[CAUT] Sperrhake Harpsichord wire

[Fred Sturm]

On Dec 5, 2009, at 9:00 AM, Ron Nossaman wrote:

> 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.


Here are the figures I get for that same B3 at 703mm, using Roberts/ 
Rhodes:
.036 139 lbs 38.2%
.038 155lbs 38.9%
.040 172 lbs 39.6%
.042 190 lbs 40%
.044 208 lbs 40.9%

Using Collins, I got:
.036 62.7 Kg 41%
.038 71 Kg 43%
.040 78.8 Kg 43%
.042 86.7 Kg 43%
.044 95 Kg 44%

So okay, there are some cases where the difference in breaking % will  
not be very significant. I did mine in the high treble, where the  
differences are greater. Still, the trend is clear. The fact that the  
Collins figures are rounded to the nearest % probably masks something.
Anyone else want to calculate it?
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu