AB Chase Concert Grand

[Delwin D Fandrich]

> -----Original Message-----
> From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]On
> Behalf Of Dean May
> Sent: April 06, 2004 6:19 AM
> To: Pianotech
> 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?

The horn is the extension of the plate located between the bass and tenor
sections that is intended to couple part of the string load down to the
bellyrail and/or the bellybraces. It is quite different both in function and
location from the bell. The bell is bolted to the inside of the rim up
toward the treble. The bolt extending down from the plate to the bell
mass-couples the plate hitchpin panel to the bell and thence to the rim.
Check the archives.


>
> 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.

This is a whole other discussion. If the plate is doing its job we tighten
plate screws for quite other reasons. As the wood into which the plate
screws are driven swells and shrinks against the unforgiving steel wood
screw looseness happens. Tightening the plate screws removes the illusion of
looseness. I continue to caution against overdoing this with rims made of
Select Hardwood. I've had reported to me an increasing number of plate
screws that have stripped out of them over a (very) few years of being
conscientiously tightened each year by the tuner.


>
> 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.

Surprisingly little. Of course, in a factory tunings aren't much to write
home about anyway.


> 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.

It depends on the plate. I'd not want to try the above procedure with a
Steinway plate. These plates are much lighter, especially those used in the
smaller pianos. They are designed with the understanding that a certain
amount of the string load will be coupled down to the belly. Hence, lighter
cross-sections, no bass overbar, etc. Plates designed to support all of the
string load must have somewhat heavier scantlings. That is, they must be
stronger throughout, especially in strut cross-section.

Yes, the rim does position and stabilize the plate. That is a different
issue from directly supporting string load.

Del