bass string problem

[Overs Pianos]

Hi David,

>            Had a string break in the low tenor 
>during a pitch raise on a 1983 Everett console. 
>Decided to put on a universal string and leave 
>it if it sounded OK.  (Would order custom string 
>if it didn’t).  Measured the string on the 
>tapered slot gauge and it said # 8, so that’s 
>what I put on.  Wouldn’t pull up to pitch – it 
>broke.  Have only had that happen maybe twice in 
>25 years.  Brand new strings can usually be 
>pulled way over pitch and still not break.  So 
>tried a # 8 ½  instead, thinking it’s meant to 
>be at a higher pitch than the # 8.  Nope, it 
>broke too! 
>
>             Now, the winding on the original 
>string is aluminum or nickel (I assume), not 
>copper, but should that matter?

It certainly matters. Copper has a specific 
density of 0.89 gr/cc, whereas Aluminium has only 
0.256 - 0.264, depending on its analysis. A 
copper winding of the same diameter will cause a 
higher tension to be required to achieve a 
certain pitch.


>  It’s the core wire that holds the tension, 
>right?  I measured them all when I got home and 
>the original string’s core wire is .037”, the # 
>8 measured .039”, and the # 8 ½ measured .038”, 
>I believe.  Shouldn’t that be close enough? 
>Should I go back and try a # 9?  

Before you get a new string made, it would be 
worth having a look at the original design on a 
scaling spreadsheet. Post up the speaking length, 
cover diameter and the note number on the piano. 
We can look at the tension to see if it is 
getting up near critical levels. Quite a few of 
us on the list have spreadsheets in which we can 
drop the numbers to see what is going on.

>P.S.  Why did they use aluminum or nickel wound 
>for the two lowest tenor strings, when all the 
>bass are copper?

Probably because the designer wanted to wrap the 
strings to avoid the usual tension drop near the 
break, but a copper wrap might have caused the 
tension to go too high. Even a small diameter 
copper wrap will cause a big increase in the 
tension at pitch. Aluminium will result in a much 
smaller tension increase on account of its lower 
density. The higher tension of the wrap will be 
more likely to be a problem if the wound strings 
are place on the same bridge as the plain wire - 
a design approach which doesn't work.

I've considered using Aluminium previously for a 
couple of adjacent break notes. I had some 
strings wound and tested the tone. But in the end 
I decided that the best approach would be to 
design the wound strings so that 0.2 mm (8 thou) 
is the smallest copper wrap used, and if they 
have to be used in the treble section that they 
are located on their own tenor bridge with a 
reduced speaking length. I've had experimental 
copper wrapped strings wound with diameters going 
right down to 0.125 mm (5 thou) as well, but I 
had to make up a special spool with a ball 
bearing mounted shaft, to prevent the wrap wire 
from breaking as the winder wrapped the string. 
Its altogether too much trouble.

Post up your string specs and we'll have a look.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
_______________________

Web http://overspianos.com.au
mailto:ron at overspianos.com.au
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