AB Chase Concert Grand

[Dean May]

Del: This is true only if there is some load coupling mechanism between the
plate
and the bellyrail and/or braces. (As with the Steinway plate horn.)
Otherwise the belly of the grand is not load-bearing.

Ron: In pianos having plates with no horn, there's no connection between the
plate and the beams. The plate holds the string tension, not the beams.

This makes no sense. Plates do not float on air. The plate bone is connected
to the rim bone (with the lag screw bone) and the rim bone is connected to
the beam bone- and don't forget about the nose bolt bones. If the beams
carried no load you would never see back frame separation in uprights. There
would be no stress trying to pull it apart.

Similarly, lifting the corner of a piano, thus flexing the wood/iron frame
assembly, would never cause a piano to go out of tune if there was no
connection.

 If you want to argue that the load is designed to be carried by the plate,
I can live with that. But it makes no sense to say that the frame adds no
rigidity to the plate or is not connected to it.

Del: It either case it is best if the bellybraces are spread across the
bellyrail
to stabilize an otherwise rather floppy structure.

Ron: Most pianos would benefit from stiffening the soundboard perimeter by
cross
bracing the long side and bracing the belly bar in the treble, not just the
nine footers.

You are both arguing my case. If the plate carries all the load, there is no
need for more rigidity in the wood frame. All we need is something to hold
up a 400 lb casting. That doesn't take much structure. Three bar stools
could handle it.

I get the feeling that I am wading into an old debate. :)

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 11:24 AM
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 7:14 AM
> To: Pianotech
> Subject: RE: AB Chase Concert Grand
>
>
> >From a structural standpoint, the beams go in the direction of
> the loading.
> Think about how the strings are wanting to fold up the piano. That is what
> the beams are resisting. So running a beam transverse to that direction of
> loading will have negligible effect on strength. It would make the overall
> frame more rigid, but it doesn't really need more rigidity in that
> direction.
>




Del


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