Pin bridge vs Pinless

[murrmac123]

Originally Posted by Otterhound

Break angle has nothing to do with pins . It is all about the string/s .
With what I am doing , you can actually increase break angle by using a thicker piece of Lexan .
Should you want greater angle without increased mass , a thicker piece with a smaller footprint will do that .

Originally Posted by charles Tauber

Now you've completely lost me.

I have to confess to being puzzled as well.

If we define the break angle as the angle formed between the vertical saddle, and the string as it passes over the saddle en route to contacting the bridge at the top of the bridgepin hole, then it follows that no matter how thick the Lexan plate is, the break angle is going to remain exactly the same.

The only way that thickening the Lexan could affect the break angle would be if the string made no contact at any point with the wood of the bridge , and went straight from the Lexan to the top of the saddle..... which seems both impractical and counter-productive.

[Rodger Knox]

Originally Posted by murrmac123

I have to confess to being puzzled as well.

If we define the break angle as the angle formed between the vertical saddle, and the string as it passes over the saddle en route to contacting the bridge at the top of the bridgepin hole, then it follows that no matter how thick the Lexan plate is, the break angle is going to remain exactly the same.

The only way that thickening the Lexan could affect the break angle would be if the string made no contact at any point with the wood of the bridge , and went straight from the Lexan to the top of the saddle..... which seems both impractical and counter-productive.

I agree with your conclusions, but break angle is the deflection the string makes as it passes over the saddle. Not everyone installs the saddle vertically, and that has no effect on the break angle. It does have an effect on the tipping force on the saddle, leaning it back reduces the tipping force and increases the downward pressure.

[murrmac123]

Originally Posted by Rodger Knox

I agree with your conclusions, but break angle is the deflection the string makes as it passes over the saddle. Not everyone installs the saddle vertically, and that has no effect on the break angle. It does have an effect on the tipping force on the saddle, leaning it back reduces the tipping force and increases the downward pressure.

You are of course perfectly correct, Rodger ...I was simply trying ( perhaps ill-advisedly ) to simplify the issue by considering only one variable , namely the varying angle between the bridge anchored string portion and the saddle as the anchor point varies, but obviously my "Occam's Razor " attempt was misplaced...mea culpa.

[LouieAtienza]

Originally Posted by Rodger Knox

Now you've got a solid mechanical couple between the top and back. That eliminates the main air resonance, and forces the main top and back resonance to the same frequency. So instead of three strong resonance frequencies, you've got one that's not as strong as any of the three and probably higher in pitch than any of the three.

I can maybe see the back plate resonating at a frequency proportional to the top. But the same? The back plate is denser material and braced heavier than the top, with a much greater dome.

There are no good ideas in this thread, but feel free to try the string through and sound posts. You might like a guitar with no bass response. I'm done here.

It would be one thing to state that you do not believe that there are good ideas in this thread, in your "humble" opinion. It's another thing totally to be condescending to someone that has some ideas, whether you agree with them or not. I don't necessarily agree with some of the idea here, yet I'm not discouraging anyone from trying them out, as there is as much to learn from proving the naysayers wrong, even if it cannot be done eventually. In fact some of this personal "discovery" should be encouraged more.

[Otterhound]

I heave been giving thought on how to make this loading thing simple to understand .
What prevents the bridge on an instrument in the violin/double bass family from simply rolling forward and falling over due to torsional force ?

[Ned Milburn]

Originally Posted by Otterhound

I heave been giving thought on how to make this loading thing simple to understand .
What prevents the bridge on an instrument in the violin/double bass family from simply rolling forward and falling over due to torsional force ?

The force is the SAME on either side of the bridge when tuned, so there is no tipping force.

When you tune up an instrument with this style bridge, sometimes tightening the strings can pull the bridge forward, but this is easily corrected as the strings are tightened to full pitch.

[charles Tauber]

Perhaps, more detailed than you'd like, but this seems a good treatment of the subject, page 35, Section 3.4, and page 49, Section 3.19.

https://books.google.ca/books?id=WbW...bridge&f=false


To summarize, unlike a guitar, the strings break over the violin bridge with no part of the string being horizontal. Instead, the portion of the string between nut and bridge forms one angle while the portion of the string from bridge to tail piece forms a different angle. This gives rise to a relatively small difference in horizontal forces being applied to the violin bridge. Friction between strings, in their grooves in the bridge, and the bridge prevents the bridge from tipping.

This is a different situation than a guitar bridge, pinned or not and is probably not particularly relevant to guitar design, unless speaking of guitars with tailpieces.

People have done the static analysis of a pinned guitar bridge: it is not something new. Here is one such example in which Alan contributed:

http://www.mimf.com/phpbb/viewtopic....=1126&start=20

[LouieAtienza]

Originally Posted by Otterhound

I heave been giving thought on how to make this loading thing simple to understand .
What prevents the bridge on an instrument in the violin/double bass family from simply rolling forward and falling over due to torsional force ?

The only way there'd be a "torsional" force on the bridge is if somehow the string tension on one side is greater than the other. If for some reason the bridge does tip over a little , as Ned points out, you can easily straighten it.

[Rodger Knox]

Originally Posted by LouieAtienza

I can maybe see the back plate resonating at a frequency proportional to the top. But the same? The back plate is denser material and braced heavier than the top, with a much greater dome.

With a sound post connecting the top to the back, they are forced to resonate at the same frequencies.

Originally Posted by LouieAtienza

It would be one thing to state that you do not believe that there are good ideas in this thread, in your "humble" opinion. It's another thing totally to be condescending to someone that has some ideas, whether you agree with them or not. I don't necessarily agree with some of the idea here, yet I'm not discouraging anyone from trying them out, as there is as much to learn from proving the naysayers wrong, even if it cannot be done eventually. In fact some of this personal "discovery" should be encouraged more.

You are right, of course. I was a little harsh, I apologize. Check out the thread Mr. Tauber linked. I'll leave it at that.

[LouieAtienza]

Originally Posted by Rodger Knox

...

I would guess that the sound from putting a soundpost on a flat top would be akin to listening to a violinist play "pizzicato". The big difference is that these stringed instruments with sounposts are bowed, not picked or strummed.

And yes you are correct about the plate frequencies; I stand corrected. But even so, both plates are not vibrating sympathetically to each other, meaning in a "mirrored" pattern.

[LouieAtienza]

I vaguely remember that whole discussion. Dave Malicky used to also post on the CNC Zone, though I haven't seem him there in a while. He is a SolidWorks whiz, and I always wanted to ask him if he could do a FEA in a model guitar top...

There is a conclusion that I had come up with a while back, and I'm sure more than a few have - that is , if one mitigates or at least controls the amount of top deformation behind the bridge, then bridge "pull" or "peel" off the top is eliminated, barring glue creep, cut fiber, or other defect. I think it's one of the side-benefits of lattice bracing that extends over the bridge-plate - that area behind the bridge have very little to no flex, reducing the rotation of the bridge about its leading edge. Thus, a rear-loaded pinless bridge would survive just fine on a top built as such (which would be one reason a pinless bridge was used in the first place)

[charles Tauber]

Originally Posted by LouieAtienza

There is a conclusion that I had come up with a while back, and I'm sure more than a few have - that is , if one mitigates or at least controls the amount of top deformation behind the bridge, then bridge "pull" or "peel" off the top is eliminated, barring glue creep, cut fiber, or other defect. I think it's one of the side-benefits of lattice bracing that extends over the bridge-plate - that area behind the bridge have very little to no flex, reducing the rotation of the bridge about its leading edge. Thus, a rear-loaded pinless bridge would survive just fine on a top built as such (which would be one reason a pinless bridge was used in the first place)

The moment causing the “peeling” action remains regardless of what bracing occurs under the top. Distinguish between deformation of the top and the moment trying to tip or peel the bridge. The forces on the glue line remain the largely the same but in, perhaps, cases of extreme deformation of the top.

[LouieAtienza]

Originally Posted by charles Tauber

The moment causing the “peeling” action remains regardless of what bracing occurs under the top. Distinguish between deformation of the top and the moment trying to tip or peel the bridge. The forces on the glue line remain the largely the same but in, perhaps, cases of extreme deformation of the top.

You cannot peel what does not bend, no matter what peeling force you apply. It could only shear, or catastrophically fail. At least one thing has to bend.. If both pieces bend, it helps resist peeling as well, which is one reason for tapering braces, or even the bridge wings...

[charles Tauber]

Originally Posted by LouieAtienza

You cannot peel what does not bend, no matter what peeling force you apply. It could only shear, or catastrophically fail. At least one thing has to bend.. If both pieces bend, it helps resist peeling as well, which is one reason for tapering braces, or even the bridge wings...

Then “peeling” incorrectly describes the phenomenon that causes separation of the bridge from the top at the glue joint.

The reason for tapering brace ends, as I understand it, is to reduce/eliminate stress conentrations caused by sudden changes in cross section.

Two rigid bodies adhered together can be separated without distortion if the separation forces, in this case a moment, exceed the strength of the adhesive or materials being adhered. Distortion is not a prerequisite for the failure. The question is then how significant a factor in guitar bridge failure is due to the distortion and “peeling” vs. Simply exceeding the material or adhesive strength, or creep of the adhesive. Since hire glue is reported to not creep, it would appear that creep could be removed as a cause in such joints.

[Bruce Sexauer]

While the rigid bridge may not "peel" away from the top, the flexible top may be thought of as peeling away from the bridge . . . Perhaps.

Properly made Violin family bridges come very close to bisecting the string's break angle, and thus are driven nearly straight into the top plate.

There is a great deal of what I think of as imperfectly understood conceptual information in this thread.