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Author Topic: non speaking reed mystery- solved!  (Read 720 times)

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hickory-wind

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non speaking reed mystery- solved!
« on: February 26, 2017, 03:07:26 PM »

I have a mystery and I would like advice from seasoned fettlers from this community. I am tuning and fixing up a very nice Colin Dipper Anglo concertina. I have finished all the reeds (80 total) but have one reed that refuses to speak while in the instrument. I have a single reed fixture and I've taken the reedplate out of the instrument and placed it on my fixture and it works perfectly (not on video). I have an air tuning table and it works perfectly on it while in its own slot on the reedpan (part one of video) out of the instrument. I used 1.0" water column (pressure), 1.5" WC and 2.0" WC and it work perfectly (push and pull). I have returned the reedpan to the bellows and using a single hole Plexiglass cover manually move the bellows and it works perfectly push and pull (part two of video). After remounting the button end on the instrument, the push note does not sound at all but the pull note works normally (part three of video).

video link https://youtu.be/vlVdDsBbn3Q

Notes: This is one of the highest notes on the instrument: G6
I have tried setting the reed gap more closed and more open with similar results.
I don't want to just experiment blindly on this fine rare older instrument.
I have lots of experience with accordion reeds (>20,000 tuned).
I don't have much experience with concertina reeds.
I don't have extra concertina reeds to swap in/out.

I'm hoping someone here has run into a similar problem and has overcome it and is willing to share how.

   Scott

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« Last Edit: February 26, 2017, 09:06:04 PM by hickory-wind »
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Steve_freereeder

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Re: non speaking reed mystery- please help
« Reply #1 on: February 26, 2017, 03:26:40 PM »

I can think of two possible things.

1. My first thought is that the reed gap is not correctly set, and the reed is choking off, but from what you have said you have eliminated this as a possible cause. Also the fact that the reed works when you sound it using the plexiglass end suggests it is not an incorrect reed gap causing the problem.

2. The next thing I would investigate is any obstruction or possible distortion of the brass reed frame causing it to impinge on the reed tongue and stop it vibrating. The clearance between the reed tongue and the frame is very small and can easily be distorted ever so slightly to stop the reed sounding.

Once again, using the plexiglass end with the reed frame in its dovetail slot, it does sound. But not when the proper concertina end is bolted back into place. So something is happening with the concertina end.

Try this:
Does the reed sound when the concertina end is simply held in place, but not bolted?
If yes, then insert the bolts and tighten them to a very loose fit. Does the reed still sound? (you may have to hold the end in place with your hand to stop any air leaks.) Does the reed still sound? If no, then check for any possible obstruction that may be contacting the reed tongue - e.g. a piece of leather gasket out of place, or similar.

If the reed still sounds with the end loosely held in place, then gradually tighten the bolts a bit at a time and see if there comes a point when the reed stops sounding. If this occurs, it is possible that something is causing the reed pan to distort when the bolts are tightened, which in turn transmits itself through to the side of the reed frame in the dovetail slot and impinging on the reed tongue. Possibly the reed pan itself is slightly warped, or its seating in the bellows frame is uneven, causing the distortion when the bolts are tightened.

Try these things and see what you conclude. Then it might be possible to discuss a remedy.
Hope this helps...

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Theo

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Re: non speaking reed mystery- please help
« Reply #2 on: February 26, 2017, 03:33:21 PM »

I've experienced similar things.  Usually the root cause is distortion of the reed pan caused by tightening of the end bolts. Colin Dipper makes his reeds with very very small side and tip clearance, which is generally a good thing, but makes them more prone to this problem. 

So what to do?  First check that the reed tongue is central on the shoe with equal clearance on either side and adjust if necessary.  Next confirm the cause. Assemble the concertina so that the problem reed is silent, then slacken off all the boxes end bolts a quarter turn and check the reed for sounding.  Repeat this process and see if the reed starts to work again.

Looking for a fix.  First check that all the feed pan supports are the correct height, neither too high nor too low.  If you find anything here fix it and try the reed again.
Next check the tightness of the red in it's slot. If it seems tight then ease it back slightly, assemble and test.  If it now works you should carefully file the side of the reed shoe to get a good (not too tight) fit.
Good luck!
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hickory-wind

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Re: non speaking reed mystery- please help
« Reply #3 on: February 26, 2017, 04:40:43 PM »

I have just tried slowly backing off the 6 end screws, testing every quarter-turn. Still no speaking up until all the reeds start to sound as is the nature of this concertina design.

I next tried loosening the reedplate in its slot slightly, then more and each time replaced button end and found no change.

I'm beginning to suspect some strange air turbulence.

Photo 1 shows the reed slot (marked by small green star) and button pad (opened clam-shell view).
Photo 2 shows a clear plastic sheet I overlaid and marked where the button air hole is located.
Photo 3 shows the marked sheet
Photo 4 shows the sheet overlaid onto the reedpan (need to move to next message as 4 photos are too large)

It does appear that the original hole/slot just barely catches the edge of the cavity. I can see that someone (probably Colin himself) had significantly relieved the inner edge of the slot to allow more flow to the cavity. I have opened that up some more but I'm still not seeing any improvement.

I have tried reedplate tight in slot, fairly tight in slot and loose in slot so I don't think it is reedplate distortion.

I'm absolutely certain the reed is not obstructed or deadened by a physical contact. This is an inner reed and it is wide open inside the bellows toward the other end of the instrument.

The reed is directly centered in the reed slot and I have inspected for interference with a microscope and backlight. Plus the reeds sounds perfectly on the bench and with the plexiglass cover.

I think I need to reset the reed on its plate but want to do it as little as possible with this tiny reed.

Thanks for your input and keep them coming.

   Scott

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hickory-wind

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Re: non speaking reed mystery- please help
« Reply #4 on: February 26, 2017, 04:43:51 PM »

Photo 4 shows the sheet overlaid onto the reedpan

{previous comment repeated}
It does appear that the original hole/slot just barely catches the edge of the cavity. I can see that someone (probably Colin himself) had significantly relieved the inner edge of the slot to allow more flow to the cavity. I have opened that up some more but I'm still not seeing any improvement.

I have tried reedplate tight in slot, fairly tight in slot and loose in slot so I don't think it is reedplate distortion.

I'm absolutely certain the reed is not obstructed or deadened by a physical contact. This is an inner reed and it is wide open inside the bellows toward the other end of the instrument.

The reed is directly centered in the reed slot and I have inspected for interference with a microscope and backlight. Plus the reeds sounds perfectly on the bench and with the plexiglass cover.

I think I need to reset the reed on its plate but want to do it as little as possible with this tiny reed.

Thanks for your input and keep them coming.

   Scott

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Re: non speaking reed mystery- please help
« Reply #5 on: February 26, 2017, 05:47:51 PM »

Pad leather detached from lever and stuck over hole?
(it's happened to me)

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Steve_freereeder

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Re: non speaking reed mystery- please help
« Reply #6 on: February 26, 2017, 06:06:08 PM »

I think I need to reset the reed on its plate but want to do it as little as possible with this tiny reed.
No - don't do that. You will never get it right again, or at least not without tremendous difficulty. When concertina reeds are made, they are made over long, with a lot of excess length to the tongue to the rear of the clamp screws. This 'tail' allows precision adjustment of the gap round the sides and tip of the reed tongue. When it is sounding correctly (in a testing port) the clamps are screwed down hard and the excess tail is cut off. Once the tail is removed, you have got nothing to hold to allow readjusting.

The fact that the reed is sounding correctly both in your testing port and when using the plexiglass end, demonstrates that the reed tongue is set correctly in its frame. Don't risk messing up that set. Your problem lies somewhere else.
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Re: non speaking reed mystery- please help
« Reply #7 on: February 26, 2017, 06:20:17 PM »

There is another problem that sometimes affects high reeds - too much air pressure. You sometimes see high accordion/melodeon reeds with a hole punched through the wax above the reed.  This bleeds off some air and prevents the reed from stalling.  High pitch concertina reeds can exhibit the same behaviour but need a different method of correction.  Easiest thing to try is removing the valve beside the problem reed.   This lets some air bleed through the pull reed when playing on push.  Something else you may see on a concertina is a gap left in the chamois gasket surrounding a high reed which achieves the same thing.

I second Steve's view about not adjusting the setting of the reed in its frame.   It works outside the box, and you already said that you have checked the reed clearance under a microscope.  No point making things more difficult that they already are!
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Re: non speaking reed mystery- please help
« Reply #8 on: February 26, 2017, 08:31:51 PM »

Colin Dipper has sold me his reeds before about £15 each(some time ago).The last time was the highest note |G\d Contact him old school through his website.You could try a another one if you get beat.
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hickory-wind

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Re: non speaking reed mystery- solved!
« Reply #9 on: February 26, 2017, 09:13:19 PM »

Thank you to all for your suggestions and advice. I ended up reducing the volume (see pic) of that specific cavity and now, without other modifications, it is working. It is not perfect because requires a little more pressure than the other reeds. It occurred to me that many reedblocks include inserts to reduce the volume on the highest notes so that is what I have done.

I spoke with the owner and he told me it is a rarely used note so my modification will stay as is. I will post a demo video before I wrap it up for shipment although I can't do justice to this fine instrument being mainly a button accordion guy.

Thanks again.
   
   Scott
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hickory-wind

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Re: non speaking reed mystery- please help
« Reply #10 on: February 26, 2017, 11:16:00 PM »

I think I need to reset the reed on its plate but want to do it as little as possible with this tiny reed.
No - don't do that. You will never get it right again, or at least not without tremendous difficulty. When concertina reeds are made, they are made over long, with a lot of excess length to the tongue to the rear of the clamp screws. This 'tail' allows precision adjustment of the gap round the sides and tip of the reed tongue. When it is sounding correctly (in a testing port) the clamps are screwed down hard and the excess tail is cut off. Once the tail is removed, you have got nothing to hold to allow readjusting.

The fact that the reed is sounding correctly both in your testing port and when using the plexiglass end, demonstrates that the reed tongue is set correctly in its frame. Don't risk messing up that set. Your problem lies somewhere else.

Steve- Thanks. Agreed. I didn't mean loosen the screws, just slightly bend the reed up or down to adjust the gap at rest. I didn't loosen any of the screws. I did try to tighten some that were mis-sounding but all the screws were fully tight so nothing moved.

I have posted a brief demo video here:https://youtu.be/u1X5FkgbVRY

Scott

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Steve_freereeder

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Re: non speaking reed mystery- solved!
« Reply #11 on: February 27, 2017, 06:37:22 AM »

Thank you to all for your suggestions and advice. I ended up reducing the volume (see pic) of that specific cavity and now, without other modifications, it is working. It is not perfect because requires a little more pressure than the other reeds. It occurred to me that many reedblocks include inserts to reduce the volume on the highest notes so that is what I have done....
Congratulations on getting it working!
If it now needs a little more pressure to get the reed to sound, this is where you could now make minute adjustments to the reed tip gap. If it needs a bit more pressure the gap is probably fractionally too wide. it is worth flexing the reed tongue gently into the frame slot a few times using a cocktail stick or whatever your preferred tool is. Test after each adjustment. You may not visually be able to see if you've made any difference to such a tiny reed but hopefully such gentle flexing will enable you to find the 'sweet spot' for the reed.
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