[CAUT] Scientific study - Stainless wire (Help!)

[David M. Porritt]

All this about controlled experiments on pianos/piano wire...has anyone
heard from Dr. Birkett lately?  I know he's deeply involved in some serious
testing.  I'd love to hear how things are progressing.

 

dp

 

____________________

David M. Porritt, RPT

dporritt at smu.edu

 

  _____  

From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Fred
Sturm
Sent: Tuesday, August 28, 2007 4:48 PM
To: College and University Technicians
Subject: Re: [CAUT] Scientific study - Stainless wire (Help!)

 

Hi Jim,

            Here are some thoughts for experiments:

1) Dealing with (quantifying) the difference you have noticed in how fast
the strings become stable. Create a jig that replicates a piano's hitch pin,
bridge, and offset between capo and aliquot, and tuning pins, but without
any wood involved (no bridgecap crushing and whatnot). Bridge should be
metal, but with pins angled like standard. Tuning pin should be Wegman style
or similar (Challis made phenolytic inserts for the tuning pins of his
aluminum soundboard harpsichords, inserts that went into thick plate webbing
holes, and gave a good even friction). 

            Set up parallel unisons of pure sound and standard wire. Do them
very carefully in terms of how the wire is installed. I think they would
need to be standard around the hitchpin strings (two sounding strings, two
tuning pins) rather than with tails, to eliminate tail movement. Make that
around the hitch bend with a jig similar to a wire bending pliers, that
presses the wire into the right shape (so it can be done consistently with
each kind of wire), then cut to length and probably make the coils on the
already installed tuning pins. Pull to a standard pitch (for the length and
diameter of wire), same for both types of wire. Try to pull just to a target
pitch, without any overshot, pulling each tuning pin alternately and evenly
(avoid pulling wire around the hitch). And wait. Note pitch after 1 hour, 4,
8, 24, 48, a week, a month, 4 months, a year. Temperature controlled
facility. This might also answer some of our questions about "wire
stretching" that recently came up on the list. 

            A supplementary experiment with the same setup could have
strings being brought back to pitch at some interval of time, with careful
records being kept.

            A sub experiment could have some wire massaging involved, in a
controlled way. Controlled how? They would need to come up with a way of
doing it in a consistent and measured way. And maybe with an overshot tuning
(50 - 100 cents sharp), seeing how that affects eventual stability.

            It would be interesting to look at each wire at the end of a
period of time, to see how much it had "permanently" conformed to the
various offsets - around bridge pins, past capo - just due to time and
tension. Take them off carefully, lay them down on the bench, and compare
bends.

2) Malleability of wire. How does it conform/deform? IOW, how much of it is
"bendy flexibility" that goes away after tension is removed, and how much is
permanent deforming. Again, using jigs similar to a wire bending pliers (two
pieces that press together to create a defined bend), do various shapes of
bend. Then release the wire from the jig and see to what extent the shape
holds. 

            Go from gradual to sharper profiles. Find the point at which
there is significant weakening (maybe using microscopic analysis). Vary from
a gradual bend (gradual in time, over several seconds) to a sudden one (a
jerk, a hammer blow) and see what differences there are.

            One thing that I wonder about is leveling strings. What
techniques work with pure sound? What should be avoided? The above could
shed some light on that question, as well as on how to treat the wire while
stringing in general.

3) Affect of temperature on pitch: any difference? (This would be affected
by the exact scaling involved, so be sure to compare high tension pure sound
and standard of equal length and diameter).

4) Affect of humidity change on pitch change of strung piano - unfortunately
individual pianos of the same model vary somewhat. I don't know an easy way
to get around that. Maybe string a piano with every other unison alternating
wires (two unisons of one, then two of the other, to have even stringing
without tails).

5) Difference in tonal spectrum: you probably need to take a single piano
and alternate types of string somewhat as above to get reliable results, so
the overall structure and materials of the piano isn't a factor (rather than
side by side same model). Or do a spectrum analysis of a note, change the
stringing on that note, do a second analysis.

            One of the major problems with this kind of analysis is getting
even ranges of key/hammer blows. Someone really needs to design a devise for
this purpose. I guess a solenoid driven player-style unit could be used,
with a good controller. A mechanical devise that acts on the keytop from
above would be better and more useful, IMO. But it needs to be capable of
doing rapid acceleration from the keytop, not a dropped weight that hits the
key after a fall (as in the tuning exam thumper). Something with
interconnected levers and moveable weights would work, I think, something
like a piano action in reverse, with the hammer as a weight, and the wipp
heel or sticker bottom on the key. Weight could be added to the hammer, and
moved in or out along the shank (or a simplified equivalent).

 

            A little food for thought.

Regards,

Fred Sturm

University of New Mexico

fssturm at unm.edu

 





 

On Aug 27, 2007, at 3:09 PM, Jim Busby wrote:





List,

 

We (BYU) finally are ready to do some scientific studies of stainless wire.
This will be conducted by Physics professors/students here at BYU. Could any
of you help me pose some "questions", "queries" or whatever you want to call
it, for these studies?

 

One of our student piano technicians is doing his senior project and his
professors (who we've bugged for years) are just now getting excited about
this.

 

Here are some things I've thought of;

 

1.	What are the actual differences in sound between stainless and Mapes
or Roslau? (Spectrum, etc.)
2.	What are the differences in inharmonicity between the two?
3.	(how?) Do bass strings with stainless core sound different than
other core?
4.	etc..

 

Jim Ellis, others, I'd really like some input on this. We have our ducks in
a row so now is the time.

 

Thanks,

Jim Busby BYU





 

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