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Thread: I Want To Lower Bridge

  1. #1

    Question I Want To Lower Bridge

    I want to lower this bridge, but not sure if I should simply replace it. It appears to be neoprene or plastic of some sort, but not really sure how to get it done. I could sand it down, but the wings(looks like wings to me) will become very thin.

    I would appreciate suggestions.

    Thanks:
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  2. #2

    Default Re: I Want To Lower Bridge

    Are you sure it doesn't need a neck reset, rather than a lower bridge?

  3. #3

    Default Re: I Want To Lower Bridge

    Even if it needed a neck reset it is not in the cards for this one. I read several old posts here and saw one in particular that describes this mandolin: "Meant to be played and the thrown in the dumpster..."

    I've been patching and glueing small repairs just as a way to learn lite repair, but I would never tackle a neck reset; even for practice.

    Using a straight-edge it looks like the neck is level, but maybe that is what I would see even if it needed repairs? Not sure.

    I have several pieces of ebony and other very hard woods in the workshop that I could use to build a new bridge. I know with enough time and patience it could be done so that is an alternative to lowering the current one.

    Thanks.

  4. #4

    Default Re: I Want To Lower Bridge

    How much does it need to come down? There is not a whole lot of foot left on that one. I would most likely go ahead and take some more off that bridge unless you want to change the string spacing or something.
    Robert Fear
    http://www.folkmusician.com

    "Education is when you read the fine print; experience is what you get when you don't.
    " - Pete Seeger

  5. #5

    Default Re: I Want To Lower Bridge

    Robert, Just a guess-ti-mate I will say about 1/16"+ maybe as much as an 1/8". I can get the calipers and get down to the mm if it's important, but in my amateur judgement I think there is not enough bridge left to drop it much. Looks like it has been worked on n the past.

    I guess it could be adjusted from the top of the bridge, but would need to be recut for strings.


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  6. #6
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    Default Re: I Want To Lower Bridge

    Don't try and cut the slots deeper. Unless your really want to.

    Get some 250 grit sandpaper and take off a pencil line. try it. take off some more. about 1/32 " at a time.

    When you're sure you've got what you want, buy an ebony bridge and do a duplicate.

    Ebony is the best. The rest is an experiment.

    Takes time.

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  8. #7
    Registered User jim simpson's Avatar
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    Default Re: I Want To Lower Bridge

    It looks like you won't end up with much string tension at such a low bridge height. Who knows what kind of neck joint this instrument has? A neck reset isn't for the faint of heart but learning on a less expensive instrument is a good way to get your feet wet.
    Old Hometown, Cabin Fever String Band

  9. #8

    Default Re: I Want To Lower Bridge

    Quote Originally Posted by epicentre View Post
    Don't try and cut the slots deeper. Unless your really want to.

    Get some 250 grit sandpaper and take off a pencil line. try it. take off some more. about 1/32 " at a time.

    When you're sure you've got what you want, buy an ebony bridge and do a duplicate.

    Ebony is the best. The rest is an experiment.

    Takes time.
    This sounds like it meets with my skill level. I can use sandpaper. However, as a long-time woodworker I think I will try to make my own bridge from an ebony scrap I have in the shop.

    Jim, in the next reply said something that caught my attention..."It looks like you won't end up with much string tension at such a low bridge height..." Since this is new to me I am not sure I understand why lowering the bridge will not allow string tension.

    Thanks.

  10. #9
    Celtic Bard michaelpthompson's Avatar
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    Default Re: I Want To Lower Bridge

    One thing to check is whether the brige is really the problem, or the nut. Before making changes, be sure you're on the right track.

    If you do want to make a bridge, there' some great information on Red Henry's site, including diagrams and instructions.

  11. #10
    Registered User jim simpson's Avatar
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    Default Re: I Want To Lower Bridge

    This may help explain the relationship of string/bridge height and string tension:

    From a 1995 Guild of American Luthiers lecture by A.Lawrence Smart, luthuer.

    Note: some of the ideas and data contained herein are out of date. Lawrence Smart's designs, skills and construction techniques have continued to evolve since this lecture was originally presented.

    "Since the soundboard of an archtop instrument is driven by downward pressure on the bridge, we need to consider just how the breakover angle is going to effect volume, response, and sustain. Simply put, the greater (more acute) the string angle over the bridge, the greater the downward force and the greater the volume and quicker the response of the top. Less (more obtuse) breakover angle creates more sustain since less of the string's energy is lost driving the top. A greater angle will produce a more percussive tone, while less angle will produce more overtones and "warm up" the tone a bit. A greater break angle will also create more string tension, which may or may not be desirable for a particular player.

    The pitch of the neck and arch of the top are the determining factors in the break angle. Since a bridge wants to be within a certain height range, all three of these factors need to be considered together. If I want to build an instrument with the greatest sustain I can achieve, I might reduce the neck angle, which by itself would make the bridge too low. This can be adjusted by lengthening the heel of the neck, thus increasing the height of the fingerboard above the top, and giving more space between the top and the raised fingerboard"
    Old Hometown, Cabin Fever String Band

  12. #11

    Default Re: I Want To Lower Bridge

    Quote Originally Posted by jim simpson View Post
    This may help explain the relationship of string/bridge height and string tension:

    From a 1995 Guild of American Luthiers lecture by A.Lawrence Smart, luthuer.

    Note: some of the ideas and data contained herein are out of date. Lawrence Smart's designs, skills and construction techniques have continued to evolve since this lecture was originally presented.

    "Since the soundboard of an archtop instrument is driven by downward pressure on the bridge, we need to consider just how the breakover angle is going to effect volume, response, and sustain. Simply put, the greater (more acute) the string angle over the bridge, the greater the downward force and the greater the volume and quicker the response of the top. Less (more obtuse) breakover angle creates more sustain since less of the string's energy is lost driving the top. A greater angle will produce a more percussive tone, while less angle will produce more overtones and "warm up" the tone a bit. A greater break angle will also create more string tension, which may or may not be desirable for a particular player.

    The pitch of the neck and arch of the top are the determining factors in the break angle. Since a bridge wants to be within a certain height range, all three of these factors need to be considered together. If I want to build an instrument with the greatest sustain I can achieve, I might reduce the neck angle, which by itself would make the bridge too low. This can be adjusted by lengthening the heel of the neck, thus increasing the height of the fingerboard above the top, and giving more space between the top and the raised fingerboard"
    Wow, I actually understand most of what was said there.

    The bridge I am working on has been moved back about 1/2" which may have been an effort to increase the string angle, thus increasing the volume. Just a guess, but it sounds possible.

    This link: Red Henry's site will be helpful when I build a new bridge.

  13. #12
    Registered User Bill Snyder's Avatar
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    Default Re: I Want To Lower Bridge

    Texas, looking at you 2nd photo I have my doubts that you will be able to lower the bridge enough to take care of it. With the bridge off of the instrument how is the string height? Does it hit the fretboard or is it still a bit high?
    If it is still a bit high then lowering the bridge won't fix your problem.
    Bill Snyder

  14. #13

    Default Re: I Want To Lower Bridge

    Quote Originally Posted by Bill Snyder View Post
    Texas, looking at you 2nd photo I have my doubts that you will be able to lower the bridge enough to take care of it. With the bridge off of the instrument how is the string height? Does it hit the fretboard or is it still a bit high?
    If it is still a bit high then lowering the bridge won't fix your problem.
    Bill, I'll give it a try tomorrow and let you know.

    Thanks.

  15. #14
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    Default Re: I Want To Lower Bridge

    "The bridge I am working on has been moved back about 1/2" which may have been an effort to increase the string angle, thus increasing the volume. Just a guess, but it sounds possible."

    If the bridge has been moved "back" it is impossible for the instrument to play or sound right. It appears from the photos that the neck has already been futzed with by someone who didn't know what they were doing. If the neck is straight, or very close to straight you can probably fix the action by changing the angle of the neck... But nothing else is going to work, so if you are not willing to change the neck to body angle your situation is hopeless.

    Give it a try. You have nothing to lose and everything to gain. frets.com has plenty of information on changing neck angle, if I recall. It will be a very interesting learning experience. You simply have to do it if you want a playable instrument.
    Bart McNeil

  16. #15

    Default Re: I Want To Lower Bridge

    Here is one more picture that is telling. Looks like a slight bow in the neck. Considering this is a cheap student—old—Mandolin I am going to remove the bridge and sand it until I lower a small amount. No doubt this old guy has been played hard and maybe it's time for retirement; maybe a nice wall hanger.
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  17. #16
    Registered User Bill Snyder's Avatar
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    Default Re: I Want To Lower Bridge

    Photos can be deceiving, but looking at that one I think the only way to make this mandolin playable is a neck reset.
    Bill Snyder

  18. #17

    Default Re: I Want To Lower Bridge

    The bridge is taller than I initially thought from the first photos, but I also think you will have trouble getting it down low enough.

    At this point, make sure the nut is as low as possible as Michael suggests, then make a very low bridge and call it good.

    Play it for a while, and then consider the neck reset.
    Robert Fear
    http://www.folkmusician.com

    "Education is when you read the fine print; experience is what you get when you don't.
    " - Pete Seeger

  19. #18
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    Default Re: I Want To Lower Bridge

    The photo of the end of the fretboard suggests that it will be impossible to get a decent player out of this instrument, The neck is certaintly bent or out of position and needs a reset. One less drastic solution you might try if the neck is only slightly bent is to remove the fretboard, replace it with a maple 1/8 inch maple veneer glued to the neck surface and shaped to match the fretboard. You may need two veneer sheets for a more dramatic bend. Once glued in place flatten the new neck by sanding against a perfectly flat surface with sand paper glued or taped to it. While sanding press firmly on the neck with emphasis on the headstock end of the neck. With very careful sanding you should be able to end up with a flat neck under the fretboard. once you have sanded the neck flat and installed the fretboard you should be able to install a decent hight bridge and have decent action and intonation up the neck. I have done this and it really works quite well eliminating the problem of a mildly bent neck.

    The beauty of this system is that it is reversable if it doesn't work, since you are taking off no original wood from the neck. Of course a new, higher bridge will be necessary.

    If you don't feel comfortable with wood working I wouldn't try this... but if you are a wood worker it is not difficult. the most difficult part is sanding the new neck surface perfectly flat to accept the fretboard and create exactly the angle you want.

    However if the problem is the neck pulling away from the body of the instrument then a neck reset is the only solution.

    of course I wouldn't recommend this on a valuable instrument but it may keep a low cost player from becoming a wall hanger.
    Bart McNeil

  20. #19

    Default Re: I Want To Lower Bridge

    Quote Originally Posted by bmac View Post
    The photo of the end of the fretboard suggests that it will be impossible to get a decent player out of this instrument, The neck is certaintly bent or out of position and needs a reset. One less drastic solution you might try if the neck is only slightly bent is to remove the fretboard, replace it with a maple 1/8 inch maple veneer glued to the neck surface and shaped to match the fretboard. You may need two veneer sheets for a more dramatic bend. Once glued in place flatten the new neck by sanding against a perfectly flat surface with sand paper glued or taped to it. While sanding press firmly on the neck with emphasis on the headstock end of the neck. With very careful sanding you should be able to end up with a flat neck under the fretboard. once you have sanded the neck flat and installed the fretboard you should be able to install a decent hight bridge and have decent action and intonation up the neck. I have done this and it really works quite well eliminating the problem of a mildly bent neck.

    The beauty of this system is that it is reversable if it doesn't work, since you are taking off no original wood from the neck. Of course a new, higher bridge will be necessary.

    If you don't feel comfortable with wood working I wouldn't try this... but if you are a wood worker it is not difficult. the most difficult part is sanding the new neck surface perfectly flat to accept the fretboard and create exactly the angle you want.

    However if the problem is the neck pulling away from the body of the instrument then a neck reset is the only solution.

    of course I wouldn't recommend this on a valuable instrument but it may keep a low cost player from becoming a wall hanger.
    Bart, I'm a long-time woodworker and I have a flat surface that is perfectly flat that I use for this purpose, so attaching a new fretboard and getting it flat will be a fairly easy task. But, do I want to do this with this mandolin—I'm not sure.

    Since I am learning repair I may consider a neck reset as a practice to learn task. This is the perfect instrument to practice with so I think of all the repairs suggested the reset will give me practice, although more that I intended at this stage.

    Thanks.

    AL Masters (Texas)

  21. #20
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    Default Re: I Want To Lower Bridge

    My only thought is that unless you can see that the neck joint has changed through movement of some sort, then you almost certainly don't need a neck reset. If you do a neck reset on the instrument when the problem is really a bent neck then you have gained nothing by the reset. The bent neck will still make good playing impossible.

    In my opinion you cannot solve your problem by futzing with the bridge.

    Unless you have visual evidence of a need for a neck reset then doing one is pointless.

    You know you have a bent neck and if you don't do something about that you will not solve the playing problem.

    The neck is a solvable problem. And certainly one of the common faults of old instruments. Once you can cure a bent neck you can bring all sorts of presently unusable mandolins back to life. They are quite cheap on ebay because they are unplayable and most owners don't want to pay for repair. But it is doable. Once you have learned to do it you will have opened up all sorts of posibilities.

    The neat thing is that you can bring almost hopeless instruments back to life and give them another century of use.
    Bart McNeil

  22. #21
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    Default Re: I Want To Lower Bridge

    Just a purely amateur opinion but since nobody has stated it specifically:

    While the bridge-to-nut view (photo 3) does show an amount of neck curvature/relief, possibly more than expected, centered around the 5th to 7th fret, it also shows a drop-off or back-bow right at the body joint, with the body frets then ramping down away from the strings (per photo 2). That could indicate that the neck has already been re-set, but that add'l relief & bending has counteracted the effort. Straightening and strengthening the neck, as suggested above, seems to be what's needed.
    Last edited by EdHanrahan; Aug-12-2012 at 11:54am.
    - Ed

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