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#3069901 01/16/21 04:22 PM
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I think I can see some twisting. Can you?.

This is a number 3 pin. I think I will try to titghen my vice even more and do a slow motion video and see if I can actually break the pin.

https://www.youtube.com/watch?v=OAR_afEMZpY


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Jean,

I twisting going on. And of course as we know a vise is not a pinblock. Good demo.

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Thanks for doing the video. It makes it easier to narrow in to what people are doing and thinking about.

What I see is that around 0:30, the jaws on the right of the vice move, but I can see the white string at the foot move with the head. So, I don't see a twist happening there. The top of the pin might be deflecting in other parts of the video, but it comes back with the pressure is released. If you look at the fingers, the end of the hammer appears to rotate upwards, which would be a flagging issue. A twist would, if anything, make the handle appear to go downwards.

However, for this to be a tuning issue, this twist needs to somehow get trapped in the block. What happens above the block goes away when the pressure is gone.

The other issue is that the vice is already much in access of the 100 inch/lbs. The point is that the vice is already outside the normal working range of the forces that we use.

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Jean,
What are you trying to prove? All metal will bend and twist.
Ian


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I'm not trying to prove anything, I was just curious.


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I can't tell from the video. If I try and defocus then I think I see rotation of the whole pin rather than twisting. Would it be possible to redo it with an absolutely straight line starting point. Then I think the movement which is happening will be shown up, either twisting or rotating.
It's brilliant of you to do this experiment.
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And if you have a torque wrench
Maybe try to get an idea of what it takes to twist the thing?


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The fatal flaw of this test is that it is painfully obvious that the vise itself is almost constantly making large movements from the various pressures the tuning lever is placing on the pin. That alone makes any efforts to isolate twisting or bending of the pin on its axis untrustworthy. We see the whole string move, which suggests that the pin is rotating within the jaws of the vise. Is that because the vise is not holding the pin securely enough, or because the pin is so rigid that it cannot twist on its own axis? One can have a point of view towards one or the other conclusion. I choose neither conclusion, because the test is insufficiently controlled.

It is also obvious that there is some slop from the star tip being a bit oversize in relation to the top of the tuning pin. You can see movement of the tip before it gains purchase on the pin.

A better test would be to start with a sturdy bench, to which one could securely clamp a slab of leftover pinblock stock after drilling a number of holes that fall inside normal torque ranges that we encounter in tuning, some holes that by intention fall within the extremely tight range, and some holes that fall in the too loose range. To that we add a tuning lever tip that has no play in its interface with the pin.

You could also use a torque wrench to assign torque readings to each of your pin holes. All pins would be driven to the same height, and should be sitting low in the block, but still within a "normal" height range. We should have a more close up view of the pin, and a scored line on the pin itself. If one could overly a strategically placed reference line by video processing, that could give us a more visible and reliable reference point.


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Folks, give me a week and I will make every effort to produce a video with pin torque and degrees of twist displayed. It's something I've been wanting to do anyway. I am curious about the residual twist. Oh, I don't have an impact tuning lever, but I can whack a regular one with a wooden mallet to get an idea.


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Upon review the pin is turning in the vise.

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Originally Posted by UnrightTooner
Folks, give me a week and I will make every effort to produce a video with pin torque and degrees of twist displayed. It's something I've been wanting to do anyway. I am curious about the residual twist. Oh, I don't have an impact tuning lever, but I can whack a regular one with a wooden mallet to get an idea.
Excellent. It will be really interesting to see. I look forward to it.
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Regardless of whether in fact the tuning pin(s) twist or not, it takes time, practice, attention to detail, and repetition, and time and practice and repetition...for a tuner to master the nuances of creating a stable situation AND be in tune.

It could be likened to someone learning computer programming. One can learn the basics of a language in a few months and be a "programmer" or "coder", however buried deep inside all these languages are methods of doing things that are far more efficient and useful that are not openly apparent to the novice but only become so after significant experience, experimentation, and observation (as well as input from experienced peers). It has been said by some that it takes roughly 10 years to "master" any new skill.

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Originally Posted by P W Grey
Regardless of whether in fact the tuning pin(s) twist or not, it takes time, practice, attention to detail, and repetition, and time and practice and repetition...for a tuner to master the nuances of creating a stable situation AND be in tune.
Whether or not the pin twists is important. Bad science leads to bad technique. I base my technique on the pin not twisting. If it can be demonstrated that it does, then I need to alter my approach. All the testing that I have done so far indicates there is zero twist happening in our normal range of operation. The head flexes, but that is something entirely different.

Conversely, many techs assume that the pin is twisting in the pinblock, and they have their entire tuning technique setup based on that assumption.

The pin either twists or it doesn't. I don't care either way, but it is important to know so that technique can be applied to things that matter, and not things that are imaginary.

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Originally Posted by WilliamTruitt
The fatal flaw of this test is that it is painfully obvious that the vise itself is almost constantly making large movements from the various pressures the tuning lever is placing on the pin. That alone makes any efforts to isolate twisting or bending of the pin on its axis untrustworthy. We see the whole string move, which suggests that the pin is rotating within the jaws of the vise. Is that because the vise is not holding the pin securely enough, or because the pin is so rigid that it cannot twist on its own axis? One can have a point of view towards one or the other conclusion. I choose neither conclusion, because the test is insufficiently controlled.
I agree with your overall standpoint here. Basically, we can't draw any conclusions. However, I observed something slightly different. I see the jaws on the right moving with the hammer. So, the pin doesn't actually move within the jaws, but in reality roll the jaws in one direction, and then rolls back. It doesn't really matter though. The end result is the same. We don't really have any new information yet to draw a conclusion.

Originally Posted by WilliamTruitt
It is also obvious that there is some slop from the star tip being a bit oversize in relation to the top of the tuning pin. You can see movement of the tip before it gains purchase on the pin.
I'm not sure how this is going to be able to be addressed. Maybe they have to file the head of the tuning pin to custom fit the tuning hammer. In any event, I just like the phrase "before it gains purchase on the pin."

Originally Posted by WilliamTruitt
You could also use a torque wrench to assign torque readings to each of your pin holes. All pins would be driven to the same height, and should be sitting low in the block, but still within a "normal" height range. We should have a more close up view of the pin, and a scored line on the pin itself. If one could overly a strategically placed reference line by video processing, that could give us a more visible and reliable reference point.
I guess we could see with slow-mo on YouTube if that scored line goes askew. But, a long straight wire crazy glued to the bottom of the pin (essentially what rontuner was talking about, just without the drilling) my help to magnify if any twist is happening. It's going to depend on the camera angle, but I guess another wire could be crazy glued to the side of the pin near the block. That would eliminate some, but not all, of the bending and flexing that is happening at the head. Either way, I guess that would show the bending, as the top wire dips/raises as apposed to the wires only going out of parallel (which would indicate twist).

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I think that the words 'pin twist' is a misnomer. In practice, whether or not the pin metal has any significant twist, the 'assembly' of the coil, the pin and the pin-hole fibres all contribute to 'a twist'.
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Originally Posted by Beemer
I think that the words 'pin twist' is a misnomer. In practice, whether or not the pin metal has any significant twist, the 'assembly' of the coil, the pin and the pin-hole fibres all contribute to 'a twist'.
I'm not sure if I understand what the fibers aspect is all about, but I think I agree 100% with the concept in general. There is a feeling of a "twist," but it is not the pin, it is the entire becket bend (the leg, the crook [aka the becket], the turns of the coil, and the bitter end) and how it is set on and interacting with the pin. Of significance is that the last turn has a pretty big impact on what is going on with the feeling of a twist. Regardless, I would love to be able to, once and for all, put this pin twisting issue to bed. It is so prevalent in people's thought process, that people think it is so obvious and stupid to even question its existence. If it can be proven to exist, then so be it--let's make the imaginary, real again.

Currently, I do not compensate for the imaginary twisting of the pin in my approach to piano tuning.

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Originally Posted by piano411
Currently, I do not compensate for the imaginary twisting of the pin in my approach to piano tuning.

Then it is non-existent and therefore a non-issue.

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The University of Wisconsin piano shop did a multi year 60 page report of calculations and analysis of tuning mechanics. They studied the upper twist of the tuning pin, lower twisting portion of the pin, rotary twisting of the entire pin, tuning pin tilting, friction resistance on the capo bar, local twisting deformation of the pinblock around the pin and many other things. If anybody is interested in it you might want to contact them and ask if they can send it to you.

The world is round and pins twist. Santa Clause and Bigfoot are probably imaginary.

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Originally Posted by P W Grey
Originally Posted by piano411
Currently, I do not compensate for the imaginary twisting of the pin in my approach to piano tuning.

Then it is non-existent and therefore a non-issue.
Just because I haven't observed that pins twist, and I don't compensate for that in my tuning technique, doesn't mean that they don't. If they can be shown to twist, then I would alter my technique to compensate. If no one can demonstrate that this is even possible, then conspiracy theories of twisting pins needs to be confronted every time it comes up. It doesn't no one any good to shove false observational science in people's faces while peeing on their feet. That is no way to learn, or to improve one's own technique.

If the University of Wisconsin shop shop did a report, then it would be public information. I won't hold my breathe that anything will come of that, but I'll FOIA it. Without seeing how the information was gathered and the research conducted, it is silly that anyone would even bring it up without siting the actual document.

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But you already have fully stable tunings on the fact that they don't twist. If you have consistent success on that basis and nothing you have ever seen, felt, or heard tells you otherwise, what then would you do if it it now "appeared" that they do twist a little? My guess is: nothing.

Which brings me back to the fact that experience teaches us how to "settle" and balance as needed, the forces (whatever they are) in the PSA.

Peter Grey Piano Doctor

Last edited by P W Grey; 01/17/21 04:32 PM.

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