[CAUT] Wire Stretch

[Jeff Tanner]

On Apr 28, 2007, at 10:57 PM, Tim Coates wrote:

>
> I think Jeff Tanner asked a question that was interesting.  There  
> was a lot of discussion about crushed bridge surface causing the  
> pitch to drop, but then the thread changed to wire stretch causing  
> the pitch to drop.  I thought his question was: which is it?   I  
> don't believe I've seen anyone answer his question yet.
>
>
> Tim Coates

Hi Tim,
I didn't mean for it to sound like "which is it?"  More of a  
challenge to the idea that wire elongation or "stretching" was of  
little factor.

The idea was brought forth by Fred and Ron that the pitch drop that  
happens after new wire is installed has little to do with wire  
elongation or stretching, but due almost completely to wire bending  
to conform to bearing points and the crushing of the bridge cap.  (My  
paraphrased understanding after having read it several times)

We all agree that these occurrences do affect pitch drop, but the  
idea that elongation has little to do with it, didn't make sense to  
me, since both wrapped wire and plain wire both go through those  
processes alike, yet plain wire continues to drop in pitch long after  
the wrapped wire seems to stabilize.  Regardless of the reasons why  
one stabilizes sooner than the other, the fact that plain wire  
continues to drop in pitch seems to indicate there is a great deal of  
elongation that happens in the process.

Jeff


Jeff Tanner, RPT
University of South Carolina



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