Kimball Uprt. rescale

[Tom Rush]

Richard Moody wrote:
> 	I "rescaled" a Kimball upright from the same era.
[...snip]
>   The idea was to get
> a scale uniform in tension.  I had read the book which was a reprint of the
> piano maker's conferences of 1915 - 1918, (Piano Tone Building) and was
> impressed by the fellow from American Wire and Steel who adovacated an
> equal tension scale.  His concern was that wide variations of tension would
> result in tuning difficulties and tuning stability problems.  He pointed
> out that the tension should never excede the elasticity limit of the wire,
> which was considerably under the breaking point of the wire.
> 	I calculated the existing tensions, then fed in sizes to get a uniform
> tension.  In end I opted for a graduated uniform tension scale that went
> from 155 lbs in the treble to 180 in the lower tenor.
[...snip]
> : (  It was my piano so I felt free to experiment.  I was pleased with the
> results.

I'm glad you were happy with the results.  My experience with that method
has not been that good; the scaling calculations should take more than
tension into account.

The biggest problem with that approach is in the low tenor (the longest
plain wire strings).  Because there is usually a recurve or foreshortening
of the bridge in that area, the equal tension method results in a very
heavy wire size which has much greater inharmonicity than the wound strings
below.  In simple terms, it sounds bad.

I asked a question about this about a year ago.  There are others on the
list more knowledgeable about this than me; some have written software
for it.  My only advice is something that Vince passed along--get a copy
of "The Calculating Technician" by Dave Roberts (a PTG book).
--
Tom Rush
tarush@mindspring.com