The Acoustic Guitar Forum

Go Back   The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Reply
 
Thread Tools
  #1  
Old 12-01-2017, 07:40 AM
hat hat is offline
Registered User
 
Join Date: Jan 2013
Posts: 691
Default x bracing crossing under the bridge?

I had a thought about moving the main X braces to where they cross right under the bridge. It just seems like moving the fulcrum point of the bracing to the point where the most string tension ( force) is, would be a more efficient setup. This would most likely require a pinless bridge. I wonder if anyone has tried such a setup?
Your thoughts?
__________________
______________
---Tom H ---

Last edited by hat; 12-03-2017 at 05:14 PM.
Reply With Quote
  #2  
Old 12-01-2017, 08:58 AM
redir redir is offline
Registered User
 
Join Date: Aug 2011
Location: Mountains of Virginia
Posts: 3,627
Default

My first thought is that there is more force in front of the bridge rather than right under it. That area is what Somogyi amusingly calls the Bermuda Triangle, that is the triangle made by the bridge coupled to the X-Brace legs.

My guess is that you would be opening up the crossdipole mode while restricting the monopole and the guitar would behave more like a classical guitar and will be brighter in tone.
Reply With Quote
  #3  
Old 12-01-2017, 01:31 PM
Truckjohn Truckjohn is offline
Registered User
 
Join Date: Feb 2016
Posts: 1,146
Default

Howard Klepper has written some interesting thoughts on forward/rear shifting the X brace legs intersection with the bridge wings.

Trevor Gore has also written some interesting observations of the same - which is part of how he came up with his "Falcate" bracing scheme...

It's worth chasing those down and reading through them...
Reply With Quote
  #4  
Old 12-01-2017, 06:27 PM
printer2 printer2 is offline
Registered User
 
Join Date: Dec 2012
Posts: 2,875
Default

With the rear ends of the bridge over the X legs the top has less chance of distorting and the bridge peeling off.
__________________
Fred
Reply With Quote
  #5  
Old 12-02-2017, 11:09 AM
Bruce Sexauer's Avatar
Bruce Sexauer Bruce Sexauer is offline
AGF Sponsor
 
Join Date: Jan 2009
Location: Petaluma, CA, USA
Posts: 4,864
Default

I view the separation between the two stiffest spots on the top as the "cantilevered spring" that creates the liveness and character of the guitar. This is not entirely unlike the juxtaposition of the bridge and the soundpost in anviolin family instrument. Putting the two hard spots together usually renders an overly dry and featureless sound.
__________________
Bruce
http://www.sexauerluthier.com/
Reply With Quote
  #6  
Old 12-02-2017, 03:20 PM
printer2 printer2 is offline
Registered User
 
Join Date: Dec 2012
Posts: 2,875
Default

Now if I were to go with anyone's opinion, well I would go with ^.
__________________
Fred
Reply With Quote
  #7  
Old 12-03-2017, 11:01 AM
mercy mercy is offline
Charter Member
 
Join Date: Jun 2007
Location: So Cal
Posts: 2,997
Default

the bridge wings should go the lower x legs just a bit
Reply With Quote
  #8  
Old 12-03-2017, 05:17 PM
hat hat is offline
Registered User
 
Join Date: Jan 2013
Posts: 691
Default

Quote:
Originally Posted by Bruce Sexauer View Post
I view the separation between the two stiffest spots on the top as the "cantilevered spring" that creates the liveness and character of the guitar. This is not entirely unlike the juxtaposition of the bridge and the soundpost in anviolin family instrument. Putting the two hard spots together usually renders an overly dry and featureless sound.
I would make that same assumption. What I was thinking was, by combining both structural components, both could be made lighter and more flexible.
__________________
______________
---Tom H ---
Reply With Quote
  #9  
Old 12-03-2017, 08:29 PM
Otterhound Otterhound is offline
Registered User
 
Join Date: Nov 2011
Posts: 3,792
Default

Quote:
Originally Posted by printer2 View Post
With the rear ends of the bridge over the X legs the top has less chance of distorting and the bridge peeling off.
Of course , should the strings/tension not be pulling upward on the bridge , this would be rendered a non item .
Just in case you are wondering , I am doing this exact thing with a pinless bridge design .
In fact , the bridge is actually being held down on to the top with my setup .
Reply With Quote
  #10  
Old 12-04-2017, 10:32 PM
Mr Fingers Mr Fingers is offline
Registered User
 
Join Date: Jan 2017
Location: Santa Barbara, CA
Posts: 910
Default

I'll simply add one more voice saying that this doesn't seem like a good idea. I don't know what you mean (OP) by "efficient." I thought that braces transmit vibrations as well as mechanically keeping the top stable; having the bridge over the X reduces that contact drastically, maximizes contact for only the middle strings, and leaves the rest of the bridge contacting only the top. I just don't get it, unless I'm missing something.
Reply With Quote
  #11  
Old 12-05-2017, 08:04 AM
hat hat is offline
Registered User
 
Join Date: Jan 2013
Posts: 691
Default

Quote:
Originally Posted by Mr Fingers View Post
I'll simply add one more voice saying that this doesn't seem like a good idea. I don't know what you mean (OP) by "efficient." I thought that braces transmit vibrations as well as mechanically keeping the top stable; having the bridge over the X reduces that contact drastically, maximizes contact for only the middle strings, and leaves the rest of the bridge contacting only the top. I just don't get it, unless I'm missing something.
I see what you're saying. I am looking at the top, braces, and bridge as one functioning unit, not 3 separate pieces that act/react with each other.
__________________
______________
---Tom H ---
Reply With Quote
  #12  
Old 12-05-2017, 08:52 AM
printer2 printer2 is offline
Registered User
 
Join Date: Dec 2012
Posts: 2,875
Default

Quote:
Originally Posted by Otterhound View Post
Of course , should the strings/tension not be pulling upward on the bridge , this would be rendered a non item .
Just in case you are wondering , I am doing this exact thing with a pinless bridge design .
In fact , the bridge is actually being held down on to the top with my setup .
Unless you are using a tailpiece you will be getting the back of the bridge being pulled up by the torque from the strings over the saddle.
__________________
Fred
Reply With Quote
  #13  
Old 12-05-2017, 09:01 AM
LouieAtienza LouieAtienza is online now
Registered User
 
Join Date: Feb 2013
Posts: 3,979
Default

Quote:
Originally Posted by hat View Post
I see what you're saying. I am looking at the top, braces, and bridge as one functioning unit, not 3 separate pieces that act/react with each other.
Well the other factor to consider is the amount of "roll" (if I may use aviation terms) the bridge may encounter as a result of placement relative to X braces. I see it as akin to standing with your feet close together, as opposed to apart. If you stood close to to the join of the X with a foot on each leg of the X, you'd find it very stiff yet it may not be so easy to balance. Stand farther from the join, and yes, the brace legs will have a little more flex but because your feet are wider apart it's easier to remain stable. If you get too far fromthe join, then your legs are too far apart, and the braces are thinner, but allowing almost no roll due to the width (unless your feet are NOT on top of the braces, which would then mean you're only relying on the top wood itself). So in my view somewhere between the two extremes gives you just enough stability, while still not being absolutely restrictive in the "roll". With any engineering problem there will always be compromise, and one must weigh which compromises need to be made.
Reply With Quote
  #14  
Old 12-05-2017, 09:12 AM
hat hat is offline
Registered User
 
Join Date: Jan 2013
Posts: 691
Default

Quote:
Originally Posted by printer2 View Post
Unless you are using a tailpiece you will be getting the back of the bridge being pulled up by the torque from the strings over the saddle.
That thought had occurred to me. In fact, using a tailpiece would bring the whole idea very close to an archtop design, with it's tone par(s) and scalloping at the bridge point. Plus, using a tailpiece would allow for an even smaller (lighter) bridge. But that is getting away from the original idea I think.
__________________
______________
---Tom H ---
Reply With Quote
  #15  
Old 12-05-2017, 01:06 PM
Otterhound Otterhound is offline
Registered User
 
Join Date: Nov 2011
Posts: 3,792
Default

Quote:
Originally Posted by printer2 View Post
Unless you are using a tailpiece you will be getting the back of the bridge being pulled up by the torque from the strings over the saddle.
And there will also be compression to the top .
With the strings breaking over the top of the bridge before reaching the saddle , there will also be a downward force at that contact point . That contact point is rearward of the saddle and will serve to counter the torque that you refer to .
With a properly shaped saddle , the torsional force will be minimized as well as providing some downward force .
With a pinless bridge as I am doing it , there is no upward force to the rear of the saddle on the bridge as is with pins . Since the conventional pins are anchored in the bridge , the strings , from below are leveraging the bridge upwards and away from the top wood .
As I am doing it , the upward force is transmitted through the top towards the bottom of the bridge , but not pulling upwards on the bridge itself . Thus , torque on the bridge itself in greatly minimized and nearly eliminated or , in the least , balanced .
I can only wonder if I am relating what I am trying to say clearly .
Reply With Quote
Reply

  The Acoustic Guitar Forum > General Acoustic Guitar and Amplification Discussion > Build and Repair

Thread Tools



All times are GMT -6. The time now is 04:40 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Copyright ©2000 - 2017, The Acoustic Guitar Forum
vB Ad Management by =RedTyger=