Down bearing

[Farrell]

I'll stick my neck out on this one. I trust that if I disseminate any mis-information, our friends will come to the rescue! See how these fly! Comments interspersed below:

Terry Farrell
  
----- Original Message ----- 
From: "Keith Roberts" <kpiano@goldrush.com>
To: <pianotech@ptg.org>
Sent: Friday, April 05, 2002 12:57 AM
Subject: Re: Down bearing


> Maybe I'm the one that's confused. Please correct any of the following
> statements. Downbearing is the pressure exerted by the strings on the
> soundboard. 

Yes. One could state it that way or "downbearing is the pressure exerted by the strings on the bridge". Same difference (I think!).

> Down bearing is altered by the thickness of the bridge and scale
> tension. 

You can alter downbearing by changing these parameters. Downbearing is determined (measured) by only two things: the angles the string makes as it crosses the bridge and the string tension.

> String geometry cannot determine down bearing without before and
> after measurements of the sound board. (Old pianos only). 

No. Downbearing in new or old pianos is determined strickly by string geometry. The angles the string makes as it crosses the bridge and the  tension on that string. Your parameters mentioned above are needed to evaluate soundboard stiffness perhaps, and its reaction to some amount of downbearing, but not an good/easy way to measure downbearing.

> Crowning is done
> so the bridge can have good downbearing without compressing the board past
> flat when tension is added.

Among other reasons (acoustic), yes.

> Keith R.
> ----- Original Message -----
> From: <Bigeartb@AOL.COM>
> To: <pianotech@ptg.org>
> Sent: Thursday, April 04, 2002 12:05 PM
> Subject: Re: Down bearing
> 
> 
> > What did y'all finally figure out ? I used to think I understood
> downbearing
> > to a degree. Now I ain't so sure any more. Do we have the same, more or
> less
> > downbearing on the board when we remove strings? Why?
> >
> > Just trying to understand!!!!
> >
> > Tommy Black
> > Decatur, Ala.
> >
>