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Raising reed pitch by traditional or other methods


wunks
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So I gather from the recent posts that at the tip of the reed it's about weight but stiffness/flex at the base.  So no qlob of solder but what about a thin spine of some sort like wire or foil tape?  There seem to be some modern materials that will offer some stiffness but are not brittle.

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Its about the ratio of the tip section and the strength of the belly of the reed, if you file the belly of the reed leaving the tip un touched the the belly is weaker and the pitch drops, The term is flexural rigidity. I guess you are talking about reinforcing the reed belly, it's working area some how. what ever you use would have to be in its self springy, at the same level as the reed steel and work homogeneously with the reed. 

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6 hours ago, d.elliott said:

Its about the ratio of the tip section and the strength of the belly of the reed, if you file the belly of the reed leaving the tip un touched the the belly is weaker and the pitch drops, The term is flexural rigidity. I guess you are talking about reinforcing the reed belly, it's working area some how. what ever you use would have to be in its self springy, at the same level as the reed steel and work homogeneously with the reed. 

I'm visualizing the helper springs on my "92 Jeep....😊

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There are a few things to know.  Actions on the reed Removing/adding metal are not uniform on the reed.  Adding weight at the tip where actual bending is least lowers pitch.  This effect continues down the length of the reed though to an ever lessening degree.  If we are not talking about solder or other soft metals,  then the extra metal starts to increase the reed’s stiffness countering the lowering effect. ( soft metal just damps vibration when it is bent)

   Removing metal at the tip causes the pitch to rise, an effect that continues down the reed to a lessening degree until the reduction of mass is countered by the reduction in stiffness which has the opposite effect.

   Likewise , removing metal at the root where bending force is greatest decreases stiffness, lowering pitch. Again this continues to a lessening degree up the reed until it is countered by reduction of MOVING mass.

  As you can see, there is a stretch roughly around the center of the reed that some refer to as the belly that has little effect on pitch, but does effect the stiffness of the reed.  Thinning a perfectly good reed in that area just weakens the reed, reducing its maximum volume and increasing the tendency to choke or blow flat under pressure.

   For practical purposes, removing metal for tuning purposes should be restricted to about the first and last quarter of the reed’s length. This wants to be spread over that distance to avoid spots that will focus the bending.

   When designing reeds, the profile ( longitudinal cross section ) needs to produce a reed that is similar in stiffness to its mates.  Lower reeds need to be about 70% of the stiffness of the mid range reeds, while higher pitches need to be only 40% or less of the stiffness of the mid range reeds.

   This is because all the reeds need to speak at very close to the same bellows pressure, but the aspect ratio length/ width and total area of the reeds varies dramatically as well as does the perceived loudness of the different pitches.  This variation of stiffness should be a smooth transition from one reed to the next, with each reed falling someplace on the overall curve depending on its pitch.

   To accomplish this, you adjust the profile so that for a given reed length, the tip is as thin as it can be but still thick enough to keep the overall bending smooth and strong enough not to be vulnerable to damage.  The tip has to have enough mass to lower the pitch while the reed still is acceptably stiff.  This creates low reeds that are thicker with higher mass at the tip, reducing thickness toward the root to keep the stiffness low enough to reach the lower pitch.  High reeds are the opposite being thick at the root and thin at the tip.   The mid range reeds are close to flat, but not quite.  
   Flat reeds can work, but they restrict the length parameter in a way that makes low or high reeds Impractically long or short, as well as making it very hard to get a good balance in volume.

   When designing reed profiles, the “central” section where the pitch raising and lowering effects of metal removal cross, is where you can adjust the reed stiffness without affecting pitch, though as the neutral area is thinned, the neutral center moves toward the tip since stiffness is reduced much faster than the mass is reduced. For a given loss of metal.  Generally reeds are never a straight taper either direction and are at least slightly thinner than a straight line would make them in order to keep the stiffness in a practical range.  
   These are the basic principles for reed design to create responsive well balanced reed sets.  Individual reed makers will make their own choices that work best in their instruments. There is still a fair amount of latitude here since the stiffness vs mass distribution can produce reeds of a given pitch and length within a range of profiles.  
   I know this is a lot of info and goes well beyond your question, but a number of people from time to time want to adjust their reeds and a good understanding of what is happening can help avoid mistakes.  Making reeds by hand is a very practical thing, not some arcane knowledge.  I measured my reed stiffnesses with a clever gadget of my own making, but when comparing one reed to another like it,  springing them with your fingers will tell you whether one is even slightly stiffer than the other.  You can make replacement reeds for yourself if you are careful with a file and ready to make a few bad ones at first.  I do most of my reeds on my CNC grinder, but there are a few I make by hand in the lowest notes like G2 and A2 since I use so few of them.

Dana

   

   

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Thanks Dana, I had to read this several times to take it all in. I need to be more explicit and refer to the root rather than the belly of the read when talking about pitch reduction, I had not realised that this could be misleading. Whilst I have known for some time that there is neutral zone where attempted adjustments in pitch yield little or no result, I have never thought of this being an area to reduce reed stiffness. Information for which I thank you. 

 

Obviously one of the factors in reed stiffness is the grade of steel used for the tongue, it's composition and and it's metallographic condition. I am not a manufacturer so I deal with old reeds made out of high(ish) carbon clock spring steel. My own Aeola has reeds tempered to straw, many, if not most instruments have reeds temped to blue. This range of tempers is achieved between 220 deg C and say 300 deg C. I mention this to caution those who feel that they can add solder near the working part of the reed tongue's length. solders come in various alloys with melting points between 90 and 400 deg C plus. the majority of general solders are around 300 deg C. the reed steel must be at least the melting point of the solder for 'sticktion' to take place. It is easy to affect the temper of the working area of the reed, softening it, increasing it's ductility and reducing the stiffness or springiness to the reed. This will adversely affect the reed performance.

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The stiffness of an alloy is defined by its modulus of elasticity, sometimes referred to as Young’s modulus which measures the amount of strain produced by a given stress, where strain is a measure of elongation under stress.  This is not the same as tensile strength or yield point which refer to the amount of stress needed to produce permanent change.  While tensile strength and yield point increase with increasing hardening of an alloy either by heat treatment in carbon steel or work hardening in brass or other nonferrous alloys, only one number is listed for the alloy’s modulus of elasticity.   I once tried hardening a reed of 1095 steel to a temper starting at file hard, where a file would not touch it, and gradually lowering the temper to light blue where it was quite soft, but not really annealed.  This didn’t change the pitch (which depends on stiffness) but had a large effect on how easily the reed was to permanently bend or change the set.  
   A long time ago I switched from 1095 steel to the Uddeholm  UHB-20C alloy which has as one of its listed uses as accordion reeds and is produced in a somewhat harder temper than the blue tempered 1095 steel.  This alloy seems slightly stiffer, and I found that a given profile will have a higher pitch.  It also  shears cleaner and holds its set better which I like a lot.  
   We normally equate stiffness with hardness but I think that is because most of the stiff things we encounter are also hard.  Brass of any hardness is less stiff than any steel.  I have a hard time letting go of this myself but  if you want to calculate the frequency or amplitude of a reed, the number you use is the modulus of elasticity.  If you want to calculate the amount the reed has to bend before it won’t return to its original position, you use the  tensile strength yield point.

     Dave’s remarks about detempering a reed with hot solder are still an issue, though since it only is used at the reed tip where the steel is at its greatest movement but least bending, done properly,  it doesn’t  influence the part of the reed where it would cause real bending trouble.    Regardless, doing no damage to a reed is the goal.  especially on old and valuable instruments.  You need to avoid heating the reed except where the solder touches it and removing the iron as soon as you see the solder wet the steel.  The flux works at the low end of the temperature, and the melting of the solder helps absorb the excess heat that might overheat the steel.  I use a Kester brand low temperature silver bearing lead free solder that melts at about 215 degrees C, with a synthetic rosin core (removable with alcohol and non-corrosive residue  ) that leaves the underside of the tip at a light straw.  It wets the steel very well and stays bright for many years.   
    Please pardon my inability to keep things brief.  For me, this is talking shop, so I get carried away.

Best wishes to all,

Dana

 

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Thanks for the in depth discussion.  Very helpful towards making a complex decision.  My Jeff duet is in old pitch (close to a semitone sharp).  I could go down to C core or up to D core or keep it as is.  Neither re-tune would be easy because of the large interval and the fact that the low 5 or 6 reeds are already heavily weighted.  I've had a suggestion of moving (some) reeds around or having a new reed pan and reeds built.  In any event I'll end up with 2 instruments ( I have a Wheatstone JD C core) at considerable expense.  On a hunch I recently purchased the set of Shakespeare ends offered for sale here( Thanx Sergio!) and Yes! the button pattern matches Jeff duet so now I'm leaning toward spending the money on a new/old build (using as many spares as I can find).  Hopefully I'll end up with 3 boxes for the money....😃1737686167_IMG_20190225_121019(1).thumb.jpg.7f8c189748f3e03f43644416a4fa2b97.jpg

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5 hours ago, Dana Johnson said:

The stiffness of an alloy is defined by its modulus of elasticity, sometimes referred to as Young’s modulus which measures the amount of strain produced by a given stress, where strain is a measure of elongation under stress.  This is not the same as tensile strength or yield point which refer to the amount of stress needed to produce permanent change.  While tensile strength and yield point increase with increasing hardening of an alloy either by heat treatment in carbon steel or work hardening in brass or other nonferrous alloys, only one number is listed for the alloy’s modulus of elasticity.   I once tried hardening a reed of 1095 steel to a temper starting at file hard, where a file would not touch it, and gradually lowering the temper to light blue where it was quite soft, but not really annealed.  This didn’t change the pitch (which depends on stiffness) but had a large effect on how easily the reed was to permanently bend or change the set.  
   A long time ago I switched from 1095 steel to the Uddeholm  UHB-20C alloy which has as one of its listed uses as accordion reeds and is produced in a somewhat harder temper than the blue tempered 1095 steel.  This alloy seems slightly stiffer, and I found that a given profile will have a higher pitch.  It also  shears cleaner and holds its set better which I like a lot.  
   We normally equate stiffness with hardness but I think that is because most of the stiff things we encounter are also hard.  Brass of any hardness is less stiff than any steel.  I have a hard time letting go of this myself but  if you want to calculate the frequency or amplitude of a reed, the number you use is the modulus of elasticity.  If you want to calculate the amount the reed has to bend before it won’t return to its original position, you use the  tensile strength yield point.

     Dave’s remarks about detempering a reed with hot solder are still an issue, though since it only is used at the reed tip where the steel is at its greatest movement but least bending, done properly,  it doesn’t  influence the part of the reed where it would cause real bending trouble.    Regardless, doing no damage to a reed is the goal.  especially on old and valuable instruments.  You need to avoid heating the reed except where the solder touches it and removing the iron as soon as you see the solder wet the steel.  The flux works at the low end of the temperature, and the melting of the solder helps absorb the excess heat that might overheat the steel.  I use a Kester brand low temperature silver bearing lead free solder that melts at about 215 degrees C, with a synthetic rosin core (removable with alcohol and non-corrosive residue  ) that leaves the underside of the tip at a light straw.  It wets the steel very well and stays bright for many years.   
    Please pardon my inability to keep things brief.  For me, this is talking shop, so I get carried away.

Best wishes to all,

Dana

 

 

Dana,

 

I like talking Shop, a bit, The original poster talked about applying something along the spine, that would be root, belly and tip (you see I am picking up your terminology). Hence so much concern about destroying the temper around the working part of the reed. When soldering at the tip I always use a clip on heat sink to protect the elasticity of the reed tongue. For a 18 months I worked as Manager of a mechanical & metallurgical test house proving the properties of aerospace & down hole materials, I want to relapse into tech speak, but I guess most of the readers just need to know that soldering, other than at the tip can be harmful to your reed's heath, and then even at the reed tip to use heat sink protection and low temperature solders where ever possible.

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I am sure my repair tech is well aware of all the pitfalls and will do a great job retuning my 1927 Wheatstone.  I find the "shop talk" to be quite interesting. It gives me a greater appreciation of the skills of every master technician in every trade.

 

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57 minutes ago, Everett said:

I am sure my repair tech is well aware of all the pitfalls and will do a great job retuning my 1927 Wheatstone.  I find the "shop talk" to be quite interesting. It gives me a greater appreciation of the skills of every master technician in every trade.

 

I agree and I'm sure we'll both attain excellent results for our instruments for having this information.

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