Coupler slider leak?

[Beemer]

I'm curious whether coupler sliders pose an air leakage risk? As far as I have seen they do not have any felt seals so could air from an open coupler window leak through a closed window and affect the sound? (Sorry if that is a silly question)

 

[debra]

This is certainly not a silly question. In most cases the sound board has full-length indentations in which the sliders fit. A thin aluminium plate with leather gasket glued to it is put on top and held in place with tiny recessed bolts. This whole "sandwitch" needs to be an exact fit so as to not have air leaking from one note to another, yet it needs to be just loose enough that the slider can move freely without any effort (and without needing any lubrication). This sandwich can easily be slightly (or more seriously) deformed when the accordion suffers any type of impact (like a fall). When the reed blocks are in place they are clamped on and that should have enough pressure to have no air leaks between the reed blocks and the leather gasket, yet little enough pressure to not cause friction in the sliders.
I have had difficulties when I got an accordion in for tuning and the bass reed blocks were somewhat stuck to the leather gasket. The reed blocks had to come out because it was a "Winkelbaß" where the block with the largest reeds is at a 90 degree angle and blocks access to the smaller blocks. The force needed to get the blocks out was enough to slightly bend the sound board and sliders "sandwich" and it was very hard and delicate to make them perfectly straight again so the sliders moved freely and the pallets still closed properly as well.

 

[Beemer]

Paul,
Your reply was very informative and descriptive. One day I hope to read about your work journey through accordion manufacture and repair. I have been watching some Castelfidardo made videos some of which are quite old and an insight into family artisans.
Ian

 

[debra]

Paul,
Your reply was very informative and descriptive. One day I hope to read about your work journey through accordion manufacture and repair. I have been watching some Castelfidardo made videos some of which are quite old and an insight into family artisans.
Ian

You give me way too much credit. I started with some minor work on accordions when I still had my day job. After I retired I attended the Accordion Craft Academy courses in Castelfidardo and started doing a bit more repair work, mainly for friends (and friends of friends). I do not have a repair business. My main activity is making arrangements of music for accordion ensembles, and playing the accordion. But while doing some accordion repair I have encountered many minor and major problems, discovered design and manufacturing defects in accordions from well-known brands, etc. But compared to JimD for instance I am an absolute beginner in accordion repair.

 

[JIM D.]

Accordion slider designs from the 50's to present when properly alinged and reed blocks installed tend to seal well even with age.
Earlier slider designs had the sliders in the reed blocks and with age & wear tend to leak air and cause adjacent reeds to sound.

I have in the past posted on this forum on remedies for slider problems but if you have a box with these problems post it
here with Pic's of your accordion and I will respond.

 

[Beemer]

Jim,
I was just curious and don't have a slider problem,
Ian