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Originally Posted by Jethro
it would seem to me that the reason why piano strings break is simply because they have been fatigued beyond their breaking point either due to corrosion or overuse. Your proposition that strings break because molecular sized razors of diamond hardness are cutting into them is hardly the simpler explanation of the two.

Ironically, your experiment above doesn't test for either of these.

But, you seem like a pretty smart guy, Jethro. I'm sure if you really work at it you could probably put together a reasonable experiment. thumb


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Strings that break from fatigue break at the capo bar usually. They go flat as the string stretches out, and then they pop.

If you look at the video of string vibration that I posted earlier in this topic, you can see that the maximum flexing is at the endpoints of the speaking length. The strongest flex will be closest to the hammer.

Breakage from corrosion is usually at the tuning pin, and loosening the string first lessens the chance of that happening. If the coils are bad, that can cause fatigue, too, especially on upright bass strings where the coil goes so low that the string is bent over it going up to the v-bar.

Strings break at other points, sometimes from defects in the string, sometimes from damage, sometimes from age, sometimes for no discernible cause, but these are rare.


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Originally Posted by Jethro
the most simple explanation of why some piano strings break

In your opinion.


Originally Posted by Jethro
strings break ... due to long-term exposure to high levels of stress that are still below the yield strength of the metal. They are simply overstretched over time from being hit repeatedly by the hammers and being stretched from repeated stress from from numerous tunings over time. I would think the yield strength is compromised if the metal had also been exposed to the elements and became corroded over time. Another contribution may be manufacturing defects. The common factor in all of this is that the tensile strength of the string had been exceeded not because something is cutting through them.

It's possible for all your conjecture to be true, and you could still divide the pianos into two groups for comparison (v-pro and non-v-pro), maybe a 1000 of each selected at random, each treated equally (same frequency of tuning, same stable climate, etc), and track string breakage. It might reveal that strings break "faster" or more frequently on v-pro plates, or it might not. But that's the issue. Not whether they break at all on one and not the other.


Originally Posted by Jethro
if it was true we, we would see strings breaking more often in V-pro plate pianos over sand casted plate pianos and as far as I know, no one can validate this observation.

Yes, exactly. It might be true. It might not be. It may happen ten days faster. Maybe ten years faster. But you can't know absolutely without doing the proper research.

And to this I would expect you to say, "yes, that's what I've been saying. You can't claim it's true without the [proper] research." But...neither can you claim the theory is not true without doing the research.


Ed hasn't proven it. He suspects it based on his professional experience.
You haven't disproven it. You just rest resolutely on your non-technician opinion.


Originally Posted by Jethro
Unless any piano builder or rebuilder wants to correct me

Any? Any rebuilder but the rebuilder you're squabbling with?


For me, that's the real odd thing here. As you pointed out above, you're not a piano technician. As far as I know you're not experiencing excessive string breakage. You don't have a dog in this fight.

So why are you so adamant about being "right"?


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Does it really matter anyway?

When I bought my U3 it was probably already 13 years old. A used U3 is not an expensive or premium piano. In 20 years of playing it, including Rach concertos, I had one broken treble string and one broken bass string. They each cost me about AU$150 to fix. Perhaps if I had bought an upright with a wet sand cast plate I would have had only one broken bass string and no broken treble string. Or perhaps not. I doubt the piano wire used in the treble is expensive, and if you really wanted to you could probably learn to replace broken strings yourself.

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Originally Posted by Sonepica
Does it really matter anyway?

WHAT? mad cursing



Just kidding. I would say, "no," but some people just always have to be "right," whether it's what repertoire is acceptable for which model, or something as esoteric as the abrasiveness of various iron casting methods. wink


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Of course, if there were this diamond-like material lurking in hardened steel, you know where you would be most likely to find it. That is right, in piano wire! So the diamonds in the piano wire will dull the diamonds in the v-bar, and they would both end up smoother and less likely to damage one another.

But that is just me, not some upstart newcomer with only 45 years of experience.


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Originally Posted by Retsacnal
Originally Posted by Jethro
the most simple explanation of why some piano strings break

In your opinion.


Originally Posted by Jethro
strings break ... due to long-term exposure to high levels of stress that are still below the yield strength of the metal. They are simply overstretched over time from being hit repeatedly by the hammers and being stretched from repeated stress from from numerous tunings over time. I would think the yield strength is compromised if the metal had also been exposed to the elements and became corroded over time. Another contribution may be manufacturing defects. The common factor in all of this is that the tensile strength of the string had been exceeded not because something is cutting through them.

It's possible for all your conjecture to be true, and you could still divide the pianos into two groups for comparison (v-pro and non-v-pro), maybe a 1000 of each selected at random, each treated equally (same frequency of tuning, same stable climate, etc), and track string breakage. It might reveal that strings break "faster" or more frequently on v-pro plates, or it might not. But that's the issue. Not whether they break at all on one and not the other.


Originally Posted by Jethro
if it was true we, we would see strings breaking more often in V-pro plate pianos over sand casted plate pianos and as far as I know, no one can validate this observation.

Yes, exactly. It might be true. It might not be. It may happen ten days faster. Maybe ten years faster. But you can't know absolutely without doing the proper research.

And to this I would expect you to say, "yes, that's what I've been saying. You can't claim it's true without the [proper] research." But...neither can you claim the theory is not true without doing the research.


Ed hasn't proven it. He suspects it based on his professional experience.
You haven't disproven it. You just rest resolutely on your non-technician opinion.


Originally Posted by Jethro
Unless any piano builder or rebuilder wants to correct me

Any? Any rebuilder but the rebuilder you're squabbling with?


For me, that's the real odd thing here. As you pointed out above, you're not a piano technician. As far as I know you're not experiencing excessive string breakage. You don't have a dog in this fight.

So why are you so adamant about being "right"?
In my busy life I could give a rats ass if I'm right or wrong about anything. I'm just enjoying a pleasant conversation here. Why are you so obsessed about this? If you look at all the posts that feature you and I it's always about you trying to prove me wrong and failing spectacularly in the process and I'm not even trying to prove myself right. That's what's so sad my friend. What we have here are several people (some highly respected in the piano industry) disagreeing with Ed on how he reaches his conclusions not necessarily what his conclusions are. In fact many times in this thread I've said he might be right I just think he needs to test his ideas scientifically before stating them as fact. I offer alternative hypothesis that might explain why strings break, some of them may just be my opinion, an idea, a question maybe? They were never stated as being a fact or being right.

Last edited by Jethro; 08/03/21 10:47 PM.

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Originally Posted by Withindale
Originally Posted by Jethro
The most simple explanation of why some piano strings break is due to long-term exposure to high levels of stress that are still below the yield strength of the metal. They are simply overstretched over time from being hit repeatedly by the hammers and being stretched from repeated stress from from numerous tunings over time. I would think the yield strength is compromised if the metal had also been exposed to the elements and became corroded over time. Another contribution may be manufacturing defects. The common factor in all of this is that the tensile strength of the string had been exceeded not because something is cutting through them.

This is the simpler explanation of why strings break, not because of abrasive elements that form in the construction of a V-pro plate- which if it was true we, we would see strings breaking more often in V-pro plate pianos over sand casted plate pianos and as far as I know, no one can validate this observation. Or has there been an abundance of piano owners coming into the shop with V-pro plated pianos complaining of broken strings?

Corrosion aside, Jethro, where does this theory predict strings will break? At contact points (tuning pin, v-bar, bridge pins, hitch pin) or at random points in between?
BDB explained it well enough, interestingly in the human there are analogous structures where we see dense connective tissue fail. Usually at insertion points, bony prominences, anatomical pulleys or anywhere there is a change in force vectors. Creep works in dense connective tissue such as ligaments and tendons much the same way it works in metals. We use the same terminology as material scientists when we describe tissue failure.


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the process for making piano wire draws the high carbon steel rod through diamond steel like dies with quenching in an oil bath after applying heat every few sizes to anneal it as it is reduced to the desired diameters in the drawing process. The annealing reduces the "diamond" like carbon in the wire to a level that allows for just enough flexibility. (I use the term "diamond like" to avoid getting into martensitic and austenitic metal phases explanations.).

So if you want to make a piano that will wear out the strings when you tune it, you will place the wire against a diamond like material which is capable of cutting into the wire, not just changing its shape.

Yamaha pianos in recording studios that get tuned often usually start to shed treble wire after about ten years. Other makes with hard V-bars will do the same and this can include some Steinway's with sand cast plates that have case hardened V-bars.

BDB my experience is with shaping many V-bars. Have you ever reshaped a V-bar to a true V-shape?


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Originally Posted by Ed McMorrow, RPT
Yamaha pianos in recording studios that get tuned often usually start to shed treble wire after about ten years.

If this is such a big issue, then why haven't Yamaha and Kawai (and other manufacturers) taken any action on this? Also, if it's only pianos that get tuned several times a week that are a problem, private owners are unlikely to encounter this issue.

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Originally Posted by David-G
Originally Posted by Jethro
Your proposition that strings break because molecular sized razors of diamond hardness are cutting into them is hardly the simpler explanation of the two.

No? It seems a simple explanation to me. Whether it is true or not I have no idea. I am not a materials scientist. I suspect you are not either.

The research of the Australian military reported in an article that I posted above found no measurable difference in hardness between castings with wet sand at atmospheric pressure and castings with dry sand at pressure reduced by a vacuum chamber.

Wouldn't that falsify the theory of diamond crystals in the v-cast plates?


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I am amazed that a thread on iron casting, on a piano forum, now runs to 11 pages.


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But the issue of hard castings at the V-bar also makes treble tone more harsh, so even if you don't get your piano tuned like a performance instrument, it affects sound quality.


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My understanding of hardness in iron casting is the significant variable is cooling rate. The slower it cools, the more graphite form the carbon becomes.

I imagine it would be possible to V-pro a plate, and have it cool as slow as a sand cast one resulting in an equality of hardness between the two methods.

All I really know is the plates that I have been told are V-pro feel harder to the file when I attempt to shape the V-bar than sand cast plates.

I also know how important proper string terminations that maximize the pivot termination are to clear, rich dynamic, sustaining tone because I have solved tonal problems in capo bars by removing the existing strings, reshaping the V-bar to a true V-shape and putting the same strings back in the piano with the end result of buzzing, pinched tone corrected.

That is a form of scientific proof.


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Originally Posted by Ed McMorrow, RPT
But the issue of hard castings at the V-bar also makes treble tone more harsh

Surely this is your subjective judgement? Even if the two casting methods produce tonal differences in the treble, surely whether it was better or worse would depend on what kind of tone one wanted in the treble?

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Quote
My understanding of hardness in iron casting is the significant variable is cooling rate. The slower it cools, the more graphite form the carbon becomes.

I imagine it would be possible to V-pro a plate, and have it cool as slow as a sand cast one resulting in an equality of hardness between the two methods.

My belief is that the notion that wet sand plates cool more slowly is a myth perpetuated by piano dealers. I believe that the water content in wet sand would cause a wet sand casting to cool more rapidly than castings in dry sand in a vacuum chamber. When molten iron comes in content with wet sand, the water will be converted to steam, and the phase shift will absorb heat from the molten iron.

Last edited by Sweelinck; 08/04/21 01:23 AM.

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Originally Posted by Jethro
Originally Posted by David-G
[quote=Jethro]Your proposition that strings break because molecular sized razors of diamond hardness are cutting into them is hardly the simpler explanation of the two.

No? It seems a simple explanation to me. Whether it is true or not I have no idea. I am not a materials scientist. I suspect you are not either.
There's a difference between simple and simpler. In my line of work I deal with the human body and we are also dealing with solid materials such as dense connective that experiences "creep" such as ligaments or tendons that overstretch and eventually can rupture or deform permanently when placed under long term.....quite/Jethro

Are you talking about chiropractic science Jethro?

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Originally Posted by Jethro
I'm just enjoying a pleasant conversation here.
Originally Posted by Jethro
I just think he needs to test his ideas scientifically before stating them as fact.

No, what you've done is said that Ed is "talking out of his ass." Not once, but twice. You've made other belittling comments too. That's not "pleasant conversation." It's overtly insulting, and condescending.

I suppose that my evil genius and powers of mind control have overcome you, and compelled you to be so unpleasant!

Ok, I'll play along: the next time you hear the name "Rumpelstiltskin," I want to you to drop what you're doing, turn three cartwheels, then dance the tango with an imaginary partner. Afterwards, close your eyes for ten seconds, wake up, and have no recollection of what you've just done!

If that transpires, then I'll accept responsibility. Otherwise, your antisocial antics are on you.


Anyway, I'm trying to be positive. Like I said above, I think if you really put your mind to it that you could probably understand all this. thumb


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Has there ever been an episode on shark tank regarding human bug spray? If not, someone really needs to invent some.


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Originally Posted by tre corda
Originally Posted by Jethro
Originally Posted by David-G
[quote=Jethro]Your proposition that strings break because molecular sized razors of diamond hardness are cutting into them is hardly the simpler explanation of the two.

No? It seems a simple explanation to me. Whether it is true or not I have no idea. I am not a materials scientist. I suspect you are not either.
There's a difference between simple and simpler. In my line of work I deal with the human body and we are also dealing with solid materials such as dense connective that experiences "creep" such as ligaments or tendons that overstretch and eventually can rupture or deform permanently when placed under long term.....quite/Jethro

Are you talking about chiropractic science Jethro?
Does science and chiropractic belong in the same sentence? Ok I kid, I Kid!


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