Protect tuba bell with tight-fitting insert?

[ralphbsz]

I'm learning about tubas (starting from nothing, and without playing them myself). It seems to me that the bell of a tuba is a surprisingly fragile part, easily deformed, dented or buckled. And if you look at the horror shops of tuba repair (Dan Oberloh and the Village Tinker post pictures that turn your stomach), it seems that bells can be horribly damaged. No wonder, they are very big things, easy to hit, made out of a thin sheet of a mechanically not very strong metal. And listening to what I read here, and to my son's tuba mentor, it seems that much of the damage happens when transporting the tuba. Makes sense. One answer is a hard case, but those are huge, heavy, and expensive. Wouldn't it be nicer if you could make the tuba sturdy enough to survive, even in a soft gig bag? Without having to modify the instrument itself?

So I had this idea, but I'm sure it is a horrible idea, just haven't figured out why yet. If one could strengthen the bell by supporting it from the inside, then it would be much less likely to get damaged. And to do that doesn't require a very strong material. Look for example at poster board: it's two layers of paper (very weak, easily crumpled, but can handle tension well), glued to a quarter inch of foam (weak and crumbly, but handles compression). These two ingredients complement each other. This is the whole basis behind composite materials. So how can we use this to make sure tuba bells don't get crushed (in the bus that takes the middle school band to a concert, or when the baritone player in the aforementioned band trips and falls on the tuba) ? In theory it's easy: fill the bell with a foam-like material. It has to fit very accurately; any gap or play, and the bell can still move and be deformed. Putting a mute in the bell wouldn't work. Turns out that this is commonly done when shipping fragile and hollow things: they use foam pillows (usually single-use), encase the fragile thing in them, fill any voids than can collapse, then remove them.

The obvious first idea is to grab a can of that yellow expanding foam, and fill the bell with it. It's great stuff (hence the name), expands nicely into all the crevices and adapts to the shape, sticks extremely well, and gets really solid. I'm sure it would work very well to protect the bell, but unfortunately the tuba would never get played again (except after heroic cleanup efforts). So this was a really bad start, and we need to improve this idea. What if we could create a foam insert which fits very tightly and accurately into the bell, but is built to not stick? So one possibility would be to treat the inside of the bell with a temporary non-stick material (coat of oil or such) that can be removed later, then spray foam into it, let the foam set, and then remove the insert after hardening. The insert would be guaranteed to fit the particular tuba perfectly. This idea might already be good enough for using it once or a few times. With a little work we can greatly improve it. Take the insert, and trim its ends nicely. Then coat it with something that's slick yet prevents the foam from crumbling. Not a problem for plastic coating experts (for example one layer of fiberglas epoxy to strengthen the insert itself, followed by depositing nice slick polyethylene on it). The top of the insert could be trimmed to be an inch taller and wider, and stick over the edge of the flair (flare?) would be protected against being hit. The whole thing could be outfitted with a convenient handle for ease of removal. While transporting the tuba, it doesn't take up any extra space. By hollowing it out, it could even provide extra storage space without weakening it (since every tuba player secretly wishes to carry a piccolo or oboe with them, and what better place to transport it than in the bell of the tuba, but seriously it might be useful for a folded music stand or tuba stand).

Next problem area: The action, keys and valves on front action (particularly rotary) tubas. Again, a similar thing could be done: Custom-fitted foam pillows, in a sturdy outer shell, which just slip over those areas. Even with very little thickness (less than an inch over the keys), this could give a lot of protection: a direct impact in that area would get distributed over a lot of the pipes, and not damage the linkages or keys.

Anyone ever heard of such an idea? Total waste of time? The only thing that a quick web search found is that some people advocate putting a basketball into the bell of the tuba when shipping it.

[basspiper]

Maybe a tuba-shaped version of this?

http://www.amazon.com/Crack-Dawn-Self-I ... B0011FZC92" target="_blank" target="_blank

Dave

[Dan Schultz]

What you are suggesting has some merit. However... I've found that the 'hidden damage' is the toughest to fix. Like when a tuba is subjected to a bump on the end of the bell... the rest of the horn tends to keep on moving causing lots of unseen damage to where the valve circuits and leadpipe enter the valve cluster.

Maybe it's somewhat of a salvation that the bell can act as sort of a 'crumple-zone' to prevent worse damage. From my experience... the type of damage that looks the worst (bell, bottom bow, back bow) is sometimes the easiest to fix. All of those 'dimples' under the braces that are caused by 'blunt force trauma' can be real nightmares.

[Art Hovey]

I tried the expanding foam idea a few years ago, first lining the inside of the bell with plastic sheeting carefully taped in place. I learned two things:

First, the foam does not harden in regions more than an inch from the outside air. It just remains a sticky goo.

Second, the goo is remarkably good at finding its way through cracks and seams in the plastic lining, and adhering to metal. I was able to clean it up, but it was a chore.

I still think a plastic foam bell- plug would be a good idea, but it probably would have to be sculpted by hand from a solid block of foam.

If the tuba has a hard case an inflated basketball or soccer ball works almost as well, for a lot less effort.

[ralphbsz]

I see that my idea gets a grade of about D. Not F, but definitely not A. And if you extend the idea to protect the whole tuba (and prevent the complicated stuff around the valves from getting bent), you are at the dimensions of a hard case. Oh well.

P.S. My son indeed just started studying with the best teacher in the area. Who coincidentally also teaches the previous tubaist of that same middle school (who has now graduated to high school). And I know about Tech Shop; a few colleagues at work go there, and hang out at the Maker Fair. Looks like lots of fun, if I only had time for it. Maybe when my kid goes to college? Or after I retire?

[imperialbari]

What if all brasses came with foam inserts for their bells?

Milling the foam blocks easily could be done on basis of the computerized design formulas for the bells themselves.

Klaus

[Mark]

To fit in the bell securely, the foam would be more or less cone shaped. If a blow was struck on the foam from the top of the bell straight down, the foam would act as a wedge. This might not be a good thing for the bell.