Checking For Airtightness

[malcolm clapp]

Just a little pet gripe of mine! This business of holding up the instrument by the strap and letting gravity allow the bellows to open to acertain the air-tightness of the instrument. This, more often than not, proves nothing, except perhaps how strong the strap is!!!

 

More indicative would be to open the bellows to its furthest *comfortable* extension and then held vertically with one end held firmly facing downwards, hand in hand-strap, and the other end held gently and allowed to fall by gravity.

 

Again, it doesn't prove much. Certainly the overall time to open/close would be similar, but at least it would indicate more quickly whether the airtightness is an issue.

 

The reason for the difference is that most (not so obvious) leaks in bellows are in the gussets and the valleys between the folds. When the bellows are almost closed, little air will leak from these places because the flexing of the leather tends to fold over any holes. However, when the bellows are open quite a way, that is when these holes will be in their most open state and air loss will show up much more dramatically

 

Aditionally, I think it is probably kinder to the bellows to do it this way, putting far less strain on them.

 

So next time you see your perfect concertina on eBay ("beautiful patina, real ivory reeds, only played by a little old lady in church on Sundays" etc etc.) where the seller says that he has held up the concertina by the end for 55.3 seconds before the bellows fully open, think to yourself: "So what?" and assume that he may well have damaged the bellows in doing so!

 

(Or am I just suffering from a bit of post-Christmas cynicism?)

[Alan Day]

I find this interesting as I have just received a similar request for information on this subject from a friend.There is a very fine dividing line between having springs so strong that the buttons are almost impossible to compress but give perfect airtightness on the pads, or that they are so weak that air escapes from under the pads.The medium position is the best but some air will escape and particularly when the instrument is new , or the pads are new and have not seated themselves in. If the bellows are in good condition,the screws holding the bellows are not loose then air escaping will be, in most cases, from under the pads.

Years ago when I repaired concertinas many held the concertina up on end and then remarked about its airtightness and I must admit Malcolm I shared your annoyance.

Al

[Helen]

Golly Al,

 

You repaired concertinas too! You are Mr. Concertina. or maybe Concertina Man.

 

Hee hee,

 

Helen

[Helen]

I must admit that I am glad to hear your comments about the bellows. I know nothing about repairing instruments, but holding them like that seemed very destructive to me.

 

I also saw a well known accordionist holding her button accordion with the bellows falling down to all the way extended. I cringed.

 

Nice to know that cringing was warranted. Or at least a feeling shared by others.

 

Helen

 

So thanks Malcolm and Al.

[d.elliott]

Sorry to take a different view chaps. Oh all right, I'm not too sorry, I just don't agree.

 

There are lots of tricks to determine the air tightness of an instrument, and from where it is leaking etc. and yes, spring condition, pad bedding, endplane gasket condition etc etc all play a part. All these aspects as well as bellow's holiness (sorry Christmas spirit) affect what becomes the 'air efficiency' of the instrument.

 

Yet a quick and dirty test, an 'is there a problem?', test is the simple test of holding the box up by one end and see if the instrument creeps under gravity (they virtually all do a bit), and if so, then to what degree.

 

It is impossible to do damage with this test, unless you have bigger problems with the instrument to start with. Have you seen Alister Anderson demonstrating bellows stretches? He does this to make sure that he gets the fullest belows opening with a minimum of stiffness at the fully open end of the bellows travel. I now occaisionally stretch my instruments (aalways with several keys pressed I hasten to add), and have done for some years. The bellows are so strong that I think that the greatest risk is in pulling out thumb strap screws from the wood!

 

Not that I treat them as chest expanders you understand.............. oops sorry ladies, no offence intended

 

So the gravity creep test has its place, if it don't creep then odds are that the bellows are either exceedingly stiff, or more likely something is causing a fall off in air efficiency.

 

The test allows a question to be asked and an answer to be sought. So where is the problem? If nothing else, after a re-assembly, it tells you that you have bedded the ends evenly and not dislodged a pad.

 

Dave

[Helen]

Oh rats, so cringing is NOT warranted. And I felt normal for just a second there.

 

OTOH, a chest expander exercise, hm.

 

Helen

[malcolm clapp]

Dave, agreed...too a point!

 

However, you seem to be suggesting that all bellows are strong enough to withstand such treatment. I doubt whether a good condition newish bellows would suffer unduly. The problem is that it is usually the suspect bellows of concertinas on eBay and from antique dealers that suffer this practice, nay, indignity!

 

And those of us who are experienced in concertina construction and repair often use techniques to do things to concertinas which I certainly wouldn't encourage others to try.

What I call the "Don't try this at home, kids...." principle.

 

And, of course, as you say, the thumbstrap screws may well come out of the wood if the "gravity creep test" then becomes a yo-yo demonsration!

 

So the gravity creep test has its place, if it don't creep then odds are that the bellows are either exceedingly stiff, or more likely something is causing a fall off in air efficiency.

 

Sorry, isn't this contradictory?

 

I still feel that starting with an open bellows and allowing them to close would be just as good a test as allowing the bellows to fall open, but with less stress, and would also give a better indication of air-loss in bellows which are a bit, or even, exceedingly stiff.

 

I will leave the chest expander comments to others less qualified....

 

Edited for grammar and punctuation (probably still not the best).

Edited December 28, 2004 by malcolm clapp

[Helen]

Ah but Malcolm,

 

If the others are less qualified ...

[d.elliott]

Malcolm

 

yes, I made a typo in the bit that you quote.

 

Setting that aside.

 

Stretching the bellows to fully open is good for them, unless they are so rotten that they need replacement anyway. I don't advocate fixing each end to a wild horse, and dragging them ino oblivion; but over the dozens of instruments that I serviced and repaired I have never known one instrument take damage from full bellows extension. SO: DO TRY THIS AT HOME, Just use a bit of common sense as well. It's good advice (not just the common sense bit).

 

Yes, all bellows will benefit and you can do some simple bellows care at the same time, like cleaning them and gently rubbing shoe cream into the gusset leather once the bellows are open.

 

Gravity creep tests will not cause thumb strap screws to fall out of the wood work, unless they are already at a falling out stage of disrepair.

 

I have used (in the past) the test you advocate, but its not easy to balance the instrument.

 

Dave

[malcolm clapp]

Dave Elliott wrote

I think that the greatest risk is in pulling out thumb strap screws from the wood!

and

Gravity creep tests will not cause thumb strap screws to fall out of the wood work, unless they are already at a falling out stage of disrepair

 

Isn't this a contradiction too?

 

Stretching the bellows to fully open is good for them, unless they are so rotten that they need replacement anyway.

 

Agreed, but I see a big difference between a controlled bellows stretch by some one who knows what they are doing (you, me etc) and an eBay seller who is trying to demonstrate a totally pointless excercise in the promotion of an auction item.

 

IMHO, bellows gradually deteriorate, they are not good one day and bad the next day (unless a Stanley knife is involved ).

So at what point of disrepair can the bellows stretch be safe? Who should make that decision, a competant repairer/owner or an eBay seller?

 

SO: DO TRY THIS AT HOME,

 

WHO??? (Sorry, shouldn't shout!)

I think that such generalised advice is dangerous. Might create work for bellows makers though....

 

...cleaning them and gently rubbing shoe cream into the gusset leather once the bellows are open.

 

Again, I can't recommend this advice. A bit of a light brush, yes, but to effictively apply a dressing to the gussets needs a little (allbeit gentle) pressure and I would suggest only doing this with the ends and reedpans removed and the gusset supported from inside the bellows.

 

 

I have used (in the past) the test you advocate, but its not easy to balance the instrument

 

Possibly true of a bass or 81 key Maccann, but otherwise....

 

I think we shall have to agree to disagree on this one, Dave.

[d.elliott]

Malcolm,

 

read the posts again, no contradiction this time!

 

I stand by my comments, but I don't understand the 'shout' statement.

 

Bellows do deteriorate over time, but that can be slowed by cleaning, storing fully closed, regular use, stretching, and basic leather care.

 

My pet gripe is that players are often put off doing simple and basic things by over cautious advice. People have brains, they know the age of their instruments, all they lack is experience and encouragement. In my repair workshops I have often seen attendees who have never opened an instrument asking most discerning questions, getting involved with discussions and some quite 'involved' jobs.

 

This whole issue of encouraging and sharing experience was one of the motivators in writing the 'book'. At that time I took a lot of hurtful critical comment because some thought that I made it sound too simple; or, I was encouraging people to actually dismantle their instruments.

 

We/ I have digressed from the start point of this thread: of the applicability of the gravity bellows test, for which I am sorry.

 

I think you are right, we should agree to differ.

 

Dave

[malcolm clapp]

.... but I don't understand the 'shout' statement.

 

Dave, fyi, words and phrases in capital letters are generally accepted on newsgroups and in emails as an indication of shouting, hence the comment. No criticism intended if you didn't know this.

Or maybe this convention no longer applies? In which case, I apologise.

 

Bellows do deteriorate over time, but that can be slowed by cleaning, storing fully closed, regular use, stretching, and basic leather care.

 

Done properly, I totally agree.

 

My pet gripe is that players are often put off doing simple and basic things by over cautious advice.

 

Qualified agreement. But where do you draw the line between what is *simple and basic* and what is not? Surely it depends on the (perceived or actual) skill level of the person concerned. I, too, have done dozens of repairs, and a fair number of them have been from people who have tried to fix things themselves, and have made matters worse. But despite this I certainly would not discourage owners from dismantling concertinas to see what makes them tick and from doing minor maintenance.

 

This whole issue of encouraging and sharing experience was one of the motivators in writing the 'book'. At that time I took a lot of hurtful critical comment because some thought that I made it sound too simple; or, I was encouraging people to actually dismantle their instruments.

 

I must confess that, although I am aware of your book, I have not read it.

(Pause for self-flagellation with stick of organically grown rhubarb ).

I should! (New Year's Resolution no. 43). I am certainly not beyond learning from the ideas and experiences of others. (One reason I subscribe to this group!)

I know nothing of past critical comment on the book and I certainly agree with your motivation, but I am unable to comment on the content.

 

Has your publisher an Australian distributor?

 

Apologies to other readers for getting a bit off topic.

 

Regards,

Malcolm

[Chris Timson]

At that time I took a lot of hurtful critical comment because some thought that I made it sound too simple; or, I was encouraging people to actually dismantle their instruments.

I hope mine wasn't among the hurtful criticism, Dave; it wasn't intended to be. I did offer a little criticism among comments which I tried to make on the whole enthusiastically welcoming. I can say that you attended to my concerns in the second edition and produced a book that I am glad to have , and I have never had any qualms in recommending to anyone who wants to be able to do some basic maintenance work on their concertinas.

 

Criticism is always a difficult thing to accept when you have produced a piece of work that is close to your heart. I remember when we brought out our CD. Published reviews ranged from the gratifyingly enthusiastic to the (thankfully only once) brutally rude. I remember that last one cost me a night's sleep, I was so upset.

Cheers,

 

Chris

[Frank Edgley]

My comments here might be a bit redundant, but I would have to agree with Dave on the bellows fall test. Far more pressure is placed on the bellows during playing, especially vigourous playing than allowing the bellows to fall from the weight of the concertina. There is another factor to consider between the two types of tests (i.e. testing from the fully closed or fully extended positions). If we are testing for general airtightness, then I guess either one would give some indication. However, the test from the fully extended position would include whether or not the springs are doing their job as the air pressure, coming from the inside out would tend to push the pads away from their seat, while the test from the fully closed position would tend to have the opposite effect, and draw the pads tighter to the pad seat, eliminating, to a certain degree, the effect of the pads as a factor in the airworthiness of the instrument. Personally, I think that both tests are necessary to do the necessary detective work.

[JimLucas]

Dave, ... you seem to be suggesting that all bellows are strong enough to withstand such treatment.

Any bellows that can't withstand the weight of one concertina end hanging from it is unlikely to withstand more than a few minutes of actual playing. (Trying to demonstrate simple harmonic motion might be a different matter.) The problem in my view is that the hanging test really provides very little information.

 

If the bellows drops rapidly, then you know that something's leaking somewhere, and you can then go searching for the leak. But there could be serious leaks even if the bellows drops slowly or not at all. E.g., (as Frank said) compressing the bellows puts "upward" pressure on the pads, while pulling the bellows presses the pads more firmly against the board. So if the springs are weak, Malcolm's compression test may reveal leakage around the pads, while the hanging test would create a tighter seal, instead. But there could also be internal leakage through space around the reed pan or between the chambers, and this can seriously affect one's playing even if there is no leakage between inside and outside, as indicated by either the hanging or compression test.

[Frank Edgley]

I think you have stated it right on the mark!

[d.elliott]

At the end of the day, its just a 'quick and dirty' test, giving an indication that a problem exists, the fun is then in finding and fixing it.

 

Happy new year to all, .............and

 

More power to your bellows, may they never fail any test!

 

Dave

[Clive Thorne]

Surely the point is that this test, however imperfect, gives a better indication as to the general condition regarding leaks than no test at all.

 

No; it doesn't detect internal leaks, it won't detect out of tune reeds or broken straps either: its not designed to. Unless you're going to inspect a concertina personally or via a third party then any information like this is surely useful, as long as its limitations are appreciated.

 

 

Happy New Year everyone.

 

Clive.