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overbent spring, bass clarinet

Author: John Morton
Date: 2004-04-21 23:47

The long keys which extend from the disassembled upper and lower joints are vulnerable, so I always try to handle those pieces carefully. But despite my precautions I have now twice overbent the spring under the first RH side key by inadvertently depressing the key. All the other protruding keys have limit stops of some sort, but that one permits travel beyond where that spring can recover.

It surprises me that the seemingly harmless act of depressing a key can render my clarinet unplayable. Is this spring worn out? Is there a way to mechanically limit the travel to guard against this problem?

thanks
John Morton

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Re: over-bent spring, bass clarinet

Author: Gordon (NZ)
Date: 2004-04-22 01:40

It can be:

1. The elastic limit of the spring is just too low - poor quality spring material for this location.
2. The effective length of the spring is too short. A longer spring spreads the bending over a longer distance. But a longer spring needs to be stronger of course. Does the key geometry allow for a longer spring to be installed? Perhaps a new screw hole would need to be drilled and threaded. Note that if a significant part of the spring is in contact with the key, then this detracts from the EFFECTIVE length, because this portion does not take its share of the bending, so...
3. The spring has not been pre-bent to an appropriate shape.

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Re: overbent spring, bass clarinet

Author: Don Berger
Date: 2004-04-22 14:21

John - I'm afraid I dont quite understand your description, is the key, which spring receives the over-bending, the lower [for Eb/Bb] of the 4 "trill" keys on the U J ? If so, its limit-stop is of course the top of the L J stack, so possibly might your assembly method for the joints be a cause? Assuming so [hope I'm not insulting you !!], my method is to take the U J in left hand , palm up, fingers in about "playing position", raising the upper bridge half, then,with the L J in right hand, fingers/palm as clear of keys and posts [on lower pads only?] as possible, assembling, with a bit of twist, the hoints, being able to observe the bridge orientation. A too-tight tenon cork might contribute also. Others, PLEASE, comment and correct me, TKS, Don

Thanx, Mark, Don

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Re: overbent spring, bass clarinet

Author: John Morton
Date: 2004-04-22 14:53

That's right Don, it is the Eb/Bb trill key, and the lower joint stack has to be in place to limit travel. I too have a very specific method for assembly which guards against interference - the damage was done in the careless handling of the upper joint when I was not aware of how easily it happens.

Thanks, Gordon, that seems like a good analysis. The guide slot in the upper joint does allow for more spring length, so another spring could be installed without changing the location of the screw or pin that anchors it to the key. Of course the spring must be pre-bent before installation, and I have fixed it each time by re-bending it. One of these days it will snap and I will be forced to really do something about it.

thanks all
John Morton

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