I'll add my data obtained from experimentation and measurement.
We cannot measure NSL tension directly. I've looked into strain gauges. They don't make them small enough. We have to infer tension changes from pitch changes.
The pitch of the string with the long NSL does not react to pin movements not because of friction, but because of length. Look up Hooke's Law which basically says a long spring of length L doesn't change tension when elongated by a length of x as much as a short spring of length ℓ. In fact, the change in tension of the long spring will be only a fraction of the change in the short spring and that fraction is ℓ / L .
The pitch of a string with a short NSL is very sensitive to pin movement due to Hooke's Law.
String segments can never be equal due to friction at the bearing points.
During hard blows, the speaking length of a string is higher because the string is longer. Think of the string being "stretched" during a hard blow. The shortest distance between two points is a straight line which is what we have when the string is at rest.
Hard blows do not equalize string segment tensions. Hard blows equalize tensions that exist during the hard blow, which produces the higher speaking length tension. After hard blows, the speaking length tension reduces, v-bar/agraffe friction leaves the NSL tension higher; hard blows actually produce
unequal tensions.
Hooke's Law says movement at the bridge is minute due to the long speaking length. Move the string at the V-bar and the string will move at the bridge by a fraction. String movement at the lower termination point is not an issue with fine tuning.
High friction causes NSL to behave like a longer NSL. Low friction causes NSL to behave like a shorter NSL.
E.g. a long NSL can result in the pin moving and pitch not changing; Long NSL tension are not sensitive to pin movements (Hooke's Law).
But adding a lubricant lowers friction and now the NSL behaves like a shorter NSL; Short NSL tension are very sensitive to pin movements and the pitch will follow the pin movement more closely. (Hooke's Law).
This effect is noticeable in other situations like short NSL where the pressure bar is not low enough. Very little friction results in the NSL behaving like an even shorter NSL where every little pin movement is followed by a pitch change resulting in a very difficult string to tune stable.
Which brings up the important idea that we need friction for stability.
Every action is followed by a reaction. Every twist of the pin is followed by an untwisting. That's why lowering pitch to target and then adding a little clockwise twist, thinking that will create a higher tensioned NSL may be dangerous and unnecessary. The pin will untwist on its own raising NSL tension. If you twist clockwise too much, the pin will untwist on its own CCW and may leave the NSL too loose.
Lube is not needed on long NSL of high friction pianos. High friction is good and may be the easiest and fastest string to tune stable, as long as the friction isn't in excess like those of old pianos with rust on the v-bar.
Just pull it up to target and leave it. The friction ensures a tight NSL. The long NSL ensures the tension stays high. (See video below)
Tuning a Stable String With a Long NSL.
FREE CLASS - How to Get Superior Stability!
Hearing small changes in pitch is essential for troubleshooting stability problems. ETDs can help but if you want to get superior results aurally, consider double string unison, DSU, where we tune two strings clean, judge the pitch, and then move one string. Pitch change is detected aurally as little as 0.3 cents.
Using DSU to tune A4 (Listen at the end where I have an unstable string that keeps going sharp)
Tuning A4 - Video Submission
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Mark Cerisano, RPT
B.Sc.(Mech.Eng.), Dip.Ed.
https://howtotunepianos.comhttp://mrtuner.com1-866-678-8637
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Original Message:
Sent: 05-02-2021 08:05
From: Jon Page
Subject: Hammer Technique
Yesterday, I tuned a Bechstein grand with 2.5~3" c/b felt expanses. The application of a counter bearing lubricant made reading pin flex instantaneous,
almost like it had c/b bars instead. No drag or ratcheting wires.
Koval Mild Vic (my default temperament) made the piano glow. My custom stretch was the icing on the cake :-)
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Regards,
Jon Page
mailto:jonpage@comcast.net
http://www.pianocapecod.com
Original Message:
Sent: 04-30-2021 17:39
From: John Formsma
Subject: Hammer Technique
I totally agree about the minute information the ETD (I use Only Pure) affords you when reading fine tuning movements of torsion flex effects on elasticity and tension. This aspect of an ETD, gets me really stable settings with hammer technique alone. I do not strike the key hard ever...it hurts both my hands and my ears, and makes the whole tuning process a chore.
I'll add my hearty agreement to the above. My ear is really good, and I usually like my aural tunings a bit better than most RCT calculations. That being said, I have learned something about hammer technique that would have been hard with only aural tuning. Not impossible, but almost impossible. For this alone, the ETD has been worth it.
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John Formsma, RPT
New Albany MS
Live not by fear or lies.
Original Message:
Sent: 04-30-2021 17:29
From: Jim Ialeggio
Subject: Hammer Technique
Because our job as tuners is to equalize tensions in the SL and NSL's, by definition, the tension in the SL segments, and NSL's, will be equal, or very close to each other. If the tension is not pretty darn close, the SL pitch will not be stable.
This means tension is a non-negotiable given in all the segments. NSL pitch will be dependent on NSL length * tension * string mass (in this case indicated by diameter).
I think you are referring actually to elasticity, and not tension. There is elasticity to consider in the various NSL's which have different lengths. The longer the length and the smaller the diameter of the wire, the greater the elasticity.
I totally agree about the minute information the ETD (I use Only Pure) affords you when reading fine tuning movements of torsion flex effects on elasticity and tension. This aspect of an ETD, gets me really stable settings with hammer technique alone. I do not strike the key hard ever...it hurts both my hands and my ears, and makes the whole tuning process a chore.
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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
Original Message:
Sent: 04-30-2021 10:47
From: Jon Page
Subject: Hammer Technique
I am continuing this discussion started in a different thread on Hearing Damage.
I just finished tuning a grand which gets delivered tomorrow :-)
Koval Mild Victorian Temperament per the new owner's request and my recommendation.
I can't conceive how a Long NSL has a different tension than a Short NSL. It has a different pitch due to its length. Maybe a factor is proportional: tension/length.
But each reacts to torsion flexing about the same, the shorter being more sensitive. How does one actually measure the tension in a confined string segment?
The short NSL's were more reactive to pin movement (torsion control) than the longer ones.
It wasn't until I started using a Counter Bearing Lubricant, that I realized the ability to fine-tune because of the improved ability to read minor torsion flexing and pitch motion.
Having a Verituner helps to see even the most minute of variations.
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Regards,
Jon Page
mailto:jonpage@comcast.net
http://www.pianocapecod.com
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