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Belly vs Back Arching Asymmetry

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Bruce and all of you must understand that an instrument supported as it was on the climate box will deflect by the dead load different as from string load. The fix point remain at the same level.

On a free violin with increasing string load the end blocks move upward/inward by rotation. How much the left and right side rotate depend on the stiffness of its structure. This means that one side may rotate more than the other. Bruce in the diagrams show that the end block remain at the same level. When this happens the sound post must rotate which is does not!!

So what we see is two complete different circumstances. When we now look at the colored figures we see that the edge of the outline does not move upward, remain mainly green. Already this made me asking myself what's wrong in this investigation. The second that I find an answer on was the duration between the loaded and unloaded string condition. Normally it takes 24 hours to reach a stable condition. The 3D phot test was performed in ca. 3 hours. So with this knowledge we cannot say we got a verifiable picture of what happen really with the instrument. I cannot say other than that the person how made the color map manipulated the result. The end blocks must remain at the same level as well as the rib level, thus the edge of the outline. The center by the load on the bridge, equal the dead load as it was in the climate chamber, also when down. This is the understandable mistake they made.  The center and the back at the location of the sound post do not move by increasing string load, Impossible. If it is that way the instrument on a scale must show an increasing weight and this is not the question. The colored images are manipulated!

Take a close look at the figure with text on C1, O1 and O2 etc. What we see is that the center is forced down(blue) the bridge feet move upward(yellow) the wing at the bass bar move even more down(dark blue). These conditions are with increasing load. We see the fingerboard tilting down (the tip is dark blue) Nothing of these cooler are correct. They are put on the figure by manipulating them not understanding the difference between the load condition Climate Chamber and Free violin. I discussed these circumstances in a visit with Bruce twice and he also in written email confirmed that he believe the rib does not bend/deflect. Now it is up to you all studying the three reports published by Bruce and read my review. Understanding how the violin structure deflect is highly important. 

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3 hours ago, reguz said:

Its for all of you to understand what the to images show.

1. the instrument fixed on a structure in the climate chamber

2. The 0,00 line show the blocks are fixed and the deflection at the bridge/sound post

clambed in the climate chamber.docx 976.48 kB · 7 downloads

It looks like the saddle and the upper block are used as the zero reference points.  You may have an issue with that, but I do not.

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David , the reference points are hold fixed. The photo show this but also the figure bellow.

If they where not the curve shape by the load must produce a longer chord line.

Laying a load on the bridge requires that the structure do not tilt side ways The resistant on the bass bar will cause tilting by that load condition. 

That's why they clamed the instrument.

Look at the figure. The deflection on the "island" is much higher than on the bout shapes.

Read what Nigel Harris found out about structural deflection. You may draw a line from end block to end block and will observe the movement on the end blocks and the movement under the bridge feet. The bass bar feet is forced upward. Compare with what Bruce produced. He produces the main deflection under  the bridge/sound post together with the back plate moving downward. 

Colin Gough made the same mistake He show cross section at the sound post widening the belly and reducing the width of the back. He also believe the end blocks do not move. Study my vector diagram. what happens. Applied string load is used to deflect the bout shapes. A lot of energi is put in the structure (bout shapes) that become used and transformed inti dynamic behavior of the structure. If the shapes are to stiff ( thickness) they will not vibrate and the resulting sound become poor

In the dissertation you can read what function special structural quality STL shape has.  In some extend you also can see these STLs on the Canone. Ones I asked Bruce checking these STL on the instrument in the museum in Cremona.Moving possiblity arc lenght20210318.pdf. He promised but never did. WHY?

In the dissertation report you may read what function STLs have produced.

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I have already read your 23(?) page critique of the Carlson et al study, and also your theories about STL shapes, applied to violins. Let's just say that you and I see things quite differently.

First of all, your STL straight lines are a very tiny portion of the total load-bearing area of a violin. If these straight-line portions were made of a super-strong low-deforming material, they would be able to take huge loads. But they are not made of such a material. These lines have a major cross-grain component, an orientation in which spruce is quite weak. That's one of the reasons we try to use bass bars with very little grain runout.

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Yes it might be that we see things different but STL structure carry no load. I never has said that. These STLs do not need to be super strong at all. This is your and other misunderstanding. Yes these lines have major cross-grain components. For a load condition these local lines are not strong but that's not the meaning and the function I have found they hold...

The bass bar hold a complete different function. The compression force that arise on the end blocks from the strings shortens the "chord line" the result of such behavior pushed the top of the curve upwards.

In fact the location the bridge feet is located and hold a downward force is not enough withholding the outward bending. When you look close on the figure Nigel Harris has measured you will see that in spite of the string load from the bridge the curve still  move outward (=upward) resisting this outward bending we must reinforce the structure and that is ONE of the reason why we have a bass bar. There is other function that is related to required stiffness for higher frequency vibration. So the bass bar is a quite good solution for two reasons.

Nigel observed deflection from four point located at the widest outline of the two bouts. He gave them equal high in relation to the zero level. If you ever read his thesis he found out that the end blocks move upward (=contra Bruce ideas since the rib does not bent he says) and the center thus the bridge feet and sound post move down. This is a very difficult condition to understand. I decided measuring from the sound post and recalculate the figures (numbers) he support is with to new ones. This give is a complete new information. The back is bend over the sound post and the bout shape become more bent and the four locations of observation now has new level. What we can say is moving those four point of observation closer the end blocks or in the direction of the sound post we get other information. I say the sound post do not move and have explained earlier why it is so. It's easy to check.

Now something about the STLs. Primary the make a pyramidal shape with a truncated top. Look at them as corner lines of a tent. The lines on a tent are stressed and straight while the canvas also may be stressed but much less stable. A wind will deflect them easy by not the corner lines. Since the connecting structure in the STL on one side is growing concave and on the other side growing convex requires that when one become more deformed (by bulging) the STL do not change shape the other side the concave shape must change shape. This make a very stable structure produced by the convex/concave structural condition. Can the STL vibrate? Yes of course a stretched string does so why not the STL. In the dissertation we have looked if these STLs really hold this quality.  STL axis function make the seesaw behavior possible. When rotation happens a downward force arises in the C-bout that widens the body. This happens on both belly and back.  Read the dissertation and you will see. What is important is that also on the inside there must be an STL just under the outside. 

We thus have tested this in practicing and thus far many violin makers make STL condition with very good result. Some say this is the best instrument I ever have made.

What's interesting is how it looks on the instrument made by Strad and Guarneri. Well I have checked 10 instruments and the hold this quality on the outside. Unfortunately I do not know anything about the inside STL

You are able checking by yourself.  All arching shape have short or long STLs but mostly in different direction. The pyramidal shape then not always is optimal


Enclosed some other figure you may like.

Length deformation at end block20210318.pdf 2D geometric layout20210318.pdf STL on geometric arching shape20210318.pdf

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Do you think that if one is able to plot these lines somewhere within the material of a structure, that these lines must be significant or important?

If you plot this pyramid shape within an egg yolk, what does it tell you?

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2 hours ago, David Burgess said:

If you plot this pyramid shape within an egg yolk, what does it tell you?

That you've been holed up in quarantine, chasing your own tail for waaaaaay too long?    :huh:  :lol:  popcorn-and-drink-smiley-emoticon.gif.2672d16e240f4b1f9cf78c2a3deb017a.gif

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As a teacher of Math I know that there are many folks that just cannot grab even simple 3D sketches and much more that won't see anything in such plots as the deformed violin.... Just fiddle with fancy red to blue varnish. There's no help for these. I tried many methods and it's futile.

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David the question you ask "dp you think ... etc" is exactly what I asked my self when I in the very first arching shape I made and found these STL condition asked; WHATY DO THEY REPRESENT TECHNICALLY.

Do they have influence on the behavior of the instrument, Is there a geometric structure that predict that they must arise. I have been studying these questions for more than 35 year and last year with the investigation done on the university in Lund Sweden two young student did their master dissertation on this question. When I read your answers I almost think you have not read the complet these. I think it is impossible denying that these STL lines arises by the geometry I found. How do these STLs when we make them precise affect the structural conditions and behavior of the instrument. One thing is sure: they do not deflect over time. When they do not they thus are "strong" in spite of being just as thin as the rest of the arching. In fact as a result of being strong and resistent other structure acting on them, the bulging bouts, may have less thickness, are more flexible, allow some deflection becoming stress, have energy loaded shape that very easy become dynamical. These question I searched for an answer and I got it but you and other say we have to do with a lunatic. I'm not. I have a lot of experience from my work as an engineer and I look always with open eyes understanding structure and function. For this reason I like you and others to understand that the investigation Bruce did in the climate chamber loading with a dead weight and finally the 3D photo mapping hold two technical complet different condition. Their problem was and is they do not see the difference. They as by other believe there is no difference by loading the instrument at the bridge with support under the end blocks contra the action of the strings on the end block loading the instrument. Let look at Figure 9 in the review on Bruce work. What do we see? Both bridge feet area move upward. This can only happen when the bridge is taken of after strings are removed. When we load whit strings the island deforms the cross arc flattens and this give the effect that the wings move upward. Depending on the stiffness of these wings the will move. On the figure we see that the wing are moving downward back to their stale unleaded condition, their color become darker showing in what direction the move just as it bis with the location of the bridge feet moving upward.  This is the result of unloading the instrument from strings. Bruce say there is something wrong with the algoritm. I say Bruce does think wrong. This figure does not show a loaded instrument this is a condition soon after taking of the strings. We don't see any of the supporting sound post. All structure still is in a downward phase just like the loading condition in the climate chamber. Bruce and co see no difference in what they have done and that's the reason why he do not understand what went wrong. Look at the edge of the out line the are green. Green means no deflection. That green color you can observe along the complete out line. Bruce as I told before told me they ignored the deflection of the rib since it is so little. That actually was to find out but they failed since they do not understand. That's the reason why they needed manipulating the coloring. You may explain for me what I did wrong what the University in Lund did wrong I will close study what you have to say.

the island.docx

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I think both studies have great value.

What's not of great value is poor communication skills, which leads to total lack of interest in studies.

There is absolutely no need to say that someone is wrong, there are much better ways to do this

- Have you considered...

- I have found that...


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Mr. Zuger, Bruce and I worked together for a while, and I would describe him as one who has an extraordinary intuitive grasp of mechanical physics. What do I mean by "an intuitive grasp"?

A friend of mine used to be the head of engineering for a major global automotive supplier, and one of his duties was hiring engineers. He described applicants as fitting into two basic categories: Those who would try to solve a problem by spending all day doing pages and pages of diagrams and calculations (and often still get it wrong), and those who could solve it in ten seconds in their head. He always hired the latter if such a candidate was available, because that's what worked out best for his engineering department and for the company.

I think Bruce would be an excellent person to learn from, rather than try to nit-pick.

If you would like to send me one of your fiddles, I will put it through some accelerated "creep" tests (using templates, not scanning), and post whether your STL's, and some other parts of the fiddle, distort or not.

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Peter K-G. Its upp you you to say Robert your idea about the color map showing the deformation outward is WRONG. Do this is you find that and describe why!!

Bruce say the algoritm is wrong at the lpocation of the bridge feet.

Why than does he not say the wings of the F-s also are wrong?

Pleas lets discus this. Thus far no one discus but answer as you do.

The better to do is discussing.


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David. Why don't you read the these and make questions? What you say is I do not believe the University is able to do good what they did and the professors are not able as well.

Visiting Cremona I became introduced to Lucchi the bow maker. We had four meetings and had very interesting talks. He put four bows on the table and asked me which one is the best.

I did and still do not much about bow function but he showed me something very interesting how to find out what He believe is the best of the four bows. You may read about this on the enclosed report where I describe that we can see the same function, the dynamical function when some energi is applied. I cam thinking of the same condition on the violin but at the two sides of the soundpost/bridge.

You may say this is crazy but I found out it worked very well and the function of the violin can easy become improved by as I did polishing on the oxidated varnish making it more flexible.

We can not as it is with the bow adjust the string load. That tension is relate to pitch on each string so we must change the quality of the stick (= the violin body) No one know when you are finished with your instrument you have reached the optimal state. Yeas you can string quality but at a point you can not come further. That's why I started polishing.

I have been practicing this for many years now and it works very well.

Polishing is done on special location but not on the STLs


20180604 About the function of the violin.docx

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54 minutes ago, reguz said:

David. Why don't you read the these and make questions? What you say is I do not believe the University is able to do good what they did and the professors are not able as well.


Why don't you send me a fiddle, so we can actually test whether or not your STL's distort?

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Dear Violin RUS, in my review of the Bruce investigation I have drawn the two STLs on the belly where we can find them. On the other side we have the bass bar there the Cannone has less good STL shape or not. The figure above show that the end blocks are at equal level and the center (= sound post /bridge) are forces down by the dead loading on the bridge. There is much higher deflection on the lower bout. They draw the line by measuring at the black point on the belly. I'm sure all measurement are correct but this is not how a violin deflect by string load, only by dead load on the bridge with support under the end blocks.

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19 minutes ago, reguz said:

David, why don't you read the these and see what the FEA accomplished.

I did read them. Why don't we do an actual test on one of your violins incorporating your principles, rather than arguing the theoretical until one of us kicks the bucket due to old age? ;)

I am not retired, and have customers who have sent me deposits for fiddles, so that's how I need to prioritize my time between now and "taking the big dirt nap".

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David the These and the plates used in them are real plates not constructive parts. Try to explain for my why you have your doubt that there might be something wrong what the FEA accomplished. It's in the first place understanding how the instrument deflect and if as Bruce do loading the bridge with a dead weight is the same as the conditions that arise by string load!

If we can't agree on that it will be useless to go on. First we must agree on what's right or wrong. 

The plates used in the these are still not completed to an instrument. 

So there is no mening. But you have instruments yourself and can search for the STLs and show me. Both in and outside as they are on my plates. Participate please.


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15 minutes ago, reguz said:

David the These and the plates used in them are real plates not constructive parts. Try to explain for my why you have your doubt that there might be something wrong what the FEA accomplished.

No thanks. As a skilled amateur behavioral psychologist :D, and having read many of your posts over the years, I am able to predict exactly how this would go. This is not the way I am willing to spend the rest of my life. :)

By the way, I think you have misinterpreted the information presented in Bruce's study.

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5 hours ago, reguz said:

David you seem now what is misinterpreted, I'm thankful to read your lines how I should understand. Pleas do this!!! Thus far you have not participated with ?????

Bruce has already explained on page 6, referring to Marty's post on the same page using images from Bruce's study, that:

"The diagram I find most interesting is the left hand diagram, second row down, which is the difference in measured deformation between the violin at rest without strings and the violin tuned to concert pitch."

Yet you seem to continue to insist, both here and in the critique of the study you have posted on your website, that the measurements weren't or couldn't have been taken this way. Why would Bruce or I continue to engage, when your main interest seems to be endless arguing?

Now, if things go according to your normal modus operandi, I expect that you will want to endlessly argue about that, too. We'll see. :D

I hereby withdraw from further discussion with you.

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