 The Clarinet BBoard
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Author: Gordon (NZ)
Date: 2002-12-11 20:14
There was a recent thread about repairing a broken greenline tenon.
Admittedly it is heresay, but any owner of a broken tenon should be aware of some information I encountered:
.... that Buffet admitted they were having problems (since corrected) with the Greenline clarinet tenons and would replace the whole joint. From what I understand they have since corrected the problem. So... maybe check with Buffet if your clarinet falls into that time period.
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Author: GBK
Date: 2002-12-11 20:17
Gordon...As one of our repair experts on the board, why do you think the tenon would fail on the Greenline?
Material flaw? Design flaw?
Just curious if you had a theory...GBK
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Author: ron b
Date: 2002-12-11 20:39
Also curious (and surprised), Gordon - do these tenons break during ordinary use? I haven't heard about this before now but it would be quite a shock to have a 'new' horn's tenon break off for no reason. I had the impression Greenlines are indestructible under normal conditions.
Does the information come from Buffet? What years are affected by this particular problem?
If you had to repair one, outside the warranty/(recall?) period, would you do it in the usual manner (pins and epoxy)?
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Author: Gordon (NZ)
Date: 2002-12-12 03:44
GBK. Three suggestions:
If there is any bending action (the extreme being when it is sat on while on a couch or bed) on a clarinet, as opposed to pulling apart, pushing together, or twisting, there are very large forces put on a very weak area, where the tenon meets the body. This is made far weaker if there is a "stress raiser" involved. In this case a stress raiser is a sharp, un-'radiused' profile where the tenon meets the wall that goes up to the end of the main body. The smaller the radius here, the weaker it is, in a big way! A stress raiser acts like a cut to get a tear started. We all know how easily a plastic bag tears AFTER it has been cut!
The same applies, to a slightly lesser extent, at the main body end of the cork groove.
It is possible that Buffet had insufficiently large radius here.
Another possibility: The composite Buffet uses includes a little carbon fibre. There is no point in having carbon fibre where the body is strong, so it is possible that Buffet is using the carbon fibre only in this weak area, if that is indeed possible. Perhaps the carbon fibre was left out. Perhaps the threads were aligned in the wrong direction.
A third, less likely possibility:
Some solvents destroy the molecular structure of some polymers. I recall washing motor bike parts in petrol, using a tooth brush. The toothbrush shattered into hundreds of pieces. Also, some alcohols do this to styrene. Is it possible that Buffet used an inappropriate cleaner that damaged the polymer in the composite?
Ron B. So many questions!
"Do these tenons break during ordinary use?" I don't know. In my view SOME bending has to be considered normal use. There is mild bending during some fingerings. I think a clarinet body should be able to stand tipping off a stand. Timber does. plastic Yamahas do.
"I haven't heard about this before now but it would be quite a shock to have a 'new' horn's tenon break off for no reason. I had the impression Greenlines are indestructible under normal conditions."
The huge structural benefit of Greenline is no longitudinal splitting. However the bonding material is a polymer, and most polymers are highly 'notch-sensitive" - i.e. notches or cuts acting as stress raisers. For a polymer instrument to be indestructible in ROUGH normal use, due design attention must be given to the weak area of the centre tenon.
"Does the information come from Buffet?" No, a technician. One technician/outlet(?) reports having over ten replaced. I don't know if they all broke.
"What years are affected by this particular problem?" I don't know. Buffet should be able to supply a serial number range, but they would no doubt like to keep this matter low key. If it was a vehicle, no doubt a product recall would be inevitable. I have mentioned it only to save large repair expenses for people when there was a replacement alternative, not to hassle Buffet. I think it only fair that owners should know. An integrity issue.
"If you had to repair one, outside the warranty/(recall?) period, would you do it in the usual manner (pins and epoxy)?"
Yes, but why should the warranty issue ever end for a known fault such as this. I suppose it is a matter of local law. In NZ the product should perform for a "reasonable period". To me, for a top-of-the-range clarinet body , in normal use, this is decades.
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Author: ron b
Date: 2002-12-12 16:33
Thank you, Gordon, for your in depth response. I'm sure many others appreciate all the time and knowledge you devote to keeping us informed. I wish there were a better way to reward you for your effort. Until that happens, please allow me to express my humble appreciation for your dedication to the craft and to us.
Thank you.
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Author: GBK
Date: 2002-12-12 17:36
Ron said: "... Thank you, Gordon, ...please allow me to express my humble appreciation for your dedication to the craft and to us..."
Ditto...GBK
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Author: Gordon (NZ)
Date: 2002-12-13 12:14
*Blush* You're most welcome. It does seem strange to me, finding an audience here in areas I very rarely find one in real life. By throwing ideas around and getting reactions I become more aware of the ever increasing areas where I know so little.
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Author: ken
Date: 2002-12-13 17:50
I was an unfortunate witness to one of these nasty breaks. A co-worker was routinely screwing their Greenline together (upper/lower joints) and the entire upper joint/lower tenon cracked off at the bore and lodged in the lower joint. When attempting to remove the severed tenon it crumbled, cork and all in a half-dozen pieces like a stale cookie ... highly disturbing site to say the least. From what the owner said the horn was a 2nd year Greenline and about 4 years old.
They called up Buffet with the grizzly tale and returned the "remains" for inspection/repair. At first Buffet balked refusing to make good on it, they wouldn't commit to a production defect but did confirm the joint was un-repairable. As a last ditch effort, the owner phoned their teacher (big name professor and Buffet advocate) and with a call from them convinced Buffet to replace the joint free of charge. v/r KEN
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Author: Bob
Date: 2002-12-13 20:19
Yes, I certainly second or third the appreciation for Gordon's excellent technical explanations. My gut reaction to the failure is surprise that the tenon took so long to fail since it sounds like an incomplete "cure" situation(curing of the epoxy or polyester..whatever it is... mix). Buffet's reported reaction to the situation isn't inspirational. On the other hand, they don't really claim the horns won't crumble.
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Author: Gordon (NZ)
Date: 2002-12-14 12:22
I didn't think of incomplete cure.
It could also result from inadequate mixing of the components, so that the tenon was sawdust with almost no binder.
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