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Discussion Starter #1
I've got a not so vintage, I think late 1960's, Bundy plastic alto clarinet that has been in storage for a long time and its body has a noticeable bend.
Is there a common way to straighten it up?
The only option that I see is moderate heating and fixing it in a straight position with some kind of mandrel running through the body but I don't know if that's going to help.
Actually that's a mistery to me why it would bend at all. Neither the clarinet itself nor its original case indicate it was neglected in any way. Nice clean horn that according to its clean condition hasn't been played much in the past.
 

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If all the keys move freely and there is no lateral movement between posts, you may want to leave well enough alone. Bending or straightening the body will have an effect on the keys. In instrument repair and adjustment it is wise to remember "everything affects everything".
 

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It is easier to stretch most materials than to compress them.
The bend is likely to have stretched the plastic on the convex side.
If you do manage to heat and straighten it without wrecking it, it is likely to happen by stretching on the currently concave side.
The end result is a clarinet that is slightly longer. That is likely to result in sloppy pivot-screw pivots, the correction of which is unlikely to be DIY territory.

BTW, I (we?) are assuming that the body tube itself is bent. But could it just be that the centre tenon or socket has broken off at some time (or suffered in some other way), and been "repaired" in a way that the tenon is no longer in line with the rest of the instrument. If that is the cause, then correction would depend on just what the problem is.
 

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Discussion Starter #5
...
BTW, I (we?) are assuming that the body tube itself is bent. But could it just be that the centre tenon or socket has broken off at some time (or suffered in some other way), and been "repaired" in a way that the tenon is no longer in line with the rest of the instrument. If that is the cause, then correction would depend on just what the problem is.
Gordon, no - this Bundy like probably all of them (at least I've never seen a different design of this model) is a one piece body. No joints in the middle.
 

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If I get a stock length of plastic rod, even reasonably thick one, and store it suspended from both ends, it gets a bend in it, just from gravity, like timber would.
Many plastics are really not that geometrically stable when under constant load.
I wonder if the case only supports the ends?

Perhaps you could unbend it the same way, especially in the sun. At least put the case upside down!
 

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I was told by someone who saw them being made at the factory, that during parts of the manufacture (like drilling holes, etc.) they were only supported at the ends. They could see the body bow very significantly. Maybe that one was always like that since it was made.
 

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Discussion Starter #8
I was told by someone who saw them being made at the factory, that during parts of the manufacture (like drilling holes, etc.) they were only supported at the ends. They could see the body bow very significantly. Maybe that one was always like that since it was made.
Hmm, I see what you mean but from my experience new plastic will rather return to its original shape if only bent for a short period of time like drilling holes as you noted.
Another possibility of course is that it was indeed made that way in the production process for some reason. This one is a later run and I have two earlier ones of the same model and they are absolutely straigth.
 

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Discussion Starter #9
If I get a stock length of plastic rod, even reasonably thick one, and store it suspended from both ends, it gets a bend in it, just from gravity, like timber would.
Many plastics are really not that geometrically stable when under constant load.
I wonder if the case only supports the ends?

Perhaps you could unbend it the same way, especially in the sun. At least put the case upside down!
Gordon - I was thinking about it being bent from storage but the inside of the case has good foam mold and there are no signs of it being supported only at the ends.
However - who knows? - Maybe it was left in a hot environment for some prolonged period of time. Maybe it came from the southern part of the US where it was stored in the attic? I don't remember where it came from.
 

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Hmm, I see what you mean but from my experience new plastic will rather return to its original shape if only bent for a short period of time like drilling holes as you noted.
Yes, what I meant is maybe something weird happened during manufacturing that caused it to remain a little bent, because it gets significantly bent. Maybe it got overly hot, etc. Just some random guesses. It could be anything else, who knows.
 

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It's an alto clarinet. I'm pretty sure someone had good reason to bend it.
 

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Well, I'm guessing that the extrusion process for the original bar stock left residual stresses in the material. When a long row of holes was drilled on one side, it started relieving those residual stresses. Plastics are well known to "creep" under long term stress. Hot storage would have made the creep progress faster as creep has a temperature dependency.

As the body tube has bent, it may or may not have caused either binding or looseness in the keywork, depending on the axis of the bend. The posts are screwed into the plastic, so there are residual stresses around their bases too, and I imagine them almost as floating in the very very viscous material of the body.

Frankly, if it's not causing mechanical problems, I'd leave it alone and consider it a curiosity.
 
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