AB Chase Concert Grand

[gordon stelter]

I think that the rim and posts are there to keep the
plate from twisting, support the soundboard, and
transfer wayward vibrations from place to place so
that they can be transformed into audible energy by
the soundboard, before they are mutated into heat by
absorption of the piano's materials.
    They are also there so that we can "Ooooh!" at how
big and strudy they are, and marvel about the day when
things were "Built to Last".
    Thump

 rather than 
--- Farrell <mfarrel2@tampabay.rr.com> wrote:
> 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.
> >
> >
> 
=== message truncated ===


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