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Thread: Building Bridges

  1. #1
    I really look like that soliver's Avatar
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    Default Building Bridges

    No, I'm not referring to mending broken relationships... thats a different kind of forum...

    I have been working on my second mandolin build and am considering building my own adjustable bridge for this one. For my first build, I ordered a CA bridge, which of course, I am pleased with. But that was rather costly and I'd like to ba able to build my own for future projects, particularly since building mandolins seems like something I'll be doing a lot more of. I found some plans for a basic run of the mill adjustable bridge here, (http://www.lutherie.net/mandolin.bridge.schematic1.gif) so I have a guide to start from, but I do have some questions.

    1. This will be for a flattop, so obviously, I will be adjusting the foot to fit that application; anything I need to be attentive to there? Are there better plans to follow for a flattop application?

    2. This mando will be a black top with cream binding. Being a fan of contrast, I thought maple would look good against the black and compliment the cream binding. Is a good quality hard maple an acceptible bridge material, or do I need to stick to harder woods such as Ebony or Rosewood?

    3. Anyone know where I can get gold hardware for the thumbwheel?

    4. Please let me know if you have any useful tips, tricks or resources!

    Thanks in advance!
    aka: Spencer
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  2. #2
    Moderator MikeEdgerton's Avatar
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    Default Re: Building Bridges

    Bill James sells the wheels on his website.

    http://www.axinc.net/Bridges_Pins_Bridge_Parts_s/61.htm
    "Bargain instruments are no bargains if you can't play them". These are the words of J. Garber.

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  4. #3
    Mandolin tragic Graham McDonald's Avatar
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    Default Re: Building Bridges

    One thing to think about is the need for an adjustable bridge at all. The standard Gibson style adjustable bridge is around 18mm /3/4" high and exerts around 50lb downwards pressure (from memory) on the soundboard . This is fine on a carved soundboard, but with a flat soundboard the height of this bridges puts a lot of unnecessary loading on the soundboard and the bracing has to off-set this stress as well as the longitudinal compressional forces from the string tension on the tailpiece. A lower neck angle and a lower bridge means less downwards force on the soundboard so you can make it lighter. The idea of an adjustable bridge is great for a production environment such as Gibson in the 1920s where there would inevitably be small variations in neck height and angle and an adjustable bridge could save time and money in the set-up room. I suspect most people rarely, if ever, change the height of their mandolin bridges. Guitar saddles tend only to be replaced or altered if there is a structural problem with the guitar.

    If you need height adjustment it is simple to make a solid bridge with a removable saddle in a slot in the top. A saddle can be easily replaced, lowered or shimmed. For a flat soundboard, a 15' radius dome on the soundboard kicks the neck back a degree or two and a 3/16" fretboard gives a bridge height of around 12mm/1/2". You can make a few bridges quite simply out of ebony, rosewood or hard maple. The maple bridge bridge will sound a little different. Not necessarily better or worse, but different. It would be worthwhile checking out the Red Henry style of solid bridge as well. You might be surprised by which bridge material best suits your mandolin.

    Cheers,

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  6. #4
    I really look like that soliver's Avatar
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    Default Re: Building Bridges

    Thanks Graham!... your book was a great guide through the first build. I had not given much consideration to a fixed bridge. That may be the way to go.

    I'd still love input from others!

    And just for a frame of reference, my previous build was a flat top with a 10' radius on the induced arch. This one is a bit more arched at a 7' radius.

    Thanks Mike for the link, I checked out Bill's website but was somewhat aghast at the shipping cost.
    aka: Spencer
    Silverangel Econo A #429
    Jacobson Nautilus Oval Hole Prototype
    Soliver #001 Flattop Pancake, Soliver #002 almost there...

    Soliver Hand Crafted Mandolin Armrests
    Check them out here

    "You can never cross the ocean unless you have the courage
    to lose sight of the shore, ...and also a boat with no holes in it. -anonymous

  7. #5

    Default Re: Building Bridges

    Don't use thumbwheels, they are super annoying. It's like "hey, let's make a nut that you CAN'T use a wrench on, that'll be great".
    I'd use a 8-32 set screw and brass hex nut, and then a 1/4" mini wrench which will allow you to adjust it under string tension. Looks nicer too, IMHO.
    Or M3 and a 6mm mini wrench.
    Maple makes a great bridge! I would use any piece of nicely quartered rock maple, ideally without figure. But I'd made some nice birdseye maple bridges that sounded just like they should, too.

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  9. #6
    Registered User Charles E.'s Avatar
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    Default Re: Building Bridges

    I wonder if persimmon would be a good choice too. It is the "white Ebony" after all and should be available.
    Charley

    A bunch of stuff with four strings

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  11. #7
    Registered User tree's Avatar
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    Default Re: Building Bridges

    Persimmon worked for me - I made a bridge out of it (the Red Henry design with the holes) and it sounded great on my '21 A2. But seasonal increases and decreases in humidity necessitated an adjustable bridge for me.
    Clark Beavans

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  13. #8
    Barn Cat Mandolins Bob Clark's Avatar
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    Default Re: Building Bridges

    Hi Spencer,

    I make my own bridges for my flat tops. The only adjustable bridges I have had a slot in the base accepts the saddle. This allows me to shim the saddle if necessary, or have a taller saddle. I prefer my one piece bridges to this design. Still, this design was useful for experimenting with different compensations.

    I have made one piece bridges from maple, cherry and black walnut. All three have been acceptable, but to my ears maple is slightly better. I do use cherry or black walnut if they looked good on a particular instrument. My favorite bridge thus far has been a maple bridge with a bone saddle epoxied to it. I have this on I my daily player but I do a lot of experimentation on this instrument (poor thing), so it changes all the time.

    I hope this is helpful. Let me know if you have any questions for me.

    Best wishes,

    Bob
    Purr more, hiss less. Barn Cat Mandolins Photo Album

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  15. #9
    Registered User Tom Haywood's Avatar
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    Default Re: Building Bridges

    My first "campfire" build was a modification of Terry's (Chrystal Forest Mandolins) plan. I added a degree or two to the neck angle and induced a 28 foot arch in the top (if I remember that correctly). The bridge location resulted in just over a half inch saddle height - just about what his plan would produce (according to my measurements). It seemed like a good opportunity to learn how to build those adjustable bridges, so I ordered posts and thumb wheels and found a couple of good pieces of ebony. Out of impatience, I made a one piece bridge with some Bradford pear wood from the front yard that I had used for some previous bridges. It took about 10 minutes to cut it out, sand it into shape on the belt station, fit it to the top, and put the string grooves in it. It sounded great, and I never did make the 2 piece bridge. I did the same style bridge for my suitcase mandolin. After a year, I lowered the action by sanding a little off it's top. Took about 2 minutes. There's not enough movement on those two mandolins to need an adjustable bridge.
    Tom

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  17. #10
    I really look like that soliver's Avatar
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    Default Re: Building Bridges

    Thanks Tom, I LOVE Bradford pear, it is a beautiful wood! I made a bench out of it for my daughter before she was born. She's 15 now and she and her sisters still use it.

    Looks like I'll be making a red Henry style bridge for this one. I spent all evening yesterday sorting out the tenon on the neck, fitting it just right in the neck block. 3 piece neck with walnut and a strip of redbud.
    aka: Spencer
    Silverangel Econo A #429
    Jacobson Nautilus Oval Hole Prototype
    Soliver #001 Flattop Pancake, Soliver #002 almost there...

    Soliver Hand Crafted Mandolin Armrests
    Check them out here

    "You can never cross the ocean unless you have the courage
    to lose sight of the shore, ...and also a boat with no holes in it. -anonymous

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