Bridge Material

[turnertj]

All...

I know there is no easy answer to the following question, so I'll throw it out there anyway if for nothing more than discussion sake. And I realize it's an entire process that needs to encompass more than what I'm asking, i.e. accounting for back and side material, soundboard, etc...

When selecting a bridge material, it seems that a general consensus is to find a material that is light so as not to encumber the soundboard and all that wonderful time we all put into our magical bracing, yet at the same time is fairly stiff so as to transfer the string energy well. I was reading Somogyi's book yesterday, and he seems to lean toward brazilian rosewood and wenge for those reasons. In engineer speak, that would put us with low density and high elastic modulus.

So has anyone tried making a bridge from Osage Orange, or even Maple? Both of those have a density about 30% less than Ebony, and have a higher elastic modulus (depending on which source you reference).

Also, just thinking out loud, has anyone tried a rift sawn or flat sawn bridge? Is there a reason it always has to be quartersawn? I can see that perhaps the transfer of the string energy could be different depending on the cut, but wouldn't a non-quartersawn orientation buy you something in terms of keeping the bridge from cracking?

I'm sure I will realize the flaw in my questions as soon as I push the "post" button...

[Darryl Young]

A bridge doens't need to be quartersawn. Some recommend non-quartersawn to resist splitting as you mention.

On bridge material; weight, stiffness, and dampening seem to be the main properties of concern. I would guess weight has the biggest influence. So for a particular bridge design (shape), the density of the material determines the weight. Brazillian Rosewood (BRW) isn't that light. It is on the lighter end compared to most rosewoods. Heavier bridges increase impedience for all frequencies but affect low frequencies the least. Lighter bridges have the least impedence......and probably help move the node lines of the ring and a half mode toward the perimeter of the guitar (and in my opinion, that is a good thing and worth pursuing........moves the node lines in the same direction as adding mass to the rim/lining as Trevor Gore proposes in his book). Adding bridge weight lowers the main frequency of the top and reducing bridge weight raises the frequency. a lot of wood choices are appropriate for the bridge.

On stiffness, the shape of the bridge affects this as much or more than the properties of the wood. If you are using a minimalist approach as far as size goes, then the stiffness of the wood selected comes into play more.

Dampening must affect the tone......but I sure dont have the experience to say how much or exactly what affect it has. Does it affect sustain? I don't know.

[tippie53]

Osage is pretty good but it takes getting used to. Maple ?? There are so many genus of maple so not all maple would work, Often maple and basswood were used then "ebonized".
For a bridge to work ,there is a balance of density and toughness. I am sure others will post on this subject. BRW was often considered one of the best materials for bridges. I would think you want to look at the wood charts , as the biggest down side would be the dampening effect of the wood selected.

[B. Howard]

good energy transfer to the X brace

I think that's it right there. If you have good coupling to the structure then I don't' think the type of wood matters as much.

[Darryl Young]

RD, google Trevor Gore and take a look at his bridges. Ultra light on both classical and steel string instruments. He uses carbon fiber and lightweight woods. The CF adds stiffness to the lightweight wood and lets the bridge overall be much lighter.

Mario Proulx likes his bridges no heavier than 20g.......roughly half the weight of a standard ebony belly bridge. He never uses a belly to save weight. It is an interesting area to explore.

I've heard some old Martin Folks that discuss the depth of the saddle slot and it's affect on tone. Supposedly a shallower slot is more "wood tone" and a deeper slot gives more "bone tone" (take it for what it's worth). I've read John Arnold say that on old Martins the slot is deeper on one end than the other. IIRC, more wood tone on the bass end and more bone tone on the treble end of the slot (deeper).

Edit: I googled it and here is a little info:
http://www.goreguitars.com.au/main/page ... idges.html

[tippie53]

On a martin bridge the slot is actually made the same point from the bottom , the radius on the bridge is at a slight cant from the treble to the base so the bridge is thicker on the bass side.
Alan Carruth did a whole thing about bridges , and what it comes down to is physics. There are mass , density , and weight. Getting the right combination is the key. Lighter can be better as long as the device can handle the stress.
I do like pyramid bridges but will use traditional designs like the belly bridge.
There are so many things that can influence this part , the bridge , string height , position of the ball ends in relation to the saddle , the foot print of the bridge and the centroid of the bridge and where the centroid of the force is. Also the bridge plate ,and even the saddle and pin material.
there is no one single thing but a myriad of things.

[Darryl Young]

John, best I recall the variable saddle depth slot was only on old Martins (like pre-war for example......but I don't recall the exact cut-off time). Have you ever noticed the depth of the saddle varying on really old Martins? That is what I remember John Arnold stating in a post on the OLF. Might be another authentic feature you can add to your pre-war copies.

I'll see if I can find that post on the OLF.

Edit: I found it. It was on the Unofficial Martin Guitar Forum, not the OLF. Also, John Arnold was discussing a "through saddle" so I'm unsure if this applieas to all saddles on old Martins or just the "through slotted saddles". Here is the quote:

"One thing that is rarely mentioned with the original through slots is that the bottom of the slot is not parallel with the bottom of the bridge. The slot is shallower on the bass side so that the total saddle height is roughly the same on both ends. In Mario's terms, that produces more 'wood' on the bass strings."

And here is the link to the post so you can read the quote in context:
http://theunofficialmartinguitarforum.y ... ply-952731