possible fix for linear cracks along bell?

NotSkilledHere · by **NotSkilledHere** » 2024-08-08 9:57 a.m.

I have a 1932(?) Olds Military Model project horn with a number of issues. There is a dent on the underside of the bell, which I know can be fixed, though hand hammering finish may forever be lost there. Slide also needs work but that's also not too worrying.

The main issue is that the bell has a number of semi-small linear cracks. They are maybe like an inch to 2 inches long. I can definitely see the cracks and feel the split when I run my hands along the area, but when I shine a light along the cracks, light does not pierce through into the inside of the bell. Would these cracks be repairable? If so, what would the expected solution be?

I'm trying to gauge if the horn can have new life put into it or if it should live out the remainder of its life as a pretty wallhangar/parts horn. I'll be keeping it in either case.

Blabberbucket · by **Blabberbucket** » 2024-08-08 11:55 p.m.

I think I have seen the instrument you are talking about. I remember there being many, many cracks.

The best option would be to remove the bell, strip the lacquer, and braze of the cracks. I am not sure it is worth the effort

NotSkilledHere · by **NotSkilledHere** » 2024-08-09 2:45 a.m.

haha you may have seen it. I'll see if i can get a few pictures up here too for everyone else wondering too. Yea there are quite a few cracks. welp if it's not really worth the effort, it will look at least look pretty on a shelf or the wall. Thanks for the diagnoses/remedy options!

OneTon · 2024-08-09 3:10 a.m.

At least you have a sense of humor about it.

timothy42b · by **timothy42b** » 2024-08-09 9:56 a.m.

I have a D5 handbell that has a hairline crack. It is small enough I couldn't see it until I polished it and looked under very strong light. Yet, it has a profound effect on the sound when ringing.

Of course in a trombone, the sound comes from the air column rather than the bell. But here is an example of the sound of a cracked bell:

~~[url]~~<LINK_TEXT text="https://drive.google.com/file/d/1c2seDv ... sp=sharing">https://drive.google.com/file/d/1c2seDvHIVUicBSRZ5EH-ypUp51OI3T2n/view?usp=sharing</LINK_TEXT>

A bell rings like a circular plate - longitudinal as well as circular flexing. I think I posted an example here some time recently.

NotSkilledHere · by **NotSkilledHere** » 2024-08-09 1:24 p.m.

As promised, here are the pics of the cracks. i know some are also scratches but there's a decent amount that could honestly be either.

ironically the inner slide tubes seem to be in great condition. i will have to take it to a tech to see if the slide needs more work than just realignment and deep clean to be brought to useable condition, but if that's all that the slide needs, I'll have the slide brought to bear. but bell will probably just be a decoration.

maybe the inners can be harvested and replaced to my other military model which functions really well..albeit inner tubes have a decent amount of plating loss, although that doesn't seem to have affect the slide's smoothness and speed on that horn.

All things considered, I did purchase this particular project horn knowing that there's a high chance it would not be worth fixing. And all in all, I'm ok with it being that. I didn't pay too much and I went in knowing this could very well be the result, so my heart isn't broken over it.

SamBTbrn · by **SamBTbrn** » 2024-08-09 3:11 p.m.

Oh man, you would have to flatten out the golfball finish, patch the cracks with thin brass patches then put the golfball finish back in.

Not difficult work, but time consuming.

If it's a good trombone then it is always worth fixing!!

Best

Sam

OneTon · by **OneTon** » 2024-08-09 4:00 p.m.

Is that red rot?

brassmedic · by **brassmedic** » 2024-08-09 4:13 p.m.

[quote="OneTon"]Is that red rot?[/quote]
Looks like it.

NotSkilledHere · by **NotSkilledHere** » 2024-08-09 4:38 p.m.

dang I had some suspicious that it might be but was more concerned about the cracks. :( im not well versed in the world of red rot but it shouldn't spread like a medival empire trying to seize all nearby territory if the bell just sits on a shelf should it? would this be worth effort into patching and/or refinishing accounting for the existence of the red rot?

timothy42b · by **timothy42b** » 2024-08-09 4:54 p.m.

A church bell can be welded. <link below> I would think a trombone bell is too thin.

I was picturing a hairline crack like on my handbell. Your bell is more crumbled than cracked. I think playing above mf might shatter it.

NotSkilledHere · by **NotSkilledHere** » 2024-08-09 5:04 p.m.

haha that would be quite the sight. might be a first to have a trombone bell shatter while playing it haha. Welp it will be a pretty sight on the wall then. :) I'll take the slide to a tech at a later date and see if it can be realigned.

OneTon · by **OneTon** » 2024-08-12 11:26 a.m.

Ammunition reloaders have trouble with brass shell casings cracking while stored after being fired. The cracks are most common in the neck. Anecdotally, they seem to think a heat stress relief and storage in air tight bags may attenuate the condition and cleaning with Windex or ammonia may exacerbate the crack probability. Hydrogen embrittlement could be a vector. There probably is enough cold work to induce enough residual stress and hard points (crack initiation sites to cause cracks without hydrogen embrittlement. It would take a real metallurgist and laboratory to find the smoking gun. Olds processes are hearsay and speculation. Experts and labs are expensive. This horn may continue to crack while hanging on a wall. Repair is porobably whack a mole. The horse race now

Is whether the cracks or red rot will win.

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possible fix for linear cracks along bell?