Rattling sound

[jakubko123]

Hi guys!
Do you know what is causing this rattling sound and how to repair it? It is a bass reed in a diatonic Hohner accordion and I put new valves and wax in it and tuned it. I thought there was some metal piece on the reed tongue that would form such sound while playing so I filed around the reed tongue but it didn't help. (The sound can be heard only when pushing the bellows harder and this is the only reed playing like that.)
Please help

 

[boxplayer4000]

jakubko123: The problem is not uncommon with large bass reeds and the subject is already well covered in this site. The most common fault is a reed valve not closing properly when the bellows are being closed. It can help if you can watch what the valve does if you blow it on the workbench.

 

[Vladimir M.]

Hi Jakubko,
on the recording, it is nice to hear how in the bass part first starts to vibrate the reed for a higher octave, and only then does the big reed with the weight at its end begin to move for the lower octave....

Please help

Check all the valves on the given voice plate for the given tone. Try to carefully deflect them and notice whether they rest symmetrically, whether they are not glued to the reed plate unevenly on their sides.

I put new valves and wax in it and tuned it

A bit of stupid advice would be to wait until the accordion is "up and running again" after the repair - this can usually take a couple of weeks. Hypothetically, the problem could disappear on its own after more intense play.

Best regards, Vladimir

 

[debra]

Apart from the possibility that the valve next to the reed isn't closing properly there is also the possibility that the valve for the reed itself does not open far enough and the reed is hitting the valve.

 

[dak]

My own take on this is that you are underestimating just how far a weighted bass reed will swing out eventually when pushed. Somewhat counterintuitively, the volume of a note follows the pressure (and the resulting air flow) comparatively immediately, but the distance that the reed swings increases (and decreases) with considerable latency.

You might be hitting the bellows frame or a bellows pin or some other part. Now you are saying that happens on push. The problem I describe is more likely on pull because pulling makes the reeds come out of the reed blocks. However, if the rattling occurs mainly when you stop pushing hardly, then it can still be the reed hitting something outside the reed block after it can swing outside of the reed block as far as inside because it stops getting pushed actively into the reed block.

 

[debra]

...
You might be hitting the bellows frame or a bellows pin or some other part. Now you are saying that happens on push. The problem I describe is more likely on pull because pulling makes the reeds come out of the reed blocks. However, if the rattling occurs mainly when you stop pushing hardly, then it can still be the reed hitting something outside the reed block after it can swing outside of the reed block as far as inside because it stops getting pushed actively into the reed block.

On pull the reed may hit the back wall inside the resonance chamber (in the reed block). For large reeds there are often cutouts inside the resonance chamber to give the reed more room (but when the reed plate is out of alignment the reed will miss the cutout and hit the wall anyway).
On push the reed may hit an opposing block, reed or valve or even the bellows. Some accordions are made just a bit too compact to give the reeds enough room. You end up with a compact instrument but then it cannot be played at high volume...

 

[boxplayer4000]

Most of the possible faults listed here will likely become apparent if the reed is 'blown' on a workbench test bed; always bearing in mind that when on the workbench the bellows action (pull/push) is reversed.

 

[Vladimir M.]

workbench test bed

Personally, I believe that if the questioner was skilled enough to own such a workbench test bed, he probably wouldn't have asked us about the problem mentioned. In my opinion, he has an instrument, has also a problem, and most likely he does not have a workbench test bed. If he passes it on to someone more skilled, who has the equipment, then he will no longer ask us questions on the forum....

Best regards, Vladimir

 

[debra]

Most of the possible faults listed here will likely become apparent if the reed is 'blown' on a workbench test bed; always bearing in mind that when on the workbench the bellows action (pull/push) is reversed.

Sadly some faults will not become apparent when the reed block is taken out and placed on a workbench. If the reed is hitting something inside the accordion (like the adjacent reed block) you wouldn't notice it when the block is not inside the accordion. Here is an example.
This is how close the reed blocks (in cassotto) are in a Hohner Morino IV M (the beloved old series still made by Hohner themselves).
It is from the later series that uses Bugari reeds. I believe that the Hohner Artiste reeds used in the older series have thinner reed plates.
With this later series you can easily see that when you play loudly the largest reeds are going to hit the neighboring reed block. When you test a single reed block on a workbench everything is just fine. Sometimes you really have to look at what's "around" the reed block where there is a problem.

 

[dak]

On my big Morino-Artiste-like instrument, the C2 in the treble L reed group on pull has a tendency to interact with one of the screws holding the rigid "bellows protector plate" in place. I've filed down the tip of that screw; when disassembling and reassembling the instrument, I have to keep track of where to put this particular screw.