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cracks in early Deagan resonators - Discussions with Dennis

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-----Original Message-----
From: Dennis
Sent: 21 January 2010
Subject: cracks in early Deagan resonators
Can you comment on problems (if any) of cracks that run up and slightly above the plugs in old Deagan brass tubes. I assume because the tubes shrank too much in unheated storage during freezing conditions.

Hi Dennis

Well I personally have little experience with sub-zero conditions for metal - in Australia we just don't have to deal with that type of thing ever - but your explanation does seem a likely one to me. Brass is prone to this type of expansion and contraction - in fact many modern commercial resonators are made from an alloy similar to brass but with more nickel and aluminium and this alloy is actually quite prone to this type of cracking as well. I'm assuming the cracks run vertically yes? What are the plugs made from? If they are a harder metal or of a more solid stock than the tubes then temperature variation olone could cause the cracks. If they are of the sort that are made from thin plate material the same thickness as the tube, then just temperature variation alone is unlikely to be the culprit. In this case I'm not sure, but a possibility might be some moisture accumulating in the bottom of the tube. If a few mm of water - maybe just from condensation - found its way to the bottom of the tube then froze.....?? I'm not sure about that one, it's just a stab in the dark.

Regardless - this does not have to be a serious issue. If the cracks actually make holes in the bottom of the tubes - ie the metal is actually split right open - then obviously the resonators will become ineffective as they are no longer sealed. The fix is to simply take them to a boilermaker or somebody with a decent skill in brazing. It would be a fine job, but brazing is the way to go - just run a thin bead into each crack then grind or file it back flush.

In a pinch - if you just want to get them functional again in a hurry, you could even simply fill the cracks by squirting in a little silicone or acrylic sealant. This would actually be a very functional solution although with a lesser degree of permanence.

Hope this helps Dennis
All the best.

Jim McCarthy

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answers by Jim MCCarthy - 28/02/2008

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