Additional pressure lever cassotto

[Pierre]

Hello,
During the maintenance of my LMMH Scandalli accordion I often strugled with finding the correct pressure to apply to the cassotto reed blocks.
The blocks were sanded flat but I have difficulties to have an equal pressure al over the lenght (extremes and middle)
Maybe the cassotto is a little warped but don’t know how to check this.
I noticed that giving more pressure in the bass or treble side can be quite critical for the sound quality and can change the tuning and cause some anoying vibration.

The best results I had is with some more pressure in the trebble but then the middle of the reed block seems to lack pressure.
I recently came across this picture from a proffessional Borsini accordion and this made me wonder I was not allone struggling withe this…
Could this be a solution?

Has someone seen this this on other accordions?
I wonder also if this could damp some vibration?
Any way, I’m thinking about to adapt a similar system to my reed blocks to give it a try…

Any comments would be great!
Thanks
Pierre

 

[debra]

I have seen this in older accordions, but not in recent ones. With long reed blocks it is a challenge to produce them such that even after 50 years they are still perfectly straight (and then the soundboard of the cassotto also needs to still be perfectly flat).
The right amount of pressure can be a challenge to find because not enough pressure and there will be leaks between the soundboard and the blocks and too much pressure and the register sliders will freeze up... So some help to regulate the pressure not just on both ends of the reed block but additionally also around the center is always welcome. But... everything you add during manufacturing adds to the weight and cost of the accordion...

 

[Pierre]

Hi Debra,
Thanks for your reply.
I forgot to mention that the problem was more noticeable with the visible reed block. I suppose it has to do with the fact that the soundboard of the cassotto is more stable where it is glued to the sides of the case than the center (visible) part which is less supported and more likely to deform?
Maybe a silly question but maybe in the case of a concave soundboard the reed block could be shaped to this deformation. In my case it would be remove some wood at the extremes…?
What makes me think it is not always a good idea to straighten the reed block base.

What I like about this Borsini system is that it gives an extra support without pushing the cassoto soundboard down in the center.

Greetings

 

[debra]

To check whether the reed block is sufficiently flush to the sound board the cigarette paper test may work: put a cigarette paper between the two, then "fix" the reed block and check how much force is required to pull the paper out. Do this in maybe 5 positions along the reed block. If the force is the same everywhere then the reed block fits well. If there is an area where you need more force then that area needs to be sanded down a bit, and if there is an area where you need little force then the other areas need to be sanded down a bit.

 

[Pierre]

Thanks for the cigaret paper tip!

To check whether the reed block is sufficiently flush to the sound board the cigarette paper test may work: put a cigarette paper between the two, then "fix" the reed block and check how much force is required to pull the paper out. Do this in maybe 5 positions along the reed block. If the force is the same everywhere then the reed block fits well. If there is an area where you need more force then that area needs to be sanded down a bit, and if there is an area where you need little force then the other areas need to be sanded down a bit.

Hi Debra,
The cigaret paper trick worked great!
Even if I still have some spots where the paper is a little less tight the improvement is very clear; better sound, better compression, and the tuning
didn’t change that much.
I’ll check all other reed blocks.
Thanks again

 

[debra]

Thanks for the cigaret paper tip!

Hi Debra,
The cigaret paper trick worked great!
Even if I still have some spots where the paper is a little less tight the improvement is very clear; better sound, better compression, and the tuning
didn’t change that much.
I’ll check all other reed blocks.
Thanks again

And you get this tip from someone who has never smoked at all!
We learned about using cigarette paper in the ACA courses.