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H.R.Fisher

Thin top /high density?

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1 hour ago, Danube Fiddler said:

Done something wrong ?

Hard to say without knowing exactly what you did.

Even with the best technique (arrogantly assuming my technique is it), sometimes there isn't a nice, clean result.  Not sure why.

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3 hours ago, Danube Fiddler said:

If one has also some other deadlines in the process as stiffness-numbers, normal graduation-ranges, weights, normal areas of mode-frequencies, then one will not ruin good tonewood so fast. However possibly one should be ready to ruin wood from time to time to find out some more.  

I can agree with all of that. 

What I have found out recently is that I should of stayed with my 15.5 to 15.8 mm maximum heights that I've always used instead of experimenting with low to middle 14 mm heights for back plates and upwards to 16.5 mm, maybe a little higher, for belly wood. 

  Stiffness formulas along with paying attention to weight is still doable but the searches for m5 and m2 turns into more work than I'd like with these lower and higher than normal heights.  Maybe I will get lucky and get something playable.  All I have now going on is a varnish experiment turning out well keeping in mind not to expect much after set up for making music -- it sure will look good though.

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3 hours ago, Danube Fiddler said:

 The M5-frequency later came out surprisingly high ( 70g before f-cut and BB / 386 Hz and 160 Hz [M5, M2] / rel. stiffness[Dr. Harris] = 1,24 / graduations del-Gesu like with a little bit more thickness in center [3mm] ). 

Is that the bullseye inside belly graduation plan or the Maggini that looks like a Del Gesu graduation scheme where the flanks are thin?  Or is there a secret plan you are using that I/we don't know about?

Me personally?  If I had 386hz with the regular sized DG belly and thought I could get a better ringing tone then it would be to remove wood from the center section and outer areas, if necessary, until I just start to lose the sonority of the m5 tap tone.  ( an old Mr. Sora idea}

There's the other old rule of thumb to consider - just make the belly the half or whole semi tone below the back plate m5, flex the heck out of it and then glue it all together.

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7 hours ago, Danube Fiddler said:

Hi Don,

why I nearly always find so many peaks in your sound-speed-examination way ? I have chosen the highest peak for determination of sound-speed. But what´s about the other peaks ? In this case I calculated 5300 m/s and a RR of 13,9. The M5-frequency later came out surprisingly high ( 70g before f-cut and BB / 386 Hz and 160 Hz [M5, M2] / rel. stiffness[Dr. Harris] = 1,24 / graduations del-Gesu like with a little bit more thickness in center [3mm] ). 

Done something wrong ?

 

Looks like you did something right!

Those numbers are close to my #5 which i just finished. The top ended up as 67g with M5 of 364 Hz. Also a little thicker in the middle (3.2mm). RR was also about 14. Best violin sofar..

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10 hours ago, aletrop said:

Whats the name of the app Peter K-G?

 

 

It's part of an Excel spreadsheet that I have made, I have shared parts of it here on MN, if I find it I'll post it again.

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12 minutes ago, Peter K-G said:

:angry: Date: 01.05.2017, what have I been doing, this violin should be ready long by now and it hasn't even been started!

i guess it's waiting for you to start :lol:

6300 m/s is pretty high, but so is the .514, RR is 12.2.. can this create the soloist sound you are after?

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25 minutes ago, Emilg said:

... can this create the soloist sound you are after?

Absolutely, there are only two people involved in that process The maker and The Soloist, shouldn't be too hard ;)

 

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6 hours ago, Don Noon said:

Hard to say without knowing exactly what you did.

Even with the best technique (arrogantly assuming my technique is it), sometimes there isn't a nice, clean result.  Not sure why.

I tried to do your method :  In particular this was to let swing a very little hard-wooden ball, mounted at a little yarn, against one end-surface of the spruce-wedge - so much in the long direction of the wedge as possible - several times. The (very little but also bad) micro recorded in 2mm distance from the other end - surface. What could be better in your special technique ?

My interpretation is, that there are more than one certain sound-speed (in the long direction) in the wood. For example one of the more softer structures like the summer-wood and another of the late-wood, possibly  even of more substructures.

Do you own a Lucchi-meter ? Would be interesting, if it also showes more than one sound-speed or if it showes (depending on its way of measuring ) only the maximal sound-speed.

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1 hour ago, Peter K-G said:

Here it is. This is a top I'm actually going to use, density ~0.50

WoodProperties.xlsx

Hi Peter,

what is Ring-M in your spreadsheet ?

I don´t know ring-modes in wedges but only e.g  the often regarded 2-0 mode. However some people claim, this mode would be a relative of the M5 - mode in the plates, which also is called ring mode. I don´t know, where this name comes from - from the fact, that it is easiest to hear as a ringing tone - or from its shape, which can have the form of a ring ( if the plate is sufficient thinned ).

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1 hour ago, Emilg said:

Looks like you did something right!

Those numbers are close to my #5 which i just finished. The top ended up as 67g with M5 of 364 Hz. Also a little thicker in the middle (3.2mm). RR was also about 14. Best violin sofar..

I hope so. 

However I am not sure, if I really can finally afford a 1,24 stiffness [Dr. Harris] in the top which it also kept after ff-cut and BB. This is 10 % more than the strongest top, Curtin reported (Testore) and nearly 20 % stronger than the stiffest Cremonese top, Curtin reported (Stretton-del-Gesú). I stopped at this stiffness, because I loved the reached graduation numbers but I possibly will have to go thinner in the outside-tuning - process - particularly if I regard, that varnish will give additional stiffness.

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45 minutes ago, Danube Fiddler said:

Hi Peter,

what is Ring-M in your spreadsheet ?

I don´t know ring-modes in wedges but only e.g  the often regarded 2-0 mode. However some people claim, this mode would be a relative of the M5 - mode in the plates, which also is called ring mode. I don´t know, where this name comes from - from the fact, that it is easiest to hear as a ringing tone - or from its shape, which can have the form of a ring ( if the plate is sufficient thinned ).

Well, Ring-M  is just a term in my spreadsheet, don't know the correct term for this two nodal lines, easy to find mode.  It has very little to do with the final M5 mode in plates, because it is determined by thickness of the wedge and elasticity of the wood (it can be calculated from dimensions and/or speed of sound and the other way around) There is some older topics about this here on MN. Something like  Old way and new way (D. Noon 2FL)

All of these are different sides of the same coin and are mostly calculated from speed of sound.

I'm sure that Don can explain this better :)

What I find important is to understand that you need:

* speed of sound

* density

* MC% in the wood

To calculate all the other "wood properties" (RR,  modulus ....) 

Another thing to understand is that density plays a big part in this, because frequencies (for a specific dimension)  is quite unimportant if you don't know density.

Ex. two wedges with the same dimension and frequency (Ring-M) can be very different if one has a density of 0.35 and the  other 0.50. 

 

 

 

 

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4 minutes ago, Peter K-G said:

Well, Ring-M  is just a term in my spreadsheet, don't know the correct term for this two nodal lines, easy to find mode.  It has very little to do with the final M5 mode in plates, because it is determined by thickness of the wedge and elasticity of the wood (it can be calculated from dimensions and/or speed of sound and the other way around) There is some older topics about this here on MN. Something like  Old way and new way (D. Noon 2FL)

All of these are different sides of the same coin and are mostly calculated from speed of sound.

I'm sure that Don can explain this better :)

What I find important is to understand that you need:

* speed of sound

* density

* MC% in the wood

To calculate all the other "wood properties" (RR,  modulus ....) 

 

 

 

However also important are the transversal properties ( not so easy to measure) as also probably damping-values (extremly difficult topic). The transversal things partly appear in the 1-1 mode of wedges and also are quite easy to measure, however only by a different micro localization at the lateral ends of the wedge.

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Yes,

Longitudinal/Transverse is good to know, too high or low and it's impossible to get reasonable final plate "numbers" (if that is important)

Important is only important if its importance for what is known (that turned out odd :))

 

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3 hours ago, Danube Fiddler said:

I tried to do your method :  In particular this was to let swing a very little hard-wooden ball, mounted at a little yarn, against one end-surface of the spruce-wedge - so much in the long direction of the wedge as possible - several times. The (very little but also bad) micro recorded in 2mm distance from the other end - surface. What could be better in your special technique ?

My interpretation is, that there are more than one certain sound-speed (in the long direction) in the wood. For example one of the more softer structures like the summer-wood and another of the late-wood, possibly  even of more substructures.

One thing to understand is that this technique doesn't really measure "speed of sound", but the first longitudinal resonance of the piece of wood.  Think of an accordion, with both ends moving in and out, and the center staying still.  It just so happens that the math works out to calculate speed of sound from this frequency just the same as a wave moving along the wood.

Your technique is too fancy.  I use a small wooden hammer ~4 grams, and smack the end of the wood as fast and hard as I can, several times per second.  It is also important to support the wood in the middle... the nodal point for the vibration you're trying to measure.

Different speeds of sound in different parts of the wood don't matter directly, as this mode is the result of the average stiffness/density (I tried gluing two different pieces of wood together to prove it).  The only problem might be that the difference could transfer energy to some other bending mode and muck up the signal.

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34 minutes ago, Don Noon said:

Your technique is too fancy.  I use a small wooden hammer ~4 grams, and smack the end of the wood as fast and hard as I can, several times per second.  It is also important to support the wood in the middle... the nodal point for the vibration you're trying to measure.

 

I use this "fancy" technique also in other concerns to avoid a keeping force after the impact - you probably reach the same by doing "hard as you can".   However I will try your technique and compare the results. I supported the wood in the middle as you described in the initial thread. 

Thanks a lot for detail-explanation !

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10 hours ago, uncle duke said:

Is that the bullseye inside belly graduation plan or the Maggini that looks like a Del Gesu graduation scheme where the flanks are thin?  Or is there a secret plan you are using that I/we don't know about?

This is my graduation-inspiration ( data calculated from some instruments of the world-exhibition in New York 1994 ):

480211477_Guarneri-del-Ges-_top-graduations.thumb.jpg.bb0bfc714dfee39ba352e575b2ea624e.jpg

My top, from which the initial data came, at the moment is about 1- 3/10 mm more all over the plate ---- > 25 % more stiffness and higher M5 -frequency ( and not yet varnished ). 

10 hours ago, uncle duke said:

Me personally?  If I had 386hz with the regular sized DG belly and thought I could get a better ringing tone then it would be to remove wood from the center section and outer areas, if necessary, until I just start to lose the sonority of the m5 tap tone.  ( an old Mr. Sora idea}

Interesting idea - but in this case too late- the violin is assembled and is subject of outside tuning ;)

11 hours ago, uncle duke said:

There's the other old rule of thumb to consider - just make the belly the half or whole semi tone below the back plate m5, flex the heck out of it and then glue it all together.

At the moment my white violin should extremly disregard this rule ( estimated M5 - frequency of back now ~ 355-360  HZ ). 

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On 6/18/2018 at 9:48 PM, Don Noon said:

The highest I have seen for non-torrefied wood has been in the 6200 - 6300 range, and that was for 30 year old stuff.  So I have to think that 7000+ is bogus.

So in your experience sound-speed increases by time/ wood ageing ? 

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15 minutes ago, Danube Fiddler said:

So in your experience sound-speed increases by time/ wood ageing ? 

I don't have any reference pieces that I have measured over decades, so I'm only going by circumstantial clues... fresher wood seems to have lower speed of sound than older wood, for similar density.  Also, assuming torrefying wood is somewhat similar to accelerated aging, there's that too.

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On 6/19/2018 at 3:13 PM, Don Noon said:

One thing to understand is that this technique doesn't really measure "speed of sound", but the first longitudinal resonance of the piece of wood.  Think of an accordion, with both ends moving in and out, and the center staying still.  It just so happens that the math works out to calculate speed of sound from this frequency just the same as a wave moving along the wood.

Your technique is too fancy.  I use a small wooden hammer ~4 grams, and smack the end of the wood as fast and hard as I can, several times per second.  It is also important to support the wood in the middle... the nodal point for the vibration you're trying to measure.

Different speeds of sound in different parts of the wood don't matter directly, as this mode is the result of the average stiffness/density (I tried gluing two different pieces of wood together to prove it).  The only problem might be that the difference could transfer energy to some other bending mode and muck up the signal.

Now I made a little wooden hammer and tried your hammer- way.

Sadly the reading was even worse than the wooden-ball made :

However I eventually 852657469_soundspeedballreading.thumb.png.c046920f736f99341c9a8096408711d4.pngcould improve the hammer by thinning the stem.

53450562_soundspeedhammer-reading.thumb.png.55d4d95c60c038cdb57ce0625028f22d.png What makes you sure, that the highest peak is the lontitudinal oszillation peak, when you also say this area can be contaminated by bending-modes ( particularly, if I don´t have your good technique and fail in hammering exactly perpendicularly to the endsurface of wedge ) ? Did you ever compare results with an established measuring instrument like the Lucchimeter ?

Is it necessary for your measuring way, to have a smooth endsurface or is just raw cutted enough ? Eventually lateral movements in the endsurface could produce more " bending contaminations" in a rough surface.

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of course you take the peak which will give you the best result :lol:

i usually go for the peak which makes the most sense by giving a SoS between 5300 and 5800 m/s, taking density into account

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