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 ARCHIVED TOPIC: DIY banjo bridge shape.


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Calv - Posted - 04/30/2013:  04:45:51


I'm going to be experimenting with different bridges over the next few weeks to see what sounds i can get from each, however i was also thinking about making my own.



I have all kinds of pieces of wood in the shed, and i'm not too bad when it comes to crafting something from wood, however it's the shape i'm worried about.



I only have basic saws and files, which is fine, but will make the job a little longer. Does a bridge have to have the arches on it like they do normally? Is there an acoustic reason for this?



I'll take a look on the net for any other ideas, but i welcome any advice from those who know here too.



Thanks,



Calv.


Fathand - Posted - 04/30/2013:  05:10:36


By arches, do you meant the cut outs between the feet? These can be started with a drill and then final shaped with files etc.


Pittsburghin - Posted - 04/30/2013:  05:17:09


Google "PETE SEEGER BANJO BRIDGE"

rudy - Posted - 04/30/2013:  05:25:18


quote:

Originally posted by Calv

I'm going to be experimenting with different bridges over the next few weeks to see what sounds i can get from each, however i was also thinking about making my own.



I have all kinds of pieces of wood in the shed, and i'm not too bad when it comes to crafting something from wood, however it's the shape i'm worried about.



I only have basic saws and files, which is fine, but will make the job a little longer.



Does a bridge have to have the arches on it like they do normally? Is there an acoustic reason for this?



I'll take a look on the net for any other ideas, but i welcome any advice from those who know here too.



Thanks,



Calv.






You can do anything you like, but it will all effect the sound produced. The bridge arches are designed to maximize sound transmission to the head while at the same time reducing bridge mass (important) in a way that minimizes the effect on sound.  The other important point is to do all of this in a way that won't weaken the bridge in it's long dimension.  You want the bridge to be able to resist any tendancy to flex or even break between the arches.  Here's a pattern that works well if you need one.




xnavyguy - Posted - 04/30/2013:  07:08:58


Some will say that your choice of materials will have a lot of effect on how well a bridge performs.  Certainly, you can't go wrong if you go with a traditional 3 legged Grover style ebony capped maple bridge.



What I've learned in my experimentation with bridges is there are 3 critical elements....total foot contact area, stiffness, & weight.  Too much foot contact area will start to have a muting effect if it becomes too large.  Too much weight will reduce focus & clarity and add unwanted tubbiness and sustain.  Too little weight and notes will become strident & dry.  For my money, bluegrass banjo bridges seem to be at their best in a weight range between 2.0 & 2.2 grams.  Clawhammer players might prefer heavier bridges.  Lack of stiffness in the bridge structure will cut down on the bridge's ability to deliver fast note attack to the head and the rest of the banjo structure.



I've built a lot of real good bridges, using all manner of materials & shapes but some of the best are made of oak or birch plywood, capped with purpleheart which is, to my ears a better choice than ebony for capping bridges.  Ebony is very dense and, while it might handle string abrasion better than purpleheart, it is far inferior in it sound transmission characteristics.



I'm attaching a photo of a plywood bridge that I call Clara Fire.



There are lots of other photos on my homepage that might give you some ideas of a place to start.  Experimenting with bridges is a lot of fun and you can learn a lot from it.



Good Luck,



Jerry



Edited by - xnavyguy on 04/30/2013 07:12:04



Clara Fire Oak Plywood Bridge

   

Calv - Posted - 04/30/2013:  08:56:06


Funny you should mention oak......i still have some of the really old oak from the lump i made my truss rod cover from the other day.



If only to have a go at the basic shape, i spent some time this afternoon giving it a go......don't laugh..... :)





I made it lower, as the high action is really bothering me at the moment, and yes i know it's not capped, but rough as it may be...it works! big



I'd say it was a little more mellow than the one that came with the banjo, but i just enjoyed tinkering around with it. At least i know that worst comes to the worst, i could knock myself up a spare one in an hour or so. Would be hard to find a bridge round here made from 400 year old oak.



I will look into the whole bridge business properly, and i appreciate your replies, the info is most helpful.



Calv.


MOUNTAIN GOAT - Posted - 04/30/2013:  09:25:11


There is a lot to making a bridge, and a million combinations. The weight needs to be around 2 to 2.2 grams. How stiff do you make the top? How large are the feet? The height? The width? String spacing? Compensated or not? What kind of wood? What kind of wood top? I too like purplehaert for the top. I have also used Wenge for the top. I have made about half a dozen bridges, all compensated, and all sound the same. They were all the same weight, but had different structural design. I also tried putting the weight higher and lower. A few were a little higher just to get the action right where I wanted it. There are endless possibilities with this contraption.

grm405 - Posted - 04/30/2013:  11:23:08


Having made around 300 bridges in the past year, here are my thoughts.



1.  Weight depends on the design.  For a standard 3 footed design the 2.2 g figure is OK.  For a stiffer design (ie. 2 footed with a truss center) that will produce a shrill, thin sound.  You really need something in the 2.4 g range or greater.



2.  Top wood has a small effect on sound, not large, and the main factor is durability.  I like African Blackwood the best, as it is slightly oily and strings slide over it easily.  It also seems to give a slightly sweeter sound.  Although tables rate it softer than ebony, it files like it is harder.  



Ebony is my second most favorite wood.  Don't like Rosewood as it is too soft.  Desert Ironwood (from the Arizona/Mexico area) is very hard and brightens up the sound.  Purpleheart is stringy and splits easily.  Other woods I have tried don't seem to have any special qualities that make them better than or as good as the ones mentioned.



I keep the top mass pretty small, no more than .090 in height.  Haven't tried a lot of testing on this, but "think" it sounds better.  Otherwise the effect of the top is magnified.



3.   Grain direction is critical.  I try to keep the grain within the area of perpendicular to either face of the bridge (I sand mine to a 9 degree taper).  If it gets too far off the sound mellows noticably.  I end up discarding a lot of blanks, any where the grain is more than about 10 degrees out of the desired range.



4.  Can't beat good old Maple.  Line density has a minor effect and varies dramatically over a single board sometimes.  Doesn't seem to relate to any change in sound though.



No other wood that I have tried works as well.  Anything you gain in one area you lose in another (clarity, sustain, "pop", etc.)  Density is a partial determinant of how the Maple will sound.  High density gives greater sustain and clarity, low density greater "pop".  However in the middle range of measurements things are not predictable.



My one piece of submerged maple worked very well.  All my banjos now sport bridges made of it.  A excellent, balanced sound with a good compromise of clarity and sustain.



All other woods don't work as well as maple, and I have tried a bunch.



I like the 2-foot design as it is very stiff and efficient.  Makes a louder bridge as it doesn't flex.



YMMV.



Gerry  



 




Padauk, Zebrawood and Teak bridges and one of my current 2-footed designs



Current Bridges 6/6/12

Calv - Posted - 04/30/2013:  13:36:04


Wow, so much info!



I'm going to print this off and take it to bed tonight, give it a good thorough read through.



I think my rushed DIY job this afternoon kind of pales into insignificance lol.



Thanks again.



Calv.


steve davis - Posted - 04/30/2013:  14:35:44


Bridges seem to like a non-direct path to the head(or fiddle top).



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