[CAUT] pre-stretching new string?

[David Love]

Sorry, I should have said "calculate the change in tension for a given
change in length and then see how that translates to a change in frequency,
you will see that the one with the lower BPP will have the greater
change"-it's early.

 

David Love
davidlovepianos at comcast.net
www.davidlovepianos.com 

-----Original Message-----
From: David Love [mailto:davidlovepianos at comcast.net] 
Sent: Monday, June 11, 2007 6:58 AM
To: 'College and University Technicians'
Subject: RE: [CAUT] pre-stretching new string?

 

 

 

In Robert's book "The Calculating Technician" the formulas are given and you
can program your own spread sheet.  The original claim was that when
comparing the degree to which two strings will go out of tune with a change
in length, the break point percentage was an indicator of which string would
go out of tune more.  The other statements below came about as a discussion
of the math.  If you do as I said and compare two strings which start out
with different BPP and calculate the change in tension for a given change in
tension and then see how that translates to a change in frequency, you will
see that the one with higher BPP string will have a greater change.  You
have to reprogram your spreadsheet to make that calculation for you since it
is not generally set up to have Frequency as a dependent variable.  

 

 

     Note               Length             Diam
BPP                  Tension                  Frequency

 


A - 7

 

70.0

 

.032

 

 

 

 

 

 

76%

 

138.64

 

3322.44


A - 7

 

60.0

 

.032

 

 

 

 

 

 

56%

 

256.85

 

3322.44

 

David Love
davidlovepianos at comcast.net
www.davidlovepianos.com 

-----Original Message-----
From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Richard Brekne
Sent: Monday, June 11, 2007 2:57 AM
To: caut at ptg.org
Subject: [CAUT] pre-stretching new string?

 

David

Below are your two posts on the matter.  The lower post clearly states your
original claim... which I fail to see you have supported.  In fact... half
of it is directly wrong as the example I gave showed. Diameter doesnt play
into it at all... tho it seems pretty clear you claim it does.  As for the
rest...see subsequent posts.

The upper quote suddenly jumps into a new claim about breaking point
percentages which is off in an entirely different tangent.  Breaking
precentage is not part of any tension formula... it is a procedure of its
own. So this fits into a claim that you can (and I quote)  

    "You can certainly rewrite the formula to isolate pitch, or tension, or
length, or diameter."  

er... how ?

Perhaps you have a way of calculating change in pitch from change in length
with some breaking % formula now ?  Please... if you have some formula the
rest of us do not... share it with us.  I spent a couple months exchanging
posts with Mark Davidson, Sarah, Alexander Galembo, Jim Ellis, Rhodes,
Askenfelt and a couple others and each and every one of them reviewed
Galembos paper to me and agreed this was the basic approach and a quite
adequate one as well of calculating change of pitch for change in length.  

Cheers
RicB


Grin
"You will find in the example you listed below that since both speaking
lengths are equal, they will both yield equal break point percentages.
While you have to increase the tension in the string with the greater
diameter, it also has a higher break point so the break point percentage
does not change.  Set up your example using two notes different speaking
lengths to begin with so that the BPPs are not equal.  Then run your
calculations for an equal change in length. "   


"Sorry, but it's not quite a complete enough formula for purposes of this
discussion.  When comparing two strings that produce the same pitch but with
different tensions, either the original length will be different or the
diameter will be different (or both), thus a similar change in length will
yield a different change in tension and thus pitch."  


  

-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://www.moypiano.com/ptg/caut.php/attachments/20070611/859ad11f/attachment.html