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Discussion Starter · #1 ·
I am not sure if this is correct to call it an arm. Anyway, i am prepared a pic to show. please see the attached.
now this part is so weak that, it moves up and down easily, and therefore leakage is easy.

now i would love to be advised, is there any way to strengthen this part? this is a low C cup arm on a soprano. Handwriting Gesture Font Rectangle Electric blue
 

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Sounds like the spring for that key needs to be adjusted for more tension. Or, are you saying the key arm actually bends? It really couldn't be that because it would just break after a few bends.
 

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Discussion Starter · #3 ·
are you saying the key arm actually bends? It really couldn't be that because it would just break after a few bends.
yes, this is what i mean. yes it is bent up and down easily. and that's what i am worried about,
so what can i do now? any way to fix it? now even a minor bent can cause leakage.
 

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You might be able to talk to a tech about adding brass on that arm - like a splint, with little "plates" of sheet brass on opposite sides where the flexing is happening.

I might work, it might not, it might just be a big pain in the butt and interfere with other stuff, it might look like crap, etc.

But, talk to a tech - you never know, they might have their own recommendations, or easy, durable fixes.

dv
 

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yes, this is what i mean. yes it is bent up and down easily. and that's what i am worried about,
so what can i do now? any way to fix it? now even a minor bent can cause leakage.
Is it cracked?
 

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If it is from a reputable brand you should be able to get a replacement key cup and arm as one part and then have a tech install a new pad and have it fitted and adjusted. failing that it depends on where the flexing is taking place a crack is the most likely cause and depending on where it is a number of ways to solve the issue can be applied from making a replacement arm to bracing supports. Either way I would say that now is the time for you to visit a tech and have them assess and advise on your options before the arm fails completely and you lose the key cup.
 

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Sooooo many keys these days are made from alloys which are too soft...so even if not a crack in the armature - this isn't all that much of a surprise, albeit more dramatic than most. But this is why so many contemporary asian horns do not stay in regulation for very long.

But given that you say it bends so easily compared to the others, there's a fair chance it's a crack or poor factory solder or some other issue to that key particularly.

The thing I would wonder is : are there any other keys on your horn are having similar issues, but less noticeable because they aren't creating leaks large enough to actually not be able to blow thru ? (A tech would need to answer this).

The "solution", for this one key, is as was already mentioned above: a tech needs to solder on add'l metal to create a 'splint'. It can probably be soft-soldered, although if it were in my shop I would lean towards silver-soldering it. If a crack or fissure in the armature, then it can be filled/wiped with silver solder if it can be located.

Don't try a home-solder (techinically 'brazing' actually, not 'soldering')...have a tech do it. If a splint, it WILL probably end up not looking too fabulous, unless you want the tech to spend an hour on filing/abrading/cleaning/buffing the new joint - but function is more important.
 

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Well, let's assume for the moment that there is nothing cracked.

There are two different phenomena that are being called "bending".

1) Elastic deformation which springs back to its original position. This causes a "spongy" feeling. Also due to the flexing it can be hard to get stack keys set up correctly. This is usually due to the design of the component in question, since all the brass alloys have Young's modulus within a pretty narrow range (x = kF where x = deflection, k = Young's modulus, a constant that is a function of the material alloy only, F = applied force).

2) Plastic deformation which does not spring back to its original position. This causes a permanent deformation. Once the deformation happens, whatever adjustment you have is lost. This is a combination of mechanical design of the component and the yield strength of the selected alloy. However, I suspect that the vast majority of keywork is made from UNS C36000 free cutting brass and that differences in the proneness to plastic deformation come from mechanical design that is inadequate to the yield strength of the material. Of course if you have one of those instruments with "nickel silver" keywork the yield strength of that stuff is considerably higher.

So you have to figure out what is actually happening to your particular mechanism before you can determine for sure the corrective action.

I have added stiffening arms to keys many times, as baritone and bass saxes are notorious for long, inadequately supported keywork that feels spongy and is difficult to get in adjustment.

On the other hand, a soprano is a small instrument with small stiff keys. If you are having trouble with this key on a soprano, I suspect you either have a badly cracked arm that is about to give way, or a post that is on the way to falling off.

If the key arm is badly cracked, it just needs to be silver soldered (brazed) back together. Any reputable technician can find out if this is the case, and repair it. If a post is getting ready to fall off, it just needs to be soft soldered back onto the body. Any reputable technician can do this, too.

It is very unlikely, though not impossible, that the key is inadequate for the purpose and needs its design changed by adding material. But given that this is a low C key on a soprano, as stated above a small key on a small horn, I guess that the design of the part is fine and it's cracked. If this was a low B on a baritone, it might benefit from adding some stiffening members in the appropriate places.

If the key itself is to be repaired, don't let anyone use soft solder to repair a crack as you'll have the devil of a time getting it out of there and replaced with hard solder.
 

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Sounds like the spring for that key needs to be adjusted for more tension. Or, are you saying the key arm actually bends? It really couldn't be that because it would just break after a few bends.
It takes many, many, many small bends of this nature to make keywork brass brittle enough to break. In practice, it doesn't happen. Keys break where they are poorly (or inappropriately) soldered, or where there is a flaw eg slag in the metal, or bent a very long way from where they should be.

+1 to turf3
 

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Or made with soft metal and an area of very small cross-section - like in the second diagram, especially if there is no soldering between the arm and the side of the key cup.
There is no end of surprises like this in substandard "brands".

How about some photos rather than just the diagram.
 

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...especially if there is no soldering between the arm and the side of the key cup...
Aaahhh - I hadn't thought of that one. Yes, if you are just relying on the thin keycup to hold alignment without the additional stiffness provided by having the solder bead wrap around and down the cylindrical side of the cup, the whole thing would be floppy as all getout, and this is exactly the kind of quality control error that could easily happen in a low budget el cheapo low cost country factory. Just get one little dab of solder between the arm and the cup, just enough to hold it in place, but don't worry about getting a good fillet all around the joint.

In the absence of any further info from OP who has never returned, I would say that's even more likely than too little material on the arm since I would expect the arms are either blanked out on a press (dimensions governed by the die) or laser cut (dimensions governed by the path programming) - although my experience in dealing with low cost overseas manufacturing shows that ANYTHING is possible. But it's hard to imagine that the el cheapo guys would "over file" the arm as part of the finishing process when experience shows they put the bare minimum of effort into finishing anything.

What is needed here, is someone with mechanical aptitude and experience to look at the thing and identify what is wrong.
 
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