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Carbon Fiber instrument manufacture

Postby duckskiff » Wed Feb 14, 2007 10:22 am

Here's a topic that I've pondered for a while now and has come up yet again in the recent serpent post. What are the pros and cons of using carbon fiber in brass applications? In other words, why would you want to make a bell out of carbon fiber, other than durability?

I've worked with carbon fiber in small quantities in the shop. It's pretty easy to work with (if you wear gloves & a mask), and I think that you could easily set up a system for making bell sections. But how would they sound? How thin could you make them?

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Postby cktuba » Wed Feb 14, 2007 10:49 am

I think this would be the guy to ask...

Image

He has played on them off and on for years, he even has one in the pic. I am sure if you e-mailed him he would answer, when he got a chance. There have been a few instances where people from the board have e-mailed him and he has answered. The time or 2 that I have met him he has always seemed to be a real nice guy and takes time to converse and answer questions.

Also, Rick (Resident Genius) Denney would be another good person to ask. He is an engineer, and I believe he recently acquired a tuba made from non-standard material (fiberglass perhaps) that he is planning on using as a "gig" horn.
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Carbon Fiber Bells?

Postby AndyL » Wed Feb 14, 2007 11:58 am

Carbon fiber tuba bell construction is a subject that has interested me for quite awhile. Reasons to make carbon bells would be: lack of available suitable bells, the cost of available brass bells (presuming carbon bells could be made at lower cost), and any audible difference(s) in playing carbon vs. brass.

I emailed Mr. Daellenbach on two occasions over the past couple years with specific questions re: carbon bell construction. I never received any response. Perhaps my inquiries were victims of a spam filter.

I wondered to what extent Yamaha experimented with wall thickness or resin content of the various carbon bells Daellenbach played. Apparently there were a number of experimental bells. I've read somewhere that projection was enhanced with carbon vs. brass; apparently more than was desired in at least one instance. Which left me wondering.......if the wall thickness was changed, would that have impacted the result?

I own a Martin Mammoth tuba, for which upright bells are quite scarce. I have a Kanstul upright brass bell with 7 7/8-inch tenon and approximately 21-inch diameter flare. Last I heard, 4 custom bells had been made by Kanstul for Martin Mammoths at Lee Stofer's request. Two friends who own original Martin upright bells prefer the sound and projection of the Kanstul "reproduction bell".

One interesting aspect of the original Martin bells is they seem rather soft, or at least the bell tenon deflects when the retaining screws are tightened. Whether this has some effect on tone production, I don't know......but it has made me wonder about rigidity as an aspect of projection.

It seems to me that a competent woodworker could make a male plug of the desired size and taper, rather like making a wooden bowl on a lathe, that could serve as a mold for laying up bells. An acquaintance with experience in carbon fiber layup has expressed interest in such a "bell project", but I haven't found anyone yet to make a suitable plug.....and I'm somewhat daunted by the number of potential variables that could affect the project.

In the case of my Martin, the _length_ of the bell would only be between 12-14 inches.....a much less involved experiment than making a replacement non-removeable type bell. It also eliminates the problem of "how to attach it", since I doubt a tenon would even be necessary. The "insert" end of the bell could just be closely fit to the female tenon on the horn, and the screws tensioned to hold it in place.

I've wondered about the repeatability of the layup process in making a short run of bells. Would the layup thickness, ratio of resin to fiber, or even the fiber orientation have a noticeable effect on the sound or projection of the bell? Would "vacuum bagging" to use less resin in the layup, or perhaps oven drying have much effect? What about polyester, epoxy, or vinylester resins? If there was any intention of marketing such bells, you wouldn't want each one sounding "randomly different".

I've also wondered if some aramid fiber (Kevlar, Twaron?) or graphite might be more suitable for bells than carbon fiber. I suspect stiffness is desireable. As none of these materials is inexpensive, it would be easy to run up a pretty large tab with extensive experimentation!

Another important aspect that could be experimented with is the rate of taper of the bell. The Rudolph Meinl 5/4 bell has a somewhat more gradual rate of taper than my Kansul, and is a shape I'd consider experimenting with.
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Postby lgb&dtuba » Wed Feb 14, 2007 12:14 pm

It would be interesting to see how a mostly carbon fiber tuba would sound; one with everything carbon fiber except the valve section. Sort of like how a fiberglass sousaphone is made.

How would carbon fiber stand up to use in a tuba constucted that way I wonder? No dents, of course, but would cracks be a problem?
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Postby JCRaymo » Wed Feb 14, 2007 12:42 pm

I think the problem with Carbon is the expense to make it. I heard through the grapevine that the carbon bells he used are around 10k each. I have not validated this info though. I am not sure how the bows would be made but I think there would have to be a seam. The bell would be straight forward once the forms were made.
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Re: Carbon Fiber Bells?

Postby Russ Kaiser » Wed Feb 14, 2007 12:51 pm

AndyL wrote:
One interesting aspect of the original Martin bells is they seem rather soft, or at least the bell tenon deflects when the retaining screws are tightened. Whether this has some effect on tone production, I don't know......but it has made me wonder about rigidity as an aspect of projection.


Schilke did a lot of experimentation with bell materials for "you know what instrument" in the brass family. He went so far as to make bells from crystal, steel, lead.

http://www.dallasmusic.org/schilke/Brass%20Clinic.html

I think you will have fun reading this as Schilke's results are a little counter-intuitive, at least they were for me.
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Re: Carbon Fiber Bells?

Postby Captain Sousie » Wed Feb 14, 2007 1:14 pm

Russ Kaiser wrote:Schilke did a lot of experimentation with bell materials for "you know what instrument" in the brass family. He went so far as to make bells from crystal, steel, lead.

http://www.dallasmusic.org/schilke/Brass%20Clinic.html

I think you will have fun reading this as Schilke's results are a little counter-intuitive, at least they were for me.


So, this implies that a granite tuba may well sound better than a titanium one.

In all seriousness, I enjoyed the article and it has gotten me thinking about some of the materials comonly used for instrument manufacuture and what might be used to improve the sound. Also, some of the implications about the newer mouthpiece materials are interesting.

Good post, thanks.

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Postby Tom Holtz » Wed Feb 14, 2007 2:22 pm

Gil Corella, USAFB, found somebody out here (Mid-Atlantic) who was messing with carbon fiber, and had made a carbon-fiber bell for, I think, one of Andy Kochenour's (Dixie Power Trio) tubas. The memory is a bit hazy on that. Anyway, Gil got said person to make a bell AND bottom bow for one of his small CC tubas. That project was enough work that said person decided not to mess with carbon fiber again.

I've played Gil's stealth tuba. The sound is definitely deader with a CF bell, but Gil's stealth CC is the lightest C tuba EVER.
      
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Postby GC » Wed Feb 14, 2007 2:28 pm

It seems like carbon fiber would be an excellent material to make tubas with no seams in the bows, only at the ends. In one of the most common processes, rayon in an epoxy matrix is usually fitted into or around a mold and then heated in multiple stages to drive out all chemicals in the rayon fiber except long-chain carbon molecules. Top and bottom bows could be easily made in one piece and removed from the mold.

However, the body's large straight tubes would have to be made separately from the bows and attached later. Since the carbon fiber parts could be made to very close tolerances, they could be glued with very little adhesive necessary, attached with ferrules, or maybe even made with screw or snap joints. Wouldn't it be wild to be able to take a tuba apart by unscrewing or unsnapping the pieces?
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Postby Tom » Wed Feb 14, 2007 4:30 pm

Tom Holtz wrote:Gil Corella, USAFB, found somebody out here (Mid-Atlantic) who was messing with carbon fiber, and had made a carbon-fiber bell for, I think, one of Andy Kochenour's (Dixie Power Trio) tubas. The memory is a bit hazy on that. Anyway, Gil got said person to make a bell AND bottom bow for one of his small CC tubas. That project was enough work that said person decided not to mess with carbon fiber again.

I've played Gil's stealth tuba. The sound is definitely deader with a CF bell, but Gil's stealth CC is the lightest C tuba EVER.


The person you speak of might have been George McCracken in VA. I think this is the same George McCracken known for building high end custom French Horns. He built the original carbon fiber bells for Daellenbach from what I understand.
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Postby jimlyon50022 » Wed Feb 14, 2007 7:00 pm

I am in the plastics industry and have had an idea of using a material similar in physical properties to CF and could be molded in a higher production scenario.

CF is way too expensive even compared to Brass and the tolerences required take very experienced people to lay them up consistently. Boeing even has issues with CF air ducts and they have very experienced craftsman doing them.

Anyone who is interested let me know and we can discuss.

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Postby Rick Denney » Wed Feb 14, 2007 10:34 pm

My experience with carbon composites is with bicycle frames. They do attenuate high frequencies, and they do deflect more than, say, steel under a given load unless designed very carefully. But my Trek 5500 bicycle frame is about half the weight of a steel frame with light tubes of approximately the same stiffness. The bike feels different than a steel bike, but Lance Armstrong didn't seem too bothered by that. Actually, it may be that it sounds different more than it feels different--sound and feel are sometimes hard to separate even for tuba players.

Another point from the bike experience: Carbon composites may attenuate high frequencies, but they seem quite elastic at low frequencies. I have a Wound Up carbon composite fork on one of my bikes. When you tap it with your fingernail, you can the standard thud of plastic. But when you remove the front wheel and whack the fork blades with your hand, it rings like a bell with little damping at maybe 200 Hz. That's similar to what I feel in my hands from my more resonant brass tubas.

Laying up bicycle frames is difficult but not that difficult. Trek makes them in sections and glues them together with epoxy. They use an inner mandrel within the tubes to provide the necessary compaction. Kestrel lays up their frames in a single piece, and use an inflatable inner mold to keep the fibers compacted when they inject the binder. It seems as though the binders are drawn into the mold using a vacuum. The binder seems to most often be an epoxy, perhaps one with a high solvent content so that it flows well in such a molding process.

Fiberglass, on the other hand, is usually made by hand-laying fiberglass cloth on polyester or epoxy resin. But I'll bet that fiberglass sousaphones (at least the bells) are not laid up but are rather molded using sheet mold compound. That's a sheet material that is, if I'm remembering the process correctly, thermoplastic binder around fiberglass, and they use a heated pressure mold to provide the correct shape and then add a catalyst or hardener (or maybe it's the heat) to improve its temperature resistance. That's how GM made fiberglass Corvettes, but it takes BIG tools to use it. The molds used for the GMC motorhome were 12x12x12 feet, weighed in the double digits of tons, and were high polished and chrome plated for durability. That would be kinda expensive for tuba bells made one at a time.

As far as the musical impact, I'm sure there is a difference. I'm not at all sure that the difference is really important, or that in some circumstances might not prove to be an advantage. My recently acquired Martin TB-31 has fiberglass outer branches, and it's roughly the same size and shape as a new King 2341. It plays wonderfully--I would have no problem using it in any gig where a horn of that size would be appropriate (and where I can live with only three valves). I will definitely being using that instrument. It's the no-brainer tuba for standing gigs that need a contrabass, for example.

I don't think Schilke's analysis with trumpets is terribly relevant. The resonant frequency of the brass is quite high--much higher than all but the very highest (and weakest) overtones in tuba sound. That statement would not, however, apply to trumpets. And it might be that a plastic tuba behaves differently when one is overdriving it to produce an edge.

And for Tom: I've handled Gil's carbon composite tuba. It's got a Conn 3J valveset, and seems to have been modeled on a 3J. But it doesn't have a 3J-shaped bell. I don't know what shape was used for the bell, but the shape might be part of what makes it seem dead. It may seem dead, but it doesn't sound dead (Gil played his final DMA recital using that instrument, and sounded great as always).

The advantage of carbon composite over fiberglass is that it is much stronger, and can therefore be made lighter and thinner.

It is possible to hand-lay carbon composite, but that might result in some significant sample variation. The materials are generally available.

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Postby Art Hovey » Thu Feb 15, 2007 12:41 am

This is something I really would like to see happen. The bell and bottom bow should definitely be made of carbon fiber; I wish I knew how to do it. My idea is to cultivate the friendship of a prostheticist. That's a guy who makes artificial legs. They routinely create sockets about the size of euphonium bells out of carbon fiber, custom-fit to the patient's residual limb. So far it's only a dream, but the technology is there waiting for us!
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Postby Chuck(G) » Thu Feb 15, 2007 1:28 am

How easy is laminated carbon fiber to repair?

This could turn out to be quite a bit more expensive than one might guess. One might want the large branches to use a threaded coupling of some sort, as you're not going to solder these parts together--and gluing them would make servicing and replacement of parts quite difficult. So add some precision machining.
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Postby JCRaymo » Thu Feb 15, 2007 7:47 am

Chuck(G) wrote:How easy is laminated carbon fiber to repair?

This could turn out to be quite a bit more expensive than one might guess. One might want the large branches to use a threaded coupling of some sort, as you're not going to solder these parts together--and gluing them would make servicing and replacement of parts quite difficult. So add some precision machining.


I used to work for United Airlines and I have been around many carbon repairs. They use Chemicals, Heat via a hot lamp, and the whole thing is vacuum packed. I think that's the difference to fiberglass over carbon. Carbon has to have the vacuum. I think that is where the trouble would come. You would have to have some sort of form for either the inside or outside of the bell and it would have to be vacuum packed from the other side.

I would think that people who are in racing like Indy and formula I cars would have more knowledge than myself. The racing teams would sometimes come to rent out our autoclave because at the time I was working in Indy we had the biggest autoclave in the US. An autoclave for those who have not heard of one is a big pressure cooker. That's the other way of forming carbon. The repairs I talked about earlier used a vacuum press but bigger stuff like car bodies and just go in an autoclave.
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Postby Russ Kaiser » Thu Feb 15, 2007 8:34 am

This is something I have thought about for a long time.

I would like to point out that there are room temperature curing resins that are compatible with glass, carbon, and Kevlar cloth making a wet lay-up process possible. Carbon cloth is about 12 times the cost of fiberglass at about $40 to $80 a square yard and Kevlar in general is about one half the cost of carbon. Both are hell on scissors by the way. A large tuba bell well would take around 4 to 8 yards of fabric. Every layer would have seams, but they wouldn’t have to be in the same location for each layer. Mold building would be identical regardless of the reinforcement used, so someone wanting to make a bell could start off using glass to get their patterns down and switch to Carbon when they had their ducks in a row. Bottom bows would have to use a split mold like my serpent for a wet lay-up type process.
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Postby JCRaymo » Thu Feb 15, 2007 9:21 am

Chuck(G) wrote:How easy is laminated carbon fiber to repair?

This could turn out to be quite a bit more expensive than one might guess. One might want the large branches to use a threaded coupling of some sort, as you're not going to solder these parts together--and gluing them would make servicing and replacement of parts quite difficult. So add some precision machining.


You would have to have a sleeve glued to the ends where it would come apart like a threaded sleeve of some sort. Carbon has strength but it would never hold up to being threaded. The strength is over a wide area and it would need to have couplings if it were to be able to come apart and not be permanently glued. Having seen lots of carbon duct work aviation I would think that bows would have good strength and the weakest area would be the bell.

Bell damage would be my biggest concern and repairs would likely affect the sound because there would be thicker areas where the cracks are repaired.

What about Linen Micarta as a bell material? I have seen that used in knife handles, hardhats, tools, etc. I don't know how it would sound but it might be work thinking about.
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Postby ZNC Dandy » Thu Feb 15, 2007 10:13 am

Walter Hilgers has an instrument made from some compound other than metal. I'm pretty sure he wouldn't play on anything that didn't let him produce the best possible sound.

http://forums.chisham.com/viewtopic.php?t=13391
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Postby Rick Denney » Thu Feb 15, 2007 10:56 am

Chuck(G) wrote:How easy is laminated carbon fiber to repair?

This could turn out to be quite a bit more expensive than one might guess. One might want the large branches to use a threaded coupling of some sort, as you're not going to solder these parts together--and gluing them would make servicing and replacement of parts quite difficult. So add some precision machining.


Seems to me that some relatively low-temp thermoplastic cement could be used, with a high-temp resin in the material itself. Then, it could be removed using a technique already familiar to us. That approach would be facilitated by metal ferrules.

Threaded connections would require some pretty tricky machine work, it seems to me. Plus, I don't think they'd be reliable in the scheme of things.

As far as repair, if you design it properly, it might never need repair except in cases where the damage is so severe that you'd just replace it anyway. Even so, I suspect sanding it down and laying another layer of material and resin, as with fiberglass repair, would be possible.

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Postby Rick Denney » Thu Feb 15, 2007 11:14 am

JCRaymo wrote:Bell damage would be my biggest concern and repairs would likely affect the sound because there would be thicker areas where the cracks are repaired.


This was a problem with brass, too, and the reason behind rolled bell rims and garlands. Fiberglass sousaphone bells endure more pain than any tuba for a grown-up, and they use a molded-in rim to add strength. Carbon would be much stronger here. It would certainly be stronger than brass, though if it failed it would be a more difficult repair, of course.

I wonder if the vacuum or pressure layups used for bicycles and airplanes are mainly to provide the appropriate strength density for a part of particular size. A tuba bell might not be quite as demanding. I do know people who have hand-laid CF bicycles, and successfully so.

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