27 replies to this topic

[Mustafa Umut Sarac]

Carbon and aramid fiber reinforced plastics have same or better youngs moduluses with zinc , brass , bronze , mild steel or stainless steel.

 

Carbon fiber comes in micro lenght fiber powder form also. Its possible to mix with epoxy , cast in flat form and than laser cut.

 

Besides youngs modulus , what should have to be similar ?

 

So is it possible today to use such a plastic ?

 

Mustafa Umut Sarac

Istanbul

 

 

[alex_holden]

Are you talking about the frames or the tongues? If the tongues, you'll also need to consider its density (how thick do the tips of the lowest reeds need to be), long-term reliability (e.g. tendency to work hardening or weakening over time), sensitivity to variations in temperature and humidity, ability to bend it to an exact set and have it keep that shape (the set is very important for startup response).

[Mustafa Umut Sarac]

I am talking about tongues. I cant help myself thinking if the carbon available at 1930 , all bandoneons would be made from it.

Classical guitars replaced with carbons but as you said density is a problem but how should one overcome from density problem ? How should be the carbon specs to make the sound the same. I am not physicist.

[Mustafa Umut Sarac]

Is there plastic reed accordeons , harmonicas or bandoneons ?

[ttonon]

Hi Mustafa,

 

As Alex said, you must consider both Young's Modulus and material density, although I believe it's only the ratio of Modulus/Density (E/Rho) that's important.  The Euler-Bernoulli governing equation for the vibration of the reed tongue contains only the ratio of E/Rho, as far as material properties are concerned.  The other parameters involve geometry (length and thickness).  Thus for two tongues made of different materials yet having the same geometry, I speculate that the sound of these two different tongues will be the same, if they have the same ratio of E/Rho.  

 

In fact, in 2012, I posted a thread titled, "Reed Tongue Materials - a Survey"  on this site, and the link is: http://www.concertina.net/forums/index.php?showtopic=14568&hl=ttonon#entry138945 I'm happy to see that the original table of material's properties is still there.  If you're interested in more on this subject, I suggest you read through this thread.  

 

Best regards,

Tom

www.bluesbox.biz

[Mustafa Umut Sarac]

Tom , this is the most wonderful thing I have ever read in here and there.

 

But I want to ask , how glass fiber youngs modulus 3 times higher than the carbon.

 

Carbon composite

Epoxy Novolac 27%, Carbon fabric 73%

0.930

0.046

0.93

0.195

Glass composite

Lytex® 9063 63% Glass Fiber/Epoxy SMC

2.610

0.066

3.50

0.379

[Mustafa Umut Sarac]

Density 7.13 7.15 Mg/m3 445.112 446.36 lb/ft3 Young's Modulus 90 110 GPa 13.0534 15.9541 106 psi

This is pure zinc Tom.

 

How should I convert to compare with your document file ?

[Mustafa Umut Sarac]

Tom , this is the most wonderful thing I have ever read in here and there.

 

But I want to ask , how glass fiber youngs modulus 3 times higher than the carbon.

 

Carbon composite

Epoxy Novolac 27%, Carbon fabric 73%

0.930

0.046

0.93

0.195

Glass composite

Lytex® 9063 63% Glass Fiber/Epoxy SMC

2.610

0.066

3.50

0.379

I think there is a typo in your document , can you confirm ?

[Mustafa Umut Sarac]

And I want to ask the ratio similarity between concrete and mild steel. Thats why they use at buildings.

 

Can I make a steel gong with replacing steel to concrete ? Same rule applies ?

[W3DW]

Getting the correct set will be a challenge - bending them just past their elastic limit as with metals won't work. You'd need to heat them and hold them in a new position until cool and hope you guessed correctly.

[ttonon]

Hi Mustapha,

I don’t think there is an error in my table.  Pure silica glass does have high modulus and, if free of surface defects is extremely strong (high yield strength).  The reason for the ? under the “Strength” column is perhaps because no one has tested such a material with a guarantee that there were no surface defects.  There are many different ways to make carbon fabric, and they vary in cost and strength.  The epoxy Novolac in the table is probably typical for that composition.  You may have in mind the modulus of a single carbon fiber, which is listed at the very bottom of the table and is very high.  For both glass and carbon fibers, single fiber strength or modulus greatly exceeds that of their composite forms.  Lastly, we are not talking here of carbon nanotubes, which I understand are many times stronger than bulk forms of carbon fiber. 

Along with modulus and density, an important parameter in the construction of practical reed tongues is the yield stress, or the fatigue strength, whichever is less.  Thus, many materials may have interesting E/Rho ratios, but they also may be unable to handle the stresses caused by vibration.  Thus, only some of the very strong plastics might work okay.

In order to answer your question about making a gong, we would have to look at the governing (wave) equation for a gong.  Acoustically speaking, a gong can be referred to as a “plate.” 

In diversion, acousticians have labelled vibrating objects according to the nature of the restoring forces that maintain their vibrations.  The simplest is a “flexible string,” or simply “string,” in which the only restoring force is caused by tension.  There is no “stiffness,” or resistance to bending.  Next up is a “stiff string,” in which the primary restoring force is one of tension, as well as a “small” contribution from stiffness.  Here, the stiffness forces produce only a small perturbation of the vibration that’s produced in a flexible string.  Next up are “bars,” which the free reed tongue is a member of.  Bars are the opposite of strings in that the only restoring force considered is stiffness, or the tendency to resist bending, with no contribution from tension.  The examples here so far involve one-dimensional objects.  The concept of a flexible string can be extended to two dimensions in objects called “membranes,” which like the string, have only tension as restoring force.  We also extend the concept of bars to two dimensions, calling them “plates,” and like bars, have only stiffness (bending) forces restoring motion.  I believe a bell could be considered a three dimensional plate, although for the very large bells (going up to hundreds of tons), gravitational forces may influence their vibrations. 

Getting back to your question, the wave equation for a plate involves the material factor, (1 – s^2)*(Rho/E), where s is Poisson’s ratio, defined by the ratio of transverse strain to axial strain when a material is compressed or stretched.  An incompressible material undergoing no deformation (stressed within elastic limits) will have s = 0.5.  In practice, s for steel is 0.27 – 0.3, for brass is 0.33, and for concrete is 0.1 – 0.2.  Thus if you plug in these material values to the factor containing poisson’s ratio, you get for steel 0.00878, for brass 0.0169, and for concrete 0.0147, where the units are the same as I used in the original table, and for concrete, I used E = 5.8 Mpsi, and Rho = 0.087 lbsm/in^3.  The result here suggests, without any other considerations, a gong made out of concrete, for equal geometries, should sound more like a gong of brass than like a gong of steel.

 

If I may ask, what kind of concrete gong are you thinking of?  How big?  Besides the simplified acoustic discussion here, there are other practical issues that should be considered in planning such an object.  For large gongs, weight might present special concerns.  I don't know about the ability of concrete to withstand vibrational stress.  There are people who study these things, and you might search them out.

 

 

Best regards,

Tom

[Mustafa Umut Sarac]

Hi Tom,

 

Thank you very much for sharing such years of researches with me.

 

I am thinking 150 cms , 60 inches diameter and 3mm thick gong.

 

I am criss crossing in various forums and I shared your modulus divided by density post.

 

here is the reply from an gong maker:

 

 

Congratulations on figuring out how to make something from 2 different materials have the same dimensions and fundamental resonant frequency. But this is only a small part of the whole picture. Does it have the same mass? What is the ultimate tensile strength? What is the elongation factor? What is the proof stress? What is the damping factor at various frequencies?

Is your concrete reed able to vibrate with the same amplitude without falling into pieces? Does it have the same sustain at the fundemental? Does it have the same sustain at the various overtones?

[ttonon]

Hi Mustafa,

 

I think this gong maker asks some very good questions.  Of course, the surest way to answer them would be to build such a gong, so it seems you have an interesting project to delve into.  I would suggest first making a small proof-of-principle model, maybe only a few inches in diameter.  Make also a brass, or bronze one and compare the performance.  I understand that traditional bell metals are a kind of bronze, about 80% Copper and 20% Tin, which produces an alloy with minimum internal dissipation (friction), providing a longer ring.  

 

It's understandable to question whether a 60-inch diameter by 3-mm thick concrete gong would shatter.  Thus, you'd want a cement mix of maximum strength, so I would suggest a pure cement mix, with a ratio one part cement and two parts sand.  Strictly speaking, concrete contains aggregate (small stones), which I think would cause problems, unless they are much smaller than the minimum gong dimension (3 mm).  This discussion takes me back to when I was a child.  My father was a brick layer, and he gave my brothers and I a few lessons on mixing cement and laying brick.  You should probably talk to someone who is knowledgeable about cement.  For Portland cement, a 1 - 2 mix gives a mortar with maximum compressive strength, but I don't know about how the tensile strength varies.  In your application, I think tensile strength plays much more of a role than with the usual applications.  Adding stones (aggregate) to a 1 - 2 cement mix does not weaken its compressive strength, but it may weaken its tensile strength.  There is a strong movement now to move away from Portland cement, because its manufacture produces a significant fraction of man made CO2 in the atmosphere.  There thus may be other forms of cement appearing on the market now.

 

In fact, you might consider other stone-like materials.  In dental work, they use (or they used to use) a substance called "stone" to make cast mouth impressions.  This stone, like cement, is a powder mixed with water, though as I recall, it may be much less gritty and maybe even stronger than cement in tension. 

 

Finally, with any material you use, since tensile strength is probably important, you might want to experiment with the addition of fibers.  These fibers can be metallic or non metallic.  If metallic, it should be non-rusting.  If non-metallic, you can experiment with glass, aramid, and other plastic fibers used in making the many composites found in industry.         

 

This thread has wandered quite a bit from concertinas, and perhaps most readers here would rather we take this discussion off the forum.  You can send me a private message if you'd like.

 

Good luck,

Tom

[JimLucas]

This thread has wandered quite a bit from concertinas, and perhaps most readers here would rather we take this discussion off the forum.

 

No, keep it going.  Anyone not interested can stop reading the thread, but I find it interesting.  Might even be useful if I ever decide to build "the world's tallest" concertina. 

 

More seriously, any information concerning the behavior of different materials and especially experiments attempting to determine general principles thereof should be useful to builders, repairers, and restorers.  Even a material with aggregate particle inclusions as in concrete, while probably not useful for making reeds, might have interesting acoustic effects if used in the fretted ends or structural parts of a concertina.  (Anybody want to give that a try?)

[Mustafa Umut Sarac]

Yes, Keep it going. I found concrete can be more interesting for indonesia or southasia. Do you know gamelan instruments ? If you want to give a complete concert , you should collect 1500 kilograms of bronze instruments together. It makes 4200 libres. Americans made american gamelan starting from 1950s, and used thick aluminum cut by a grinder. Today , if you buy 4 , 600 cms x 150 cms , 6 mm thick aluminum , for industrial laser cutter , its a 1 hour business.

 

But lets keep the costs less and there are vase shaped bronze instruments cant be made with machine but can be cast in silicon mold with concrete.

 

I dont want to go in to kevlar , carbon route. If you have money to buy them , you would not interested in this thread , you order from indonesia and your patron would pay it.

 

Concrete , there are two cheap fibers for it , glass fibers and steel fibers.

 

In Istanbul , if you want to buy glass fiber , there are two class , e class and s class. e glass is electric glass and far cheaper.

 

E glass , one kilogram is 4.5 dollars in rowing form , 1 kilogram is 1 square meters.

 

But glass fiber is extremelly sensitive to humidify and touch.

 

If you buy unpacked old glass fiber , you can expect , it loses its % 60 of strenght.

 

Steel fibers are cheap but shorter the fiber , better the strenght. It must be around 3mm long but here , they sell 25mm long fibers.here.

 

Steel fibers are like an needle and it looks concrete like cactus , dangerous thing.

 

Concrete , better the concrete , less water inside , smaller size the powder particles and mica powder is a must. You must use plasticizer inside.

 

And there are reactive concretes , many many times stronger.

[Dana Johnson]

Hi Mustafa,
 
I think this gong maker asks some very good questions.  Of course, the surest way to answer them would be to build such a gong, so it seems you have an interesting project to delve into.  I would suggest first making a small proof-of-principle model, maybe only a few inches in diameter.  Make also a brass, or bronze one and compare the performance.  I understand that traditional bell metals are a kind of bronze, about 80% Copper and 20% Tin, which produces an alloy with minimum internal dissipation (friction), providing a longer ring.  
 
It's understandable to question whether a 60-inch diameter by 3-mm thick concrete gong would shatter.  Thus, you'd want a cement mix of maximum strength, so I would suggest a pure cement mix, with a ratio one part cement and two parts sand.  Strictly speaking, concrete contains aggregate (small stones), which I think would cause problems, unless they are much smaller than the minimum gong dimension (3 mm).  This discussion takes me back to when I was a child.  My father was a brick layer, and he gave my brothers and I a few lessons on mixing cement and laying brick.  You should probably talk to someone who is knowledgeable about cement.  For Portland cement, a 1 - 2 mix gives a mortar with maximum compressive strength, but I don't know about how the tensile strength varies.  In your application, I think tensile strength plays much more of a role than with the usual applications.  Adding stones (aggregate) to a 1 - 2 cement mix does not weaken its compressive strength, but it may weaken its tensile strength.  There is a strong movement now to move away from Portland cement, because its manufacture produces a significant fraction of man made CO2 in the atmosphere.  There thus may be other forms of cement appearing on the market now.
 
In fact, you might consider other stone-like materials.  In dental work, they use (or they used to use) a substance called "stone" to make cast mouth impressions.  This stone, like cement, is a powder mixed with water, though as I recall, it may be much less gritty and maybe even stronger than cement in tension. 
 
Finally, with any material you use, since tensile strength is probably important, you might want to experiment with the addition of fibers.  These fibers can be metallic or non metallic.  If metallic, it should be non-rusting.  If non-metallic, you can experiment with glass, aramid, and other plastic fibers used in making the many composites found in industry.         
 
This thread has wandered quite a bit from concertinas, and perhaps most readers here would rather we take this discussion off the forum.  You can send me a private message if you'd like.
 
Good luck,
Tom

I built my old house with a ferrocement roof of 10 hyperbolic paraboloids alternating pointing up and down to get 5 peaks and 5 valleys. It was quite lovely. I added an acrylic modifier to the cement sand mix that greatly increased its otherwise poor tensile strength. The result behaved much more like wood than concrete. A friend gave me a large stone that I think must have been a lava bomb, it was somewhat vitrified in any case and rang like a bell when struck. The graininess of the structure seemed to protect it from cracking, much like the Corning pyroceram or Corelle table settings.
Dana

[nicx66]

There are some aftermarket reed blocks for moped engines (and I would guess motorcycles too) that use carbon fiber for the reed tongues. While a completely different application, they behave much better than the plastic ones that they replace https://www.treatlan...force-v351b.htm

[Mustafa Umut Sarac]

Tom,

 

Lets talk about bronze and same modulus/density FRP.

 

My friends asks me if the modulus density ratio is the same , the fundemental frequency is the same. They asks me what will be the harmonics and their sustain for each different.

 

I read your post on concertina reeds and as fas as I understand , you defend every characteristics would be the same.

 

Is it true ?

 

Is total mass of the gong would be the same also ? Or is it not important ?

 

What makes bronze does not dissipate energy ?

 

I learned carbon fiber or more exactly epoxy does not waste energy when hit ? Is it true for e glass epoxy laminates ?

 

Thank you,

 

umut