 The Clarinet BBoard
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Author: John Gibson
Date: 2002-07-13 02:24
Keep having to have MPCs and tenon joints re-corked. When they're first done...they're fine.....after a couple weeks..it seems like the corks have shrunk and the MPCs and joints start wobbling.
What the heck is the problem? Do i need to tell my repair tech to put fatter corks on, or what?
How's about I soak the cork ends in water for a while to swell them up?
John
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Author: Gordon (NZ)
Date: 2002-07-13 06:10
1. Your technician may not be making the fit firm enough. This COULD be because he does not know about good cork grease.
2. He is not using synthetic cork, is he? Some of this looks real but is actually pretty useless.
3. If you leave the instrument assembled for very long periods the cork eventually gives up recovering.
4. If you use a low qualityh cork grease that turns into a very stiff, cakey material as the more volatile ingredients evaporate (i.e. almost every type on the market) then you have a situation where the grease is so thick that it 'claims' significant space between the cork and the tenon socket. This overcompresses the cork, and in extreme cases this is to a diameter smaller than the socket!
A sign of this happening is that when you use a solvent, perhaps lighter fluid, to clean off all the grease, the joint actually slips together MORE easily. The lard-type greases, especially home made ones, are probably the worst. Use only Alisyn or Doctors Products cork grease. These are vastly superior.
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Author: ron b
Date: 2002-07-13 06:33
I may be missing something but, if it lasts only two weeks something's definitely not right - probably the 'cork'.
Two weeks seems pretty quick for inferior grease to have the detrimental effects you describe, John. I'm not disagreeing with Gordon - it just seems soon to me.
Ask your tech to make sure what you have on there now is replaced with real cork. It has to be re-done anyway and, after only two weeks, there should be no charge. Then, follow Gordon's suggestions about caring for it. As usual, all of Gordon's points are right on target.
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Author: Bob
Date: 2002-07-13 11:36
Gordon: thanks for the tip on "lard". Ive been experimenting with some home brew made from "bird" suet with vitamin E added, perhaps I'll give up on it...
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Author: L. Omar Henderson
Date: 2002-07-13 14:11
Bob - Gordon's points are right on. Even cork treated with the "bad" petroleum based or animal fat based greases should not deteriorate after only two weeks, after say two months I would call the grease to question. These "bad" greases eventually cause the structure of the cork cell itself to collapse and you get shrinkage and lack of rebound when the cork is not compressed. Cork is a pretty amazing thing - it has more compressability and rebound characteristics than any manmade product and the duty cycle (numbers of compressions and rebounds) is great. When the cellulose of the cork cell becomes infiltrated with petroleum products or animal fats it destroys some of the lattice structure bonding of the cellulose molecules and eventually causes the cell wall to become less strong and lowers the duty cycle measurably.
The Doctor
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Author: Bob
Date: 2002-07-13 17:17
Thanks Doc, as usual good information. As an aside...I'm wondering why no mfg. appears to have utilized "rubber" (neoprene, nitrile etc) O-Rings for tenon sealing. Seems like a pair of them on the tenon would work and they sure would be easier to replace than cork or string. I must be missing somethng.
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Author: jbutler
Date: 2002-07-13 17:37
Bob,
Actually, the new Vito bass clarinet is utilizing the O-Ring concept. Now all the techs are adopting a "wait and see" if it is worthwhile, but why try to fix something that's not "broke"? Cork, if maintained, will last for years. I've got the same neck cork on my Selmer Mark VI that I put on back in 1974. It still compresses and seals wonderfully. I always clean the cork well before applying new cork lube (from the Doctor) and will probably get a few more years worth of service from it. Meanwhile, let the ozone play havoc with the neoprene of the O-ring.
<a href="http://www.cork-and-pad.woodwind.org">jbutler</a>
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Author: Gordon (NZ)
Date: 2002-07-14 06:50
I thought one of the latest Yamaha student models had some O-ring system.
The function of the cork is both to seal, and to stop the tenon falling apart or wobbling. A variety of properties of the material such as elasticity, resilience, surface friction, and lubricant retention are critical, in conjunction with the properties of the lubricant, if any, and the effect of the presence of moisture which may well alter somes of these properties.
O-rings do a good job of sealing, but they so far do not measure up well for the cork's other function of keeping the joint together. I do not recal seeing any use of o-rings where easy assembly and disassembly is frequently required.
Bayonet or screw fitting tenon joints with O-rings comes to mind as a possibility, but this makes it difficult to provide provision for adjustment.
The cork tenon is a pretty close to perfect solution to a tricky set of parameters. I believe there will eventually be a synthetic, say the very stable 'viton' or perhaps a urethane polymer for firmness, perhaps as a close-cell foamed like cork for easier compressibility, and with an incorporated lubricant - perhaps like polyethylene or teflon - scattered appropriately in the molecular structure, to emulate the effect of cork grease. Of course the back may have to be modified, perhaps chemically etched, or laminated, in order to make glue stick.
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