Jump to content


Photo

Leakage Testing

Leakage Test Experiment

  • Please log in to reply
65 replies to this topic

#19 Geoff Wooff

Geoff Wooff

    Heavyweight Boxer

  • Members
  • PipPipPipPipPip
  • 2099 posts
  • Gender:Male
  • Location:France

Posted 27 April 2014 - 02:26 AM

Buttons pressures have been discussed and a search here should reveal some opinions. I have my 110 sec. instrument's buttons set to about 60 grams and the Pads are probably the originals from1898. This is an early metal ended Wheatstone 48 EC and there is not much space in the Action box for modern Pads, which are considerably thicker, I'd have to bend all the levers to get the buttons to give enough travel and 'lift' with new pads and then those leather grommits on the ends of the levers would start banging into the  fretwork before I got maximum elevation . So untill I get around to making my own pads it'll be a case of making do with only 110 second ;).

 

Compression is the part of the airtightness which is most appealing to the player... like  having enough Rosin on your Bow.... bellows direction changes are crisp and instant thus helping with expression.

 

 

I think those wine boxes in France are 5 litres, not that I'd know of course as buying that much at one go would break the bank :huh:


Edited by Geoff Wooff, 27 April 2014 - 02:32 AM.


#20 adrian brown

adrian brown

    Chatty concertinist

  • Members
  • PipPipPipPip
  • 460 posts
  • Gender:Male
  • Location:Amsterdam, NL

Posted 27 April 2014 - 02:38 AM

Using Geoff's method:

Jeffries CG, 6 fold bellows with two small, visible holes: 25 seconds
Suttner BbF, 7 fold bellows: 90 seconds

I don't perceive any difference in playability between the two, I've simply got used to the leaky Jeffries and compensate with the air button. Far more annoying are instruments that consume air when you depress the buttons - when you play a beefy chord with lots of welly and your bellows close in 1 second. Fortunately none of my instruments are like that, so I think tightness of valves, reed fits, chambers etc. are far more important.

Adrian


Edited by aybee, 27 April 2014 - 02:40 AM.


#21 Terry McGee

Terry McGee

    Chatty concertinist

  • Members
  • PipPipPipPip
  • 356 posts
  • Gender:Male
  • Location:Malua Bay, NSW Australia

Posted 27 April 2014 - 04:50 AM

Thanks Geoff.  Sixty grams feels good to me, whereas double that was really off-putting.  Does anyone have a sneaky way of measuring button pressure other than using a weight and a little table to connect the weight to the button? 

 

I found this comment very interesting: Compression is the part of the airtightness which is most appealing to the player.... bellows direction changes are crisp and instant thus helping with expression.

 

Now, I'm imagining that the "compression" is an outcome of airtightness, isn't it.  A symptom, if you like.  It's not something additional.  But perhaps requires a very good level of airtightness to allow it to manifest itself?  On my proposed scale, somewhere around "tight"?

 

Terry



#22 Geoff Wooff

Geoff Wooff

    Heavyweight Boxer

  • Members
  • PipPipPipPipPip
  • 2099 posts
  • Gender:Male
  • Location:France

Posted 27 April 2014 - 05:03 AM

Thanks Geoff.  Sixty grams feels good to me, whereas double that was really off-putting.  Does anyone have a sneaky way of measuring button pressure other than using a weight and a little table to connect the weight to the button? 

 

I found this comment very interesting: Compression is the part of the airtightness which is most appealing to the player.... bellows direction changes are crisp and instant thus helping with expression.

 

Now, I'm imagining that the "compression" is an outcome of airtightness, isn't it.  A symptom, if you like.  It's not something additional.  But perhaps requires a very good level of airtightness to allow it to manifest itself?  On my proposed scale, somewhere around "tight"?

 

Terry

Compression can also come from good reeds and valves as Adrian points out.  A reasonable amount of leakage can also just mean an increase in movement of the Bellows and the player can be used to this and not find the amount of air useage a problem. I have another similar instrument to my 'tight' one which has a much shorter Bellows ( the folds are not so deep and only five of them) and it will be a 25 second closure at the moment ( some more work to be done ) but the the reeds and valves allow a sense of Compression so the feel to play can be similar  BUT  when a more deeply chordal style is used  the lack of air capacity rapidly becomes apparent.



#23 Geoff Wooff

Geoff Wooff

    Heavyweight Boxer

  • Members
  • PipPipPipPipPip
  • 2099 posts
  • Gender:Male
  • Location:France

Posted 27 April 2014 - 05:05 AM

 

Thanks Geoff.  Sixty grams feels good to me, whereas double that was really off-putting.  Does anyone have a sneaky way of measuring button pressure other than using a weight and a little table to connect the weight to the button? 

 

I found this comment very interesting: Compression is the part of the airtightness which is most appealing to the player.... bellows direction changes are crisp and instant thus helping with expression.

 

Now, I'm imagining that the "compression" is an outcome of airtightness, isn't it.  A symptom, if you like.  It's not something additional.  But perhaps requires a very good level of airtightness to allow it to manifest itself?  On my proposed scale, somewhere around "tight"?

 

Terry

I have a small pressure gauge that I picked up at a flea market. I'll try to describe it later...

 


Edited by Geoff Wooff, 27 April 2014 - 05:06 AM.


#24 Terry McGee

Terry McGee

    Chatty concertinist

  • Members
  • PipPipPipPip
  • 356 posts
  • Gender:Male
  • Location:Malua Bay, NSW Australia

Posted 27 April 2014 - 05:08 AM

Using Geoff's method:

Jeffries CG, 6 fold bellows with two small, visible holes: 25 seconds
Suttner BbF, 7 fold bellows: 90 seconds

 

So, let's derate your 7 fold Suttner to 6 fold at 90*6/7 = 77 seconds.  So, our table now looks like:

 

Unplayable:

Really leaky:

Leaky:

Slightly leaky:    28 seconds, 25 seconds

Tight:

Very tight:         77 seconds, 77 seconds

Near perfect:   110 seconds

 

 

 

I don't perceive any difference in playability between the two, I've simply got used to the leaky Jeffries and compensate with the air button. Far more annoying are instruments that consume air when you depress the buttons - when you play a beefy chord with lots of welly and your bellows close in 1 second. Fortunately none of my instruments are like that, so I think tightness of valves, reed fits, chambers etc. are far more important.

 

Now, that's probably an area we can investigate too.  What flow rate does a reed consume, how do big reeds compare to small reeds, etc.  Looking around the musical acoustics literature, I'm not seeing much on free-reed physics.  

 

Terry



#25 Geoff Wooff

Geoff Wooff

    Heavyweight Boxer

  • Members
  • PipPipPipPipPip
  • 2099 posts
  • Gender:Male
  • Location:France

Posted 27 April 2014 - 09:41 AM

I just thought to make a comparison test between compression and depression and see if the difference can point to an area needing improvement ... the Pads or Springs for instance.... but the results are somewhat inconclusive:

 

So either holding the concertina in a vertical position supported on the lower end (compression) or the more normal 'hang' test (holding the upper end).  One concertina with original 90 year old bellows showed an increase in time with the hang test of plus 150% whilst my very airtight model with the new-ish bellows never reached fully extended using the drop test and my arms go tired after several minutes. So the last part of the bellows extension on a new construction needs a little extra physical force to fully open.

 

One thing that came out of my current fiddling with these things is that, as with my favourite concertina,  30-40 seconds on the compression test is perfectly usefull as a playing instrument and my definately leaky but otherwise playable model has only a 15 seconds compression test.

 

 

Terry,  the pressure gauge that I found  has a lever connected to a variable rate spring, and a dial calibrated in grammes  ( 0- 150g). It might not be terribly accurate but it helps to get an idea  . It looks old, perhaps government surplus , used to set relays ??


Edited by Geoff Wooff, 27 April 2014 - 09:44 AM.


#26 Terry McGee

Terry McGee

    Chatty concertinist

  • Members
  • PipPipPipPip
  • 356 posts
  • Gender:Male
  • Location:Malua Bay, NSW Australia

Posted 27 April 2014 - 06:30 PM

Yes, my Simpson has that "don't really want to open that last little bit" feel, so a full hang test would be quite inconclusive.  But it also has a "don't really want to close that last little bit" feel too, so perhaps I should be letting it fall between the 1/4 and 3/4 points and doubling the result!

 

 

 

One thing that came out of my current fiddling with these things is that, as with my favourite concertina,  30-40 seconds on the compression test is perfectly usefull as a playing instrument and my definately leaky but otherwise playable model has only a 15 seconds compression test.

 

So, adding that to the growing list, we get:

 

Unplayable:

Really leaky:

Leaky:               15 seconds

Slightly leaky:    28 seconds, 25 seconds

Tight:                 30-40 seconds

Very tight:         77 seconds, 77 seconds

Near perfect:   110 seconds

 

(unless you'd characterise "definitely leaky" as "really leaky", rather than plain old "leaky"?)

 

 

 

Terry,  the pressure gauge that I found  has a lever connected to a variable rate spring, and a dial calibrated in grammes  ( 0- 150g). It might not be terribly accurate but it helps to get an idea  . It looks old, perhaps government surplus , used to set relays ??

 

Sounds useful.  Even if not deadly accurate, it's nice to have the objectivity and repeatability of a measuring tool.  We're not very good at estimating pressure, but we know when something is uneven.  I've used weights in both the harpsichord world and the carillon world to regulate keyboard and pedalboard pressures.  Interestingly, in the carillon world, the player is moving big masses (the clappers) around, so its not just the static pressure but the inertia you have to deal with.  I use a falling weight approach to emulate the players acceleration of the clapper.  Not a lot of inertia in a concertina button.

 

Terry 



#27 Terry McGee

Terry McGee

    Chatty concertinist

  • Members
  • PipPipPipPip
  • 356 posts
  • Gender:Male
  • Location:Malua Bay, NSW Australia

Posted 27 April 2014 - 07:49 PM

Now, if I add my pair, and do some calculations based on our estimate of volume being around 3 litres, we can start to see some figures coming through.

 

Concertina Leakage Rates.gif

 

It would be nice to get some data in the Unplayable and Really Leaky categories.  Anyone have an old clunker or two out there that can be pressed into service?

 

On early trends, my new flowmeter (still making its way on its slow boat from China) should prove very useful.  It's 2 to 20LPM range equates to Very tight to Unplayable.



#28 Terry McGee

Terry McGee

    Chatty concertinist

  • Members
  • PipPipPipPip
  • 356 posts
  • Gender:Male
  • Location:Malua Bay, NSW Australia

Posted 27 April 2014 - 08:26 PM

Silly me.  If you have a good concertina, you can easily make it into a leaky one by stabbing the bellows with an ice pick!  Or even inserting a few pieces of paper into the joint between the bellows and the end to spill some air.  I chose the latter path, although I'd still like data from others if possible.

 

Anyway, here's the augmented chart:

 

Concertina Leakage Rates.gif

 

Terry



#29 Terry McGee

Terry McGee

    Chatty concertinist

  • Members
  • PipPipPipPip
  • 356 posts
  • Gender:Male
  • Location:Malua Bay, NSW Australia

Posted 27 April 2014 - 09:50 PM

I thought it might be helpful to see what this test rig looks like.

 

Concertina leakage test rig.jpg

 

In the foreground, the test rig, with some leather clamped in it to test the leakage through the gap, in or around the leather.  You can see it reads just under 4 on the meter.

 

In the background, the Magnehelic leakage detector.  The knob at bottom left sets the test pressure (normally set at about 200mm (8") of water).  The perspex block at left has a needle valve at the bottom to set the flow rate with the test connection open.  The floating bead in the column above that indicates flow rate and is normally set full scale when open.  Full scale is 1 Standard Cubic Foot Per Hour - approximately 0.5 Litres per minute.

 

The big Magnehelic meter reads the test pressure under the same conditions, but once the connection to an instrument is made, the Magnehelic gauge switches to measuring flow.

 

Incidentally, the leather sample shown is the one I mentioned earlier.  It initially read 4 but dropped to about 3.5 after an hour or so.  Further clamping time didn't make any further change.  Turning it over (so that the air pressure is now applied on the other side) produced the same results.

 

Terry


Edited by Terry McGee, 28 April 2014 - 02:24 AM.


#30 Don Taylor

Don Taylor

    Heavyweight Boxer

  • Members
  • PipPipPipPipPip
  • 1103 posts
  • Gender:Male
  • Location:Ontario, Canada

Posted 28 April 2014 - 09:47 AM

Terry

Those plastic clamps do not apply much pressure at all. Have you tried some more manly clamps?

Don.

#31 alex_holden

alex_holden

    Heavyweight Boxer

  • Members
  • PipPipPipPipPip
  • 580 posts
  • Gender:Male
  • Location:Lancashire

Posted 28 April 2014 - 12:37 PM

It would be nice to get some data in the Unplayable and Really Leaky categories.  Anyone have an old clunker or two out there that can be pressed into service?


What information are you looking for? The point at which a concertina becomes so leaky it's unplayable? I have a restoration project English here with extremely leaky bellows that only takes a second or two to close with no buttons pressed, but I am just about able to squeeze a (quiet) tune out of it by constantly pumping it in and out.

#32 JimLucas

JimLucas

    Ineluctable Opinionmaker

  • Members
  • PipPipPipPipPipPip
  • 10128 posts
  • Gender:Male
  • Location:Denmark

Posted 28 April 2014 - 01:48 PM

I just thought to make a comparison test between compression and depression and see if the difference can point to an area needing improvement ... the Pads or Springs for instance.... but the results are somewhat inconclusive:

 

So either holding the concertina in a vertical position supported on the lower end (compression) or the more normal 'hang' test (holding the upper end).  One concertina with original 90 year old bellows showed an increase in time with the hang test of plus 150% whilst my very airtight model with the new-ish bellows never reached fully extended using the drop test and my arms go tired after several minutes. So the last part of the bellows extension on a new construction needs a little extra physical force to fully open.

 

Are you guys assuming that all leakage is through these materials, and not around/past them?

 

In a compression test, the pressure will tend to push the pad open, while in a hang test, the negative pressure will tend to suck the pad tighter against the pad board (as well as compress the cardboard-felt-leather laminate).  You seem to be assuming that this has negligible effect.  I'm not so sure, though at present I have no capability to do any testing.

 

Also, I'm not sure how you expect the permeability of gasket materials to affect/effect leakage.  I believe the purpose of chamois and other gasketing materials (I have high-end instruments where the gasketing is leather with a smooth finished surface) surrounding the reed pans and atop the chamber partitions is to prevent leakage between and around the chambers.  So the relevant measurement should be "sideways" through a significant "width'" of the leather, not simply through its thickness, and the measurement should also be made with the leather compressed, as it is when the pad board is pressed down by the fretted end when the end bolts are tightened, thus pressing the reed pan into the bellows end and against those gaskets end, while also compressing the strips atop the chamber partitions.

 

In particular, I suspect that far more significant than the permeability of the gasketing material is the tightness of the seal between the reed pan and the bellows frame.  I've known instruments where the seal seems "tight" even though the reed pans need almost no pressure to seat them, while others need significant pressure to seat them properly into the bellows frame.  Do the former still have residual leakage compared to the latter, or is there a relatively "loose" threshold beyond which there's not much change?  We all know what happens when there's a visible gap between the reed pan and the bellows frame, no?

 

A  possible exception to my above argument would be the valves, where leakage through their thickness -- especially when multiplied by the number of valves, if many are open for chordal work -- might possibly be significant.  But this also raises the spectre of what happens when valves don't fully close/seal.  And then there's the fact that a few of the highest reeds (at least in a treble English) normally don't have valves, so the amount of leakage past those reeds has been judged not to affect playing.  Just how much is that, and how does it compare to the parameters you're trying to measure?



#33 Geoff Wooff

Geoff Wooff

    Heavyweight Boxer

  • Members
  • PipPipPipPipPip
  • 2099 posts
  • Gender:Male
  • Location:France

Posted 28 April 2014 - 03:03 PM

 

I just thought to make a comparison test between compression and depression and see if the difference can point to an area needing improvement ... the Pads or Springs for instance.... but the results are somewhat inconclusive:

 

So either holding the concertina in a vertical position supported on the lower end (compression) or the more normal 'hang' test (holding the upper end).  One concertina with original 90 year old bellows showed an increase in time with the hang test of plus 150% whilst my very airtight model with the new-ish bellows never reached fully extended using the drop test and my arms go tired after several minutes. So the last part of the bellows extension on a new construction needs a little extra physical force to fully open.

 

Are you guys assuming that all leakage is through these materials, and not around/past them?

 

In a compression test, the pressure will tend to push the pad open, while in a hang test, the negative pressure will tend to suck the pad tighter against the pad board (as well as compress the cardboard-felt-leather laminate).  You seem to be assuming that this has negligible effect.  I'm not so sure, though at present I have no capability to do any testing.

Well Jim, that is exactly what I was considering by comparing  ' free end up' drop test with the 'free end down' hang test... to determine what effect positive or negative pressure had on  seal at the Pads.

 

You make an interesting point regarding some concertinas that you own having " gasketing is leather with a smooth finished surface".  My thoughts on this are that I have leather which , when suck tested, is pefectly airtight  so why would I go to the Hardware store to buy  Chamois which leaks like a sieve  when I could use a  staunch material ? I could imagine that having airtight leather as a gasket between the bellows frame  and the screwed down ends ought to be better than chamois  although I did have a small leak between the ends and the bellows due to the way I had cut the replacement chamois... detecting the leak with a wet tongue... I scrubbed the chamois to cover the slight gap I had left. Perhaps if one were to bring the bellows' outside end frame cover leather back over the chamois further than normal, say 2 or 3mm , it might improve or stop leakage at the joint between the end boxes and the bellows frames ?

 

Internal leaks between chambers and down between the reedpan egdes and the bellows frame will surely only affect efficiency whilst playing.  Air usually will take the least path of resistance which should mean that the absolute airtightness of Valve leather is less important than the chosen materials ability to open and close correctly and reliably I would imagine.


Edited by Geoff Wooff, 28 April 2014 - 03:05 PM.


#34 Terry McGee

Terry McGee

    Chatty concertinist

  • Members
  • PipPipPipPip
  • 356 posts
  • Gender:Male
  • Location:Malua Bay, NSW Australia

Posted 28 April 2014 - 05:36 PM

Terry

Those plastic clamps do not apply much pressure at all. Have you tried some more manly clamps?

Don.

 

I haven't.  Those clamps are probably stronger than they look.  I measured the closing force at about 10KG, or 22lbs.  So six of them amounts to 60Kg or 132lbs.  I'd be confident that you couldn't get that out of 6 concertina screws without really messing up the woodwork.

 

Terry



#35 Terry McGee

Terry McGee

    Chatty concertinist

  • Members
  • PipPipPipPip
  • 356 posts
  • Gender:Male
  • Location:Malua Bay, NSW Australia

Posted 28 April 2014 - 05:40 PM

 

It would be nice to get some data in the Unplayable and Really Leaky categories.  Anyone have an old clunker or two out there that can be pressed into service?


What information are you looking for? The point at which a concertina becomes so leaky it's unplayable? I have a restoration project English here with extremely leaky bellows that only takes a second or two to close with no buttons pressed, but I am just about able to squeeze a (quiet) tune out of it by constantly pumping it in and out.

 

 

That would be perfect, Alex.  Can you give me a timing on that?

 

More data from across the range of leakiness invited.  

 

(You notice we're not so much testing leakiness, but the players' perceptions of leakiness.  Later, my psychological assessment department will launch a study into players feelings about their perceptions of leakiness.  That's really what this whole charade is about.)

 

Terry



#36 Terry McGee

Terry McGee

    Chatty concertinist

  • Members
  • PipPipPipPip
  • 356 posts
  • Gender:Male
  • Location:Malua Bay, NSW Australia

Posted 28 April 2014 - 07:21 PM

Woah, heaps of good stuff there, Jim.  I'll take it in bits....

 

 

Are you guys assuming that all leakage is through these materials, and not around/past them?

 

In a compression test, the pressure will tend to push the pad open, while in a hang test, the negative pressure will tend to suck the pad tighter against the pad board (as well as compress the cardboard-felt-leather laminate).  You seem to be assuming that this has negligible effect.  I'm not so sure, though at present I have no capability to do any testing.

 

No, I'm expecting to see leakage through and around, and to be able to tell the difference.  And I think I will be able to pull together the resources to test situations like the pad/board interface in both modes - suck and blow.  Forming methodologies in my mind as we speak...

 

Now, would I be right in saying this.  If a concertina is really leaky, the relatively small difference in leakage one way or the other through the pads is unlikely to affect the overall speed of closing or opening significantly.  Whereas if the concertina is really tight, that (hopefully) small difference might be more noticeable.  So it's people like Geoff, afflicted as they are by tight concertinas, who might be in a better position to detect a faster hang speed compared to closing speed?

 

 

 

Also, I'm not sure how you expect the permeability of gasket materials to affect/effect leakage.  I believe the purpose of chamois and other gasketing materials (I have high-end instruments where the gasketing is leather with a smooth finished surface) surrounding the reed pans and atop the chamber partitions is to prevent leakage between and around the chambers.  So the relevant measurement should be "sideways" through a significant "width'" of the leather, not simply through its thickness, and the measurement should also be made with the leather compressed, as it is when the pad board is pressed down by the fretted end when the end bolts are tightened, thus pressing the reed pan into the bellows end and against those gaskets end, while also compressing the strips atop the chamber partitions.

 

The test pictured above, with the leather sandwiched between the two sections of the test rig, conforms to that specification.  The leather is clamped by about 10mm (3/8") all round the outer edge of the 150mm (6") hexagon.  That's probably a bit more than would be clamped in a real concertina, but we can fiddle all that as we go once we see where it's leading us.  The leakage I detected easily there, using the Magnehelic on full strength, was 0.4 of a cubic foot per hour, or about 0.2 LPM.  We could afford 10 times that leakage and still have a "near perfect" concertina.

 

 

 

In particular, I suspect that far more significant than the permeability of the gasketing material is the tightness of the seal between the reed pan and the bellows frame.  I've known instruments where the seal seems "tight" even though the reed pans need almost no pressure to seat them, while others need significant pressure to seat them properly into the bellows frame.  Do the former still have residual leakage compared to the latter, or is there a relatively "loose" threshold beyond which there's not much change?  We all know what happens when there's a visible gap between the reed pan and the bellows frame, no?

 

Measuring leakage inside the concertina presents greater challenges than leakages from inside to outside, but we should have a look at it once we've mastered external leakage testing. I don't even know how concertina makers and repairers approach the internal leakages.  I'd be inclined to put a bright (but cool!) lamp in behind the reed pan and clamp the reed pan down with a sheet of glass or perspex.  Has that any merit, or are there better ways to find out what's going on in the dark?

 

 

 

A  possible exception to my above argument would be the valves, where leakage through their thickness -- especially when multiplied by the number of valves, if many are open for chordal work -- might possibly be significant.  But this also raises the spectre of what happens when valves don't fully close/seal.  And then there's the fact that a few of the highest reeds (at least in a treble English) normally don't have valves, so the amount of leakage past those reeds has been judged not to affect playing.  Just how much is that, and how does it compare to the parameters you're trying to measure?

 

I think they are matters we can look into and put some numbers against.  I've always been intrigued by the reeds with no valves.  I guess it's not just a matter of "we can get away without them", but also a matter of "on these tiny reeds, valves would present a problem"?

 

It sounds like there are many issues that we could (and therefore should!) investigate, one I get the less sensitive flow meter and find a way to incorporate it into my test setup.  I'll start an agenda list.

 

Now, we should essentially regard this, at this stage, as "pure" research - there may be no practical outcomes.  But, who knows, finding out what flows where and why may lead to some better understandings and may lay our minds to rest on some issues that are just not worth worrying about!

 

Terry







Also tagged with one or more of these keywords: Leakage, Test, Experiment

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users