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Bridge support...Don’t laugh too much
http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=3883		 Page 1 of 1
Author:  Philip Perdue [ Wed Nov 23, 2005 11:22 am ]
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Don’t laugh too much just because I’m not a builder yet and operate from a limited set of skills and knowledge. I did have a thought about bridges and the rotational pull from the string tension. Could one use actually bridge support theories on guitar bridges?



Could this work like a suspension bridge and give upward pressure to the sound board to counteract some of the rotational pull from the steel strings? Could it help in any way to transmit string energy to the top plate?

This thought was based on an observation of a structure that an engineer built where the structural components were upside down. What he built works but looks strange.

Philip
Author:  Don Williams [ Wed Nov 23, 2005 11:52 am ]
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What's to laugh at? It's an interesting idea actually. Using the string to anchor the bridge creating an opposite rotational torque vector. Interesting....this might be worth looking into with a pinless design.
Author:  Brock Poling [ Wed Nov 23, 2005 12:21 pm ]
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Isn't that sort of what the Bridge Doctor does? I have never used one (or looked into them too closely), but I seemed to think that was one of the general ideas behind that product.

Author:  BlueSpirit [ Wed Nov 23, 2005 12:46 pm ]
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Very interesting. That's the kind of thinking to applaud, not laugh at.
Author:  Parames B [ Wed Nov 23, 2005 1:01 pm ]
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I like the idea but I'm still concerned about the difficulty in inserting the strings. It seems some sort of tube is still needed to guide the strings to go through those two holes easily. Also, there should be a piece of hardwood for the pinball rest to protect the top.

After all, how's tone going to be affected from the system has yet to be considered.
Author:  old man [ Wed Nov 23, 2005 2:14 pm ]
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Slide the support toward the bridge and create a continuous sine wave. Kinda neat.

Ron
Author:  DaleH [ Thu Nov 24, 2005 2:18 pm ]
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Carbon fiber would be a great material to use on something like that.
Author:  tippie53 [ Fri Nov 25, 2005 1:00 am ]
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   The only dumb question is the one that is not asked.
Author:  sfbrown [ Fri Nov 25, 2005 4:20 am ]
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If you can think of how to re-string it without killing the builder, I think you have something.

I like the idea but getting new strings in would be a nightmare. Solve that and put a piece to buffer the ball ends (to keep from denting the top) and you're a millionaire!

Maybe if the first set of holes were short slots? Those being the holes closest to the neck. Put a short curve in the strings and thread them through like a carpet needle? Hmmm... If it works, cut me in for a 1/3!

Or how about this: The top piece is simply widened while the underpiece is made with some sort of guide for the string that curves it around. All you need is a way to keep things registrered during glue-up and you have it made!    Given the plethora of great ideas, I'll now take 1/2!

Good luck with it, Stevesfbrown38681.5153935185
Author:  sfbrown [ Fri Nov 25, 2005 4:59 am ]
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OK, so I'm bored and really don't want to go back and sweep up more sawdust. How about this:




Just a thought, Steve
Author:  letseatpaste [ Fri Nov 25, 2005 5:22 am ]
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I can't really wrap my brain with how this is supposed to help... You're going to have downward pressure on the bridge and upward pressure on the support bridge. Rotationally speaking, you're pulling in the same direction, not opposite.

Unless you transfer the moment to some other solid part of the structure (i.e. like a bridge doctor does), you still have the force from the string creating a rotational force on the top, no matter how the string is anchored.
Author:  sfbrown [ Fri Nov 25, 2005 6:18 am ]
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[QUOTE=letseatpaste] I can't really wrap my brain with how this is supposed to help... You're going to have downward pressure on the bridge and upward pressure on the support bridge. Rotationally speaking, you're pulling in the same direction, not opposite.

Unless you transfer the moment to some other solid part of the structure (i.e. like a bridge doctor does), you still have the force from the string creating a rotational force on the top, no matter how the string is anchored.[/QUOTE]

If I've got it right, you are not any longer attempting to pull the bridge away from the guitar top. You could, theoretically, use a smaller bridge or one shaped to better acoustic advantage. On the other hand, the design could deaden the sound. There is no doubt, it would take some experimentation.

Steve
Author:  letseatpaste [ Fri Nov 25, 2005 6:42 am ]
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Yeah, but with a traditional steel string, the ball end of the string is pulling against the bridge plate on the inside of the guitar, not the bridge itself. No matter how complicated you make the way the string winds around and anchors after the bridge, the overall top structure of the guitar still has to counter the moment from the string tension pulling x pounds force at d inches above the top.
Author:  letseatpaste [ Fri Nov 25, 2005 7:18 am ]
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Looking again at your sketch, Steve, your design could keep the bridge from tipping up (or partially relieve stress on that glue joint) since the back end would be held down by the pressure of the ball end of the string pulling the back end of the bridge down. For that matter, though, you could bolt down the back of the bridge with a nut on the inside against the bridge plate for the same effect. Or you could just do a really good job of gluing it. :)

But it seems to me that the overall effect on the stresses the top structure has to endure would be the same as a traditional bridge.
Author:  tippie53 [ Fri Nov 25, 2005 3:18 pm ]
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     After looking at your drawing and thinking about this I doupt that your system is of any value. The forces are still there and you have added double the mass at the bridge.
     You havn't stopped the rotational forces just spread them out. The strings will apply force to your filler by pushing that against the top causing a serious detriment of motion on the top. The roational force caused by the strings on the saddle is still there but the added mass won't allow the bridge and saddle to work the way it should.
      I have been building a long time and what I found is that the relationship is with the mechanics of the bridge/saddle and top and bracing. If you increase the mass you need even more energy to drive the top. The laws of physics apply and you can't change that. The forces are still there you just added more mass and weight.
   Build one and then see what it sounds like. I don;t think you would like the result. Think of the bridge as the magnet to a speaker . the better the bridge can drive the top the better the sound.
john hall
blues creek guitars
Author:  sfbrown [ Fri Nov 25, 2005 11:52 pm ]
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[QUOTE=tippie53]      After looking at your drawing and thinking about this I doupt that your system is of any value. The forces are still there and you have added double the mass at the bridge.
     You havn't stopped the rotational forces just spread them out. The strings will apply force to your filler by pushing that against the top causing a serious detriment of motion on the top. The roational force caused by the strings on the saddle is still there but the added mass won't allow the bridge and saddle to work the way it should.
      I have been building a long time and what I found is that the relationship is with the mechanics of the bridge/saddle and top and bracing. If you increase the mass you need even more energy to drive the top. The laws of physics apply and you can't change that. The forces are still there you just added more mass and weight.
   Build one and then see what it sounds like. I don;t think you would like the result. Think of the bridge as the magnet to a speaker . the better the bridge can drive the top the better the sound.
john hall
blues creek guitars[/QUOTE]

That's what I said in my post. The mass would be a concern. My only point was seeing if you could find a way to keep the forces from wanting to pull the bridge away from the top, not reduce them. Would it work in practice? I have no idea. I simply expanded on another's idea and tried to come up with a feed mechanism.

Makes you wonder though about guitar innovations through the years. I can just imagine the first guy who stuck a truss rod in a guitar.   

Regards, Steve
Author:  Michael McBroom [ Sat Nov 26, 2005 3:53 am ]
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Interesting concept, and I had one not unlike yours. My idea was to install cantilever supports under the bridge to spread out the forces. But then I read Siminoff's book, The Luthier's Handbook, and noted that his experiments showed that most of the sound production of a guitar with a fixed bridge was due to the bridge rocking in a fore-to-aft motion. I realized then that trying to stabilize the bridge against fore-to-aft movement would probably result in a quiet guitar. So I abandoned the concept.

Best,

Michael
Author:  tippie53 [ Sat Nov 26, 2005 4:32 am ]
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Steve
     Please don't take this personal. The best ideas are sometimes things that seem odd or unusual.
john hall
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