Has Any Builder Ever Reinforced a Pyramid Bridge with Carbon Fiber?

[justonwo]

I love pyramid bridges. The look and the historical significance just ring my bell for some reason. However, ordering a pyramid also means accepting a certain amount of risk that the bridge will crack. This is especially true if the saddle is particularly tall.

It seems to me that one could install some carbon fiber reinforcement when making a pyramid bridge. Perhaps inset from the bottom of the bridge so as to be completely invisible once installed. Perhaps an “I” shaped beam close to both edges of the saddle slot?

I’m wondering if any builder has ever attempted this?

[justonwo]

I guess the other idea would be to run two pieces of carbon through the front/back of the bridge on either side of the saddle slot, pull and glue under tension, then release so the carbon pulls into compression. Countersink the carbon and plug with ebony. Probably close to invisible.

[Bruce Sexauer]

As far as Pyramid bridge issues go, the one you are addressing is not the biggest, IMO, and is easily addressed by being careful not to put the slot too close to the front of the bridge, and using the drop-in style rather than the through saddle style, leaving 1/8" of material beyond the slot.

The more common problems with the Pyramid bridge, IMO, are the bridge cracking through the pins, and the relatively small gluing footprint. I address the first by putting the bridge pin holes out of line with the grain of the bridge, parallel with the saddle, which has the additional advantage of allowing the saddle angle to be increased to facilitate better string intonation. And a very slight increase in the bridge footprint gives a much greater chance of a reliable glue join to the top, without being obvious to the educated observers eye.

[justonwo]

Interesting. Just to be clear, I’m talking about bridges with drop in saddles. I have seen two failures. What distance do you leave between the front end of the saddle slot and the front of the bridge?

In my case, the bridge cracked the top of the drop in saddle slot on the bass side (furthest from the front of the bridge). I have heard of bridges cracking through the pins as well.

[dbintegrity]

a pyramid bridge would be more prone to cracking if the saddle wasn't a perfect fit... too loose of a fit would cause it to lean a little... a nice snug fit would almost make it as "one" with a stronger structural integrity

[justonwo]

Originally Posted by dbintegrity

a pyramid bridge would be more prone to cracking if the saddle wasn't a perfect fit... too loose of a fit would cause it to lean a little... a nice snug fit would almost make it as "one" with a stronger structural integrity

The saddle itself is like a little crowbar trying to split the bridge in two. The leverage of the saddle on the bridge is not really influenced by the snugness of the fit. The same force is exerted regardless of whether the saddle fits tightly in the slot or loosely (except in the extreme case of a VERY loose fit, in which case the force is actually lower as the saddle leans far forward). The lever force of the saddle is actually highest when the saddle is perfectly vertical (i.e. a perfectly tight fit).

[dbintegrity]

Originally Posted by justonwo

The saddle itself is like a little crowbar trying to split the bridge in two. The leverage of the saddle on the bridge is not really influenced by the snugness of the fit. The same force is exerted regardless of whether the saddle fits tightly in the slot or loosely (except in the extreme case of a VERY loose fit, in which case the force is actually lower as the saddle leans far forward). The lever force of the saddle is actually highest when the saddle is perfectly vertical (i.e. a perfectly tight fit).

I'm not sure I totally agree with that.... I believe a perfectly fit saddle with the correct height, will transfer force evenly throughout the bridge. A loosely fit saddle will have uneven force on different pressure points distributing the force unevenly and exposing any weaknesses in the wood. Obviously a saddle needs to be the correct height or it will act as a fulcrum causing the bridge to split or the top to have excessive belly roll...
With that said, I will apologize, for slightly derailing your thread .... And now back to our regular programming....

[IndianHillMike]

Originally Posted by justonwo

The saddle itself is like a little crowbar trying to split the bridge in two. The leverage of the saddle on the bridge is not really influenced by the snugness of the fit. The same force is exerted regardless of whether the saddle fits tightly in the slot or loosely (except in the extreme case of a VERY loose fit, in which case the force is actually lower as the saddle leans far forward). The lever force of the saddle is actually highest when the saddle is perfectly vertical (i.e. a perfectly tight fit).

This is the main reason why I like to tilt my saddles in two ways -- rotated to account for intonation and tilted back to split the break angle. The idea is that with the height of the saddle evenly splitting the break angle, the force is directed down to the bottom of the saddle and reduces the torqueing force on the saddle slot.

[sinistral]

Originally Posted by Bruce Sexauer

As far as Pyramid bridge issues go, the one you are addressing is not the biggest, IMO, and is easily addressed by being careful not to put the slot too close to the front of the bridge, and using the drop-in style rather than the through saddle style, leaving 1/8" of material beyond the slot.

The more common problems with the Pyramid bridge, IMO, are the bridge cracking through the pins, and the relatively small gluing footprint. I address the first by putting the bridge pin holes out of line with the grain of the bridge, parallel with the saddle, which has the additional advantage of allowing the saddle angle to be increased to facilitate better string intonation. And a very slight increase in the bridge footprint gives a much greater chance of a reliable glue join to the top, without being obvious to the educated observers eye.

I just have to say, this is brilliant how much thought was put into this bridge design.

[justonwo]

Originally Posted by IndianHillMike

This is the main reason why I like to tilt my saddles in two ways -- rotated to account for intonation and tilted back to split the break angle. The idea is that with the height of the saddle evenly splitting the break angle, the force is directed down to the bottom of the saddle and reduces the torqueing force on the saddle slot.

Yep, Mike Baranik and a few others do that as well. Not sure there is room on a pyramid though.

[justonwo]

Originally Posted by dbintegrity

I'm not sure I totally agree with that.... I believe a perfectly fit saddle with the correct height, will transfer force evenly throughout the bridge. A loosely fit saddle will have uneven force on different pressure points distributing the force unevenly and exposing any weaknesses in the wood. Obviously a saddle needs to be the correct height or it will act as a fulcrum causing the bridge to split or the top to have excessive belly roll...
With that said, I will apologize, for slightly derailing your thread .... And now back to our regular programming....

Hmmm . . . it’s hard to imagine with a perfectly flat/straight saddle and a straight saddle slot (and 6 strings holding them in place) that the contact between the saddle and the bridge is any less continuous with the saddle tight vs loose. The pressure is going to be uneven anyway since the string tension is different across the strings. But it’s a moot point for the builders I’m contemplating.

Let’s assume the builder is sufficiently skilled to ensure the slot is properly made.

[srick]

Juston - so the amateur engineer in me wonders if the bridge slot isn’t a big part of the problem. What if there was minimal, or no slot, and a thin piece of bone supporting the strings? This leaves a lot more solid wood in the weakest area. And Bruce’s suggestion of slightly canting the bridge pins is very elegant.

If you were using carbon fiber, I am wondering what configuration it would take? I suppose that you could embed two thin rods parallel to the strings and adjacent to the sides of the nut. Or, you could inlay a bar of carbon fiber in the area of the bridge immediately in front of the nut where breakage would likely occur.

Just musing, and doing a finite element analysis in the back of my brain.

[IndianHillMike]

Originally Posted by justonwo

Yep, Mike Baranik and a few others do that as well. Not sure there is room on a pyramid though.

It would of course depend on the design/builder, but there would most likely be plenty of room even with a standard pyramid bridge width. Tilting back only adds about 1.2mm to the required real estate need for the saddle (depending on depth of saddle slot, break angle, etc.). Even if you had to add that amount to the total bridge width, it should pretty imperceptible to the naked eye.

[Bruce Sexauer]

The problem with a shallow saddle slot is that the leverage against the lead edge of the bridge is greatly increased. Though there is more "meat" in the bridge below the saddle, the wood adjacent to the saddle is taking a lot more pressure.

Many guitars have less than 1/8" between the upper edge of the bridge and the extreme treble end of the saddle, and I like to make are there is slightly over 1/8", but not more than 5/32 or it doesn't look right. On a traditional pyramid bridge there isn't a lot of extra real estate to mess around with. For instance, early Martin pyramid bridges do NOT have enough saddle angle to accomplish proper intonation. This is due to having only 1" of width to work with, and their propensity for keeping the bridge pins in a line parallel with the bridge itself. This causes the low E string's pin to be so close to the saddle that some brands of string have their ball-end reinforcement hang over the saddle!

As far as Juston's original question is concerned: My experience with dowels, assuming I get your concept, shows me that while they are great for alignment, they remove some of the critical strength of the joinery they are theoretically facilitating, and unless they are somehow bonded to the substrate (the bridge, in this case) better than I find likely, they will weaken rather that enhance the bridge no matter how strong they are.

[justonwo]

Originally Posted by Bruce Sexauer

The problem with a shallow saddle slot is that the leverage against the lead edge of the bridge is greatly increased. Though there is more "meat" in the bridge below the saddle, the wood adjacent to the saddle is taking a lot more pressure.

Many guitars have less than 1/8" between the upper edge of the bridge and the extreme treble end of the saddle, and I like to make are there is slightly over 1/8", but not more than 5/32 or it doesn't look right. On a traditional pyramid bridge there isn't a lot of extra real estate to mess around with. For instance, early Martin pyramid bridges do NOT have enough saddle angle to accomplish proper intonation. This is due to having only 1" of width to work with, and their propensity for keeping the bridge pins in a line parallel with the bridge itself. This causes the low E string's pin to be so close to the saddle that some brands of string have their ball-end reinforcement hang over the saddle!

As far as Juston's original question is concerned: My experience with dowels, assuming I get your concept, shows me that while they are great for alignment, they remove some of the critical strength of the joinery they are theoretically facilitating, and unless they are somehow bonded to the substrate (the bridge, in this case) better than I find likely, they will weaken rather that enhance the bridge no matter how strong they are.

Yeah, I figure it’s not a slam dunk. I am intrigued by gluing the carbon rod dowels under tension so that they pull the wood into compression. Who knows, perhaps could help. I’m no woodworker.