Fw: rescaling

[Tom Cole]

pianoman wrote:
> 
> ----------
> > From: pianoman <pianoman@inlink.com>
> > To: piano tech <pianotech@byu.edu>
> > Subject: rescaling
> > Date: Saturday, September 27, 1997 5:09 PM
> >
> > A few questions for you experienced ones.
> > 1.  What happens if in the rescaling the number of notes of a given size
> > wire changes from an odd to even or vice-versa.  Where does the added
> hitch
> > pin come from?

The idea is to not make wire size changes that require a lot of hitch
pin changing. I personally don't like to make a change that causes the
tail lengths to be at a different angle than the original since this
affects the side bearing on the back bridge pins and also looks less
than professional. Try not to be too finicky about the ideal wire sizes
determined by the computer. One less or one more of a particular size
will never be noticed.

> > 2.  I understand the rule used to be not to change sizes at a plate
> strut.
> > Is this not necessarily true?

If the dog leg in the bridge is sufficient, IOW, speaking length changes
go smoothly across a strut, there is no reason to change wire size at
that time also.

> > 3.  What happens when the plate is too low and the bridge surface is
> cut
> > out for the bridge to fit?  How does or does it at all affect the sound
> as
> > to the size of wire used.  I was under the impression that this was
> always
> > a bad thing.  Yes-No?
> > 4.  What measurements on the scale are taken for measurement.  Point of
> > contact in the front and the front bridge pin.  What other measurements
> are
> > needed?

Wrapped length of wound strings, diameter of wrapped length, diameter of
core. Also, of course, the diameter of the plain wires.


> > 5.  Is the re-scaling programs glorified spreadsheet programs and do all
> > the different programs use the same measurements and give you a choice on
> > in-harmonicity and tension?

They may use a spreadsheet. They could also be a data base type program.
The ones I've seen are linked to a charting program. They are all based
on the same measurements, offer similar choices but may use slightly
differing string formulas.

> > 6.  What data do they give you to send away for bass strings?

The program I devised deals with the English system but some string
makers require metric. Check with the person you will be dealing with
what lengths you'll need to specify and whether inches or centimeters.

> > 7.  Can you take measurements on a strung piano to see just how good that
> > scale is for that piano and calculate things like amount of
> in-harmonicity
> > and tension level?

I have done this but it is clearly the hard way: speaking lengths of
tenor wires are difficult to measure under the bass strings. You can
measure diameters with digital calipers but if you have a micrometer,
you may have to let down the tension of some of the strings to measure
them.

Some words of caution: don't go crazy changing wire sizes. Adding in
half sizes is always a plus. Strings that are too close to break point
(more than about 65%, say) need to be changed. This is easier to do in
the bass. In the treble, the speaking length really needs to be
shortened (yeah, right, just move the bridge a little).

Good luck,

Tom

> > Thanks,
> > James Grebe
> > R.P.T. from St. Louis
> > pianoman@inlink.com
> > "Do it because it is right"
> .-

-- 
Thomas A. Cole RPT
Santa Cruz, CA