[pianotech] Breaking bass string

[David Love]

The maximum safe tension for a given string that I have used is T =
.557d^1.667 representing 60% of the breaking strength,  d given in mils so
for your #13 gauge I would come up with .557*31^1.667 which equals about 170
lbs.  That’s quite a bit different from your 137 lbs even if you figure in
the differences for metric  versus English diameters.  I realize there is
some disagreement in how one figures the maximum allowable tension but on
the surface it appears that your numbers are a bit low or I’m not
understanding it correctly.  It’s certainly not unusual for a piano to have
a 52 mm note #88 with #13 gauge wire which pushes the tension up to about
163 lbs without a breakage problem.  So please correct me if I am
misinterpreting your chart or better please provide the formula that you are
using so that I can have some means of comparison.    

 

David Love

www.davidlovepianos.com

 

From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of John Delacour
Sent: Sunday, April 10, 2011 12:25 AM
To: pianotech at ptg.org
Subject: Re: [pianotech] Breaking bass string

 

At 16:35 -0700 09/04/2011, David Love wrote:

 

 

That will tell you the tension but it won't tell you the break point
percentage for which you will need the core dimension factored in.  The
issue with respect to this question of breakage is really at what BP% is the
string made.

 

So why not enlighten your readers with some numbers,  as I have tried to do
on several previous occasions.  For bass strings the green (or orange)
column in the table below gives the maximum tension to which the string
should be subjected when at pitch to eliminate the risk of breaking.  The
green column is the values I use (for Röslau/Giese wire) and the orange
column the values Paulello* gives for his 'M' (modern) wire.  As you will
see, they are very similar.  26 years of bass string making have allowed me
to test the validity of these figures in practice.

 

 

 



 

*<http://stephenpaulello.com/pdf/PJ3-Wire-Paullello-prices-characteristics.p
df>

 

JD

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