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hk1997
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1342309826[/url]' post='549754']

Me and I argue all the time.

I often imagine Strad and GdG owners stroking their violins in the middle of the night, saying "My own, my precious." unsure.gif

Addie, that's completely OT.

Comparing one guy doing acupuncture to hundreds or even thousands experimenting with tap tuning requires a good imagination too. Not to mention dismissing the Messiah as a fake, just because, well, just because.

Point taken.

Oh, and please don't clown around on a public forum.

Hey, that was you, not me!

I beg to differ.

Don't beg, it's demeaning.

Hey, I wonder what CT is having for dinner?

Which CT?

Oh, right. Dunno.

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I knew that you did not have anything on the matter to share. But if you do come up with something I would be interested to see. I know you do FEA and that with a decent violin model you could do tests like that. There are also other ways this could be done. E.g. track the modes from free plates by varying the elastic parameters of the ribs from very low values (e.g. thin paper or mylar) to natural values for maple. This is a method utilized by Colin Gough in his FEA studies.

I'm not sure that FEA is really the right tool for violin studies. I recently looked at a paper where they made a careful model of a known violin and then compared the simulated modes to the real violin. I don't remember all of the details but I do remember not being excited by the level of agreement. I think tests on real violins is the only way to go.

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Accidental catch about CH.

She seems pretty aware of what is lacking in free plate tuning, demonstrating Energy Tuning by tapping assembled body.

Enough data If I know how to use it.

The first thing I get from this movie, the iron will, the determination, courage of a true believer.

She used the word hostility once.

What is the intersection with this thread?

Make a hole in the river bad, instead of putting a rock.

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She used the word hostility once.

I'm sure hostility was a huge problem. It is my understanding that she occasionally generated some of it, and was also given a great deal of it. It is part and parcel of this interest we share.

All you have to do is post here - to see how it goes generally, and things are getting even more idiotic and argumentitive as time goes on, and more actual experienced makers simply find a better experience for their time than posting here.

Burgess is still here, but I think he LIKES the arguments - it will be interesting to see what happens there over time also.

I find it interesting who doesn't post here any longer - many of whome I still communicate with, and none of them regrets finally making the change apparently.

... interesting, (and tempting in a way) isn't it?

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but for a couple "dearly" departed members, were now blessed with some really serious top expert contributors, for the most part recent arrivals, bruce carlson, roger hargrave, jacob saunders, peter ratcliff are making major contributions to this sight with regularity, how is that worse than the old maestronet, what im seeing a lot less of is big mouthed amateurs trying to tell professionals how to do things, so contradictory to your asessment, ct, i see things getting a lot better,

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but for a couple "dearly" departed members, were now blessed with some really serious top expert contributors, for the most part recent arrivals, bruce carlson, roger hargrave, jacob saunders, peter ratcliff are making major contributions to this sight with regularity, how is that worse than the old maestronet, what im seeing a lot less of is big mouthed amateurs trying to tell professionals how to do things, so contradictory to your asessment, ct, i see things getting a lot better,

Good deal Lyndon.

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in other words in the old days it was the professionals that were afraid to say anything, for fear of being ridiculed by amateurs. now were seeing a lot of amateurs afraid to contradict the professionals, i know you see that as a turn for the worse, ct, but to me its now almost as it should be

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but for a couple "dearly" departed members, were now blessed with some really serious top expert contributors, for the most part recent arrivals, bruce carlson, roger hargrave, jacob saunders, peter ratcliff are making major contributions to this sight with regularity, ....

agree, ..

Just simple example,.. weight of Il Cannone,

I don't even remember how many different numbers were being whispered around..

All these detailed pictures, especially inside of old master works..

..Or sound post pressure..

It is priceless to an amateur like my self.

CT,

I think, appreciation of the culture of an open society may not be simple, if never felt the lack of it.

I am aware of it and enjoy it.

I post my posts, and will do so. It is too late for any intimidation for myself honestly.

The only reason, I am posting here is to get feed back on my ideas and practices. There is no bad feed back, as long as it is directed to the idea not the presenter. There are several types of deceptions, I think the worst one is the self-deception, which I may fall in easily, because violin is such a darn romantic object. I am ready to skip any thing that might be offensive, as long as I learn some thing out of it.If am I am in an illusion, it is the worst, no the ideas, words, or disagreements.

The only thing I can tell you, it is always safe, to look at the idea first, rather than who presents it.

I may not understand it, fine, this does not qualify the idea is wrong, but assigns me some home work..:)

I like your style, shooting straight without bending the words.

I like and appreciate it here in this little town as well.

I think Glenn summarized very well,

Rational thinking will work in any case.

Lets use it.

Apologies, no intention for any temptations for new bets.. I am out.

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I'm not sure that FEA is really the right tool for violin studies. I recently looked at a paper where they made a careful model of a known violin and then compared the simulated modes to the real violin. I don't remember all of the details but I do remember not being excited by the level of agreement. I think tests on real violins is the only way to go.

Usually there is a model calibration step, where parameters are adjusted so that the model matches the known mode shapes and frequencies of the actual article. Perhaps that was missing, or there were other shortcuts in the modelling.

The main benefit I see for FEA is sensitivity analysis... seeing how things change with tweaks to shape, thickness, or material properties. That's REAL hard to do on an actual violin and get a result that is positively due to just the parameter you're trying to change, and not a zillion other things that are accidental.

Also, I believe there was an idea to use FEA and the Strad3D results to back-calculate the wood properties... via the "calibration step" I mentioned.

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CT,

I think, appreciation of the culture of an open society may not be simple, if never felt the lack of it.

I am aware of it and enjoy it.

I post my posts, and will do so. It is too late for any intimidation for myself honestly.

The only reason, I am posting here is to get feed back on my ideas and practices. There is no bad feed back, as long as it is directed to the idea not the presenter. There are several types of deceptions, I think the worst one is the self-deception, which I may fall in easily, because violin is such a darn romantic object. I am ready to skip any thing that might be offensive, as long as I learn some thing out of it.If am I am in an illusion, it is the worst, no the ideas, words, or disagreements.

The only thing I can tell you, it is always safe, to look at the idea first, rather than who presents it.

I may not understand it, fine, this does not qualify the idea is wrong, but assigns me some home work..:)

I like your style, shooting straight without bending the words.

I like and appreciate it here in this little town as well.

I think Glenn summarized very well,

Rational thinking will work in any case.

Lets use it.

Apologies, no intention for any temptations for new bets.. I am out.

Yes, good points Selim.

Your arguments here are always your arguments - and I have noticed that even when you get challenged here, you keep your cool and reply simply and straight foreward, without a whole lot of regard to posters who attempt to turn it into a personal argument... which must be occasionally a tall order...

Usually I just ignore the "problem posters" also, after all, the most they can do, really, is distract for a bit, if you allow it. And it's possible to just ignore such distractions and listen to the makers who reply and who will usually add interesting points which they are able to discuss rationally - though I do get sidetracked occasionally by one or more of the the "somewhat challenged" posters here - I probably should just learn who not to respond to whenn they tend to get attackish on a personal level - not that difficult a thing really.

Thanks'

ct

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Off topic now, but thought I'd share a slide from Colin Goughs ASA meeting talk from 2010 where he show how the modes of a body with very weak ribs change its resonances when the ribs are made stiffer in steps, I think beyond what is natural.

I do not know what region the natural stiffnes will lie within yet, although I have data on maple which could be used for that asessment. The thickness of the ribs also would probably matter.

Gough is preoccupied with the idea that resonances show veering action when they come close enough to each other and think that modes do not cross. E.g. that the B1+ and B1- never cross so that the B1+ comes below the B1-, but I think that can indeed happen if the back plate is thin enough. So I think that assumption is wrong in general, although the veering effects do appear.

I think that assumption has led to not letting the coloured lines cross in the attached figure. I think they do, and therefore it would be interesting to repeat this test, but then carefully monitor the mode shapes as they close each other and see if they actually do cross or not in frequencies.

I think it can be done with John Masters Abaqus FEA model in a simple way. The model is not easy to "calibrate" but the modes of the free plates look pretty ok, and changing the rib strength is easy to do.

Maybe Gough keep the same colour on the lines to keep track of the sequence the resonances appear in. Would be the fastest way to compile these data. Just copy the text file sequence with the calculated resonance frequencies and paste it into a spreasdheet for each calcualtion. To keep track of which modes actually follow each other would take something of a puzzle to accomplish. But just following the most important ones would be easier. Maybe there can be made a track between the signature modes and certain free plate modes? The vibration shape would change through the process.

Another method would be to vary the input plate parameters, graduations, arching and wood properties and see how that influences the resulting model. Changing wood properties is the easiest part to do.

Goughs slides can be seen here: http://scitation.aip.org/confst/ASA/data/12/2aMU2.pdf

post-25136-0-54740600-1342367880_thumb.jpg

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Usually there is a model calibration step, where parameters are adjusted so that the model matches the known mode shapes and frequencies of the actual article. Perhaps that was missing, or there were other shortcuts in the modelling.

The main benefit I see for FEA is sensitivity analysis... seeing how things change with tweaks to shape, thickness, or material properties. That's REAL hard to do on an actual violin and get a result that is positively due to just the parameter you're trying to change, and not a zillion other things that are accidental.

Also, I believe there was an idea to use FEA and the Strad3D results to back-calculate the wood properties... via the "calibration step" I mentioned.

You must've read the half page I ended up not sending. :) :) :) and re-arranged it shorter and MUCH, MUCH better.

The calibration is very important. If, for example, the model was for an Aluminum violin one would expect less than 4% discrepancy and 1.5% is common and indicative of a professional result. With a violin the main problem is the material model. Wood is the most complex material I am aware of and I truly believe that if there is a more complex one it must be of extraterrestrial origin.

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Off topic now, but thought I'd share a slide from Colin Goughs ASA meeting talk from 2010 where he show how the modes of a body with very weak ribs change its resonances when the ribs are made stiffer in steps, I think beyond what is natural.

I do not know what region the natural stiffnes will lie within yet, although I have data on maple which could be used for that asessment. The thickness of the ribs also would probably matter.

Gough is preoccupied with the idea that resonances show veering action when they come close enough to each other and think that modes do not cross. E.g. that the B1+ and B1- never cross so that the B1+ comes below the B1-, but I think that can indeed happen if the back plate is thin enough. So I think that assumption is wrong in general, although the veering effects do appear.

I think that assumption has led to not letting the coloured lines cross in the attached figure. I think they do, and therefore it would be interesting to repeat this test, but then carefully monitor the mode shapes as they close each other and see if they actually do cross or not in frequencies.

I think it can be done with John Masters Abaqus FEA model in a simple way. The model is not easy to "calibrate" but the modes of the free plates look pretty ok, and changing the rib strength is easy to do.

Maybe Gough keep the same colour on the lines to keep track of the sequence the resonances appear in. Would be the fastest way to compile these data. Just copy the text file sequence with the calculated resonance frequencies and paste it into a spreasdheet for each calcualtion. To keep track of which modes actually follow each other would take something of a puzzle to accomplish. But just following the most important ones would be easier. Maybe there can be made a track between the signature modes and certain free plate modes? The vibration shape would change through the process.

Another method would be to vary the input plate parameters, graduations, arching and wood properties and see how that influences the resulting model. Changing wood properties is the easiest part to do.

Goughs slides can be seen here: http://scitation.aip.org/confst/ASA/data/12/2aMU2.pdf

Have you got the original paper ? I don't understand a thing...more so once I look at his post pics - they don't look right.

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Have you got the original paper ? I don't understand a thing...more so once I look at his post pics - they don't look right.

I do not think there are any paper on this, or at least I do not know of it. He uses Comsol, and he probaly does not calibrate carefully. But this is for the idea. Now, I think you got to be more spesific in your criticisms. To much fuzziness in your input to be taken seriously :-)

There are an other really important idea in that presentation, the coupling between bending and breathing components of the B1 modes. Mastering these are important in getting these two modes strong in the radiation responses. Most good makers does that intuitively correct I think. Useless information for most, but important for those who do modal analysis on violins I think. At least if one wants to do something about the balance between these modes.

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modal analysis will give you an approximation of what is happening to the structure, but what information does it offer on how to change the structure to make it to radiate the way you want it to?

Oded

Modal analysis give close to the exact behaviour of the structure, but for most on accelerometer users only in the out of plane direction. E.g. the volume change calculations that can be taken from the modal analysis data give some evaluation of the different modes 'breathing capacity' or just how much air is moved from their breathing action. The amount of bending of the body can also be caluclated by just taking the sum of the plate movements, while the breathing data comes from the difference of the plate movements. This is done after the vibration velocities or acceleration is transformed to displacement. I think this is an useful tool in the analysis.

The modal analysis does, of course not, tell you what to do about the modes in order to make the breathing component of a certain mode stronger. So some thinking and knowledge is needed to influence that in a sucessful manner. Asking George Stoppani what to do is the simplest action to do. Building experience on the matter takes a lot of time.

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I do not think there are any paper on this, or at least I do not know of it. He uses Comsol, and he probaly does not calibrate carefully. But this is for the idea. Now, I think you got to be more spesific in your criticisms. To much fuzziness in your input to be taken seriously :-)

There are an other really important idea in that presentation, the coupling between bending and breathing components of the B1 modes. Mastering these are important in getting these two modes strong in the radiation responses. Most good makers does that intuitively correct I think. Useless information for most, but important for those who do modal analysis on violins I think. At least if one wants to do something about the balance between these modes.

I'm not criticizing anything. If you want to "share" something then share stuff we can figure out how was done. Or, as it happens MOST of the time with you "sharing" it is irrelevant to the problem at hand. You can't run forever on "maybe", "I think", "probably", etc. Is there ANYTHING you are sure about ? ( Besides the fact I think like an old fart ? ).

If you want to be the scientist of the forum, please stop pasting pictures you don't know EXACTLY how were arrived at.

And by the way he uses Cosmos/M and he has NOTHING to calibrate. Cosmos/M is notorious for a couple of nasty quirks in the interface and it's a piece of software which has been discontinued for quite a few years by now with no suport. Dassult bought SRAC.

Oh ! I forgot. Do not "share" if you don't like to be criticized by morons like myself.

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I'm not criticizing anything. If you want to "share" something then share stuff we can figure out how was done. Or, as it happens MOST of the time with you "sharing" it is irrelevant to the problem at hand. You can't run forever on "maybe", "I think", "probably", etc. Is there ANYTHING you are sure about ? ( Besides the fact I think like an old fart ? ).

If you want to be the scientist of the forum, please stop pasting pictures you don't know EXACTLY how were arrived at.

And by the way he uses Cosmos/M and he has NOTHING to calibrate. Cosmos/M is notorious for a couple of nasty quirks in the interface and it's a piece of software which has been discontinued for quite a few years by now with no suport. Dassult bought SRAC.

Oh ! I forgot. Do not "share" if you don't like to be criticized by morons like myself.

I can of course run as I want to at any time. You are simply holding up a mirror here. What does not look right?

Yes I think you are very negative and I seriously doubt you have any real insights into violin acoustics yet. I know you run FEA and have some experience with that. But I still have more insight in FEA on violins and wood than you, with my limites experience. Abaqus does orthothropic materials and can therefore deal with wood. In Goughs model he solves that using narrow strips of material with high and low E-modules to emulate the wood properties.

You are not reading my post properly. COMSOL Multiphysics is the tool he uses, Most likely the 'Structural mechanics module'.

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modal analysis will give you an approximation of what is happening to the structure, but what information does it offer on how to change the structure to make it to radiate the way you want it to?

Oded

Which is why, some people have worked out methods that they say work with various abstract methodolgys having to do with this particular (Hutchins) method of analysis for example..

People can use information in variouis personal ways, that tells them various things about the violin being constructed. There is no question that the information gained by such testing might be usefue to some people, who use it in various different ways, that perhaps disclude the more popular or published way of applying the information gained.

The people I have spoken with who have modified this proces, found it works for them, and have found it useful, have moified it in conjunction with their own needs - which only coincide with the necessity for such information and using the Hutchins 'conclusions' to make the plates work.

Not only that, they apparently do not choose to popularize their process here, for example, I would guess because they don't really care too much who will "buy" it and who will not. And they (well ,not really that many makers) don't want to deal with a public, which can be difficult to deal with. But the fact is that a couple of them are great violin makers - So I always hold out that a method has been found that can be learned that uses the information gained by such an experimental methods as those that are are revealed by plate measurementsor "tuning methods", that works using the information gained, but with a different application or conclusion.

Personally, such information (about the plates) gives me nothig I need to finish my own work to my own conclusion.

But does it work for them? From examples I have heard (& tried playing), yes definately it does.

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I can of course run as I want to at any time. You are simply holding up a mirror here. What does not look right?

Yes I think you are very negative and I seriously doubt you have any real insights into violin acoustics yet. I know you run FEA and have some experience with that. But I still have more insight in FEA on violins and wood than you, with my limites experience. Abaqus does orthothropic materials and can therefore deal with wood. In Goughs model he solves that using narrow strips of material with high and low E-modules to emulate the wood properties.

You are not reading my post properly. COMSOL Multiphysics is the tool he uses, Most likely the 'Structural mechanics module'.

I don't have ANY insights in violin acoustics. I don't know what violin acoustics is.Mr. Goughs should rather type two numbers in Ansys than tinker with "narrow strips of material".

And aproximating wood as a linear orthotropic material fails immediately in practice. Wood is a very complicated thing and that complexity bites almost immediately but for the lowest frequncies and stresses.

No valuable information can be derived from steering at wobbly pictures of plate modes. Nothing. Zilt. Nada. That's of course my "old fart" incompetent opinion.

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1342375420[/url]' post='549840']

Which is why, some people have worked out methods that they say work with various abstract methodolgys having to do with this particular (Hutchins) ...

But does it work for them? From examples I have heard (& tried), yes definately it does.

This implies multiple pathways to the same result. But it seems the Post-Hutchins methods have not been reduced to a simple repeatable protocol.

So, are the post-Hutchins makers any better than well trained traditional craftspeople? Are the two even comparable?

Addie = not trying to extend the page count with this post.

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Mr. Gough should rather type two numbers in Ansys than tinker with "narrow strips of material".

Now, you know the price of these packages and Mr. Gough have not asked for any advice. I leave it to himself to decide what tool he should use, and I am grateful that he shares his ideas and findings. He has come up with some good ideas and he is a very skilled, enthusiastic and creative lecturer. Maybe his best contributions yet is on the mechanincs of bows. He has a JASA article on the subject where he also uses FEA.

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