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Graduation tolerance


FiddleMkr

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Some educational thoughts {facts} about wood, moisture, shrinkage, hammers,egypt and such

1. In this world we have what are called "regional humidity zones" for example the usa is divided into several regions and likewise all continents/countries have their own divisions of regional moisture or regional emc {equilibrium moisture content} within all of those regions there can be micro climates and seasonal changes to the emc based on that.

Some USA regions as example...these are from memory from us forest service so don't quote me, just examples....northern california 6-8%....most of Arizona 4-6% most of Florida 8-12% Hawaii the same...what this simply means is that on average an average piece of wood will achieve an equilibrium moisture content of "your" region, in my case No. Cal. if I stick a piece of wood with a moisture meter it will read about 6-8% moisture content {hardwood and softwood have their own differences in the region, softwood reading on average 2% higher than hardwood} and if I lived in Miami it would be as wet as maybe 12%

Now about hammers and hardwood floors, as they are demonstrating the same wood science called "compression setting" Compression setting is when a wood object is either stacked and fixed next to other hard wooden objects or in the case of the hammer surrounded by a harder material that has a dissimilar expansion rate and what you are seeing is as the wooden handle cycles through daily expansion and contraction {particularly if left outside as many hammers are during building projects} the wood will swell dramatically at certain times thus smashing the wood cells and grain into the surrounding hammer head, permanently compacting and crushing the grain, as this happens over the course of several years the compression setting can loosen the head to the point where it could fly off...In the case of wood floors {particularly Maple} compression setting will show in the form of large permanent gaps in between boards that just last year when installed were not there, but as the boards expand and contract the grain gets permanently smashed and show as gaps

About Egypt, I don't know the process that was used to transport, but I can tell you any damage is from improper acclimation from one emc region to another with a large differential between the two places, the process must be done slowly depending on dimension, species and if there are fasteners/glued parts

About "permanent shrinking" barring compression setting, which can appear to be "shrinkage" wood has very little dimensional change over hundreds of years, it could be likened to live corral vs dead corral. As uv rays oxidize everything, including wood the photo degradation of the cellular structure may hollow out the interior a wee bit in the form of pinholes resulting in bound water sacks being perforated thus ending up with slight moisture loss but just like dead corral, its kinda the same size when its alive just "hollowed out a bit" so to speak.

Fortunately for us wood has been the number 1 building material for 1000's of years and because peoples lives depend on information about wood being correct, related to engineering, all this stuff has been figured out

Given enough time it will all turn to dust

 edit: it should be known that moisture content does correspond to size in a dimensional sense

so for example dimensional wood manufactured to 8ft spec in No. California, one load goes to Az. the other to Fl. the wood in Az will be smaller than the wood that "lives" in Fl. once they achieve equilibrium. If l rip out a 2x4 from the Fl. house and rapidly transport it to Az. the Fl. board may be 8ft + 4mm whearas the Az board may be 3mm shy of 8' thus "shrinking" in the eye of the beholder, the board will only be a true 8ft if it goes back to where in was cut in a 6-8% region it can not be 8ft. in a 4-6% region nor a 8-12% region , thus making it "seem" like wood can shrink, but it'd just responding to an environment

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3 hours ago, Dennis J said:

Anders, I don't dispute that humidity levels can get fairly high in Cremona. Where I live, near the sea, they can also. As a matter of fact violin plates that I plane flat one day can change to cupped or bowed from day to day depending on humidity levels.

I just can't see any wheresense in having extremely thin patches, say less than 3 mm, on violin plates. And as far as weight is concerned I don't understand why that is of such a concern. I'm sure early makers didn't  worry too much about that.

I think the power to weight ratio of a bowed violin is pretty high, so weak elements in its structure wouldn't be too wise.

 

That is where ALL the magic happens, thin patches under 3, knowing where and how to use them, why and how it changes from instrument to instrument, imo

to avoid dealing with overly warped plates it a good idea to keep thinned plates clamped to a hard flat surface that is not wooden when being stored overnight, I like to use a plastic cutting board

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1 hour ago, Dennis J said:

I get the impression that is the theory Jezzupe. Is it valid though? A lot of older violins showing these variations may have been thinned in those areas after they were made by people trying to "improve" them.

I don't think we know the exact history of the Weekend at Bernie's violins as far as regrads go, so I can't speak to that, I do have lots of experience making lots of instruments, many with "thin areas" and many without

Most of my early things did not have thin spots, or if they did it was accidental or there was no rhyme or reason to it, I call it "my early experimental phase"  and as time went by and I developed what works for me, based on pro musician feedback, I have come to find that thin spots, which I have many names for, are what can give sensitivity, volume and color to a "decent" 3 mil violin, this assumes many other things are happening right, particularly arching.

I personally think you should do whatever makes you feel ok with what you are doing, and that really there is no way to prove anything one way or another nor even any agreement on some patent benchmark tone , so it's all for not speculation anyway and all anyone cares about or how they judge you is if you sell lots of instruments and that they end up in "famous" peoples hands and you get lots of money for them, and all that is not necessarily based on tone, even if they say it is.

There is music, and then there is the music business, they are not really the same thing, same with violins

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On 6/17/2023 at 1:25 PM, Anders Buen said:

Graduation or thickness of a plate is important acoustically, so is the surface mass, damping, dimensions and so on. The material propertie can be determined, or asessed, by bending, tapping, just by working the wood and the weight. 

Curved plates are somewhat less sensitive to graduations than flat plates.

In large datasets, mass, average thickness, tap tones, probaly bending stiffness, all correlate closely. So in princiuple any measure may do for an asessment. Any violin plate will have a graduation, tap tap tones, bending stiffness, damping and a surface mass regardless if it is measured or not.

I do not think the violin is very sensitive to small mass, thickness or stiffness variations. Big changes are needed to see clear changes. This is one of the reasons why the Bilbao project probaly not is going to tell us something new in relation to free plate to assembled violin data, as compared to Morals work at KTH during the 80ties. However the Bilbao instruments are likely to be better, as they are CNC copies of the Huberman Strad and made on similar wood. 

Was a final report written for the Bilbao project?  I never saw any frequency response curves for the  violins made from all these different top and back plates.

 

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I wonder how people think and understand. The shown dynamic behavior i high degree becomes affected by the shape of the structure the wood quality and the thickness graduation. If we know little or nothing about the quality of arching shape quite a bit about wood quality how than do we combine these qualities and graduate for a specific function. The bending of curves of the winter grown wood will happen between the action and reaction location. It is to know where that reaction location is found. If we do, we can start thinking graduation what happens on the curve(s). Yes, they become dynamic. But in what condition. Strings produces to specific condition.

! the deflection on arching shape

2. the frequency input on structure.

Ask your selves can the frequency input under the bridge feet drive the bout shapes sometimes 20 different in one second or is there other mechanism that produce the bout shapes producing frequency behavior.

Arching shape, wood quality and thickness graduation has big influence in this process. Why is it this not discussed?

Where do we find reactive structural conditions and curve bending?

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No Martin I live together with you. But if you believe string forces do nothing with the violin structure you certainly are on another planet. On my internet site you are bale to find a holographic iamge that show the deflection on structure. What we must assume is that thickness is involved in the process. Don't you think so?

 

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The tension of the violin strings stiffens the entire violin structure and reduces the amount of bouncing the scroll has.

This principle is also used with guy wires for telephone and radio towers, support cables on crane arms and sailboat masts, and an example is attached for a camera boom and cable which looks like a side view of a violin.image.thumb.png.329f1827247ff3ee24311410a3ebdac5.png

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4 hours ago, reguz said:

No Martin I live together with you. But if you believe string forces do nothing with the violin structure you certainly are on another planet. On my internet site you are bale to find a holographic iamge that show the deflection on structure. What we must assume is that thickness is involved in the process. Don't you think so?

 

You misunderstand me - it's blatantly obvious and agreed by everyone on my planet that "Arching shape, wood quality and thickness graduation has big influence in this process".

 

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15 hours ago, Marty Kasprzyk said:

The tension of the violin strings stiffens the entire violin structure and reduces the amount of bouncing the scroll has.

 

Could this be part of the ‘play-in effect’? 

On the other hand, what happens if the entire structure is more rigid and here I am thinking of the rib garland and how the scroll is fixed in this structure?

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5 minutes ago, Andreas Preuss said:

Could this be part of the ‘play-in effect’? 

On the other hand, what happens if the entire structure is more rigid and here I am thinking of the rib garland and how the scroll is fixed in this structure?

I hand my fiddles over to the local middle school orchestra for playing in. They antique them for me, too. All free of charge! Hell, I even get a tax write off. 

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15 hours ago, Marty Kasprzyk said:

The tension of the violin strings stiffens the entire violin structure and reduces the amount of bouncing the scroll has.

35 minutes ago, Andreas Preuss said:

Could this be part of the ‘play-in effect’? 

To be picky, it's not the tension of the string that stiffens the structure, but the longitudinal stiffness of the string.  Admittedly, you DO need some amount of tension to to get the string stiffness to take effect.

I suppose that in the first few weeks that a newly built violin is strung up, you might think the time related reduction in damping is "play-in".  Otherwise I don't see tension being part of play-in, assuming (questionably) that there is such a thing as play-in.

 

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There may be a change of the initial arch shape when the tension comes on the instrument. The arch also changes with the climate variations as well, because wood shrink or swell different in the different directions. Maybe there is some permanent creep, increased or reduced contact between non glued elements?  

There certainly is a adaptation process going on while learning to play a new strung up instrument. Most of the «playing in effect» is probably in the players perception, spine and head.

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This is really beating a dead horse, but if makers would just listen to players, who know a LOT more about their own instruments, they'd understand that instruments do change with time, both short term effects (warming up daily) and long term. But I guess you guys know better even though a lot of you are virtually deaf and only hear through theories and FFT.

Anders, there is definitely a permanent change over time. When I worked at WH Lee setting up all their instruments I'd put the posts a mm or two inside final position and cut them slightly more pointed. A month or so later I'd come back and pull them out and they'd fit.  What appeared to be happening what that the plates were puffing out a bit and thus the slope near the post became more steep. Always six months later I want to see previously un-set-up instruments again for potentially a completely new post. Of course anyone who has ever worked on old instruments KNOWS the varied and many ways their shapes consistently change over time, so there should be no disagreement here, either.

John Masters (where is John these days, anyway) told me that using his computer violin model he'd decided that given a lot of flexibility that wood doesn't really have the plate arches would theoretically tend to migrate to curtate cycloid shapes--that this seemed to be the shape that best neutralized the forces involved--and that was why he gave some credibility to the idea that this might make a good idealized arch.

In my setup work I have noticed that you can get a lot of tonal mileage out of imagining how the various parts of the instrument deal with the idea of preloading so that certain tensions seem to be reduced when the instrument is strung up, and conversely you can find places where the instrument seems to need to reach a certain distortion under tension and then stop decisively (which I visualize as postloading to completion--I don't know if there's an engineering term for that) so they don't flap around, relatively speaking, and ruin everything.

 

 

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11 hours ago, Michael Darnton said:

This is really beating a dead horse, but if makers would just listen to players, who know a LOT more about their own instruments, they'd understand that instruments do change with time, both short term effects (warming up daily) and long term. But I guess you guys know better even though a lot of you are virtually deaf and only hear through theories and FFT.

Sometimes, players know more about their instruments than makers and those who maintain them, and sometimes they don't.

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7 minutes ago, jacobsaunders said:

What is "FFT" please?

It is short for Fast Fourier Analysis. It is an acoustic and vibration related analysis method for extracting the response in fine frequency resolution. I think the background for it is in rocket science. In my study years I borrowed a single two channel HP unit for doing such transfer function measurements. At that time it was a very expensive tool.

Short time after software emerged for desktop computers, and PC's utilizing the soundcard for similar analysis, also for room acoustic measurements.

Today it is one of several metodes used for analysis of sound and vibrations, and most of us can do it on a phone app. Sonograms are a nice presentation of sound. Basically the tool used in sound analysis under water and in many biosciences.

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In sound analysis it is customary to listen to the samples in combination with the analysis. There are strengths and weaknesses to both listening and to the presented analysis. In some way the impression and documentation may be used for others to read and assess. 

Not much can beat the grown human brain at assessing complex sounds, recognition e.g.. Now how do you share your impression if you have to? 

Sonograms are FFTs or wavelet or other frequency analysis on one axis and the time on the second. The sound is sort of "pictured". I think featured like this is used in AI speech and voice recognition. 

A Fourier analysis is a decomposition of a wave signal into sums of sine waves of different strengths and frequencies. Any waveform can be reproduced that way. We do such analysis with pen and paper at university level for a given fixed waveform. To do this for a real time sound signal is very computer capacity demanding, at least at the time they developed FFT, which made "real time" analysis or at least fast analysis possible by the computers they had at hand.

I think that any nation with a marine and a military force would suffer if these methods did not exist. Warfare without it would lead to severe losses.

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