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Woodland

Boxy, honky nasal sound.

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7 hours ago, Blank face said:

"Relative to the body" is a bit neboulous. If I replace it with "height over the arching at the bridge position and angle there" this is close to the ideas Martin was describing, where the overstand is just one variable beneath others like nut, bridge or saddle.

I was deliberately nebulous, because there can be many different measuring methods, and terminology, which will result in the same loads.

2 hours ago, martin swan said:

Sorry I just don't see it. The top block will be stressed exactly the same way however high the overstand is. It's a rigid assembly.

A higher overstand results in a longer lever arm. When the same force is applied to a longer lever arm, twisting force (torque) increases.

2 hours ago, martin swan said:

Ok here's my drawing.

overstand.thumb.jpg.f944a2b8f9701e3d9b476af18a91a532.jpg

In A we have a "standard" set-up with a regular overstand - the triangle represents the neck and the block represents the body of the violin (just in case that's not obvious)

In B we have a vastly raised overstand and nut position, just so we can see what's happening. The first thing we see is that the bridge has got higher AND the string angle has increased. 

The question for me is whether the B scenario actually pulls the saddle and the nut together more than in A. And if so why ...

Can you see the longer lever arm from the greater overstand in your B drawing?

1 hour ago, martin swan said:

 In a properly built and well glued up violin, I don't believe that raising the overstand will cause the top block to tilt more. Yes there may be more torque (I take Don's word for it) but there's plenty to resist it.

It will cause the top block to tilt more, both when string tension is initially applied, with more when the effects of "wood creep" have had time to come into play.

1 hour ago, martin swan said:

I'm sure I haven't set as many soundposts as you, but I'm well over a thousand. On violins they all without exception get tighter under string tension.

Not all will. On violins with some combination of a sufficiently high arching and a sufficiently high overstand, the soundpost will get looser when string tension is applied.

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12 minutes ago, Don Noon said:

I wouldn't even bother testing that.  Compressive stress on a curved (arched) structure will make it curve more.  Maybe not much, but it would be like doing a test to see if necks tend to pull up or pull back.

The force diagram tells what the forces have to be, and then you have to figure out what those forces are doing to the structure.  With the top under compression and back in tension, the arching will tend to bow outward for the top and flatten for the back..... but ONLY FOR THE SEGMENT FROM THE NECK BLOCK TO THE BRIDGE AND SOUNDPOST.  There everything changes, and you need to make new force diagrams to account for the vertical forces of the string over the bridge, and how it gets through the top and soundpost.  More complicated.

So with these differing forces, does that account for differences in changing overstand as opposed to changing saddle height?

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5 minutes ago, Jerry Pasewicz said:

So with these differing forces, does that account for differences in changing overstand as opposed to changing saddle height?

They would have very different effects.

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5 minutes ago, Don Noon said:

They would have very different effects.

Thank you Don for your answers and your patience.  It is nice to have the science to go along with the observations.

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1 hour ago, Don Noon said:

It might help to do a force diagram just around the block area.

682748277_Forcediagram.jpg.49dfbaa011b5de4fb8e1996118903d79.jpg

String force S is the same for both.  Therefore the sum of the top and back forces must be opposite in sign and equal in magnitude to the string force.

However, there is the moment to contend with, and with diagram B, the string force is much farther away from the block, and the forces in both the top and the back must rise to counteract the moment.

Also - if the thick wedge neck-block in the bottom diagram were to be trimmed down to an oblique triangle keeping nut and button position but trimming the top down to meet the table top - then the forces would not change at all even though the overstand could be said to have become zero. 

So what matters for forces and resistance to deformation is nut position relatice to top of top block and top of bridge - and overstand is incidental and a result of standard neck shape. Whether the overstand influences sound is a completely different question.

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1 hour ago, David Burgess said:

It was deliberately nebulous, because there can be many different measuring methods, and terminology, which will result in the same loads.

A higher overstand results in a longer lever arm. When the same force is applied to a longer lever arm, twisting force (torque) increases.

Can you see the longer lever arm from the greater overstand in your B drawing?

It will cause the top block to tilt more, both when string tension is initially applied, with more when the effects of "wood creep" have had time to come into play.

Not all will. On violins with some combination of a sufficiently high arching and a sufficiently high overstand, the soundpost will get looser when string tension is applied.

Ok even a simpleton like me (who has erected entire buildings single-handedly with the use of levers and pulleys), knows that a longer lever arm can apply more force.

No I don't see how raising the neck as in B lengthens the lever if the string length remains the same (as it must to preserve the essential playability of the instrument).

I also don't see how it will cause the top block to tilt more unless the otherwise rigid structure of a well glued up violin is somehow compromised. I don't think the force is quite enough to overcome the resistance.

In other words, I accept that more torque is exerted, but you can exert as much torque as you want on an immovable object and it won't move. I can't see that raising the overstand by 1 or even 2mm will overcome the essential integrity of the joint in the short term.

As I understood it, Jerry was attributing some immediate sonic benefit to raising the neck, and claimed that this was because the top was being strengthened. I felt there were a lot of assumptions in that, and questioned it. I'm still questioning it.

The main thing that has become clear to me (though I kind of think it was my starting position) is that nut position and overstand are entirely independent, and that unless you monitor each very carefully you end up increasing the string angle. This is true in either direction, whether going up or going down.

In other words, there is no way of controlling/maintaining the string angle unless you are thinking about the nut position and the overstand independently. 

 

 

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7 minutes ago, Felefar said:

Also - if the thick wedge neck-block in the bottom diagram were to be trimmed down to an oblique triangle keeping nut and button position but trimming the top down to meet the table top - then the forces would not change at all even though the overstand could be said to have become zero. 

So what matters for forces and resistance to deformation is nut position relatice to top of top block and top of bridge - and overstand is incidental and a result of standard neck shape. Whether the overstand influences sound is a completely different question.

Yes, thankyou. At last I feel understood.

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2 hours ago, martin swan said:

Ok even a simpleton like me (who has erected entire buildings single-handedly with the use of levers and pulleys), knows that a longer lever arm can apply more force.

No I don't see how raising the neck as in B lengthens the lever if the string length remains the same (as it must to preserve the essential playability of the instrument).

I also don't see how it will cause the top block to tilt more unless the otherwise rigid structure of a well glued up violin is somehow compromised. I don't think the force is quite enough to overcome the resistance.

In other words, I accept that more torque is exerted, but you can exert as much torque as you want on an immovable object and it won't move. I can't see that raising the overstand by 1 or even 2mm will overcome the essential integrity of the joint in the short term.

As I understood it, Jerry was attributing some immediate sonic benefit to raising the neck, and claimed that this was because the top was being strengthened. I felt there were a lot of assumptions in that, and questioned it. I'm still questioning it.

The main thing that has become clear to me (though I kind of think it was my starting position) is that nut position and overstand are entirely independent, and that unless you monitor each very carefully you end up increasing the string angle. This is true in either direction, whether going up or going down.

In other words, there is no way of controlling/maintaining the string angle unless you are thinking about the nut position and the overstand independently. 

 

 

Don't know what else to say Martin, you seem to hold on to all of your beliefs despite all of the evidence to the contrary.  I guess we could have ended this a couple of days ago. C’est la vie.....

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39 minutes ago, martin swan said:

I also don't see how it will cause the top block to tilt more unless the otherwise rigid structure of a well glued up violin is somehow compromised. I don't think the force is quite enough to overcome the resistance.

I think it would be a mistake to think of any good-sounding violin as an entirely rigid structure.

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15 minutes ago, Jerry Pasewicz said:

Don't know what else to say Martin, you seem to hold on to all of your beliefs despite all of the evidence to the contrary.  I guess we could have ended this a couple of days ago. Se le vie.....

Actually i'm quite open and keen to learn, I'm just waiting for a moment of enlightenment.

Maybe if you were to pin down what it is you want me to understand, then I could see if I understand it or not.

From my point of view we are tossing around some concepts in a very productive way. I don't think anyone's going to turn out to be right about this stuff.

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4 minutes ago, David Burgess said:

I think it would be a mistake to think of any good-sounding violin as an entirely rigid structure.

Of course.

But I'm specifically asking if the forces applying torque to the top block are enough to overcome the design and to make it tilt immediately upon stringing up a violin.

I assume you've measured these things - do you find that the projection drops as soon as you've put strings on? I haven't found that it does, but I can't say I've measured it very often, maybe 2 or 3 times.

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1 hour ago, martin swan said:

Actually i'm quite open and keen to learn, I'm just waiting for a moment of enlightenment.

Maybe if you were to pin down what it is you want me to understand, then I could see if I understand it or not.

From my point of view we are tossing around some concepts in a very productive way. I don't think anyone's going to turn out to be right about this stuff.

Sure, consider this pinned:

"No I don't see how raising the neck as in B lengthens the lever if the string length remains the same"  This goes against the multiple drawings that show a longer lever.

"I also don't see how it will cause the top block to tilt more unless the otherwise rigid structure of a well glued up violin is somehow compromised."  The structure is not rigid as would be hinted at by soundposts becoming looser as the string tension is applied.

"In other words, I accept that more torque is exerted, but you can exert as much torque as you want on an immovable object and it won't move."  This goes against your first point as to where are you getting more torgue if the lever hasn't changed, and the fact that it is not an immovable object as referenced above.

"As I understood it, Jerry was attributing some immediate sonic benefit to raising the neck, and claimed that this was because the top was being strengthened."  This was only one of the points I speculated the other being that by raising the overstand you raise the "point of equilibrium" which refers to the higher nut/pegbox.

"The main thing that has become clear to me (though I kind of think it was my starting position) is that nut position and overstand are entirely independent"  I explained multiple times, as did others, that we do not measure nut position and that raising the overstand assumes projection and all the other measurements remain the same..to spec...so nut position is not independent if the measurements are to remain consistent.

We could just leave it at C’est la vie.....:mellow:

 

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22 minutes ago, martin swan said:

Of course.

But I'm specifically asking if the forces applying torque to the top block are enough to overcome the design and to make it tilt immediately upon stringing up a violin.

It will, unless the violin is pretty far outside of normal measurement parameters. But it will also depend on what your frame of reference is, for any sort of movement. Movement, relative to what?

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Sometimes these things can be pretty complicated. There are more factors at work than we think and sometimes the curvature of the top and back can completely change how the system changes when forces are applied. For my own thinking about these angles and forces I usually take the heel cap as the rigid point of the structure and back being the stiffest part with least deformation.

Similar example of counterintuitive design is the original McHugh truss rod in Gibson Guitars or mandolins. What will happen when you tighten the rod built into the neck? The rod will want to straighten when tightened... that's clear... so the neck will bow forward... WRONG! The neck will bow the other way is the correct answer.

truss-rod-mchugh-large.jpg

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3 hours ago, martin swan said:

I also don't see how it will cause the top block to tilt more unless the otherwise rigid structure of a well glued up violin is somehow compromised. I don't think the force is quite enough to overcome the resistance.

In other words, I accept that more torque is exerted, but you can exert as much torque as you want on an immovable object and it won't move. 

2 hours ago, David Burgess said:

I think it would be a mistake to think of any good-sounding violin as an entirely rigid structure.

Nothing is infinitely stiff; everything has a modulus of elasticity and will act as a spring, although some structures can be very stiff springs.

That said, I agree that a decently constructed and glued violin would be stiff enough so that the movement of initial stringing up would be small enough to be unnoticeable for practical purposes.

If the arching is extremely curved near the block, and graduations thin, then it would be less stiff to rotation of the neck block.  Also, creep over time can do a lot more than the initial stiffness/force elastic deflection.

A millimeter or two difference in overstand might make ~10% difference in the torques and forces, probably not a huge deal.  I would expect that the arching and graduations near the block as well as the wood properties would be the major players.

 

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2 minutes ago, Don Noon said:

Nothing is infinitely stiff; everything has a modulus of elasticity and will act as a spring, although some structures can be very stiff springs.

That said, I agree that a decently constructed and glued violin would be stiff enough so that the movement of initial stringing up would be small enough to be unnoticeable for practical purposes.

If the arching is extremely curved near the block, and graduations thin, then it would be less stiff to rotation of the neck block.  Also, creep over time can do a lot more than the initial stiffness/force elastic deflection.

A millimeter or two difference in overstand might make ~10% difference in the torques and forces, probably not a huge deal.  I would expect that the arching and graduations near the block as well as the wood properties would be the major players.

 

As usual I appreciate your sanguine and infinitely understandable explanations.

I do struggle with Jerry's model which seems largely based on an observation of soundposts getting looser as you increase string tension. I can see this might happen in very high arched violins with thin plates, but I just haven't experienced it, so it can't be anything close to the norm.

 

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5 minutes ago, martin swan said:

I do struggle with Jerry's model which seems largely based on an observation of soundposts getting looser as you increase string tension. I can see this might happen in very high arched violins with thin plates, but I just haven't experienced it, so it can't be anything close to the norm.

I too have not experienced anything like a soundpost getting looser when string tension is applied.  I can only hypothesize that extreme longitudinal curvature, i.e. high arching, could make it happen.  Also high overstand and high saddle, which would both increase the longitudinal compressive forces on the top and reduce the downforce at the bridge.

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4 minutes ago, Don Noon said:

I too have not experienced anything like a soundpost getting looser when string tension is applied.  I can only hypothesize that extreme longitudinal curvature, i.e. high arching, could make it happen.  Also high overstand and high saddle, which would both increase the longitudinal compressive forces on the top and reduce the downforce at the bridge.

If you are installing strings and first tune the E string up to correct pitch and then bring the other strings up to pitch does the open E string go flat or sharp or stay the same? 

Do all violins behave the same way?

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Marty, there's the little problem of the string connection to the movable tailpiece; as the other string tunes up, the tailpiece yaws over and changes the tension on the E.

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Let me suggest that Jerry"s example in which the post becomes looser with tension is possible if the neck block moves (tilts) toward the bridge when under tension. This will compress the top and make it bulge upwards. If the saddle block also tilts, the effect will be magnified. We cannot always presume that the garland is inflexible. Let me say that any violin that has this flexible defect is truly poorly made.

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27 minutes ago, Don Noon said:

Marty, there's the little problem of the string connection to the movable tailpiece; as the other string tunes up, the tailpiece yaws over and changes the tension on the E.

You're right.

How about if the E and G strings are first brought up to pitch simultaneously and then the A and D tuned up simultaneously to keep everything straight.  Will the E and G notes drop in pitch, go up, or stay the same?

This might give a clue whether the top plate was deforming outward (sound post getting looser) or inward (sound post getting tighter).

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6 hours ago, David Burgess said:

I was deliberately nebulous, because there can be many different measuring methods, and terminology, which will result in the same loads.

A higher overstand results in a longer lever arm. When the same force is applied to a longer lever arm, twisting force (torque) increases.

Can you see the longer lever arm from the greater overstand in your B drawing?

It will cause the top block to tilt more, both when string tension is initially applied, with more when the effects of "wood creep" have had time to come into play.

Not all will. On violins with some combination of a sufficiently high arching and a sufficiently high overstand, the soundpost will get looser when string tension is applied.

 

With older, thinner instruments the post definitely can loosen slightly under string tension and on all but the stoutest instruments that are set up in a dry environment the post will loosen slightly with just a short time at greater humidity. Days not weeks and usually the change will not reverse completely when the instrument returns to the initial humidity.

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2 hours ago, Marty Kasprzyk said:

How about if the E and G strings are first brought up to pitch simultaneously and then the A and D tuned up simultaneously to keep everything straight.  Will the E and G notes drop in pitch, go up, or stay the same?

This might give a clue whether the top plate was deforming outward (sound post getting looser) or inward (sound post getting tighter).

You'd be looking at the net effect of several things... the top could compress along the grain, or arching could deform, or the back could straighten, or the tailgut could stretch.  Hard to separate out the effects, but in my experience, the tailgut (nylon) would be the biggest variable.  For your test, better to use braided titanium tailgut.  But there's also the problem that G and E tensions are different, and the tailgut would still yaw to some degree unless you were somehow able to balance the forces so the tailpiece stayed exactly in the same position.  Not an easy test, I think.

How about a soundpost with a strain gage or force sensor?

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39 minutes ago, Don Noon said:

You'd be looking at the net effect of several things... the top could compress along the grain, or arching could deform, or the back could straighten, or the tailgut could stretch.  Hard to separate out the effects, but in my experience, the tailgut (nylon) would be the biggest variable.  For your test, better to use braided titanium tailgut.  But there's also the problem that G and E tensions are different, and the tailgut would still yaw to some degree unless you were somehow able to balance the forces so the tailpiece stayed exactly in the same position.  Not an easy test, I think.

How about a soundpost with a strain gage or force sensor?

Are you referring to the back flattening due to the pull from the neck, or some other effect?  This would also be interesting to understand how it interacts as a  variable to control the post.  

 The force sensor would allow us to see what is happening and when, any idea what to use.....some electronic piezo pad possibly?

 

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