the massive front end. Only that the wooden frame adds
> rigidity and thus, stability.
>
> I really appreciate your insights, Del.
>
> Blessings,
>
>
> Dean
>
> Dean May             cell 812.239.3359
> PianoRebuilders.com   812.235.5272
> Terre Haute IN  47802
>
> -----Original Message-----
> From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]On
Behalf
> Of Delwin D Fandrich
> Sent: Monday, April 05, 2004 11:18 PM
> To: DeanMay@pianorebuilders.com; Pianotech
> Subject: RE: AB Chase Concert Grand
>
>
> > -----Original Message-----
> > From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]On
> > Behalf Of Dean May
> > Sent: April 05, 2004 8:02 PM
> > To: Pianotech
> > Subject: RE: AB Chase Concert Grand
> >
> >
> >
> > Del wrote: ... a couple of large wood screws on
> > each end don't count. Dowels and glue joints do as long as they are
still
> > structurally sound. But many pianos do not have glued-in
> > pinblocks. So then we have to consider how stress from the strings is
> supposed to
> > coupled down through the two ends of the pinblock, across a floppy
> bellyrail
> > and into the bellybraces which are supposed to be carrying all this
string
> load.
>
>
> >
> > Stress will be transmitted through the two screws, across the
> > "floppy" belly rail and to the beams. I have never done a pull test to
see
> how much load
> > those large screws will hold before they pull out, but I suspect it is
> > significant, at least 1000 lbs. And I've seen many pianos with screws
> > through the plate into the rim and belly rail, bypassing the pinblock.
>
> What happens in a short-term test does not matter. It's over the long term
> that matters. Screws, even big ones, that are side loaded tend to deflect
> over time by virtue of compression set in the wood.
>
>
> >
> > And the floppy belly rail supported by the keybed makes for a pretty
> > substantial member, it seems to me. I guess it would be easy
> > enough to load test and measure deflections. (something tells me you've
> already
> > done this).
>
> Again, not over any prolonged period of time.
>
>
> >
> > I am not arguing that the beams are carrying a significant portion of
the
> > string load, only some, and in that measure they are adding to
> > the rigidity of the plate.
>
> Consider also all of the old grands that had one or more bellybraces
simply
> removed to accommodate pneumatic player or reproducer mechanism. If the
> bellybrace is no longer there it can't very well be supporting any string
> load.
>
>
>
> Del
>
>
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