[pianotech] Jack Springs

[Ron Nossaman]

John Ross wrote:
  It is from Schaff, item number 527A, upright jack spring.
> The physical properties are equal taper from top and bottom, to a 
> compacting of a couple of coils, in the centre, like each end.
> The old springs were a double at each end, and the winding went wider in 
> the middle.

John,
I haven't used any of these yet, but there was a Journal 
article (don't know when) on how the design was arrived at. 
There's less torsion stress on the wire because there are more 
coils within the compression range, pretty much eliminating 
breakage and producing a more constant spring rate, and they 
don't tangle into one giant permanent spring in the bag. I 
don't see a reason they'd be noisy, but I don't really know. 
I'd try them.
Ron N