[CAUT] Sperrhake Harpsichord wire

Ron Nossaman rnossaman at cox.net
Sat Dec 5 09:00:56 MST 2009


Fred Sturm wrote:

> Alan was kind enough to send what I originally asked for off list: a 
> couple spreadsheets (in Xcel) containing all the formulae and actual 
> entered data for real pianos. Two different spreadsheets (ie, set up 
> differently with different formulae, one based on Dave Roberts done by 
> Doug Rhodes, the other with the name Collins attached). I ran some 
> sample figures, and it came out precisely as I predicted. I took sample 
> notes, F5, C6, F6 and lowered the string diameter for each, then raised 
> it. In each case, lowering the string diameter resulted in a lower 
> calculated tension and a lower calculated tension as per cent of 
> breaking point. And increasing the diameter resulted in higher
> calculated  tension and higher calculated tension as percent of breaking 
> point.

Tension change, certainly, as has been indicated. What exactly 
is calculated tension as percent of breaking point? That isn't 
break%. Break% is the percent of tensile limit of the string 
at it's current tension, and that number doesn't change with 
wire gage changes. For instance, one wire in a B-3 of 703mm 
length with 0.042" diameter will be at 190lbs at 43% of it's 
breaking tension. That's a break% of 43. Change the wire gage 
to 0.044" diameter and the tension goes to 208lbs, while the 
break% remains at 43.


> I'd be happy to send these along to any skeptics who want to try for 
> themselves. I am sure there are others on this list who already have 
> their own spreadsheets, similarly populated with real piano (or 
> harpsichord) data, who can try it out for themselves. I would be happy 
> to hear of any results.

Then you'll be thrilled with the above.


> I view the matter as settled, Ron Nossaman's carping notwithstanding.

It was settled before we started, Fred. The empirically 
derived math says the break% doesn't change with a wire gage 
change. If my unsuccessful attempt to inform you of this basic 
fact is carping, then it's still carp diem.
Ron N


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