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Reed Tuning Question


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#1 Willum

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Posted 15 July 2017 - 12:36 PM

Hello experienced people, I'm retuning a Wheatstone English from old 'high' pitch to A440 and its all going reasonably well. I notice though that every time I file metal from the base 1/3 or so, no matter how little, the tongue always ends up inside the housing and needs to be bent out in order to get it back to the 'speaking' position. Im putting a feeler gauge under it while filing. Initially I thought this is the friction of the file warming up the outside of the reed and causing it to expand but it never recovers to the original place once its cooled down. Is this a fact of life I wonder. 

Phil 'Willum' 



#2 Chris Ghent

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Posted 16 July 2017 - 02:40 AM

Yes, that happens. I have a suspicion it happens to a greater degree when you use a finer file, ie. a diamond file.

#3 Jake Middleton-Metcalfe

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Posted 16 July 2017 - 11:53 AM

you will find you have to just bend it back to the correct position. The set of the reed usually also affects its pitch to a small degree so you always have have to bear that in mind and do tuning and setting together. Try playing the instrument gently and then loudly after you have tuned the reeds to make sure the set is correct. You will normally find you have to go back and adjust the set on some reeds, which again may mean a little bit more tuning but only a small amount, changing the set of the reed never makes it go far off the pitch you are trying to reach. At least that is what I do. Others may differ


Edited by Jake Middleton-Metcalfe, 16 July 2017 - 11:54 AM.


#4 Dana Johnson

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Posted 17 July 2017 - 04:25 PM

When reed steel is hardened and tempered, it retains stresses that are balances in the flat stock. When you remove material from one side, the now unbalanced tensions curve the reed away from the side that had been pulling the opposite direction. Reed vibration eventually allows tensions to equalize again. ( not always at their original set ). Some kinds of iron castings are treated with intense vibration prior to further machining to remove stresses that could cause later warping.
Dana

#5 d.elliott

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Posted 19 July 2017 - 02:50 PM

Yes it is all about stress release, and the heat treatment of the original strip material and subsequent distortion. This is perhaps the worst aspect of reed tuning. In play a phenomenon called vibration stress relief will allow the reed to find it's natural position, in the old days this was referred to as 'playing in'. I have used vibration stress relief to de-stress welded joints, it can be used on the big titanium fan blades on jet engines, and I have read about the technique being used on the main gun barrels on the Abraham's tank.

 

Dave


Edited by d.elliott, 19 July 2017 - 02:52 PM.


#6 David Hornett

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Posted 20 July 2017 - 12:14 AM

Is it this 'stress release' that seems to affect the tone and playability of a new concertina reed?

 

I notice that with the reeds i make, they sound better after playing, although the pitch does not change. I originally thought i was imagining it, but if I omit to also give the accidental row a work out they sound nowhere as good as the C/G or G/D (etc) row i have played in. I have also noticed the same thing on the diatonic accordions I play. Or am I really imagining it -- because I have got used to the instrument's tone?

 

David



#7 Michael Marino

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Posted 20 July 2017 - 12:03 PM

No not imaging it. Well documented fact of metal stress and tuning/shaping of metals. The preceding post are very correct in that. Nothing I can add fro my own experience as they have pointed pretty much all of it out.

 

Michael 



#8 d.elliott

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Posted 20 July 2017 - 02:05 PM

I have a theory, and it is only a theory, which seems to be backed up by observation. The idea is that there is a best and natural degree of gapping (set) between a reed tongue and it's reed frame. That air flow will cause the vibration in the reed to stress balance around that natural position, a position where the reed tongue shaping settles in static equilibrium when air flow ceases. I suggest that when a reed is settled in this way then the reed is played it becomes more responsive and the tone fuller. I cannot prove this theory but the experience seems to support the idea.

 

Or perhaps playing in is all about the player getting used to his instrument, it's quirks and foibles and is thus happy with it.

 

Dave



#9 David Hornett

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Posted 20 July 2017 - 06:16 PM

Thank you. I tend toward supporting your theory, however a gap too wide (too widely voiced) does seem to remain so, no matter the amount of playing in, and a closely voiced reed that stalls seems to retain this propensity also. Maybe all the in-between reeds find their natural position, certainly seems to be the case.

 

David



#10 d.elliott

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Posted 22 July 2017 - 08:28 AM

David, I was talking about playing in, rather than expecting an instrument to self-heal reed setting problems.

 

Dave



#11 Willum

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Posted Yesterday, 10:34 AM

Interesting stuff and having just retuned a full set of Brass and another full of Steel from old pitch to concert, then I re-read this thread with a greater understanding. Especially having made all the mistakes that beginners like me will learn from. A number of the reeds, post filing, were found to touch the end of the housing and had to be microscopically reduced in length to allow clearance. Also you're right about the 'set', that is a black art, but you can tell when its right as the reed speaks much more quickly when is in the sweet spot. After a few thousand I expect it gets easier! 



#12 alex_holden

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Posted Yesterday, 11:58 AM

Interesting stuff and having just retuned a full set of Brass and another full of Steel from old pitch to concert, then I re-read this thread with a greater understanding. Especially having made all the mistakes that beginners like me will learn from. A number of the reeds, post filing, were found to touch the end of the housing and had to be microscopically reduced in length to allow clearance. Also you're right about the 'set', that is a black art, but you can tell when its right as the reed speaks much more quickly when is in the sweet spot. After a few thousand I expect it gets easier!


That's because filing the top surface tends to leave a tiny burr; I scrape it off with a little tool I made by grinding the teeth off an old flat needle file.




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