[pianotech] Downbearing

[David Love]

I know this was intended for Ron but FWIW I've noticed that there is a lot
more forgiveness in these designs than we tend to think.

David Love
www.davidlovepianos.com


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Will Truitt
Sent: Sunday, November 23, 2008 2:16 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] Downbearing

Hi Ron:

Boy, I go out to the shop and string for a few hours, and I come back to a
flood on downbearing.

I'm disappointed in your answer.  I was really looking forward to the
Henbane and the toads, and chanting, "Fair is foul, and foul is fair; hover
in the fog and filthy air."  (That's the three witches in MacBeth)

But then I realized those are the kinds of incantations one uses for
Compression Crowned Soundboards, along with Magic Pixie Dust.

I will take your answer to mean that, as long as the rebuilder practices
reasonable quality control and controls the variables that will affect the
front and back bearing relationships (pinblock thickness, plate height,
bridge top level, etc.), small variations will not have an audible tonal
effect or affect the performance and longevity of the soundboard.  


Will Truitt




-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Ron Nossaman
Sent: Sunday, November 23, 2008 9:30 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] Downbearing


> Hi Ron:
> 
> As the practical man we all know you to be (and I think it is of real
value
> for you to occasionally bring us out of the clouds with your nuts and
bolts
> perspective, thank you very much!), what steps do you take in practice to
> insure that the front and back bearing angles are roughly equal?  Since
you
> are usually installing a new soundboard (and presumably a new pinblock),
> where in the combined processes do you make adjustments that will at least
> get you roughly in the ballpark of where you want to be?
> 
> Will Truitt 


It's very mystic. Get yourself some Henbane, a small round 
rock, and a toad... No, wait, that's something else. Ok, 
here's the deal. A bridge with the top parallel to the bottom, 
strangely as if it had passed through a planer, sitting more 
or less centered on a line of crowned ribs, will make the 
bridge top close to parallel to a line from agraffe to hitch, 
which will get you positive bearing on both front and back of 
the bridge. Where the comparison of these angles ends up 
depends on the final net downbearing angle, and how much it 
has deflected the board.
Ron N