xnavyguy - Posted - 02/11/2010:  20:21:55

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I've noticed that, occasionally, the subject of Pete Seeger's banjo bridge comes up. As far as I know, only two of these were ever built by Stu Jamieson. One went on his banjo and the other one went on Pete's and is still on it. On the threads about Pete's bridge, I've offered to and have sent the plans to several hangouters who may or may not have followed through with plans to build their own. I've decided, out of curiosity, more than anything else, to build one using Stu's plans.

Today I picked up some scrap printed circuit board material and will cut it out tomorrow and build one that I will test to see how it performs. My friend, a fellow picker and retired Lucent engineer/scientist, who gave me the scrap PC board material has offered, if I give him sample components, to use his computer controlled router to cut some more. I thought it was a nice gesture on his part to make the offer.

I thought I would take a poll and, mind you I'm not making any promises, to see if there was any interest in the banjo community for anyone else to have a bridge like Pete's to go on their banjo. I figure, if there is enough interest, I might be able to make a limited production run and make the bridges available at a nominal cost either in kit form that could be assembled or as complete bridges. If anyone is interested, send me a PM via the hangout, detailing your string spacing/height specs. and I will put your request into a separate folder with any others that I receive. After I have finished building and testing the prototype I am building and evaluate the demand if any, I will make a decision on whether or not to pursue this any further.

I will post the results of my tests and my decision on this thread.

This is the bridge design I am talking about:

Bill Rogers - Posted - 02/11/2010:  21:01:54

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I'd be interested. But I've heard that Pete's bridge is made of the old circuit board (phenolic resin??) that you can no longer get, and that the current stuff is different and the dust is poisonous. That said, I'm sending a PM.

Bart Veerman - Posted - 02/11/2010:  21:29:52

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Read all about it in the January edition of Banjo Newsletter or wait till the end of the month when I'll post the entire article on my website:



Bart.

devoall - Posted - 02/11/2010:  21:34:42

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I read Bart's article in jan issue of BNL and it was very informative and had good pictures to work from, for anyone wanting to attempt this. Good work Bart.

mastertone250 - Posted - 02/11/2010:  22:31:39

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Xnavyguy, my dads the District Technology Manger at the board of education, hes got a masters in computer tech. He said the dust from the "Green" Pc board material is very VERY toxic. Can kill you, so please try to find an old OLD computer to cut one out of or Wear a GOOD dust mask. Good luck and be careful.

eMike - Posted - 02/12/2010:  00:03:59

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Looks like you'd need a mechanical engineer and apparently a hazmat team to change the strings. How is this supposed to help the sound of the banjo?

xnavyguy - Posted - 02/12/2010:  06:13:17

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quote:

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Originally posted by eMike

Looks like you'd need a mechanical engineer and apparently a hazmat team to change the strings. How is this supposed to help the sound of the banjo?

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The whole idea of this bridge is to drive the head over a larger area, with less mass & contact surface area. I believe the design premise was that this bridge excites the head in a manner much like the head wants to vibrate on its own. If that is true, then one could expect quite a bit more sound output, with a given picking input, using this style bridge.

mike gregory - Posted - 02/12/2010:  06:22:39

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Bart: I notice that yours is on what certainly apears to be a FRAMUS banjo, like
<-----that one.
Am waiting to see your end-of-Feb posting.

Mastertone250: Thanks for the warning that the dust is poisonous.

Xnavyguy:I'd like a bridge of that shape, if one were available without the doom factor.

xnavyguy - Posted - 02/12/2010:  06:23:55

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quote:

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Originally posted by mastertone250

Xnavyguy, my dads the District Technology Manger at the board of education, hes got a masters in computer tech. He said the dust from the "Green" Pc board material is very VERY toxic. Can kill you, so please try to find an old OLD computer to cut one out of or Wear a GOOD dust mask. Good luck and be careful.

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David,
Thanks for the words of caution. Sometimes we forget about the many hazards that are present in even the simplest of tasks. I always wear a mask or respirator anytime I am working with this stuff and when working with some of the very toxic hardwoods that I used in some of my experimental bridges.

xnavyguy - Posted - 02/12/2010:  06:25:34

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quote:

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Originally posted by Bart Veerman

Read all about it in the January edition of Banjo Newsletter or wait till the end of the month when I'll post the entire article on my website:


Bart.

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Nice bridge Bart. Looks like your usual fine craftsmanship went into it's construction.

Jerry

Bart Veerman - Posted - 02/12/2010:  07:05:28

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It was a really cool project to do up this thing and you should really get your copy of Banjo Newsletter (they really deserve anyone's business!!!). I can't really talk about the article because of exclusivity until March 1.
Having said that, if you've ever wondered where/how Pete Seeger got that unexplainable clarity and driving tone - wonder no more. As some of you may know I'm a bridge maker and after many years of futzen' around with bridges I don't impress easily. This crazy thing though, it totally blew me away!!!
Anyhoo, like I said, I'll post the article unedited, unshortened, on banjobridge.com on March 1.
Oh, and Maestro Mike, duh, what else

Bart.

mainejohn - Posted - 02/12/2010:  07:48:18

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Count me in as an interested party. especially if it would improve the volume and add to the authenticity of my home-made "copy". PM sent.

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Edited by - mainejohn on 02/12/2010 07:49:30

TTreppa - Posted - 02/12/2010:  08:10:38

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Since the circuit board is toxic, how about making the bridge out of hard maple with an ebony cap? The purpose is to get a good tone and this is achieved by the transfer of sound from the strings to the head of the banjo.
Just a thought. If it works great, if not try, try, try something else - not toxic!
Terry Treppa

dickinnorwich - Posted - 02/12/2010:  08:21:36

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Sure, count me in, too
As an old bridge builder (emphasis on old), I'm always on the lookout for another good idea.
I recall reading something about this bridge a few years ago. Of course, I can't recall the source but I do remember speaking to a banjo-playing friend about it who works in the electronics end of the defense industry but he wasn't able to get any of the circuit board material. In retrospect, it's probably a good thing because I wasn't aware of the requirement for a resident Haz Mat team to be on site at all times.

xnavyguy - Posted - 02/12/2010:  10:30:29

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A little progress report here and some of my thoughts so far. I had originally planned to glue this thing together with JB Weld but decided to go with clear epoxy to keep it from looking so ugly. Mine's not as pretty as Bart's but it should come out looking OK when I finish it. I cut the bits a little bigger than the plans so that I would have room to do the final shaping. This is how it looks right now. In it's current state it weighs 4.9 grams:



I have a little better understanding why Stu Jamieson didn't want to build any more that the original 2 that he built. This stuff is NASTY to work with by hand. I trashed 2 saw blades just cutting it out and. I wound up with dust in my hair, in my clothes and, even though I had on a good mask, I probably got some in my lungs. My plans are to finish this prototype and test it. If I think it merits further effort, I will take it to my friend who has the CC circuit board cutter and see if he can measure it and figure out a way to cut out the bits without endangering my health.

My bride just came home with the epoxy so I'm going to go and glue it together.

Later,
Jerry

BrittDLD1 - Posted - 02/12/2010:  11:46:51

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Wasn't Stu Jamieson involved in either some type of physics, or acoustical engineering,
professionally? I seem to remember something like that, though I could easily be
mistaken.

I think it was developed on some acoustical principles -- and not just the mechanics
of keeping Pete's bridge from falling over, when he whammed on it.

I met Stu, once -- at a party for the MIT Banjo Exhibit, back in 1984. Got to inspect HIS
bridge, up-close, and chat with him about it...

Best-
Ed Britt

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Edited by - BrittDLD1 on 02/12/2010 11:47:34

trick420 - Posted - 02/12/2010:  12:07:38

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Jerry,

I design PC boards as part of my living as an electrical engineer. I'm going to take some scrap home this weekend and try my hand at it.

Why did you choose to angle the bridge part at ~45 degreees? Just curious.

As for cutting it. Most Green colored PC boards are typically made from FR4, which is flame-retardant fiberglass reinforced epoxy resin. About the best tool for cutting it is going to be a dremel with a diamond coated fiberglass cutting wheel. You can get the wheels at Harbor Freight for dirt cheap. Saws through like a hot knife through butter. A steel saw blade will experience a very short life up against this material, as I'm sure you've experienced.

PCBs, especially modern ones, aren't THAT toxic. The big issue is with the ultra fine dust particulate getting into your eyes and lungs. Just use due diligence with it. The nasty stuff that used to be common in electronics has been outlawed with the ROHS standards. You could easily just go to an electronics supplier and buy a square of PC board that is coated with copper on each side and use that. Same stuff. Now, I wouldn't use a "used" PC board unless you're sure the solder that was used on it is Lead free. That's where the danger comes in (for me anyway).

Jeff

xnavyguy - Posted - 02/12/2010:  12:57:17

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quote:

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Originally posted by trick420

Jerry,

Why did you choose to angle the bridge part at ~45 degreees? Just curious.

Jeff

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Jeff,
I didn't choose the angle. I cut the bridge parts from some plans that appeared online that were a reprint from the June 1987 issue of Frets magazine. The online source was banjoresource.com which, I believe, is no longer in existence. According to Stu Jamieson's notes, the angle was calculated so that the arm extensions account for 38% of the force exerted on the head by the bridge. Depending on the size of the banjo head and bridge position, the arm length, as I understand it, has to be modified to prevent spurious resonances from occuring. I have a suspicion that a lot of physics went into the design of this bridge.

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Edited by - xnavyguy on 02/12/2010 12:58:39

trick420 - Posted - 02/12/2010:  13:14:02

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Oh, OK thanks. I was just comparing yours against the two at the top of the thread - they both look vertical - is it just the camera angle?

Now all I need to do is get my hands on the plans!

Jeff

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Edited by - trick420 on 02/12/2010 13:15:15

xnavyguy - Posted - 02/12/2010:  14:07:10

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quote:

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Originally posted by trick420

Oh, OK thanks. I was just comparing yours against the two at the top of the thread - they both look vertical - is it just the camera angle?

Now all I need to do is get my hands on the plans!

Jeff

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Probably the camera angle. I measured the one I made and it is tilted forward around 40 degrees as best I can tell. I checked the published drawing and it is about the same. I can't say what the angle is on Bart's bridge. I've heard that the specs. were published in the January BNL article but I don't know if the angle specs. were published.

Bart Veerman - Posted - 02/12/2010:  20:39:36

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quote:

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Originally posted by xnavyguy

[quote][i]
I checked the published drawing and it is about the same. I can't say what the angle is on Bart's bridge. I've heard that the specs. were published in the January BNL article but I don't know if the angle specs. were published.

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The original article in Frets Magazine mentioned you need to experiment as the results vary with each banjo. My angle is "about-this-much," give or take a smidgen but of course, these measurements are subject to change without prior notice
Yes, the results do vary and it took me some while to dial it in just right. Jerry - here's a hint: you're too heavy @ 4.9 grams.
To those who want to experiment please be careful - you'll be playing with nasty stuff from start to finish. Remember the acid is hazmat stuff for sure and you can't just flush the leftovers it needs to be disposed of properly (check with your municipal office).

Bart.

mastertone250 - Posted - 02/12/2010:  20:51:18

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quote:

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Originally posted by xnavyguy

A little progress report here and some of my thoughts so far. I had originally planned to glue this thing together with JB Weld but decided to go with clear epoxy to keep it from looking so ugly. Mine's not as pretty as Bart's but it should come out looking OK when I finish it. I cut the bits a little bigger than the plans so that I would have room to do the final shaping. This is how it looks right now. In it's current state it weighs 4.9 grams:



I have a little better understanding why Stu Jamieson didn't want to build any more that the original 2 that he built. This stuff is NASTY to work with by hand. I trashed 2 saw blades just cutting it out and. I wound up with dust in my hair, in my clothes and, even though I had on a good mask, I probably got some in my lungs. My plans are to finish this prototype and test it. If I think it merits further effort, I will take it to my friend who has the CC circuit board cutter and see if he can measure it and figure out a way to cut out the bits without endangering my health.

My bride just came home with the epoxy so I'm going to go and glue it together.

Later,
Jerry

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Jerry, thats a good job and you lucked out. Thats not the posionus stuff, the toxic stuff is green. Nice job

Basic Strum - Posted - 02/13/2010:  03:42:26

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Count me in. I'd be interested in buying one if you decide to go into production. Bill

xnavyguy - Posted - 02/13/2010:  04:44:23

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I did a bit more codgitating this morning and a bit of piddling. Right now, roughed out, at 4.9 grams, my bridge is too heavy. Seems like Bart's bridge came in around 3.5 grams. I don't have a copy of BNL but it seems like the PCB that Bart used was around .050" in thickness while mine, with the copper peeled off measured .0625". When I cut the bits of my bridge, I intentionally cut them larger than the drawing because I knew I wouldn't be able to make accurate cuts and could always grind them down during the finishing. My target will be to get the weight down to around 3.5 grams to start.

I will be on the lake today racing sailboats but I should be able to get the bridge ready so that my bridge test buddy, Art Horan (Roll Player), and I can put it through it's paces tomorrow. We'll give it a run at full weight but I plan to, gradually drop the weight down, testing along the way, until it is down to around 2.2 grams, which seems to be about right for most "bluegrass" setups, which is the way our test banjo is setup.

Since the glue on this thing is mostly cured, I did a bit of piddling with it this morning. Using a gram scale and calibrated weights, I tried to take some measurements with the thing with a vertical load and unloaded. Unloaded, 20% of the weight is on the front arms and 80% is on the back saddle. As the vertical load increases, the weight starts to shift forward to the arms and got up as high as 30% on the arms and down to 70% on the saddle with a 100 gram weight. I don't have the means to make any measurements at string load levels but I thought it was interesting how the geometry of the design and the tilt angle of the saddle transfers the load to the front arms.

More Later,
Jerry

Edit: I also took an accurate measurement with a digital angle meter and the saddle is tilted 40 degrees forward from vertical, which is about what I measured on the drawing.

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Edited by - xnavyguy on 02/13/2010 04:50:28

Bill Rogers - Posted - 02/13/2010:  15:58:26

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My hat's off to you, Jerry, and Bart and all the others with the skills and technical acumen to make these bridges. My short stint trying to learn violin repair taught me where my limits are--so I buy my bridges.

frianm - Posted - 02/13/2010:  17:01:24

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I like this - sending email - this is fun

xnavyguy - Posted - 02/13/2010:  17:08:10

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quote:

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Originally posted by Bill Rogers

My hat's off to you, Jerry, and Bart and all the others with the skills and technical acumen to make these bridges. My short stint trying to learn violin repair taught me where my limits are--so I buy my bridges.

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Bill, my hat's off to anybody who tries to build one of these things, for sure. Building some of my oddball bridge designs can be a challenge, but this thing borders on being nightmare-ish. Part of that feeling has to do with my lack of the right tools and not really understanding the mechanics of the design.

I finished my prototype and strapped it on my junk parts "OhBeeWon" openback this afternoon. Since I don't have an ear that is that accustomed to openbacks, I'm going to reserve commenting on it until tomorrow when Art is over and we have two sets of trained ears and hands to run it through its paces. Under string load, at least with my prototype, I noticed some strength issues with the PCB material that I used. Part of it might be that I put a few degrees more rake angle in the base than in the original drawing. Hopefully, I will learn enough from all this to be able to teach a machine to do most of the work.

Later,
Jerry

xnavyguy - Posted - 02/15/2010:  10:31:04

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Art came over yesterday and we were able to try out my prototype on two banjos. This is a link to a recording that we made so thay you might be able to get some idea of the difference between my prototype and the bridges that were on the banjos:
banjohangout.org/myhangout/med...archived=
The first two cuts were played on my Oscar Schmidt bottlecap banjo that is fitted with a black Remo Ebony Ambassador 10 mil drum head. Note that Art calls it a "bottleneck" on the recording. The second 2 cuts were played on Art's Fender Artist which is fitted with a regular frosted banjo head. Before the test, both banjos were fitted with Dam Hybridges that consisted 60% horizontal grain wood on top and 40% vertical grain wood on the bottom. The Oscar Schmidt banjo bridge was Purpleheart over Maple and the Fender Artist bridge was Bloodwood over Sitka Spruce.

One of the things that concerned me before we started our little test was the fact that when I resized the drawing to make a 5/8" Jamieson bridge, I resized it both horizontally & vertically, making it way wider and way heavier than the original and, at 3.9 grams, heavier even than the one that Bart made for his BNL article. My other mistake was that I put too much rake angle in the saddle. All this made my prototype want to sag in the middle. I re-sized my drawing and, in this image you can see this difference between my prototype and the re-sized drawing:



These are the two banjos that were used to record the audio file linked above. I took these photos while Art was playing. You can see the Shure SM-57 microphone that we used for the recording.



I trust that the recording will give you a feel for the performance of this bridge. We did not notice any excessive sustain with this bridge in spite of it weight. If anything, and it is slight, it is a little weak on the 3rd string because feet on the saddle are too wide. The most profound effect is that while both banjos were fitted with AMB Cryo light gauge strings, the Jamieson style bridge made the banjos sound like they were fitted with much heavier strings, but retaining the right hand response of the lighter strings.

This morning, I took my prototype & the recording over to my friend who has the PC board CC router. He looked at my prototype and listened to the recording. His response was like "no sweat", we can crank these things out very easily. His engineer is going to put the drawing into his CAD system, and they are going to cut some out today because my friend wants to put one on his banjo and take it to his banjo lesson. We're supposed to meet again tomorrow. Hope to have some good news.

Later,
Jerry

Roll Player - Posted - 02/15/2010:  10:58:51

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Just a few things to add here: I was amazed that the 3.9 g. weight produced no muting. The Seeger style bridge reminded me more of a light conventional bridge with fairly heavy strings, even though I use light gauge AMB strings. The overall sound was slightly warmer and the note attack was definitely different, which I think you can hear in the recordings. The Seeger bridge had a slower attack, but then the note took a longer time to decay before finishing with a fairly short sustain. The Dam Hybridge was just the opposite - fast & dramatic note attack, quick decay and longer sustain. Both resulted in good note separation but each in its own way. The volume on the Seeger style bridge was at least as good and I didn't find the legs interfering with my picking -- but, I don't pick that close to the bridge.

Overall, I'd have to say this is a viable bridge design with its own unique sound and characteristics. I had fun testing it out too. By the way, that bottlecap "Oscartone" of Jerry's is an amazing little banjo!

Art

Bart Veerman - Posted - 02/16/2010:  14:10:05

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The two posts above show how & why you cannot judge a bridge, or its design, by weight/mass only.

Anyhoo, I just came across a nice video clip of Pete Seeger himself with a cool show & tell about his bridge:
youtube.com/watch?v=7gkprOVqjwA

Bart.

xnavyguy - Posted - 02/16/2010:  14:18:42

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My friend's engineer just called & told me they had cut bits for two more sample bridges, using their high fangled machine. I'll try to pick them up tomorrow and give them a bit of a test. If things work out, I should be able to get some more made real quickly.

Jerry

Stringbean45 - Posted - 02/16/2010:  21:44:09

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Hey Jerry, and Art,
I really like the deeper sound of the Seeger style bridge, but they sure are going to be hard to make with a belt sander and drill. I think you have done jumped into the space age, 21st century, with this one.
Guess I'll have to go out in the woods, and see if I can find one of them printed circuit trees, to get some boards out of, and try to make one.
Keep on having fun,
Don

xnavyguy - Posted - 02/17/2010:  04:26:41

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quote:

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Originally posted by Stringbean45

Hey Jerry, and Art,
I really like the deeper sound of the Seeger style bridge, but they sure are going to be hard to make with a belt sander and drill. I think you have done jumped into the space age, 21st century, with this one.
Guess I'll have to go out in the woods, and see if I can find one of them printed circuit trees, to get some boards out of, and try to make one.
Keep on having fun,
Don

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Ya' know Don,
In a lot of cases, when making recordings and then converting them to MP3's, it's hard to detect the subtle differences between bridges on a given banjo, because most bridges don't necessarily alter the sound characteristics that much. In the case of my Jamieson bridge prototype, the differences are pretty evident when you compare the recordings. Art did some waveform analysis on the recordings that we made and he was able to confirm that what we were hearing wasn't our imagination.

Now, that could have been because of the huge weight differences between the prototype and the reference bridges. I think the second round prototypes, closer to the "accepted norm" for bridge weight, and nearer to the dimensions specified by the originaly designers, might offer a few more clues to what is happening with this bridge. It's obviously a viable design but it in no way resembles what Earl uses on his banjo so I doubt there would be a lot of interest from the large group of banjo pickers who want to be like Earl, regardless of how it improves (or not) the sound of their banjo. The "headwinds of tradition" are pretty strong when it comes to bluegrass banjos and pretty much blow down anything that deviates from the accepted norm. On the other hand, there are probably a lot of OT/Clawhammer, Plectrum & Tenor players who are more into not so much sounding like anyone else but are into making the best music they can.

Enough of that. The only place I am aware of that has printed circuit trees are right here in Austin, TX. I guess the soil here must be just right for growing them. I did discover that they will certainly eat up normal tools. That's why I feel fortunate to have a friend & fellow banjo student who has laid out the cash to own the right tools and is willing to help me with this little project.

mike gregory - Posted - 02/17/2010:  06:43:15

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Printed circuit tree.........
Printed circuitry.........

Ain't words fun?????

As a former Radio Shack employee, I would suggest that they might also grow near corporate HQ, over by Foat Wuth, which is (by Texas standards) not far from Austin.

I myself have never seen the place, but I imagine it should look like either a big radio, or a big shack.

Stringbean45 - Posted - 02/17/2010:  09:46:13

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Hey Mike,
Nice catch on the word play.
Jerry,
I like the way the Seeger Style Bridge, dampended down some of the highs, on the Bottlecap Banjo, but still left a good tone, and volume, on those notes. Can't wait to see how the lower weight Seeger Bridges will sound.
Hey, if I could get a lard can, with a 2X4, for a neck, to sound good, I'd play it. I've got so accustomed to the Spillway Dam Bridges on my banjos, when I play one with a regular bridge on it, it just seems like something is missing.
Don

mike gregory - Posted - 02/17/2010:  09:53:31

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1x2 stock is a lot closer to an easily playable dimension, unless you're going to profile the neck on the 4 inch side, and saw off the waste.
See video for details.
youtube.com/watch?v=97EfvhFgRBY

I will probably at least TRY the Seeger style bridge on the Squared Eel.

Stringbean45 - Posted - 02/17/2010:  11:17:29

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I tip my hat to you, Mike.
You are the master of the 1X2's. Guess I can get two banjos out of a 2X4.
Don

banjo_brad - Posted - 02/17/2010:  13:38:21

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One person I sent the plans to (I got them from somebody on Banjo-L, as I remember), was kind enough to send me one he made. I had it on my Goodtime for awhile, and liked the sound. I haven't put it on the Chuck Lee, yet.

xnavyguy - Posted - 02/17/2010:  13:49:59

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These are what the pieces look like that my friend cut, using his CAD system and T-Tech computer controlled PCB router/shaper:



I picked up two sets and just glued them together. Since they are more closely dimensioned to the original specifications they are quite a bit lighter at 3.0 grams. As soon as our schedules permit, we will do some tests at these new dimensions and weight. If I don't have to tweak anything else, size wise, I'll try to get some more made.

Jerry

mike gregory - Posted - 02/17/2010:  16:48:16

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The historical sweep just impresses the heck out of me.
This ancient instrument, developed before Methusala was old enough to walk to school by himself,
now being equipped with a bridge made, using a computer-assisted design, and microchip controlled power tool.

Looks like it would be simpler to ship the pieces unassembled, and let the final epoxy or CA glue be done by the individual, since it would be a flatter envelope, possibly cheaper.

xnavyguy - Posted - 02/17/2010:  17:08:54

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quote:

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Originally posted by mike gregory

The historical sweep just impresses the heck out of me.
This ancient instrument, developed before Methusala was old enough to walk to school by himself,
now being equipped with a bridge made, using a computer-assisted design, and microchip controlled power tool.

Looks like it would be simpler to ship the pieces unassembled, and let the final epoxy or CA glue be done by the individual, since it would be a flatter envelope, possibly cheaper.

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As always Mike, it seems like you've been snooping around in my brain again. I thought the same thing about the ease of shipping the pieces flat. Right now, with these latest bits, the tabs needed a bit of work to fit the holes. That, and the saddles are 1/4" too tall and need to be cut down to final height once the bits are glued together. Those machine cuts are so darned accurate the pieces fit very well together.

If I can pull this thing off and convince myself that these things will work, I'll poll the folks that have expressed interest and see if they want them completely assembled or in kit form.

Edit:

I forgot to mention that I cropped the extra 1/4" off the bottom of the saddle in the photo, so folks could see what it looks like with everything to scale.

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Edited by - xnavyguy on 02/17/2010 17:10:48

Stringbean45 - Posted - 02/18/2010:  08:23:33

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Hey Jerry,
That space age machinery looks like it is doing a super job.
Put me on the list too.
Don

xnavyguy - Posted - 02/18/2010:  14:30:55

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Well, the space age machinery does, in fact, do a nice job with less damage to my tools. These are what the 2 latest prototypes look like, weighing in at 2.7 grams.



I strapped one on my Oscartone bottle cap, the first banjo in the recording linked on page one of this thread, and didn't like the way it worked. At the lighter weight, mostly built exactly like the plans, it seemed to be way too overpowering for my Oscartone. I also tried one on my engineer friend's Gold Star GF-85 and felt the same about it on that banjo as I did with it on my Oscartone bottle cap. I came home and put one on my OhBeeWon openback and like it much better on that banjo.

Right now, I'm going to step back and try to get my brain wrapped around what I need to do next. I find it odd that the very heavy bridge with longer legs seemed to work so well on the resonator banjos but I did not like it on my openback. Now, with the lighter, smaller, prototypes, I don't like them on a resonator banjo but they seem to work on the openback. The openback is a junk parts banjo that I built that has a 10 3/4" head mounted on a 1 piece Maple rim with a 1/4" round galvanized steel tone hoop.

Art and I will be getting together again tomorrow, after we do a performance at a nursing home, to practice with our group. After practice, I'm hoping we can get together and figure out what to do next on this thing.

Stay tuned.

Jerry

mike gregory - Posted - 02/18/2010:  14:41:47

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Too bad the stuff is toxic.
Otherwise, you could ALSO sell them to the teen fans of all these vampire shows, as really long fangs, get richer quicker.

And maybe that explains why dentists call false fangs a "bridge"!

mastertone250 - Posted - 02/18/2010:  15:33:29

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quote:

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Originally posted by mike gregory

Too bad the stuff is toxic.
Otherwise, you could ALSO sell them to the teen fans of all these vampire shows, as really long fangs, get richer quicker.

And maybe that explains why dentists call false fangs a "bridge"!

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The "green" stuff is the toxic board, the stuff jerrys got is not toxic according to my dad(who has a masters in computer tech).

xnavyguy - Posted - 02/19/2010:  06:02:28

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This morning, over coffee, I went back over the original plans, checking my prototype dimensions against the original plans & specifications. I still don't understand the math nor the design philosophy but based on some measurements that I took this morning, my original hand-made bridge, on the right in the following photo, & the one we used to make the test recording is closer, from a relative dimensional standpoint, to the specifications. The one on the left is one of the two that my friend cut on his CC router, using the original plan drawings which do not appear to accurately portray the bridge based on the math specifications. When time permits, I'm going to build another couple of prototypes, based on the math, not the drawings in the instructions.

In case anyone missed the earlier link to the test recording, here it is again:

banjohangout.org/myhangout/med...archived=

xnavyguy - Posted - 02/20/2010:  06:51:23

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Last evening, after band practice, Art stayed so we could do a bit of piddling with the most recent prototypes. Early in our practice, he played my OhBeeWon openback during a couple of tunes & I thought it sounded pretty darn good, mixed in with the rest of the instruments. I realize that how "good" a banjo sounds is pretty subjective so you'll just have to take my word on that statement. After everyone left, we put one of the prototypes on his RK-80 which, as far as I am concerned and again, it is my personal opinion, is one of the best sounding bluegrass banjos on the planet. I think Art will have a few thoughts to share later on. I'm heading out to the lake to do a bit of sailboat racing today so I won't be around for awhile.

We both agreed that these smaller versions of the Pete bridge had an "evil" quality that is a bit hard to quantify. On both my openback and the RK-80, up the neck somewhere around the 15th fret & higher, on the smaller strings, there seem to be some rather harsh, metallic harmonics generated by these bridges. Both the banjos are set up pretty tight with light gauge AMB Cryo strings. The overall note shapes on the smaller bridges were very much like the larger bridge. Art did some experimenting by adding weight, using putty, to different parts of both the bridge and on areas around where the bridge contacts the head. Results were different, depending on where the putty was placed, and the amount of putty that was used.

For now, I think the proposed changes I made for the next build, will both add more weight and re-distribute it and, if all goes well, will tame the "evil" that exists in these last two.

Art played some clawhammer stuff on both banjos and the results, in that mode were very promising. I'll let him comment about his thoughts in that regard.

Roll Player - Posted - 02/20/2010:  09:38:44

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It's very hard to describe sound, but I'll do my best. The dynamic characteristics were very similar to the earlier, larger Jamison bridge -- slower attack, longer decay, then a final dropoff to a short sustain. The lighter version maybe even had a little more of these characteristics. Like the bigger bridge, it also reminded me of the change in going from light to medium-heavy strings, but with the smaller Jamison bridge, there is a certain harshness in the tone, (what Jerry calls "evil") and it gets worse up the neck. Up around the 17th fret, it was downright unpleasant with a metallic "wolf" note on the high g.

I'm not much of a clawhammer player. My old-time repertoire is Buffalo Gals and a bad version of Cripple Creek, plus some doodling in G tuning, but I was surprised at how well this bridge worked for that style, especially on the RK80. I played it up near the neck in the bluegrass Y position and it seemed to make each note stand out better. The harshness turned into clarity. On the open back, it wasn't as good, but that banjo doesn't have as much low end - the rim is 10.5", so that could be a factor.

It'll be interesting to see what effect the changes in the next batch will have.

xnavyguy - Posted - 02/22/2010:  06:15:46

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After having a couple more days to think about this project and surviving what, to me, was a pretty brutal sailboat race on Saturday, I came up with a few more design modifications to try on the Jamieson bridge. Unlike the earlier, dimensional changes that I proposed to make to "tame" the harsh, up the neck, overtones, I also hope to make some weight distribution changes based on what Art and I learned when we were experimenting with the putty while we had that bridge on Art's RK-80. Yesterday evening, I drew up another set of plans that should mimic some of the things that we did with the putty while we were "puttying around". They won't look exactly like the Jamieson bridge but they should exhibit better, overall perfomance characteristics. We won't know until we get a chance to try them out.

Stay tuned.

Jerry