Carbon Fiber instrument manufacture

[AndyL]

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.

[lgb&dtuba]

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?

[Captain Sousie]

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.

Sou

[Tom Holtz]

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.

[GC]

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?

[Tom]

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.

[Rick Denney]

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.

Rick "thinking the idea of plastic may be worse than the reality" Denney

[Art Hovey]

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!

[Chuck(G)]

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.

[ZNC Dandy]

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.

viewtopic.php?t=13391

[Rick Denney]

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.

Rick "thinking innovation is always difficult at first" Denney

[Rick Denney]

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.

Rick "who thinks it can ultimately be practical" Denney

[Chuck(G)]

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.

Rick, your idea of damage and mine must be different. I'm talking about "stupid horn player trips and falls on the tuba", "tuba bounces out of truck bed and lands on freeway" and "tuba gets into the hands of middle school student who hates band" type of damage.

All of the above can be fixed in brass, but how would one fix a flattened bell in carbon fiber?

[jacojdm]

All of the above can be fixed in brass, but how would one fix a flattened bell in carbon fiber?

I think that the point he is making is that these kinds of things wouldn't happen with the carbon fiber. It'd either survive such incidents, or, it'd be damaged so badly, it'd need to be replaced.

[lgb&dtuba]

All of the above can be fixed in brass, but how would one fix a flattened bell in carbon fiber?

Unscrew the damaged bell, screw on a new one?

If they can mass produce PVC elbows, pipes and fittings it seems they could "mass produce" tuba components for this new type of tuba. Once you get away from the idea that each instrument is hand built then interchangeable parts are very feasible.

I realize that's a gross over simplification of the economics involved, but it does seem like some of these new materials could be utilized in a more mass produced and less expensive fashion.

Not good news for intrument repair folks, of course.

[Chuck(G)]

I realize that's a gross over simplification of the economics involved, but it does seem like some of these new materials could be utilized in a more mass produced and less expensive fashion.

Let's start with valve sections.

If you're going to go to mass-produced parts, then you'll have to simplify the number of models and configuration variations down to a handful, otherwise economy of scale won't apply.

So, does everyone here want to play a King 2341?

[lgb&dtuba]

I realize that's a gross over simplification of the economics involved, but it does seem like some of these new materials could be utilized in a more mass produced and less expensive fashion.

Let's start with valve sections.

If you're going to go to mass-produced parts, then you'll have to simplify the number of models and configuration variations down to a handful, otherwise economy of scale won't apply.

So, does everyone here want to play a King 2341?

Hmm, that's a larger stretch than mass producing all the major tubing in carbon fiber and making those parts interchangeable between horns of presumably the same manufacturer and model. I wasn't stretching the idea to include interchangeability across manufacturers.

I was thinking more along the lines of the bell is crushed, so what? Unscrew it, order a prepacement, screw it back together. Bottom bow cracked? Take it apart, replace the bow with a new one, put it all back together. No soldering. No dent removal. No polishing, buffing, or lacquering. No more trouble than replacing a mouthpiece.

OTOH, with standardization and interchangeability of all the various parts (in a single model or series) there could even be an after market set of parts. Different materials. Different colors. Different bell sizes. Bell up. Bell front. Many custom possibilites for frankenhorns.

Want 5 rotors instead of 4? Swap out the valve section as a unit. Reuse the rest of the tuba. Many possibilites.

I had a Jupiter euph that the valve section was designed to be removable. Really made cleaning easy. Just a small wrench to loosen the bracing. Didn't even need a snake to clean it. Think of the advantages of being able to clean the valve section separately. Or working on the sections of the horn without the valve section being attached.

I never looked into it, but replacing that whole valve assembly would have been trivial. No more effort than putting it back together after cleaning it. If the rest of the horn had been made out of carbon fiber it would be exactly like what we've been discussing.

[Chuck(G)]

Mark's right--spinning is one of the cheapest ways to form something like a bell shape out of a hunk of metal. I suppose that CNC spinning of 201 stainless steel might be cheaper, but I don't know if the world is ready for stainless steel tubas yet.

[Rick Denney]

I was also informed that fiberglass sousaphones were not any cheaper to manufacture than all brass instruments. I would think that carbon fiber, although it's sexy and hip material these days would be a very expensive way to make a tuba.

I didn't realize that being cheaper was a requirement. Carbon composite bicycles certainly are not cheaper than their metal counterparts, except for titanium. And most of the cost of that is in the tooling necessary to weld it without ruining it.

I would think a clamp system count be deviced to replace the main bottom-bow ferrules, instead of more traditional joints. I'm thinking something like a band clamp used on high-end exhaust pipes, but a little nicer looking and a little more tailored to the application.

The point of CF would not be to make it cheaper--tubas are already cheap compared to many instruments--but rather to make it lighter and more durable.

There are a couple of repaired cracks on my fiberglass Martin, and the braces were reglued with something not really strong enough (I will be fixing that), but despite 45 years of regular use and an old story of serious shipping damage it's still basically sound and undented.

Brass is easy. That's why it was used 150 years ago and why it is still used. It's the labor that drives up the cost of a tuba (not to be confused with the price). CF layups would require just as much labor, at least at first. But it would be possible for people without the ability to spin bells to experiment with hand layups. Different skills that would be easier in some ways but maybe harder in others.

Rick "noting the downward price pressure on CF bicycles" Denney