Bass machine felt

[KiwiSqueezer]

When frustration levels allow, I'm slowly rebuilding a small Paramount accordion. It feels like almost everything that could, does require attention. There's still masses to do, including a complete re-valve, which I'm not looking forward to...

Below the bottom of the bass 'pistons', there's a felt strip, presumably to provide the pistons with a 'soft landing' and/or to prevent any mechanical clatter. However, even with the bass button pressed as far as it can be, before the finger is stopped by the surrounding woodwork, the bottom of the piston is a couple of mm clear of the felt. I can believe that it's better for the finger's travel to be stopped, rather than the piston's, because that prevents the possibility of the piston being buckled by excessive compressive force, but if that's the design intent, what's the purpose of the felt? Belts and braces? Or should the pistons' movement be limited by the felt acting as a buffer (for instance for better tactile feedback)? In other words, just how far down should a bass button be able to be pressed?

 

[Ikesaccordions]

When frustration levels allow, I'm slowly rebuilding a small Paramount accordion. It feels like almost everything that could, does require attention. There's still masses to do, including a complete re-valve, which I'm not looking forward to...

Below the bottom of the bass 'pistons', there's a felt strip, presumably to provide the pistons with a 'soft landing' and/or to prevent any mechanical clatter. However, even with the bass button pressed as far as it can be, before the finger is stopped by the surrounding woodwork, the bottom of the piston is a couple of mm clear of the felt. I can believe that it's better for the finger's travel to be stopped, rather than the piston's, because that prevents the possibility of the piston being buckled by excessive compressive force, but if that's the design intent, what's the purpose of the felt? Belts and braces? Or should the pistons' movement be limited by the felt acting as a buffer (for instance for better tactile feedback)? In other words, just how far down should a bass button be able to be pressed?

There is no standard that I know of, except the button doesn't need to go down further than the top of it being level with the grid plate. Bass mechanisms are idiosynchratic, and most of them don't have that felt. Maybe it's just for looks, like some people consider parsley on steak.
Consider yourself privileged.

 

[debra]

The strip of felt is for the pistons to return back to the "up" position without making a clacking noise. It has no function when you press the button, only when you release it. There is not "stopper" felt like on the treble side because indeed your finger cannot push the button beyond the plate with the holes.
Some accordions do have a kind of stopper felt or fabric that prevents the levers inside from being pushed down too far (and then "jump" over the end of the lever). You may have seen the odd "accident" where someone drove over a bump and then finds upon opening the case or gigbag that many bass buttons have fallen down. That is because the levers were not stopped by that felt or fabric and jumped the pins (on the pistons). It's a tricky job to put all the buttons back up without bending anything out of shape. Even when there are no jumped pins the end of one or more levers may also be stuck in the felt or fabric.

 

[Ikesaccordions]

The strip of felt is for the pistons to return back to the "up" position without making a clacking noise. It has no function when you press the button, only when you release it. There is not "stopper" felt like on the treble side because indeed your finger cannot push the button beyond the plate with the holes.
Some accordions do have a kind of stopper felt or fabric that prevents the levers inside from being pushed down too far (and then "jump" over the end of the lever). You may have seen the odd "accident" where someone drove over a bump and then finds upon opening the case or gigbag that many bass buttons have fallen down. That is because the levers were not stopped by that felt or fabric and jumped the pins (on the pistons). It's a tricky job to put all the buttons back up without bending anything out of shape. Even when there are no jumped pins the end of one or more levers may also be stuck in the felt or fabric.

I thought the strip was below the bottoms of the pistons.
Anyway a strip below the bottoms of the pistons wouldn't prevent collapse IMHO. Keep it vertical when in transport.

 

[debra]

I thought the strip was below the bottoms of the pistons.
Anyway a strip below the bottoms of the pistons wouldn't prevent collapse IMHO. Keep it vertical when in transport.

The "strip" of felt that I mean can be seen in the picture below. In this picture (of a somewhat broken convertor mechanism) you can see that the end of the pistons has a "hook" (a 90 degree bend). When you release the button the piston is blocked by that hook, and the felt dampens the noise of the piston going back as far as it can.
The other thing you can see are the red stubs on the pistons. When the buttons are pressed these stubs push the levers. But because the levers rotate (you can see the axles down below) when the buttons are pushed too far they will "jump" the end of the lever, and that causes the collapse.

 

[debra]

Here is another picture where you can see the (green ) strips of felt and the hooks at the end of the pistons. The felt dampens the potential noise caused by the pistons flipping up when your finger releases the bass buttons.

 

[KiwiSqueezer]

Thanks for the comments so far.

The upwards-movement limits are faced with suede leather on my box too. However, it's the downwards-movement limiting felt buffer strips that I'm asking about. The pix above show none, so it seems they may be optional. I can't show pix of my box, because it's all in pieces, but it looks very similar to the one shown in George Bachich's 'Accordion Repair made Simple', part 1. I'd better respect his copyright, and not copy the image. The 8th image ('Here is a typical bass machine') shows a bass machine with these buffers that puzzle me. They lie in the alloy angles, and look like brown suede leather. To have gone to the trouble of engineering the buffers and their supporting structure suggests they were thought important. Their only function that I can think of is to prevent chaos resulting from a massive jolt or drop, as explained above. But then you don't really need resilient facing, do you? So, belts and braces?

 

[debra]

Thanks for the comments so far.

The upwards-movement limits are faced with suede leather on my box too. However, it's the downwards-movement limiting felt buffer strips that I'm asking about. ...

There are accordions with "mushroom" shaped bass buttons (mostly "French style"). The holes in the base plate for the button "stems" are too small for the whole button to go through, so these accordions need a "stopper" to prevent the buttons from slamming into the base plate.
Not sure that this is what you are describing though...

 

[Ikesaccordions]

The "strip" of felt that I mean can be seen in the picture below. In this picture (of a somewhat broken convertor mechanism) you can see that the end of the pistons has a "hook" (a 90 degree bend). When you release the button the piston is blocked by that hook, and the felt dampens the noise of the piston going back as far as it can.
The other thing you can see are the red stubs on the pistons. When the buttons are pressed these stubs push the levers. But because the levers rotate (you can see the axles down below) when the buttons are pushed too far they will "jump" the end of the lever, and that causes the collapse.

Any Italian Stradella machine will collapse, but only the chord buttons. The bass pistons will not normally collapse. 80 chord pistons are supported by 12 springs, but 40 bass buttons are supported by 80 springs. Usually the pistons don't slip off the ends of the levers, but more often sideways.