On 11/26/2013 7:31 PM, John Parham via Piano Technicians Guild wrote:
> "If you or anyone else can come up with anything more detailed from
> any minimally credible source (NOT public opinion, reading tea
> leaves, or intuiting), I'd very much like the reference."
>
> It's interesting finding out what kind work has been done on this
> subject. Nowhere do I find any really long-term studies on steel
> creep.
Neither have I, over a number of years of looking. No one bothered to
put the information on the internet. Why? Did no one bother to run
tests? I find that hard to buy given all the information posted about
high temperature creep. Or is the knowledge that measurable long term
creep at mid level loads and room temperature is of such indetectable as
to be discountable altogether a commonly known fact, so obvious it's not
worth the mention?
> It is called "Tensile Stress Relaxation in
> High-Strength Spring Steel Wire." It tested music wire with a
> diameter of .56mm for periods of both 100 hours and 400 hours between
> temperatures of 23C and 140C. The abstract states that the wire
> stretched more in the earlier stages of testing than it did in the
> later stages (which is not news to us). At least this study had 4000
> hours in it. It costs $25 to get the entire details. I'm not willing
> to spent $25 for data that probably won't answer questions about
> longer-term creep.
Because it almost certainly won't.
> All other studies I have found suggest that steel creep is
> negligible, but it does not define what negligible means. Negligible
> in the context of steel beams in a building may be one thing, but
> negligible creep in a piano string (of much smaller mass) may have
> much different implications.
If negligible was conditional, it would have been quantified like all
the details, tables, and charts I found outlining high load, high
temperature creep. I can't see a committee writing a handbook for tool
designers being irresponsible enough to not supply details if there were
any to be had.
> At this point I'm willing to keep my
> mind open to the latter.
I find it telling that everyone is open minded about every possibility
EXCEPT the absence of measurable long term creep in piano wire in real
world conditions.
> I'm betting that funding for these kind of projects come
> from companies that have expectations of industrial applications with
> a payback verses satisfying the curiosities of piano technicians with
> a zero financial return.
I seriously doubt that piano technicians were ever considered.
> Most of the data I have looked at, however, suggests that whatever
> creep occurs in a steel string will occur fairly early.
Yes. I said that up front. Near simultaneous and permanent deformation
at initial loading. Stable unless loading is increased, resulting in
more immediate and permanent deformation, and once again becoming stable.
> The real question
> should be where has the string in the piano not been stressed enough
> yet...in the rear duplex? Between the rear duplex and the aliquot
> bar? Between the aliquot bar and the hitch pin? The bend around the
> hitch pin? In the coils around the tuning pin? At the termination
> points where a bend occurs? Between the front and rear bridge pins?
I disagree. Look at a freshly installed string as it comes off the
bearing points. It loops off plane until the bends at the bearing points
are tightened, which drops the pitch. If this isn't done manually, the
pitch will continue to drop for weeks, months as the strings are
gradually driven straight. That's not stretch, that's seeking the
straightest path.
> You have inspired me to decide for myself what I
> believe a piano string is actually doing on a piano:
Based on what?
> 1. In the manufacturing process of trying to control the atoms that
> affix themselves between the iron atoms in steel wire, I think there
> could be some inconsistencies in the molecular alignment of the wire
> on the piano...every atom is just too hard to control. How much will
> that affect the tendency of atoms to move once the string is under
> tension and changing temperatures? I don't know, so I can't just
> summarily discount that possibility.
I'm surprised this took so long. Techs typically go straight for the
molecules without even considering anything more detectable.
> 2. Energy transfer (movement) between atoms in a wire can occur at
> elevated temperatures. Does that mean when the stage lights turn on
> and the piano goes flat, that molecular rearrangement could place in
> a way that left the string in a slightly longer state? If so, there
> may come a time when it sounds flatter when it cools down.
Measure it instead of speculating in the direction of presupposed string
creep, as one with an open mind might consider reasonable.
Ron N
Original Message------
Ben Gac, and maybe others, in recent Journal article(s), have advocated tuning with no temperament strip, i.e., tuning the entire A4 unison, then the next interval of the temperament along with its unison strings, then the next, etc. This is one form of the "unisons as you go" method.
When using an ETD, you can start at A0 and go to C88, doing unisons as you go, either with a temperament strip or using a rubber mute. The temperament gets set automatically. You can keep a key pounder in one hand and the tuning hammer in the other, and seldom have to set them down, if you can keep them in your hands while you pull the mute strip or move the rubber mutes.
However, with the first method of tuning the entire unison, you can't efficiently use a key pounder since you have to keep putting it down to tune an interval, then pick it up again to bang in the unisons, then put it down again to tune another interval, then pick it up again for the unisons . . . . no good.
So, I assume those who tune aurally, tuning the whole unison before moving on to the next note, are not using a key pounder. (?)
--David Nereson, RPT
P.S. Do tunings and regulation jobs on pianos in the southern hemisphere eventually "go north"?