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Secret Knowledge and violins


Craig Tucker
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Nothing really. Just keeping it for further reference.

Thanks, I feel good about that. I also admit that I am not sure yet what to do with the deformation numbers. Maybe subtract from the original model. If I just magnify the y axis only, I will get a non-CC which I call a Pseudo-cycloid. Perhas I should subtract them and then adjust the height. Don't know until I start monkeying with it.

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I think it is too soon to discuss actual violins. My new thread tries to make my hypothesis more clear as to how to optimize an arching.

In fact, Carl Becker said that Saconni had shown him a similar strap and pushed on it. I don't recal what they discussed, as it seemed vague to me. I believe the important issue would have involved the ease of shifting the bump, and the small amount of work required to move the inflection a small amount.

Do you have the material for a longer strap?

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I've been really interested in resistance to static deformation, but I can also see how that could tie into resistance to useful sonic deformation, since deformation is required to produce sound, and many of the loads are in (approximately) the same places.

I don't see a problem, because when everything in either a strap or a 2-D surface are in equilibrium with forces, there are no forces normal (perpendicular) to the surface. The only thing that I can think that would be of interest is if a restoring force (to zero normal forces) is not the same either side of equilibrium.

Geometry can cause a restoring force to not be symmetrical, CONSIDER : A vertical mast in gravity. If it is leaning a bit by bending, as you push it upright, the force causing it to bend become less. If you make it weaker in the materials, it will bend over more. There is condition when the material is too weak to support it from collapse.

One can look at EULER BUCKLING in Wikipedia. I don't think the math is too much. An axially load beam that is pinned (free to rotate) at the ends will fail if it is skinny enough. The actual normal modes (of transverse vibration) change so that the fundamental drops to zero. This is the condition for buckling failure.

Fixed-fixed end conditions behave differently. We have that extended into 2-dimensions in a violin plate.

So just beware that I call a violin top a 2-D surface even though it extends into a third dimension of height.

I suppose one could make a transformation where the plate is "flat" in a non-Euclidean space. (Just like Einstein did with General Relativity) I am no mathematician, but this approach might actually be the best for someone familiar with that kind of math.

My wife knows a couple of really smart mathematicians at Ohio State. Maybe if the problem is really well-stated, I could eventually talk to one of them.

He will be at parties for the Chinese New Year. We two both usually stand around doing nothing at such parties. Maybe he would take an interest. He may even have some immediate reactions.

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I've been really interested in resistance to static deformation, but I can also see how that could tie into resistance to useful sonic deformation, since deformation is required to produce sound, and many of the loads are in (approximately) the same places.

The typical deformations are from in-plane forces. They should be independent of any normal force involved in a vibration.

If a restoring force is asymmetrical either side of the zero position of a wave, will that hurt tone? It would depend on the size of the wave deformation.

I recall that early static experiments gave deformations on the order of thousands of an inch, and I really have to go back and look at these things.

Schelling early on (1960 about) said that maximum vibration would be on the order of 3 or 4 thou maximum. That is about the thickness of a complete varnish. Also maybe of the same magnitude of typical vibration excursions.

I have a new computer and lost my ABAQUS FEA software. There is a version several years newer, I don't mind buying another for $150 (handled and shipped). I will certainly be using much more than that money in time. But all I have is time; hopefully a good deal of it.

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I was kinda hoping you'd like draw it out for us.

Do you mean full scale? I can't do that on your monitor. Please go down and ressurect my thread on Longitudinal Archs. It is getting buried.

I am interested in math, not helping make violin patterns for others. I use my results from spreadsheets to program my cnc machine.

Ultimately, I think the thing to do is make another pantograph and use the CNC to make patterns. I canabalized my own plus a larger one for cellos (never finished) to get parts for the CNC.

And by the way, if you consider the time and effort to make a CNC plus a method to put in numbers, you would not belittle CNC. YOU tell it exactly what to do. I made the spreadsheet programs to generate transverse CC's. These were based on a longitudinal arch I calculated with experiments in MATH-GV. So go get that free software.

You can take the function MATH-GV shows to be "nice." Then calculate the curve in a spreadsheet. And then plot the points out as you wish.

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ABOUT SPREADSHEETS:

I use an old (1985) DOS LOTUS spreadsheet which was copied by EXCELL to be the first MSDOS EXCELL. Lotus did it first. My program has the ability to write nice compact macros right on the spreadsheet. It is very powerful and simple.

I am sure EXCELL has a provision for this, but I did not want to learn a special form of BASIC to do it. I had over the years learned to use the DOS LOTUS very nicely for all my recordds and work. I still use it. That is 30 years of usage. It will never wear out.

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I've been here at MN for under a year now and I've never heard anyone belittle CNC other than it"s back in the corner somewhere.  I think It's great you would want to try it for plate carving- you only live once, may as well do it in this lifetime. 

 

  I'd prefer not to keep the other thread going.  I wouldn't know how to help anyone there or get any good out of t for myself.  I have the violin I may want to copy one day.  Kevin Kelly's and Davide"s method for arches makes sense to me.  I have Mr. Darnton"s radius numbers I need for the circles.  What I don't have is a method for copying an exact long arch on an existing instrument- maybe there isn't away afterall.

 

Keep doing what you're doing John, fall and winter will be here and others will be looking for something to do or help with. 

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I've been here at MN for under a year now and I've never heard anyone belittle CNC other than it"s back in the corner somewhere.  I think It's great you would want to try it for plate carving- you only live once, may as well do it in this lifetime. 

 

  I'd prefer not to keep the other thread going.  I wouldn't know how to help anyone there or get any good out of t for myself.  I have the violin I may want to copy one day.  Kevin Kelly's and Davide"s method for arches makes sense to me.  I have Mr. Darnton"s radius numbers I need for the circles.  What I don't have is a method for copying an exact long arch on an existing instrument- maybe there isn't away afterall.

 

Keep doing what you're doing John, fall and winter will be here and others will be looking for something to do or help with.

If you take five minutes to get the graphing software at MATH-GV.COM, I can send you map files. I agree on the CNC. I have used it once and made no more violins, and I made the machine in 2011. Since then, I have changed my fillers and have been using Chinese whites to experiment with that.

I had no more ideas about arching until now. If my hypothesis is correct, and if I can find a slightly better arching than given by CC's then I could take those numbers directly into my calculating proograms. Perhaps by then, I will have a new pantograph and make patterns with the CNC.

The reason for the pantograph is that it is much faster than the CNC.

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ABOUT SPREADSHEETS:

I use an old (1985) DOS LOTUS spreadsheet which was copied by EXCELL to be the first MSDOS EXCELL. Lotus did it first. My program has the ability to write nice compact macros right on the spreadsheet. It is very powerful and simple.

I am sure EXCELL has a provision for this, but I did not want to learn a special form of BASIC to do it. I had over the years learned to use the DOS LOTUS very nicely for all my recordds and work. I still use it. That is 30 years of usage. It will never wear out.

 

Lotus 1-2-3 was awesome at that time.

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Lotus 1-2-3 was awesome at that time.

It still is, simple and the macros are fast. You can even make a macro instruction in the line before by concatenating different bits of text.

I made a nice convergence program to calculate CC's that cycled until a given error was less than a number I picked (one in a million error, say) And when the error was small enough, it branched to a new line in the list of data.

It took only three or four short lines plus three or four cells to store something.

I will happily send Symphony 2.2 plus a loading batch file if you send me a thumb drive.

It uses the command prompt found in you accessories folder. It is 1-2-3 with a rudimentary word processor. One can export spreadsheets as text files for WordPad. I use it all the time to make txt files for my CNC G-code or other things.

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Well, I've been thinking about this series of questions and answers for a while now, and my basic understanding is that, probably no one, or mostly no one, has really looked up and created a series of cycloid arches that are created, by the numbers that exist for a particular instrument being considered.

 

There is no mystery and no great theoretical problem that must be overcome to do this simple thing.

The simple factors that are needed are; the height and width numbers to plug in to the "rolling circle"... or, the numbers that plug in to the simple equation.

 

http://mathworld.wolfram.com/CurtateCycloid.html

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I've been really interested in resistance to static deformation, but I can also see how that could tie into resistance to useful sonic deformation, since deformation is required to produce sound, and many of the loads are in (approximately) the same places.

 

Frequency matters a LOT.  At low frequencies, certainly some concepts apply.  The higher you go in frequency, the more the plate breaks up into many small vibrating areas which have very little to do with the arching and related static analysis.

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Well, I've been thinking about this series of questions and answers for a while now, and my basic understanding is that, probably no one, or mostly no one, has really looked up and created a series of cycloid arches that are created, by the numbers that exist for a particular instrument being considered.

 

There is no mystery and no great theoretical problem that must be overcome to do this simple thing.

The simple factors that are needed are; the height and width numbers to plug in to the "rolling circle"... or, the numbers that plug in to the simple equation.

 

http://mathworld.wolfram.com/CurtateCycloid.html

 

Craig, I don't know how you arrived at that "basic understanding" but lots of people ( myself included ) are doing exactly what you claim it isn't being done. In order to improve one's violins ( or one's thinking about them ) , one needs a system.  Without a system one is clueless in figuring out which does what to whom.

 

Of course, one can always fall back to the "it looks to me like a picture I saw" method. But that doesn't work particularly well.

 

By the way, have you made any violins based on cycloids ?

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Could be. But don't you worry, all it's fine as long as you have an opinion about everything.

Not everything.  I just pay attention to everything.  Seems you have no faith in Johnmasters or Peter,  any particular reasons?

 

I know I have what I need to start and finish curtates but can't decide if to go back through the archives here or dig through my own rubbish to re-discover.

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By the way, have you made any violins based on cycloids ?

 

No.

Unfortunately for me (perhaps) I had my stroke before I had a chance to use the set of templates I did make - but I was, sort of, in on the "introductory" phase of cycloids, with regard to making violins based on whatever premises is being used (and at that time, cycloids were sort of new here, whether or not they were commonly used anywhere else, in the violin field - I don't know, as I was vary aware of most "systems" available and no where and no one had yet brought up the idea of using (simple direct) cycloids yet.

 

 

and at that point, I was just getting familiar with cycloids and perhaps using the information gotten from them on a violin, that I would make myself - as I had made many instruments in the past including about fifty violins.. I never was particularly laborious with regard to numbering them correctly. So, I'm giving as close a number as I have records of here.

 

After the stroke (please excuse me from even mentioning this here - but it was a great changing period of my life, and I find it hard to tell of certain things, without mentioning this period, and why it happened this way.) I tried to set myself re energized making violins, and I was going to make one based on cycloids - but I (after relearning how to speak English properly again, and going through about a year of three day a week at the therapist (never mind dialysis also three days a week (sheesh! -you might see how I got disabused regarding making violins again)

 

I still have the violin I started then - with the back, and neck finished, but with the belly just joined and roughed out - when I simply started in on making bows. Then I met Josh Henry here and he was kind enough to "take me under his wing" so to speak - so I can argue cycloids allday long, but I haven't made a violin out of them YET that is.

 

But who knows. I'm now sixty, and I truly believe that if and when I learn this new and all absorbing interest to my ( and Josh'es ) satisfaction - I may get back into making violins again, (yawn! I know, this is a long winded answer...) but I seriously doubt that I'll live that long.

I hope that your own venture into cycloids is prosperous.

As I had really high hopes for using them, and they are so absolutely simple to arrive at with the height and width's available - I'm really happy, and a bit surprised to hear the many makers are now adopting them - however successful they may be.

I'd like to hear from some of them? here? 

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Craig, I don't know how you arrived at that "basic understanding" but lots of people ( myself included ) are doing exactly what you claim it isn't being done. In order to improve one's violins ( or one's thinking about them ) , one needs a system.  Without a system one is clueless in figuring out which does what to whom.

 

 

What I see most often, or what I hear of most often, is that cycloids are very difficult to arrive at - and who knows exactly HOW you arrive at them, and who could POSSIBLY relate such an OFFBEAT idea to violin plates... etc.

 

I never found them difficult to arrive at, or create, or deal with, once the basic proposition was understood properly. I simply never used the set I had made, as I have never finished a violin - since I made them.

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Oh, and by the way Carl... you always stretch my credibility - and make me think, and answer your questions and all.

 

For which I must thank you, as I know that many people here are probably thinking exactly what you are posting. But you have the nerve to simply ask me to explain, which I am always happy to do.

Am I ever right with my observations or with my ideas? All I can post, is what I've actually done - what I have accomplished.

 

Who knows ? - all any of us can do, is the dance.  

And we all dance, at least slightly, differently.

Please Carl, keep posting your ideas and challenge me whenever you feel I have given a weak or improper post, theory, or method.

I'll continue to answer up to anything - I don't really care what it is about, I will have at the least an answer or explanation.

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What I see most often, or what I hear of most often, is that cycloids are very difficult to arrive at - and who knows exactly HOW you arrive at them, and who could POSSIBLY relate such an OFFBEAT idea to violin plates... etc.

I never found them difficult to arrive at, or create, or deal with, once the basic proposition was understood properly. I simply never used the set I had made, as I have never finished a violin - since I made them.

For Uncle Duke and anyone else... Don't use a cardboard circle and do it with a mechanical drawing. Just use the functions of x and y parametric in variable t........

X= t+.5*h*sin(t*pi/L)

Y= .5*h*(1+cos(t*pi/L))

In a spreadsheet, make a list of distances along the longitude and the width and height you wish. L is the half width from center to edge. h is desired height at middle. There are two unknowns in the original formula, usaually called a and b. Now there are still two unknowns, L and h. So .. we are OK.

For each value along the longitude, make a table with a list of t's from 0 to 1 in decimal fractions. Find each x and y for each contour as functions of t. Then use nice graph paper that has 1" squares divided into ten subdivisions. You can make all the templates very easily.

UNCLE DUKE: You can do this and also make any longitudinal arch with another spread sheet.

List distances from middle to ends. I took the geometric middle and said it was 7 inches to each end. You could easily measure from the bridge and have two curves.

Then make columes to make each distance to ends in decimal fractions of pi: x*pi/length. (A list of multipliers .000 to 1.000)

Then make a colume to raise this to any fractional power. Depending on spreadsheet, maybe have to use logarithms.

Then take cosine AFTER taking the power.

And multiply this by maximum height.

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