Jump to content

Test For Air Tightness


Recommended Posts

Smoke it by drawing in air from selective burning source, then push bellows together and watch the smoke pour out leaky places.

 

Or, swab a tiny bit of soapy water around suspected places, watch the bubbles rise as you push the bellows together. Wipe off immediately!

Link to comment
Share on other sites

Or, swab a tiny bit of soapy water around suspected places, watch the bubbles rise as you push the bellows together. Wipe off immediately!

Apply a bit of spit with the end of your finger - watch for it bubble when you push the bellows - wipe off immediately.

Edited by SteveS
Link to comment
Share on other sites

OK, I am pretty sure that I have found my leak, well I have definitely found one leak in the bellows and I hope that is the only one.

 

I thought that I would document what I did.

 

First I wanted to confirm that the ends were sealed and that the leak is in the bellows. (I did find two slightly leaky pads using a version of the leak detector described in an earlier post).

 

I bought some chamois leather from the local auto supply shop and cut two rough circles about 2" larger in diameter than the end of the bellows. I made a paper template with small holes marked where the end-bolt holes go through and transferred the locations of these holes to the pieces of chamois. I punched small holes in the chamois at these points. I then covered each end of the bellows with a piece of chamois and fastened the ends back on with the end bolts passing through the chamois.

 

Here is a picture with just one end chamoised up, I did both ends:

 

IMG_5076.jpg

 

 

I then tested the bellows by holding the concertina closed with its axis vertical and letting go of the bottom end. The bellows opened up over about 12-15 seconds so air was being drawn in somewhere in the bellows.

 

When I removed the ends and examined the chamois circles I could clearly see that the ends were sealing OK because the original gaskets indented the chamois nicely on both the top and the bottom:

 

 

IMG_5058.jpg IMG_5059.jpg

 

I then made up a light to fit inside the concertina. It is just a piece of plywood with a notch cut in through to the centre and a small led lamp poking through. The tape is make sure that light does not leak out of the top.

 

IMG_5069.jpg

 

 

I then held the concertina vertically again inside a dark room, and lo! I had a pin-hole leak where the post-it note is in this picture.

 

IMG_5071.jpg

 

On close examination it was probably the obvious place to look, a bottom outside corner where the concertina had rested on somebody's knee.

 

IMG_5079.jpg

 

It is a very small hole. I could not hear it and the spittle test was not conclusive so I stuck my tongue out and felt for it. I could feel it if my tongue just touched the leather. So this is what I must fix.

 

All of the outer corners along the join shown in the photograph look a lot more worn than any of the other corners on the bellows. In general, the bellows look in great shape apart from this strip of outside corners. I think that I should patch all of these corners while I am at it, do you agree?

 

I am also assuming that these cannot be patched on the inside - is that correct?

 

Is there any acceptable way to temporarily patch the leaking corner while I acquire the materials for a proper patch? I am guessing that duct tape is not good ...

 

Here is a picture of a good set of corners:

 

IMG_5080.jpg

 

The corners look good, but does anyone have any idea what those turquoise streaks are? They look to me like crystals of copper sulphate but that does not make much sense.

 

Anyway, onwards and upwards ...

 

 

Link to comment
Share on other sites

  • 1 year later...

Don, (how) have you dealt with your "bad corner" problem?

 

Albeit this is not a big problem as for me, I have spotted one similiar "hole" at the bellows of my instrument and would like to settle it.

 

I'm considerung filling the hole with acrylic "medium" and then glueing a very small patch of the tiniest leather on top.

 

Thank you in advcance - Wolf

Link to comment
Share on other sites

Fine, thin goat leather matched for color and skived on the edges is the very best choice. A modified diamond shape with the points trimmed off seems to work best. Make it large enough to cover the leak but small enough to clear the bellows papers. I use a PVA (white glue) from Tandy called "Leatherweld". There is also a membrane product called "zephyr" which takes some practice in applying but when properly dyed can make a nearly invisible patch.

 

Some of this advice may not be readily practical for the average concertina player who rarely does repairs. However, taking the time to find a good piece of leather and then properly thinning the edges (you can use a taped down piece of sandpaper) will yield infinitely better results than a slap/dash repair.

 

Worth the trouble in my opinion to do right.

 

Greg

Link to comment
Share on other sites

Don, (how) have you dealt with your "bad corner" problem?

 

Albeit this is not a big problem as for me, I have spotted one similiar "hole" at the bellows of my instrument and would like to settle it.

 

I'm considerung filling the hole with acrylic "medium" and then glueing a very small patch of the tiniest leather on top.

 

Thank you in advcance - Wolf

 

Wolf,

 

please don't fill the hole, any filler will set hard and then you have an impediment to bellows movement that will put more stress on the older glue joints and leather around the site of your 'patch'. If you must fill then I suggest the leather parings from a skiving operation, rolled into PVA glue and then packed into the crack or hole whilst wet.

 

For single holes then read Greg's comments, but do degrease the bellows corner and the area where you anticipate glue setting, with a small dab of solvent, oil free ladies nail polish remover works on a tissue. For multiple corner holes in a fold, then consider re-binding the fold or folds concerned.

 

Dave

Link to comment
Share on other sites

Thanks a lot Greg and Dave for the advice, much appreciated! Were I in the UK or US, I might have fixed it by one of you and the likes here on the forum...

 

Thank you Don too, and does that mean you'll be continuing with your playing the EC when you'll have the instrument back?

 

Jim, that's a good one... :D

Link to comment
Share on other sites

Greg and Dave, would you say these (already skived) gussets would fit? maybe too large for just the outer "corners", aren't they?

 

leatherbindL.jpg

 

If they don't fit, any other supplier to get skived small "diamond-shape" patches from?

 

Thank you in advance - Wolf

Edited by blue eyed sailor
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...