bass string problem

[John Delacour]

At 2:55 am -0600 26/9/06, David Nereson wrote:

>OK, the core wire diameter is .0365", the overall diameter with 
>aluminum wrap is .070", the speaking length is about 32 1/4", maybe 
>32 3/8" -- can't tell exactly because it's out of the piano and the 
>bridge pins didn't leave very discernible bends.  It's the 
>right-hand string of a 2-string unison on F#3 (note number 34).

You need 0.15mm copper wound on a No. 16 core for this note.  0.15 is 
the thinnest wire we use in bass string making and it gets very 
little used -- in fact I am still using the 1 Kg. reel I bought when 
we set up the string-making factory 20 years ago.  You could also use 
a 0.20mm. copper cover.  This would bring the tension to 73% of 
breaking strain, rather than the 70% maximum I adhere to, but 
provided you are aware that the string is near its limit and are 
careful not to take it more than a few beats above pitch when fitting 
it, there is no danger of its breaking.

You need no fancy software to calculate whether a string is too 
tight.  You can do it as accurately as you need with a standard 
calculator following the steps below.  As you will see, the tension 
on your No. 16 wire would be about 326 lbs. whereas is ought to be no 
more than 184 lbs.

F  ( Frequency note 34 174.61 cps.)
L  ( Length 32 3/8 = 82.2 cm.)
D  ( Diameter 0.07" = 0.178 cm.)


F    174.61
*
L    82.2
     --=> 14353
*
D    0.178
     --=> 2555
*
=
     --=> 6527124
/
20000
=
     --> 326
_____________

To recap (USE CENTIMETRES!)  :  F * L * D * = / 20000

Very simple.  This is what I myself do to check the tension of all 
odd strings I am sent for replacement.  When you order a replacement 
string, you should always tell the string-maker what note it is so 
that he can calculate whether the string has broken through excessive 
tension and make adjustments.  If he can't do that, use a serious 
string-maker.

JD