[CAUT] Wire Stretch

[RicB]

Hi JD

Thats what I thought.

Unfortunatly, you can not calculate the change in frequency for change 
in string deflection this way. Or so I am told by a few of the worlds 
physisists.  Please see the following for what according to these is a 
more correct way of doing this. 

http://www.pianostemmer.no/files/String deflection_files/brekne.doc

I started out on this little journey with the same basic formula as you 
used below... and got shot down immediately by just about everyone on 
this and pianotech list who knows a bit of physics right off the bat.  
You will find using the above approach both agrees with experimental 
data far better and yields significantly different result for a 0.5 mm 
change in string deflection for a 100 C/ mm string at standard pitch 
using usual design deflection figures as a starting point.  Such a change

I can send you the exchanges of posts I had with 4-5 of these folks 
explaining why your <<basic>> approach doesnt work if you are interested.

Cheers
RicB

    By Pythagoras' theorem the _maximum_ extension of the original length
    is calculated thus:

    l_hyp = sqrt((l^2)+(h^2))

    where l_hyp is the length of the hypotenuse of a triangle of base l
    and height h.

    Having calculated the altered length you can use the formula here to
    calculate the frequencies for the two different lengths:
      <http://strings.pianomaker.co.uk/formulae.html>

    The precise figure would depend on the original gradient of the
    speaking length and could vary between zero and the maximum I gave,
    but the quantity involved is so small as not to matter.

    A little basic mathematics saves a lot of chatter.

    JD


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