 The Clarinet BBoard
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Author: kilo
Date: 2020-02-13 20:26
Thanks to the information provided on this site (and the in depth article by Clark Fobes provided by Tim Dufka) I was able to address the finicky register vent mechanism on my Selmer 33 bass. The needle spring controlling the Vent Suppression Lever was tired and needed replacement.
I noticed that the post holding the spring is canted slightly (to the right, towards the tone holes) which requires the spring to be bent in order to control the lever and close the vent on the body.
Why is this done, when canting the spring in the opposite direction would apply force without needing to be bent?
The other question I had is whether a slightly larger, more powerful, spring would work if I drilled the appropriate sized hole, or would that over-compensate and upset the balance of the mechanism?
Images:
https://imgur.com/lNNjYqN
https://imgur.com/gKcRyNr
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Author: clarnibass
Date: 2020-02-14 08:50
Springs are a complex subject, but in short (sort of)...
At first I was going to suggest the post might be loose and rotated a bit (loose posts often rotate from the spring and the screw/rod being a little loose), but this is the type that is mounted and aligned with the tab and screw. I guess it's still possible that screw is slight loose, making the post a little loose, so rotating... but just a fraction (by as much as the tab in its cutout would allow, which is usually very little if at all).
What makes you say it is "scant" and in what direction? Are the "wings" for the guide of the hinge rod significantly not aligned with the hinge (angle of the photo makes it unclear)? If that's the case, it doesn't necessarily matter, but it might have been brazed crooked to the tab.
If you mean the spring is not aligned with the clarinet body, that could be from the above (if it is aligned with the guide post itself) or it might have been drilled at a wrong angle (happens occasionally).
Both of these things could be considered a "manufacturing defect"... however bending the spring to the correct tension is the regular method to do it so if that is the "problem"... it's not a problem.
Re enlarging the spring, it is possible and in rare cases a good idea. Very generally, the thicker a needle spring is compared with its length (or maybe better to say, the shorter a spring is compared it with thickness), the more the difference in tension is felt through its movement. Meaning installing a larger spring might help in giving more strength but could have a poor feel. This depends on the specifics of the spring thickness, length, key, etc.
It's not that rare to bend springs to their maximum tension possible to work well so if you can add more tension try it first. The spring would resort to its maximum if it passes its elastic limit. Try to attach the spring to the cradle when mounting the key. Using a spring hook (or equivalent) if fine is almost all cases, but since it has to climb over the cradle, it makes it move a bit more back, weakening it slightly (if you want to have its maximum tension possible).
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Author: Steven Ocone
Date: 2020-02-14 15:51
Bending the spring to the proper strength/position is part of the manufacturing process. There is the chance that the post has rotated slightly and that is why it is off center.If It rotates enough the key while bind or be sluggish. The smallest diameter spring that can do the job usually gives the best feel throughout the entire movement of the key. Longer springs are usually preferable to very short ones.
Steve Ocone
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Author: Chris P
Date: 2020-02-14 19:02
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Attachment: P5210003 (2).JPG (703k)
You need the bend/curve/bias in the needle spring to provide the correct tension you need on any given key or sprung part of the mechanism.
At rest it should form a gentle arc (1st attached photo) and when hitched up to its spring catch, it should be straight as is demonstrated by pushing the free end with a spring hook (2nd attached photo).
If it's left straight and bent at an angle directly where it meets the pillar (or has been mounted in a hole drilled at an angle), then it will bow out between the pillar and spring catch. Sometimes needle springs need to have special bends formed in them for whatever reason and the spring should still retain its tension, but generally a single gentle curve is best.
On threaded pillars, needle springs should be biased in such a direction that they want to push the pillar in a clockwise direction as that will keep the pillar in position.
Sometimes they're sprung in the opposite direction and will want to turn the pillar anticlockwise and effectively unscrewing it which isn't good. The Ab/Eb spring in the attached photos is in the wrong pillar as that wants to unscrew the pillar, so it has to be hitched up once the key is fitted and the rod screw is tightened. Selmer have for some strange reason sprung the throat G# key on their clarinets in the lower pillar which makes refitting the G# key a pain if you want to hitch the spring up before fitting the rod screw as the pillar can rotate in the process.
Ideally these pillars should be anchored or locked in position with a locking screw to prevent them being undone by the spring tension. With anchored pillars (with a baseplate secured by one or two wood screws), the spring can be biased in any direction - likewise with pillars soldered to the body or to a baseplate as you see on flutes, piccolos and saxes. The LH F/C lever pillar in the attached photos (the one with the spring I'm pushing with a spring hook) is anchored so the direction of that spring's bias isn't an issue.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
Post Edited (2020-02-15 01:22)
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Author: kilo
Date: 2020-02-15 01:21
Thanks to everyone. Any tips on achieving a single gentle curve? To avoid bending directly at the post can it be bent around a dowel held vertically near the middle of the spring?
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Author: clarnibass
Date: 2020-02-16 11:19
That sounds a little difficult and cumbersome. The usual method is using spring pliers which have either two curved jaws or one curved jaw. I have several but just as often I use round nose pliers. Though if it is works fine now it doesn't really matter and I would leave it unless there is an issue. Having a nice looking single curve won't necessarily make it feel different or better.
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Author: Chris P
Date: 2020-02-16 15:10
You can put the curve in the spring by holding the flattened end securely in a hand vice and gently drawing round nosed pliers over the length of the spring to put the bend and curve in them, then fit them in the pillar once done. Same with flat springs.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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