Crown in Bass Area & Downbearing

[Farrell]

I should probably backtrack somewhat on my statement of "very little crown
in the bass" - but only somewhat. I think many designs will have ribs in the
bass area that are cut to a 60-foot radius (some even larger). That to me is
little crown. Some soundboards are made from flat ribs and it seems it does
not take too terribly long on some of these to get flat-ish. These are
definitely little (or no, or negative) crown. Regarding downbearing on the
bass, I am aware that some reputable folks building and installing new
soundboards just have bass strings kiss the bass bridge top - zero
downbearing - regardless of backscale length. Apparently, they find that
works to their satisfaction with the design of their soundboards.

As David points out, the expression of downbearing as a unit of length not
only lacks clarity, it is meaningless without a backscale length
specification. I wish downbearing was commonly characterized with an angular
measurement - or better yet, two angular measurements - bridge front and
back downbearings.

Terry Farrell

----- Original Message ----- 
From: "David Love" <davidlovepianos@earthlink.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: Wednesday, May 12, 2004 10:59 PM
Subject: RE: Crown in Bass Area & Downbearing


> The amount of downbearing in the bass should, as I understand it, depend
on
> the backscale length.  The greater the backscale length, the more
> downbearing is not only tolerated but needed in the bass area.  A next to
> zero downbearing would probably be advisable where the backscale is
> extremely short.
>
> David Love
> davidlovepianos@earthlink.net


>But many designs incorporate very little crown in the bass and zero or
>nearly so bearing on the bass bridge. So how could you tell that such
>characteristics were a problem (at least in terms of deviation from
original
>design)?
>
>Terry Farrell


> Regarding bass crown, I'm not sure how much is design intent, and how much
> is the result of the cantilever under positive bearing destroying what
> crown was there. I tend toward the notion that the crown was originally
> there, designed or not, and the cantilever killed it - if it is indeed no
> longer there. The downbearing would ideally be dependent on the length of
> the back scale, like David Love said. I consider zero crown and zero
> bearing to be a problem in a piano with a conventional soundboard,
anywhere
> in the scale.
>
> Ron N


> > Terry said: "But many designs incorporate very little crown in the bass
> and
> > zero or
> > nearly so bearing on the bass bridge...."
> >
> > Terry,
> > Where did you get such an idea. It's simply not true!
> > Regards,
> > Joe Garrett, RPT, (Oregon)