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Hands Free Bellows Testing


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I don't know if anyone else uses a system like this, but I thought it might interest/help someone.

 

I've found I have a some leakage in my concertina bellows. Usual problem - how to find the source of the leak? Obviously, one can squeeze the bellows while hunting for the leak(s), but you start to run out of hands. Well at least I do, more experienced repairers and makers might not!

 

So, I looked for a way to keep the bellows inflated, leaving me free to turn the instrument around and over while looking for leaks. Having just built my concertina pneumatics lab, it seemed a good starting point.

 

Here's the arrangement I settled on:

 

post-11004-0-49972800-1404818271_thumb.gif

 

The bellows leakage is considerably higher than the lab's internal aquarium pump can supply, so I'm deriving my air supply from the workshop compressed air line. You can see it coming in to the regulator via the blue tube at the left top of the control unit.

 

The regulator output is then fed through a flow controller. Not really essential, but gives me some added insurance from over-pressurising the bellows if I wind the regulator up too fast. These regulators are not really intended to work down to zero pressure, although it seems to work well. You can see that the pressure meter on the regulator is not off its end stop.

 

The air then passes through one of the two 20 Litres-per-minute airflow meters before going on to the adapter on the end of the concertina. You might be able to make out the tiny silvery bead sitting up at 18LPM.

 

A second connection to the concertina adapter attaches to the Maghehelic pressure meter, allowing us to monitor the pressure inside the bellows. I've adjusted it for 4" (100mm) of water, which is equivalent to loud playing.

 

Once fired up, the bellows inflate fully and will sit there inflated all day. If I press a button I get a note. But I'm not here to play one-handed concertina, I'm here to find leaks.

 

I sniffed around for a while looking for the leaks, but without success. There were places that raised suspicion, as I could feel a general waft of air, or thought I could hear a hiss, but it was all dreadfully unfocused. I tried all the usual tricks - wet fingers, eyes, open mouth, listening. Feeling I needed to direct my hearing, I then tried putting a length of the poly tubing in my ear and using the other end to find the leaks. Immediate success, but not very comfortable. So I dug out my stethoscope, pulled the diaphragm end off it, and substituted it with a little probe. The probe has a hole up the end, and four side holes near the tip. This makes waving it around much less critical as air coming from any direction will be rendered audible. You can still then direct the end of the probe to locate the leak more accurately. And the binaural stethoscope is much more sensitive than a piece of poly tube in one ear. Using it quickly found a number of leaks, none of which were obvious to the naked eye.

 

The other nice thing is I can actually measure the current leakage - 18LPM at a pressure of 100mm WC - so I'll know how much improvement I've achieved after fixing each leak.

 

You might wonder why I've made two connections to the concertina adapter rather than using a T junction to connect both the air supply and the pressure meter via one tube. I tried that first but found that at that flow rate, the tubing imposes a very significant pressure drop, reducing the accuracy of my pressure meter. The separate connections prevent that occurring.

 

Now all I have to do is to learn how to fix the leaks!

 

Terry

Edited by Terry McGee
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This reminds me of the dark ages when we would locate a leak in a bicycle inner tube by immersing it in a bucket of water and giving it a squeeze and watching for bubbles.

The last time I had a tubeless car tyre puncture plugged the bloke appeared to locate the exact spot by dabbing around with what seemed to be some sort of soap solution and watching for bubbles. (I forgot to ask him if he played a Concertina.)

My current new car came with no spare wheel but with a kit, of which I am deeply suspicious, with an aerosol to be emptied into a punctured valve to seal the tyre from the inside.

There is no need to tell me that this waffle has no particular relevance to the world of Concertinas.

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Yes, the detergent solution is also the standard test for gas line testing. Which is all very fine on copper and brass fittings, but not so attractive on leather, especially if there's a risk of sucking it into the bellows when refilling the air. But it remains the ultimate test for small leaks like seepage, as I may well find out when I've fixed my pinholes but still have leakage to account for. Detergent makes the bubbles a lot stronger and therefore easier to see, but might pose a problem for subsequent gluing. Or can it be rinsed off adequately? Anyone tried this? Better to stick with spittle? Hmmm, what does glue think of spittle?

 

At least with the externally pressurised bellows approach, it's unlikely any liquid will get inside, so maybe the detergent approach would be OK. Rinsing off should be possible.

 

My little sports car came with a silly little spare wheel - a sort of "bare minimum" wheel, much narrower and smaller than the four on the car. I haven't had to use it yet, and I'm not looking forward to it. Maybe this is the strategy. If the driver fears getting a flat enough, they will keep their road wheels in very good shape!

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Now, I realised that, as in the image above, I'd left the other end of the concertina on the other end of the bellows. Which could mean that leakage through pads is contributing to my 18LPM loss of air.

 

I replaced the other end of the concertina with a flat sheet of MDF, held on with the concertina's end screws. The MDF was lacquered, to make sure there was no leakage through it. No change to the result, so at least there is some good news - I'm not loosing any significant amount of air through the pads.

 

But it really makes you wonder where all that air is going. That's four winecasks per minute, to put a number on it, so I'm not being fussy.

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Well, the method went fine for finding pin-holes and I found a lot. I found it helpful to write numbers 1 to 6 on the adapter board, to keep track of where I was finding problems, and where I'd been. And where there was doubt as to which side of the valley the hole was, slipping a thin steel rule down one side of the probe and then the other quickly cleared that up.

 

And repairing those pinholes did bring a measurable improvement - the original 18LPM came down to 13LPM, a quarter of the leakage fixed. But what about the other three quarters?

 

Time to get out the water, as I could no longer detect leakage by ear. We probably are a bit unnecessarily nervous about water, as animals tend to stand in the rain quite a bit, and don't seem to dissolve.

 

And sure enough, pretty much what I expected, seepage in most of the gussets I tried. When we divide 13LPM by 42, the number of gussets, the average gusset must be leaking at a rate of around 0.3LPM. Remembering that a gusset is about 4 square cm in area, compared to a pad around 1, those figures seem credible.

 

So, next I need to research ways to prevent gussets leaking....

 

Terry

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I have no reason to believe that there is any air escaping through my bellows but, as a part of my regular occasional maintenance routine, I apply leather shoe cream to the entire outside surface of the bellows taking particular care to ensure that the polish reaches well down into the inner folds of the bellows. This can only be done effectively by using an artists paint brush of appropriate stiffness, quality and dimensions. Open the bellows whilst doing this to ensure that the polish can reach right down into the crevice of each fold. These folds obviously take the lions share of the bellows action and would probably be the first area to break down as the years roll by. An additional advantage is that the polish acts as an absorbent lubricant which must also help to seal any pores and latent cracks that might eventually start to appear in the leather. When the polish eventually begins to dry and lose its initial flexibility simply apply a little more. I do this once a year or thereabouts.

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Interesting. I wonder what happens to the cream when the pressure and suction come on? Does it sit in the pores, resisting the pressure and stopping the flow, or is it forced out one way or the other? Why do I feel an experiment coming on?

 

I do have some leather that isn't perfectly airtight. I could make some samples of this, and subject them to a range of doping agents. Then test them for:

  1. improvements to airtightness
  2. effect on flexibility
  3. any sign of migration under pressure
  4. change of appearance
  5. other tests, please specify.

But what treatments to consider? So far I've thought of or heard of:

  1. Shoe cream
  2. Dubbin
  3. Neatsfoot oil (First catch your Neat....)
  4. Silicone rubber
  5. Spray varnish
  6. Rubber shoe glue
  7. Other treatments, please specify?

And which direction to apply it from:

  1. the furry inside, where it's less visible?
  2. the shiny outside, where it should only enter the pores?
  3. Both, the last resort of the desperate?

Terry

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OK, OK, I can't stand the suspense. Experiment time!

 

The leather is in the form of a coat from St Vinnies that Jesse had bought to make bears from, but had somehow escaped this fate. I cut a chunk of the sleeve off, and opened up the seams to make it flat. Testing it in six places, at 250mm WC, gave a range of 0.25 to 0.375 LPM leakages. One test ran over 0.5LPM, so I discarded it. So far so good.

 

I rummaged around in the shoe-shine cupboard (a place I have never been in the 8 years we have lived here) and found an applicator container called Kiwi Leather Instant Wax Shine (KLIWS). Clearly specially formulated for concertinas, I resolved to give it a go. Taking one sample patch of the leather, I found:

  • furry side to pressure, 0.325LPM leakage
  • shiny side to pressure, ditto
  • shiny side treated with KLIWS, 0 leakage (<0.05LPM)
  • furry (untreated) side of same piece, 0 leakage (<0.05LPM).

The leather was very thin and pliable (as suits a coat), and a very light brown colour. The treated shiny side is now a "half-hearted" black colour - i.e. it's less than a dye and more of a finish. There is no sign (either with the naked eye or zoom microscope) of bleeding from the shiny side to the furry side. Looking on the shiny side, you can see holes (presumably follicles) which now contain the black polish.

 

post-11004-0-66459500-1404969779_thumb.jpg

 

No sense of stiffening, but the stuff is still recently applied. I'll need to allow some hours to go by and retest again to make sure the improvement wasn't simply temporary.

 

So, on the face of it, a dramatic improvement. How about I go and finish making the flute I should be working on, and we'll meet back here later to see if the results are still as good...

 

Terry

Edited by Terry McGee
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Terry, I don't like the sound of your 'Kiwi Leather Instant Wax Shine' which has been sitting around for way beyond its sell by date. I'm even suspicious of its name ! It sounds like one of those products which is simply designed to make leather look better for minimum effort, but you and I know better than to fall for nonsense like that don't we ? The shoe cream to which I referred is an excellent product which I see as a preventative conditioner for the leather, which must of course always be encouraged to retain its initial flexibility. It works a treat for me and as a result I shall probably be dead and gone before I am faced with the need to repair any leaks, or so I hope!

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I wouldn't be too dismissive of the KLIWS (Hmmm, sounds like a subversive organisation, doesn't it) - the KIWI company is well regarded down this way and have been around forever (well, 1906). Now owned by Sara Lee. Hurrumph!

 

I think we really need to know what's in these goups, and unfortunately, they probably aren't going to tell us. (Do have a look at your shoe cream and let us know if there is an ingredient list. It might be mentioned on their web site if you can tell us the brand name.) The only clues that KIWI give us on this product are expressions like "Thick, wax-rich formulation to nourish and protect leather". I think these are industry buzz-words you'd find everywhere.

 

So, I expect it's going to be up to us to determine which of these substances are going to help us and which pose a danger. Chris Ghent has suggested (in private correspondence) that perhaps we should be careful about formulations containing Neatsfoot or other oils as they may make subsequent gluing impossible. KLIWS claims to be "wax-rich", but what is the solvent for this wax? It could be water, an oil, or some other solvent. Your cream must have a base, but is it an oil, water or some other solvent?

 

I happen to have another KIWI product here, their old fashioned "Shoe Polish". This is a cake of stuff in a tin you're supposed to push your shoe brush into, and then rub it on your shoes. So I tried a bit of that on a different sample of the leather. Usual 250mm WC pressure, and applied to the shiny surface.

  • fresh leather, 0.275mm LPM (slightly better leather)
  • shoe polish rubbed on, 0.05 LPM (far better than fresh, but not quite as good as the liquid product used previously)
  • massaged in a bit with fingers (personal touch with a bit of warmth). Hmmm, weakened at 0.1 LP
  • applied more, 0.025, but still not quite the resounding 0 we had before. Wouldn't complain though.

So, I suspect almost anything we add to the leather will reduce its leakage. But how are we to determine if we are laying a trap for ourselves further down the track?

 

P.S. It's seven hours since I tried the KLIWS, so far no loss in effect.

 

Terry

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I used Meltonian neutral shoe cream (manufactured by Kiwi I believe) on my bellows, based on a recommendation in Dave Elliott's book. Cost me a small fortune to import it from a US supplier because I couldn't find anywhere that stocked neutral in the UK, and I didn't want to risk discolouring the bellows papers.

 

I've been tempted to try Renapur leather balsam on them, which is more of a soft wax than a cream. It did a lovely job of rejuvenating various other leather items including my concertina case. The main thing that makes me hesitant is the concern that it might prevent glue sticking to them if I need to apply patches in the future.

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Alex

 

I also bought some neutral Meltonian shoe cream based on Dave's recommendation but I have been reluctant to use it for fear of spoiling the bellows papers.

 

I am guessing that you got at least a little bit on your papers so what was your experience with its effect on the papers?

 

TIA

 

Don.

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I have been reading this forum for a while as I have recently bought a cheap an inexpensive Ebay Hohner D40 which I am slowly learning. I finally signed up just to post a thought on leak finding.

 

Instead of using soapy water on your fine leather bellows I would recommend a smoke pen like the one shown here: http://www.energyefficientsolutions.com/smoke_pen.asp. the pen releases a very fine, but visible smoke-like powder designed for locating air leaks. It works very well, or at least it does on This Old House.

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I am guessing that you got at least a little bit on your papers so what was your experience with its effect on the papers?

I didn't notice any effect on the papers, Don (though I applied it very sparingly and tried to avoid getting it on the papers).

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Terry, In answer to your question about the polish I recommended, it is ' WOLY ' Shoe Cream manufactured by melvo GmbH 71640 Ludwigsburg Germany ( www.melvo.com ). No clue regarding the ingredients. Over to you. I can buy it just down the road here in Somerset UK from our local cobbler who stocks it in a variety of colours, in 50 ml glass, screw-top jars very similar to the old ' Meltonian variety, which may still be available for all I know. I purchased the black version for my black bellows. I am pleased that I do not have to worry about decorative papers which I can happily live without.

 

Aren't we lucky we haven't got more important things to fret about !

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Re. Smoke Pens. I was watching the smoke curl up from a mosquito coil today and wondered about using that as a smoke source for leak testing. I might try it tomorrow.

 

For those of you in countries that do not suffer from mosquitoes, a coil seems to made out compressed sawdust and some sort of additive that mosquitoes do not like. You light the outer end of the coil and it smoulders away emitting smoke and a not unpleasant smell.

 

This page has a picture of one burning along with a good reason not to use them:

 

http://globalexcellenceonline.com/beware-smoke-from-mosquito-coil-equals-100-cigarette-sticks/

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I used Meltonian neutral shoe cream (manufactured by Kiwi I believe) on my bellows, based on a recommendation in Dave Elliott's book. Cost me a small fortune to import it from a US supplier because I couldn't find anywhere that stocked neutral in the UK, and I didn't want to risk discolouring the bellows papers.

 

I've been tempted to try Renapur leather balsam on them, which is more of a soft wax than a cream. It did a lovely job of rejuvenating various other leather items including my concertina case. The main thing that makes me hesitant is the concern that it might prevent glue sticking to them if I need to apply patches in the future.

 

Hi Alex

 

I saw the reference to Meltonian neutral shoe cream in the Materials list on page 21 of Dave's book, but couldn't find any mention of what to use it for and when. I imagine it's for general care of the leathers, but perhaps I missed a relevant hint?

 

At least the Renapur people tell us it includes beeswax and jojoba oil.

 

Terry

Edited by Terry McGee
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I have been reading this forum for a while as I have recently bought a cheap an inexpensive Ebay Hohner D40 which I am slowly learning. I finally signed up just to post a thought on leak finding.

 

Instead of using soapy water on your fine leather bellows I would recommend a smoke pen like the one shown here: http://www.energyefficientsolutions.com/smoke_pen.asp. the pen releases a very fine, but visible smoke-like powder designed for locating air leaks. It works very well, or at least it does on This Old House.

 

Hi JimR and welcome aboard!

 

Interesting about the smoke pen. I guess it's a modern equivalent of the incense stick.

 

I was wondering how long it might take to test a concertina for leakage, when I came across the purpose of the smoke pen being to test a whole house!

 

 

Don, I'll be interested to hear how the mosquito coil goes. A sobering report on their long-term use though!

 

I have reason to venture into the village today, so I'll visit the cobbler and see which unguents he might have to hand.

 

Terry

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