[CAUT] String scaling help svp?

[Ron Overs]

Hi Mark,

>from the comments below (kawai kg-2A string breakage, november 
>22/06) I'm not sure if we resolved whether string gauge was a factor 
>in excess breakage on these high-tension scales?
>
>Anyone with scaling software mind running some numbers for me?
>
>note            string diameter     speaking length
>
># 75 (B6)     .033" (#14)            105mm

That's about 61%

>
>#80 (E7)     .033" (#14)              80mm    

That's about 63%.

In both cases, I don't think the tension is high enough to be the root cause.

>  I'm curious about the % of break point, and what consequence there 
>would be in replacing these with .032" wire. 

Changing the wire gauge will make very little difference to the break 
%. It mostly changes the inharmonicity. I'd look for problems with 
either the counter-bearing or Capo bar and/or the string approach 
angle.

>  Within the last two years, I've had Jeremy re-string trebles in a 
>half-dozen KG-2 incarnations as "prevention." However, string 
>breakage seems as rampant now as it did with the original strings.

The half round brass counter-bearing bars in the KG pianos can grab 
the wire a bit, and the KG capo bars are very soft, which also allows 
the wire to dig in. Apart from the poor tonal result, it also causes 
the bar to 'grab' the wire when rendering. The string approach angle 
on some of the KG Kawais can be a bit excessive, which can also 
encourage string breakage.

Sometimes when re-stringing I grind the plate thinner where the 
counter-bearing bar sits, or file the counter-bearing bar base to 
lower the profile, or both. I don't like a  string approach angle of 
over 15 degrees as a general rule.

If you've got a case of 'bashers' using the practice room pianos and 
fatiguing the wire early, bringing the strike a little closer and 
reducing the dip can be a good way of extending wire life.

I used to tune for a known 'basher' concert pianist here for many 
years. I would invariably bring the strike up to around 40-42 mm for 
his performances just to reduce the problems created by his 'meat 
cleaver' hands and his approach to performance. I always used to 
think the guy should have been a race car driver instead of a pianist.

How did the Wapin conversion on the SD10 turn out?

Best regards,
Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
_______________________

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