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Bridge Rectifier Approach Halves Number Of Reeds Needed In Ec


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I haven't thought this through (which may become very obvious), but I wondered if anyone had tried making an English concertina with only one reed per note, and using a "bridge rectifier" approach to always direct the air through the reed in the right direction? The bridge rectifier uses 4 diodes (or leathers, in concertina parlance):

 

path_current_in_full_wave_rectifier.jpg

As you can see, it doesn't matter which polarity the power source is (positive or negative, suck or blow), the diodes (leathers) steer the current through the load (reed) in the same direction. It does require 4 leathers rather than 2, but gets away with one reed rather than 2. That would seem very attractive on a 56 key English for instance, offering half the number of reeds, and no tonal, tuning or volume balance issues between reeds. But is it possible to come up with a physical structure that would accommodate all that? I reckon it would have to put you in line for a Nobel Peace Prize.

 

Here's a rough analog of the EC, with two leathers sending the flow in the right direction through two reeds:

 

 

|------>|-------/\/\/\/\----------|

--------| |--------

|-----/\/\/\/\------|<------------|

 

 

Terry

 

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Its been done Terry. There are pictures of it somewhere on the net, as I recall the reedpan has tubes under the padholes which have a reed and a valve which acts like a rocker switch. It might be in the Horniman collection. I'd like to see the pic again, does anyone know where it is..?

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Damn! I'll go back to my groundbreaking work on inventing penicillin....

 

It struck me after I reinvented the bridge rectifier approach, you could avoid having all those separate bridge rectifiers by having a double acting pump arrangement. Whichever way the bellows moves, it just provides push. Then you don't need any leathers. Did old smarty pants invent that then, eh?

 

Terry

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So the real question is, if a "one-way airflow" system has already been thought up, why are we not using it? Not just in concertinas, but chromatic accordions too?

 

There must be some fatal flaw. Maybe the response when changing bellows directions was too slow or loud or otherwise annoying?

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One possible reason is because it is too complicated - it is easier to put two mass produced reeds in a single chamber than make a complicated two-way chamber (in Wheatstone patent the reed is placed in a chamber-dividing wall and there are with lots of valves involved).

And acoustics of such obscured reed probably weren't satisfactory - too much sound bouncing, so probably they had muffled or at least very mellow tone.

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So the real question is, if a "one-way airflow" system has already been thought up, why are we not using it? Not just in concertinas, but chromatic accordions too?

 

There must be some fatal flaw. Maybe the response when changing bellows directions was too slow or loud or otherwise annoying?

This would be my guess too. As for me, concertina playing is very much about bellows controlling the tone, the attack in particular. I would believe this to be hardly done at the point of bellows reversal. If you'd thus have to care for the monent of reversal, you would be playing just like we're use to play our ECs or Duets. This would still leave it open to reduce the amount of reeds, but you wouldn't expect a revolution of your playing capabilities from that any more...

Edited by blue eyed sailor
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I played with that system back in the mid nineties. All the arrangements I tried ( with an eye to duet use ) all had either poor reed orientation and or over long air paths which made them impractically quiet. The same held true for the double acting bellows sysem where the pad valve set up was too complicated. Seemed like such a good idea, but in the end it was easier to make another set of reeds. Anglo players manage with two different reeds per chamber and use the frequent direction change of the bellows for both phrasing and rhythm accentuation. Theoretically that is possible on Englishes and duets, but it is a rare player who actually does it. The thumb pinky arrangement isn't really conducive to rapid direction changes.. Someone may have had better luck than I did, but if it really had been superior, I'd think we'd see them around. My experience backs up Lukaz's conjecture and one system was very like the Wheatstone method. If the sound doesn't work, there is no point.

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Apologies for this rather tardy response, too many enquiries need replies.

 

This sensible query has probably been around since double action concertinas were first produced. Indeed it has appeared several times within these pages over the last ten years.

 

Recent modern theories for ways of accomplishing the rectification of airflow in concertinas have been proposed by some and we await confirmation of any successful outcome.

 

I believe the instrument referred to by Chris G is ‘The Blue Meany’, first brought to our attention by Howard Mitchell, a member of these Forums, back in 2004.

 

And of course, some accordions makers are reportedly producing instruments incorporating a working system.

 

I think we have to be wary of accepting what Wheatstone actually did i.e. what was made, or what was a theoretical proposal?

Sure, he suggested/claimed things as improvements, some of which are carefully presented with detailed drawings in Patent documentation and we know were implemented by the existence of concertinas incorporating those ‘improvements’.

However, other claimed improvements that, although, suggested for the concertina and textually described are only supported by simple drawings that have little or no indication as to how they were, or could be, incorporated.

 

Based on my own investigations some 35 years ago, I came to the conclusion that ‘Improvement number 4’ in the Patent of 1844, although committed to paper, may have been an unproven theoretical idea that never progressed beyond the ‘drawing board’.

This conclusion, which I still hold today, was based on:

The absence of any original instrument examples.

The lack of Patent detail as to how a full set of modified ‘chambers’ could actually be arranged and accommodated within a concertina of acceptable size and shape.

The disregard of any disadvantages that I would have expected to be apparent, visualised or investigated during concept and

Lastly, but more importantly, a design flaw that, in practice, prevents the reed tongue vibrating freely. This can be overcome but the resultant reed response is poor. I have attached a portion of my updated notes that may be of interest. Many more pages could be added but life is to short.

 

In conclusion, I would agree with Lukasz and Dana.

 

Geoffrey

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Very interesting, Geoffrey, thank you. So, not impossible, but probably impractical.

 

I guess I'll shelve it for now, along with my plans for time travel and the perpetual motion engine....

 

Terry

YesTerry, not impossible but with the Wheatstone suggestion, from my own rough calculations an hexagonal 48 English Treble with a radial arrangement would be 10 inches plus across the flats.

 

Good idea to shelve it, I have a virtual shelf that grows ever larger with failed or impractical suggestions.

 

Geoffrey

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