Leaky bellows chamois

[RWL]

My Edeophone has never had a particularly good air seal.  A "drop test" takes all of 10 seconds.  The bellows looks good although I haven't inserted a light bulb inside and looked for pin holes.  The valves look pretty straight.  I can put my lips to some of the air holes and the pads don't seem particularly leaky although they're certainly not air tight.  The one thing that's really different compared to my responsive and air tight Aeola is that the Edeophone's reed pan pulls out of the bellows really easily.  I can slip a .015" feeler gage between the reed pan and the bellows gasket for about half of its circumference, mostly in the area of the larger reeds.  It's not hard to move the reed pan a little side to side by pushing it.   I can slip an .008" feeler gage pretty much the whole way around the periphery, but I think the reed pan is sliding a little bit when I insert the shim.  From reading here, it seems the approach is to carefully pry up the chamois along part of the perimeter and put a strip of .008 card stock behind the chamois and try it rather than replacing the chamois.   The 3x5" index cards I have are .006 to .008" thick depending on the card.

 

I'm looking for advice from those who have done this.  Is there a better way to look for air leaks or something I've overlooked as the source before I try shimming?  How to lift the chamois without tearing it?  Should I drip or paint a little water at the edge of the chamois and pry up or keep water away from the chamois entirely?  How much of the periphery to lift and shim?  Can I just shim one half of it and let that push the reed pan closer to the opposite side?  Do I put a double thickness of shims on one half and no shims on the other side of the bellows gasket or put the same size shims the whole way around the periphery?  I was planning on gluing things with liquid hide glue (in the brown plastic bottle).  Another reversible alternative glue is washable "school glue", a clear glue unlike PVA.  Are either of those glues acceptable?

[Chris Ghent]

Your drop speed will not be affected by a leak between pan and bellows frame.  
 

To locate leaks here are a couple of tricks.  Put a couple of pieces of printer paper between the action boxes and the bellows and screw it back together (just push the screws through the paper) and see how it drops. If it is at about the same speed the issue is in the bellows. If it is in the bellows put pressure on the bellows and place it near your face and you will feel air on your face. This is best done by running your tongue through the valleys as your tongue will more easily feel any jet of air. Don’t touch the bellows with your tongue. It tastes awful. Don’t ask me how I know.  

 

The gap between pan and bellows frame will be affecting the performance of your concertina. Lifting the chamois and putting card behind will work. You will not have to lift it all, just 6 contiguous facets. Don’t glue the chamois plus card back down until you are satisfied the card is adequate to make the chamois seal. I wouldn’t use water on the chamois, others may differ. I have always worried about tearing the chamois when lifting but it has never happened. That is not the same thing as saying it won’t! 

[d.elliott]

Chris is exactly right, a slack pan to bellows frame gasket will not affect overall airtightness. His advice about the potential leakage between the action box and the bellows frame is pertinent and he describes a useful way of determining if that is the source of your problem,  however experience would dictate that the issue is more likely to be a pad or pad board issue, a slightly misaligned pad, weak spring or two, even a screw hole around those long thumb strap or finger slide structural screws that are not sealing the air path, or screws that are too short, or just missing. Whatever don't over tighten the end bolts or your next query will be about broken bolts! Also check for shrinkage gapping around the padboard and the action box outer frame. 

 

Personally I would take the top off the action box, without moving the keys or doing anything to disturb where the pads are. I would check the pads to see if any look as if the pad sandwich has 'slipped' (it will make sense when/ if you see it). Edeophones  are often subject to abnormal wear in the pivots of some of the action arms that have been bent or cranked to navigate round other key positions, this can cause pad problems. Having given the action a visual inspection without disturbing the pads, then hold it up to a bright light shining from the key side of the action plate. Looking from the pad hole or underside of the action through the pad holes carefully inspect  for any glimmer of light. sometimes you only see a hint of light, the sign of a pad not sealing properly, sometimes the problem is more obvious.

 

Hope this helps

 

 

[Theo]

15 hours ago, RWL said:

I can put my lips to some of the air holes and the pads don't seem particularly leaky although they're certainly not air tight. 

 

I think you have identified the source of your air leaks.  Good advice above for checking pads, but sometimes pads leak with no visible evidence.   A simple pad testing device will allow you to test the pads more easily than by applying your lips direct to the action board.   The picture shows two versions that I have.  To use you apply the end facing you in the picture to the pad hole and blow gently down the opposite end.  You will hear air escaping if there is a leak.

[RWL]

1 hour ago, Theo said:

 

 A simple pad testing device will allow you to test the pads more easily than by applying your lips direct to the action board.   The picture shows two versions that I have. 

 

Thanks to both of you for your experience and advice.  Since I have a lathe I can make the pad testing devices illustrated.  What material is on the flange at the end of the tube to seal it against the pad board?  Not being "in the trade" I don't have spare pneumatic leather on hand as a seal so I'm trying to figure out what else I could use.  I may have some 1/16" neoprene or old cork sheeting somewhere among my automotive repair scraps but I don't know if either would seal well without screw type pressure to hold the "gasket" in place.

 

I may have further questions as I try out the other suggestions. 

[d.elliott]

my device has a pad with a hole through it and a bit of plastic pipe to blow through, but Chamois leather glued onto a  flange will work just as well 

 

 

[Theo]

3 hours ago, RWL said:

I may have some 1/16" neoprene or old cork sheeting somewhere among my automotive repair scraps

Any of those would work, or even a reasonably thick paper gasket material.  The material on my plastic pad tester is a synthetic gasket material.

[RWL]

Here's where I am at this point.  I put two sheets of printer paper between the action box and bellows on each end and tried the drop test.  It again took about 10 to 12 seconds to finish.  I can feel one tiny spot of air coming from the bellows but can't spot it when I put a light inside, so I'm not entirely sure at this point where the bellows lead is.  Although less than optimum, I'm not sure how significant it is since I did the drop test on my Aeola, which to me plays pretty well and the Aeola also has about a 10-12 second drop time.  When I find the exact location, I'll repair it, but it's not the main leak.

 

 

Next I did as David suggested and carefully took the top off the action box and shone a light through the holes from the bellows side.  I found three pads that were misaligned.  There may be other pads that are leaking but I need to figure out how to make the tester that Theo illustrated.  

 

Here's the first leak.  You can see a tiny crescent of light along the outer edge of the pad hole.

 

Here's the 2nd leaking pad on the left side.

 

And here's the left end's offending pads with the green dots.  The ring of leather (I'm forgetting the name) is glued to the arms or I'd try sliding the pads to try and cover the holes better.

 

I'll illustrate the single leak on the right side in a follow up post in case the appearance of the leak suggests a specfic remedy other than the first two.

 

 

 

 

Edited February 2, 2022 by RWL

[RWL]

Here is a photo of the pad leak from the right side.  Although I've shrunken the file size, I apparently am at the limit for amount of photos I can upload to this post.  If the leather bead weren't glued to the arm I might be able to slide the pad a little to better cover the hole.

 

 

[d.elliott]

well done,  R.

 

where the light ingress is on the flank of a pad gently bend the arm but only between the pivot and the pad. if the light shows at the 'top' or the 'bottom' of the pad then remember that the leather bead is on a sort of screw thread, rotate the pad to move it up or down the arm. If the pad comes off, no matter. Just clear the old glue off the top of the pad's hole relocate the pad so that the pad hole is covered and apply glue, I use PVA or Elmer's White in the US. if you are able to screw the whole pad into position, the settle the pad flat to the pad board, with key vertical,  and apply a spot of glue to anchor it in position.

 

Next step, a bright LED light in the bellows paying special attention to the corners of the bellows folds and around the gussets. I use a very small square of masking tape to cover each hole as I go, otherwise you will lose their locations. The tape to be removed at the time of each fix.

[Don Taylor]

My pad tester made out of an old marker pen body, some electrical tape and a felt pad as used on the feet of furniture with a hole punched out of it:

 

 

[RWL]

I needed to make a pad tester too.  I wanted the tube to fit into the hole so I'd know I was relatively centered.  The smallest holes are the oval ones at .290" x .430" [ 7.5 x 11 mm] so I needed a tube that was 1/4" OD.  I had a six inch piece of 1/4" brake line ( a generic commodity available at any auto parts store) lying around so half of that became the tube.  The gasket support was a piece of 5/8" dia. aluminum that I cut to 1/2" length.  I epoxied those two pieces together and used some 1/16" neoprene sheet (the remains of a  tub & shower liner) for the gasket.  It works.  I have not had time to test all of the pads, but did discover that a major leak was the left end's bowing valve / air valve - more so than the leaks above that I had spotted with the light.

 

Knowing that I would need at least one pad - the bowing valve pad - I bought a chamois and a piece of poster board at WalMart.  The poster board is about .017" thick and I picked the thickest chamois I could spot visually in the store.  The chamois measures from .032 to .036 thick.  I have some felt of unknown type that measures approximately .080 (about 2mm) thick.  It's hard to measure the felt because it compresses so easily.  Now, none of these materials is optimum, but I wanted to keep moving on my air leak work and local sourcing is relatively inexpensive.  I will start another thread on pad materials rather than changing the subject of this discussion.

Edited February 4, 2022 by RWL