Curve on Bridge Bottom

[Erwinspiano@AOL.COM]

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In a message dated 5/4/2002 8:22:43 AM Pacific Standard Time, 
Richard.Brekne@grieg.uib.no writes:


> Subj:Re: Curve on Bridge Bottom 
> Date:5/4/2002 8:22:43 AM Pacific Standard Time
> From:<A HREF="mailto:Richard.Brekne@grieg.uib.no">Richard.Brekne@grieg.uib.no</A>
> Reply-to:<A HREF="mailto:pianotech@ptg.org">pianotech@ptg.org</A>
> To:<A HREF="mailto:pianotech@ptg.org">pianotech@ptg.org</A>
> Sent from the Internet 
> 
> 
> 
>                               Farrell wrote:
>         The only bridge I had laying around was from an upright and it was 
> notched at the tenor/treble break, so I followed your suggestion over the 
> 39" tenor segment - it bowed 5/16" with 100 lbs applied in the middle (my 
> son stood on it).
> >
> > I'm not sure what I was supposed to observe. Kinda seemed to act like a 
> big rib.
> >
> >                           Richard wrote
> Thinking from a "every little bit does some good" perspective one would 
> easily buy into the idea that a crowned bridge would contribute to the 
> soundboard crown at least to some degree. And 100 lbs is a nice big round 
> figure.... half a
> mans weight and well so at that. You might take one of those pre-crowned 
> ribs... one of the long ones and see how much it takes to press it flat as 
> well for comparision.....
>                                              
                                       Richard, Terry
                      It doesn't take much to flatten an unsupported rib as 
it  doesn't really take on its maximum stiffness till after it becomes part 
of the ply wood componet comprising the whole soundboard system at which 
point the cumulative resistive forces of cross banded woods and compression 
takes effect.  I agree with Ron that the bridge because of its shape simply 
rotates as the board flattens but there is still some nominal resistance to 
bearing. Every little bit does some good. 100 lbs is a 100 lbs which IF that 
is what it is, is roughly the same reisistance as one rib
> 
> --
> .>>>>>>>Best>.................Dale Erwin


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