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Łukasz Martynowicz

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Everything posted by Łukasz Martynowicz

  1. Well, as I'm more of an experimental than theoretical person, I have just performed a very quick and simple experiment which you can easily reproduce and which I think proove my approach definitively: I've taken my largest reed (the same I've mentioned earlier, which was choking under typical bellows pressure) and a drinking straw (flattened at the end to improve selectiveness of the jet produced), pointed it at the gap (*) and I blew hardest I could. I did manage to start the reed vibration and got a low volume sound. I was holding the reed in my hand in the ambient air, so there was no perpendicular pressure force on the tongue other than resulting from the jet of fast moving air and those two phenomenons I've mentioned eariler (or some additional turbulent effects on the bottom side of the tongue). (*) you have to hold the straw end with your fingernail very close to the gap and tongue.
  2. @ Tom: Of course that all those various fluid dynamics effects come from calculations of the same equation, but used at different scales (both spatial and time) resulting in looking at a different geometry and airflow. I think that our missunderstanding comes from looking at the reed tongue at two different scales. You look at the reed as a divider between high pressure reservoire and low pressure reservoire and try to describe it at this "large" scale of an airflow. I on the other hand, focus only on the flow through the gap "magnifying" it. I'm not particularily interested in pressure differences between the bellows and the chamber and the steady oscilation phase, because I try to understand only the first cycle of movement, which we already agreed cannot be explained by this "large" scale (P1-P2)*A approach. It should be clear by now, that I think that the reed would close even when subjected to a very selective jet of air pointed only at the gap (prior to introducing this jet, the reed as a whole subjected only to ambient air pressure, equal both above and below the tongue).
  3. To be clear - I think that at the later stages of the reed oscilation the effects I have described coexist to some degree with the direct effects that the pressure gradient has on the oscilating reed.
  4. Tom, all theoretical papers I've found on free reed analysis skip the starting period and focus on sound generating properties of steady oscilation. I also think, that slow motion, smoke airflow analysis is the only logical step in verifying my assumptions. Unfortunately I'm bound by the capacities of my workshop here which does not include high speed camera I'm also aware, that my explanations weren't as clear as they should be, and there are two main reasons for this: first is the language barrier and the second (more important) is that my times at university are long past and I haven't done serious math for more than a decade now. This is why I can only operate on simple illustrative experiments, observations and intuitions and must withheld from throwing any calculations into this discussion. Instead I did some digging and I think I have finally found a well-described principle that I was trying to ilustrate with my paper experments. It's called Coanda effect http://en.wikipedia.org/wiki/Coandă_effect and describes the tendency of a fluid jet to be attracted to nearby surfaces and is one of the fundaments for the lift force generation and numerous other fluid flow phenomenons. This combined with the third Newton's law makes the tongue to be atracted towards the jet as well and is what I think draws the tongue into the shoe at an early stage of the oscilation. The second principle which I have tried to describe with "the paper corner reed" example (in the part of airflow acceleration) is Venturi effect http://en.wikipedia.org/wiki/Venturi_effect which speeds the airflow and significantly lowers the pressure locally at the gap below P2, and in consequence increases the force generated by Coanda effect. Both of the effects above are generated only dynamically and are significant only when there is fast enough airflow, so as soon as the gap is closed (*) the tongue can spring back upwards against the pressure gradient. Because there will be some time needed for the airflow to reestablish after reopening of the gap, the tongue can have enough time to swing higher than initial position. In my opinion this combined effect is present also at a stable stage of the reed oscilation. This effect can also be present at the second (and third) point in the reed cycle, when the tongue crosses the bottom of the shoe, creating another gap - this time with the force acting upwards. But those both statements heavily depend on whether or not there is enough time for the steady jet to be formed at those later stages of tongue oscilation. Those effects are of course dependand on pressure difference P1-P2, tongue area and all sort of reed parameters, so they will be proportional to them in some way or another, so those "microscopic" effects may be in fact omitted in "macroscopic" description of the stable phase of reed oscilation, when the focus of description is mainly on acoustics of the free reed (as is done in all reed-related articles I could find on the web). I hope this time my point of view is finally clear enough to be seriously considered (either as true or false) as a coherent "theory" based on actual physics (*) there will probably be a slight delay between cuting the airflow and upward acceleration of the tongue because of inevitable turbulence below the tongue caused by a sudden cut-off of the airflow.
  5. This is exactly why I think that (P1 – P2)*A is not a maximum force acting on the reed and an airflow through the gap must create force larger than this - you are seeking an additional mechanism that causes an amplified return in the first cycle, I seek the different mechanism which draws the tongue into the shoe in the first place, so the return mechanism is plain and logical. This force created by the gap airflow and it's relative value to the pressure applied to the tongue is easiest to observe on the lowest/largest possible reeds as the scale and frequency of movement is observable with a naked eye. If I experiment with my lowest reed on my tuning rig, this is what happens: 1) if I act on the bellows with normal force (pulling on the bellows, so I can observe the tongue motion above the shoe) the tongue is pushed into the shoe (just the thickness of the tongue below the edge, so the whole reed is flat) by the (P1-P2)*A force and does not speak, it acts only as a pressure valve. (by "normal force" I mean the force that makes treble reeds speak) 2) in order to make it speak, I must start the airflow through the gap with a much lesser force on the bellows (so that (P1-P2)*A is to small to draw the tongue into the shoe and in the same time is too small to keep it inside on the "agaist the pressure" part of motion). The tongue start to vibrate (at the stage in which it does not even sink into the shoe with all it's thickness and almost all of the oscilation happens slightly above the shoe) and only then I can increase the force on the bellows to make it louder. (I can recreate this reed-starting behaviour with weights attached to the bellows, so the eventual unsteady motion of the hand is not a factor in this) Another "paper experiment" for you to ilustrate that lift is generated: take a small piece of paper (I have used 5x10cm strip) and place it so it is horizontal (rest it on your finger) and has one (short) edge firmly held against your lower lip and then blow on it. As long as you blow there is an airflow speed difference between the upper and lower sides of the paper, so you can take your figer away and the paper will stay horizontal. The curvature of the paper is not important, it does not need to be an airfoil - an airfoil shape is necessary to divide the single pressure enviroment into two enviroments of different pressure but in this case we divide the enviroment by introducing the selective airflow by blowing just on the upper side(*). As soon as you stop blowing, the paper bends naturaly downwards, but you can lift it again by blowing (in this "freely hanging" starting position it does resemble an airfoil at the begining, but it becomes more flat the harder you blow and this shape is not essential to lift the paper as shown above in "resting on the finger" starting position). If you look at the closeup of the reed tongue at the gap, it looks very similiar to this experiment: due to the tongue/gap/shoe geometry there is significant airflow only on the single (lower) side of the tongue. And my above example with the low reed shows that this effect occur at pressure lower than needed to push the tongue into the shoe and that this is essential for the reed to speak. So I must disagree with you Tom on your statements that my illustrations are incorrect. My interpretation seems to be coherent with all different reed types: free, beating and double (and double oboe reed is the most close realisation of the "two sheets of paper" experiment, just with the hinge points on the oposite ends of sheets). And especially beating and double reeds cannot be explained by the approach in which (P1-P2)*A is the largest acting force, as this would just cut the airflow completely and hold the reeds closed as long as there is high pressure acting. And as you Tom admit, your interpretation fails to explain how the reed goes back against the pressure to higher position. Mine may of course be entirely wrong, but it does at least explain this and can be illustrated by all sort of different experiments. (*) to be perfectly correct there is a secondary airflow on the lower side of the paper to ensure the continuity of the flow speed gradient across the enviroment (the flow is laminar, no turbulence is created or necessary), and is caused by the upper airflow, but it is much slower than the upper flow.
  6. Not to start any further debate, but just to clarify what I had in mind all this time, I have finally found a proper english name for what I have called a "suction effect" - I have previously used the direct translation from polish "zjawisko przyssawania" but it is called a Bank Effect in english: http://en.wikipedia.org/wiki/Bank_effect (as you can see now it is not a partial vacuum which makes drinking with straws work). This was my first physics debate in english and I can only apologise for not using proper english terminology (I have tried to find this name then, but have failed to…)
  7. First, the price: cost of a set of 62 DIX reeds from Harmonikas.cz for my Hayden was 400 euros. When it comes to wet/dry tuning, then it is a matter of tuning, not changing plates - dry tuning is just two very closely tuned (a spot-on or couple of cents apart) reeds playing the same note at once, while wet tuning are those same two reeds when tuned wider apart. But it is not a simple matter of changing the reeds if you want to modify the layout. You have strict chamber sizes on the other side of the lever when you press a button… So it is possible to make unisonoric instrument from bisonoric one, but the resulting layout could be even more bizarre. Reeds come in sizes, here is a size chart for harmonikas.cz: http://www.harmonikas.cz/admin/files/ModuleText/16-sortiment-sizes.pdf So if you want a strict layout after your modification, it might need tampering with chamber sizes also. That can lead to a mayour rebuild on the reedblocks/reedpan and depending on instrument may or may not be easy or even possible.
  8. Depending on your budget and dedication, you have three options available: - starter Elise from Concertina Connection at 425$: 34 button, limited instrument, but perfectly capable of learning all of the Hayden techniques on it. And it can be traded in for a discount when upgrading to either of two of the following: - Concertina Connection Peacock at 2900$: 42 "almost standard" instrument. Not perfect because of those missing 4 buttons, but the cheapest, fully usable instrument. - Morse Beaumont at 3950$: 52 button instrument, the highest range available "off the shelf" with some very good opinions on the build, tone and action. All of the above are hybrid concertinas, with Peacock being the only one with flat mounted reeds (Beaumont has a mix of both reedblocks and flat mounted reeds). For the cheapest, traditionally reeded instrument you have to pay almost 6k$ and wait 6 years... You could also contact Bob Tedrow and ask him if he's willing to build one, he has done it before. There is a very little chance for finding something larger/older/more traditional second-hand, there were only few offers of used Peacocks recently.
  9. The answer is beating reed. The difference is that in free reeds, the tongue swings freely through the opening in the shoe, while the beating reed is slightly larger than the opening that it's fitted onto so it is beating against it to cut the airflow.
  10. Thanks for that! I didn't knew that there was any recording of this tune on concertina (there is a typo in the name of it on YT site, it should be "ostatnia niedziela" so search engine sadly doesn't return this recording). It is one of my "tunes to learn" when I'll finaly have an instrument with all necessary accidentals and range and one of my all time favourites. I have even suggested it a while ago as a TOTM material. It is very popular amongst polish accordeonists and a song with a long (and sad) tradition. It's telling a story of a break-up and it is said that this song has been often requested from bands by men (officers mostly) just before commiting suicide (because of a broken heart) in the interwar period.
  11. While the options are certainly limited, complicated, and somewhat formidable undertakings, they do exist. Despite the liklihood of incurring the wrath and criticism of the purists here, I will share with you that my two Jeffries duets are two such examples. The 58-button was converted from a C-core duet to a Stark layout and the 62-button A-core duet was converted to a C-system CBA layout with extraordinary results. This is certainly no undertaking for the faint of heart. It requires the skill, expertise, vision, and willingness of a superbly qualified individual like Wim Wakker, substantial planning and engineering, finding and acquiring an instrument with the proper range of notes that can be suitably adapted while preserving its originality and maintaining its fundamental integrity, the willingness to invest the necessary funds, and the ability, as Lady Macbeth so aptly puts it, "to screw one's courage to the sticking place." It takes time (months, really) to properly analyze and suss it all out and determine the feasibility. Then it requires far more time to complete the work properly as it involves a meticulous and sophisticated series of intricate processes. But in the case of these two concertinas, the risk paid off and produced a handsome reward - two extraordinary concertinas that were previously lying dormant are now readily playable and regularly fulfilling the purpose for which they were originally constructed. I meant "no valid purchase options", my imprecision... Of course you can always buy a different system concertina and convert it to your liking (the route suggested by OP and the one you had taken) or build one from scratch yourself (as I and few others have chosen to do). 5 years of waiting is long enough time to even aquire and train necessary skills. This is true even if you have no background in any craft at all but you are dedicated and have enough spare time and are not easily discouraged by inevitable and numerous smaller or bigger failures along the way. And in my case this "from scratch" aproach is even saving me money, as I desire a large box but I'm happy with a hybrid, so my "budget to beat" is a pricetag on Wakker W-2/H-2, the only 60+ Hayden box currently out there. With your taste in systems, you had certainly even more limited choices than Hayden players have. And your story is a great example of the oposite side to a "moral dilema" that Stuart has raised - you have converted a very rare instruments into ones even more singular and far more usefull to the owner. A sort of "player before an instrument" approach, which I share deeply.
  12. I do use very straightforward and cheap solution with my Elise. I just put some thin foam sheet in the "fretwork" and it dampens the volume significantly (around 15-20 dB), with only a slight effect on the tone. One important thing - each such "insert" must be cut roughly enough for the air to leak slightly through each of the existing fretwork holes. To tight fitting will cause the reeds respond poorly and sound weak. The added bonus of such baffles is that there is less air consumption, so it is easier to play rich harmonies with the small bellows the Elise has. But be warned: as this is of course a fully reversible process it does teach you different habits (you won't be able to play some tunes with same belows direction phrasing with and without the baffles)
  13. You're welcome Wolf, and thank you for expressing your appreciation of the effort taken
  14. What I understand from "your physics description" is that in your opinion such terms as lift (your "partial vacuum formed due to airflow") which is the common and precise level of description on academic level of fluid mechanics and aerodynamic studies, are a jibberish, non-physics and unnecessary complication in trying to describe phenomenons emerging from dynamic motion of a fluid flowing around solid objects… And I understand, that there is the same principle behind this approach, as in centrifugal (aparent) vs centripetal (real) forces. But your refusal for aknowledging their existence as useful descriptive tools is a mystery to me. Even if they answer your questions precisely, are constructed in a strict, physically proper way with a clear underlying mechanism (in much simplification, the Bernoulli's principle in case of lift), and solve the mysteries of observable reed behaviour. And yes, dynamic pressure (lift force) on the low pressure side of the tongue is what drives the oscilation, which I was telling you from the very start of this whole debate. And obviously, there is no difference between raising the tongue a bit or filling the shoe a bit to create a gap - the relative position is what matters. As long as there is assymetry in relation to the tongue resting position, the reed will speak as the airflow will be as in my fig.1 image. If I can recall correctly I have even saw a concertina or harmonium reed filled this way. "since it requires that reed be sealed off from ambient air pressure for it to work" - you have clearly never seen a reed tuning rig, have you? Or even took a reed, placed it between your lips in front of a mirror and draw breath through it? "If the amplitude of the oscillation is of the order of millimeters as you say, the design won't work with a single cutoff point on the low pressure side." It is and it works just fine and you should finally get "your physics" straight with the observable facts... This is my last post in this lecture, I wish you best of luck with your understanding how the reed works. Feel free to disprove my statements by actually building a bidirectional reed of your design. [edited to add some clarification to the first paragraph]
  15. @ Chris: But all his tools listed on his webpage work in connection with a hobby-level Dremel multitool. Of course his rigs and setups are rigid, durable and clever (but sometimes "an overkill" for a one-time use, like his bellows mould or hexagonal cutter or slant tapering rigs, and could be easily substituted by one, versatile milling machine with compound table and tilting capabilities and much simpler add-ons, or even by hand tools in some cases. Of course they are more than justified if he is thinking about making more than a single concertina with them), nevertheless they are anything near industrial level pieces of machinery, and are a lot easier and cheaper to aquire/make than even the home-grade CNC router that Don have mentioned (I should have quoted the exact Don's sentence I was reffering to). But I indeed may have a quite biased view of what a "hobby workshop" looks like, because I consider myself a hobbyist "object maker", but have invested a lot of time, money and effort in completing/designing my workshop and tools...
  16. No offence intended, but with this post you have again proven, that you still know very little about observable reed behavior… Some facts then, that you can observe even with a naked eye, actually looking at a sounding reed: Low A=220Hz reed on moderate volume (gravitational pull on the bellows only) has an amplitude of tongue movement of 5mm (10mm total travel) and to a naked eye this amplitude is symetrical and I don't think that there is any significant assymetry even when measured with apropriate instruments. Plate thickness is usually around 2mm, so with your symmetrical design there would be at least 1mm of tongue movement outside the shoe at each side (if your reed would work) . And this is still at moderate volume. Largest bass reeds can have an aplitude easily exceeding 10mm. What you have described in your opening post, about the lift force created on a tongue is finally true - that the tongue is more similiar to a plane wing than a pressure valve and static pressure of the higher pressure side has neglectible direct effect on it's movement. But after carefully analysing your design, I must say that you forget about orders of magnitude of involved effects and in your latest post strongly overrate the effect of a static higher pressure on the tongue. Again, look at the actual reed - even when no leather valves are present to cut unwanted airflow, only the sounding side reed moves, the other just leaks air, it does not bend in any signifficant way. With your model it should bend proportionally to the pressure gradient in the same way as the sounding reed. Please understand, that the whole process of sucking the tongue into the shoe and resonant amplification of oscilation happens at this tiny area near the point on the tip of the reed tongue and the only significant aerodynamic force act only there. Pressure gradient is needed only for creating wind, which moves almost parallel to the shoe and reed tongue "meeting point". What I have overlooked in my first reply to your proposed design is the flow which you think will drive this design in the first place. Now I think that it won't even start or will have a very slight vibration only. Here is a quick picture, that may help you understand the relative values of forces involved, and an actual airflow shape. Little grey arrows represent the higher pressure acting on entire tongue. Blue arrows represent the airflow, which is faster in the areas when the lines are closer together. Green arrows represent the lift force, resulting from the airflow. Fig.1 represents the typicall reed in it's starting position. The lift force is orders of magnitude higher than the force from pressure gradient. The same effect would occur in your design on the upper shoe-edge crossing point if somehow your reed could start. Fig.2 represents your design. You can see how the lift is created on both sides of the tongue, with values much smaller that on the "classic" assymetric reed. The similiar forces (however even smaller) are created in normal reed due to flow through tongue fiting tolerances. See how the upper flow creates a significant dampening force, which I have mentioned earlier. Fig.3 represents an additional lift force created when tongue passes through the shoe. It is again working towards the resting point and propels the resonant oscilation slightly. It is weaker than on the upper side of the reed, because airflow is not instantaneous and it works within a shorter time than on the upper side. To illustrate orders of magnitude of involved forces, I have another quick and simple experiment for you. Take a piece of typical printer paper. Place it at some distance from your mouth, with one of the corners pointing upwards at mouth level (with corner point at a level of the top of your upper lip), holding it stretched firmly in two hands about 5-10 cm from the corner. Then start blowing gently, silently and steady through a small hole between your lips (so the pressure gradient between your lungs and ambient pressure is the same throughout the experiment) and at the same time start closing the paper to your mouth. At some point you will start to hear the slight noise of air accelerating due to obstruction of pathway. Keep closing the paper slowly to your mouth. There is a very distinctive moment (at few mm from the mouth), when closing the paper even slightly closer will rapidly change the direction of the airflow (down along the paper) resulting in a gentle "pat" of the paper corner on your lips. This is the moment when gap suction aerodynamic effect occur, sucking air from above the corner, creating dynamic underpresure on the closer surface of the paper, moving the paper and closing the gap. Note that there will be no audible change in noise volume (but there will be change in tone from a high pitch whistle to a lower pitched noise due to paper dumpening energy). Then fiddle around with blow direction, paper position and blow strenght and you will find a "sweet spot" when a paper stretched between hands will start flapping or even sounding with a reed-like buzzing sound (in addition to a whistling noise of airflow). You can observe that the paper movement at this distinctive point is much stronger that even slightly further away and that your blow force is bending the paper only slightly outwards. This is the physics of a beating reed ilustrated in a simplest experimental form. The physics of the free reed is different in details but general principles and involved forces remain the same.
  17. @ Don: have you seen this guys effort of doing traditional reedpans with hobby-level tools? http://concertinamatters.se/page38/styled-8/index.html @ Geoff: my thoughts exactly. If one wants something bigger than Beaumont, traditionally reeded or with certain tone, then there are absolutely no valid options...
  18. I must say I was expecting something like this exactly, as this design was the first idea that came to my mind when you wrote about bidirectional reed I have only one, but probably "end game" note on this design: you have now effectively two flow cutting points - one in each half-cycle of the swing motion. So while this type of reed will probably vibrate, it will probably has a very low amplitude (only around the central V inset), probably in almost inaudible range. The "agaist the airflow" (I'll call it upper) cutting point works effectively as a very efficient damper. In traditional reed, in the stable oscilation phase, the upward movement above the shoe is almost unrestricted (as we have agreed, that pressure force is much smaller than spring force) and an airflow around the tongue is almost free, and downward movement is accelerated by suction caused by airflow. But now you have introduced a part in the cycle that counteracts the resonant effect which drives the traditional reed. After achieving the upper flow cutting point any further increase in amplitude is IMHO impossible with this design.
  19. From what I have found about asian type reeds on the last couple days, all eastern instruments are mouth blown and require a pipe resonator for reed to work. From my personal experience with a clarinet (which has a beating reed, so physics is a bit different) and from musicians of various wind instruments, I know that you cannot simply attach a bellows to such instrument - to be able to play on them you must first learn how to sound them, how to "manually (mouthually?) jump start" the reed by combination of blow strenght, slight temporal variance and precise direction (probably causing a proper turbulence at the reed point). I don't know for sure that this is a solid fact, but it sounds to me as a very solid reason why bellows driven reeds have to have a different construction and principle (are blown-closing in oposition to blow-opening asian reeds) and are dependant on gap suction mechanism.
  20. I think there is one other way: you could glue a piece of thin plastic (preferably a foamy one) on the button plate itself (not the lever), and make an apropriate hole in it with a sharp, thick needle. The plastic will warp around the needle and fit snugly into existing button hole, imitating exactly what a felt bushing does. As Don, I and Wim (the very maker of the instrument), have said - the problem has nothing to do with reeds or humidity.
  21. I'm very curious about your new bidirectional reed design and looking forward to your thread
  22. Suction effect in fluid mechanics, as well as lift on the wing of the plane, are two emanations of the same effect, generating force caused by speed difference of particle movement, as you have described above. So I really don't understand what you mean by stating that suction effect is not a force (obciously it is not a force field) and then describing this effect on a microscopic level... And because you can hardly expect an airflow around moving tongue to be laminar, then probably turbulence occuring with sudden cut-off when tongue sinks in the shoe is as significant here as in bumblebee flight, increasing the effect of drawing a tongue into the shoe by airflow.
  23. Regarding seting a tongue into movement, this is exactly what has to happen - a lot of air has to move in a wind form, which propagates at a lot slower speeds than soundwave. And my comment on tube dampening the volume was completely missunderstood (probably due to my imprecise language): the tube will dampen the volume and muffle the sound due to lots of bounces of soundwave and resulting energy dampening with each bounce. Especially when it is not a straight air duct but a maze with two straight angle corners like in Jakes design. I have even proposed a simple experiment on that matter for anyone to perform for themselves. Each concertina builder will confirm, that the loudest and brightest ones are the ones most open, with the shortest possible route of air from the reed chamber to the outside of the concertina, with least of the energy dampened in between…
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