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

[Jim Busby]

Wow, thanks Fred! I will pass this on to the "scientists". I'll have to
take more time with this post...

 

#5 below is all we have attempted so far. We did devise a thumper, but
I'm wondering is a Disklavier would be the way to go. Consistency was
definitely an issue with our meager spectrum studies. I'm really hoping
that these "science professors" will take the ball and run with it. That
is what they do. 

 

Good stuff.

 

Regards,

Jim

 

________________________________

From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Fred Sturm
Sent: Tuesday, August 28, 2007 3:48 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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