Tailpiece on an acoustic or classic guitar?

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James Mc
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Tailpiece on an acoustic or classic guitar?

Post by James Mc » Sun Dec 09, 2007 10:16 pm

Hi all
This is my first post so a bit of background may be in order. I built a few guitars about 20 years ago when working with a very old German Luthier while taking a break from uni. Now all these years later I’m about to embark on a couple of guitars projects as gifts for friends. I’m in the process of trying to work out what I’m going to build, something traditional or maybe experiment a little, so I have a question or three.

My first question… It seems logical to me (from an engineering perspective) that removing the stress from the soundboard by attaching the strings to the end block or sides using a tailpiece would be a good thing, but you don’t see this done much in modern acoustic or classical guitars. I figure there must be some drawbacks from doing so but I can’t see what they are. So… I was wondering if anyone had some insights into the pros and cons of using tailpieces on acoustic or classical guitars or had experimented with alternate string attachment as described below?

Vic (the old luthier I worked with) had an old guitar he picked up in Europe; it fascinated him and was in his opinion the best sounding guitar he had ever heard (it was a beautiful sounding guitar). It was a classical that I suspect may have been built as an experiment.

General
Almond back and sides (only time I’ve seen it used for a guitar) laminated Maple/rosewood neck, German spruce soundboard and simple rosewood binding. The workmanship was good but the finish was rough, looked like a quick n nasty sanding job then a slap of shellac and no binding on the back. While generally it could have been an old Torres in size and shape, it was the bridge, bracing and string attachment that were very different.

Construction
The bridge was rosewood about 15mm wide and 130mm long with a bone saddle in the middle. The saddle had deep groves and the strings sat in these and then fanned out to a tailpiece (for want of a better word). The tailpiece/string attachment point was very strange. As best we could tell using mirrors, it was a piece of hardwood glued to the underside of the soundboard shaped to follow the side about 10mm from the kerfing and recessed into endblock. String attachment was via rectangular bone blocks 7x9mm that went through the top and the hardwood and were glued in place with about 8mm protruding from the top and 60mm inside the body where they were attached to the side by small timber blocks. These attachment points were spaced from about 45mm or so apart on the base side and 20mm or so on the treble.

Bracing seemed like a standard fan brace but the main cross brace (I know it has a proper name but I can’t think what it is) was scalloped out and the fan braces went through it almost to the soundhole plate. There was a removable brass tube in the soundhole that penetrated about two thirds of the way into the body cavity. The other remarkable thing about this guitar was how light it was. The timbers must have been much thinner than average yet there wasn’t any sign of distortion anywhere on a guitar that must have been around 50 years old at the time.

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Post by Bob Connor » Sun Dec 09, 2007 11:37 pm

G'day James and welcome to the forum.

Re your first question there are two forces that are stressing the top of the typical steel/nylon string guitar.

The tension of the strings is attempting to pull the bridge toward the peghead of the instrument. This I guess produces two forces due to the fact that the strings are sitting on the bridge saddle which is a point of rotation. Because of this rotational force the strings are trying to lift the back of the bridge up from the soundboard while the front of the bridge (nearest the soundhole) is being forced downward and in to the instrument.

I think it is reasonably accepted that most of tone of our current guitar designs comes from the lower bout so the forces that are being exerted in modern guitar design are actually desirable to load the soundboard so that string vibration is efficiently transferred through the bridge into a light, yet still structurally stable soundboard.

This is the tone that we associate with modern steel/nylon instruments ( say the last 150 years.)

So yes, there are stresses that we have to deal with but they are part of what constitutes the currently accepted guitar sound so I don't know whether removing the stresses would be a good thing.

It would be a different thing and it might be a bad thing depending on what you are trying to achieve tonally from the instruments you are planning to build.

Dennis Leahy has been experimenting with designs that centre around the rotational bridge forces so I'm sure he'll jump in here with a few ideas.

The string attachments that you describe sound a lot like guitars being built in the States by Jeff Babicz. There's a thread floating around in here about them and I think from memory anyone who had played them did not like the tonality of the instruments that much. Again this is neither good nor bad. It simply means that it didn't suit their musical taste.

The metal tube that you mentioned sounds like a Tornavoz. I believe Torres and a few other classical luthiers experimented with it but it never really took off.

Joshua French who is a very fine classical builder is producing instruments which include the tornavoz so there should be some more information on his website.

Sorry I can't give you definitive answers on this because there aren't any.

If you are getting into experimental areas you really have to build the instrument and form your conclusions based on what you hear from the finished product.

Most of us here are steel string builders whose designs are based around the Martin X-brace, standard bridge setup with some variations in the bracing. We do have, however, some mandolin, double bass and cello builders whose construction techniques include tailpieces but with the difference of a carved top. So you'll certainly get some different input on this subject.

I guess the most important question is what do you want to achieve tonally in your instrument and will your design theories achieve that sound.

Cheers

Bob

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Post by Dennis Leahy » Mon Dec 10, 2007 2:45 am

Hi James,

I'll post a couple of pictures, then I need to run and will be away from my computer today.

Image

Image


I encourage you to experiment. I believe that the break angle over the saddle is critical to making the instrument sound more like a typical steelstring guitar rather than like a flattop archtop. In my case, using a pinless bridge as a "tunnel bridge" achieved the break angle. This bridge eliminates most of the shear force from the strings, but not the torque force. My next attempts will get close to the Ned Steinberger patented "stress free bridge", by moving the exit holes on the back of the bridge higher. That will greatly reduce the torque from the bridge to the top.

You still need to handle the shear force, however. Either extremely stiff rims (laminated, probably), or some sort of support between the neck and tail blocks.

Gotta run...

Dennis
Last edited by Dennis Leahy on Tue Apr 21, 2009 11:58 am, edited 1 time in total.
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Post by Allen » Mon Dec 10, 2007 6:45 am

Welcome to the forum James.

I really have no experience with your questions, so I'll sit back and learn from some of the others who will be sure to fill us in some more.

Cool looking guitar Dennis. I like that a lot.
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Post by Hesh1956 » Mon Dec 10, 2007 8:37 am

Hi James and welcome to the ANZLF!!!!

No experience here either with what you are proposing but that never stopped me before...... :D

What I think should be the very most important thing to you is the intended sound/tone that you would hope to gain from the instruments that you build - form follows function.

A typical/traditional steel string or classical guitar is really a pump as well as a medium to resonate and produce sound. Although the engineering that we see on steel strings does seem like there are built in fails over time - this is by design. Not to have the instrument fail or the bridge to tilt and the lower bout to belly but in order for the guitar to be responsive and produce sound that is loud enough it has to be built, and engineered, to be close to the edge of structural failure.

As famous makers like Martin backed away trembling for fear of warranty claims from that implosive edge their guitars started to sound worse.......

So the trick is to build them strong enough to survive but weak enough to vibrate, pump, and produce a pleasing sound.

Archtops are a whole different animal and have far greater reliance on resonating then on the pumping action of the top and back on the air inside the box. And archtops use tail pieces as well. The sound board mass is greatly increased and the body thickness is greatly reduced.

Howard Klepper, a fantastic builder has built guitars that look like traditional steel strings but use tail pieces. Actually a number of builders have done this. But from what I see they would do one and move on.

Any way I applaud experimentation as well just so that you keep an eye on what the desired outcome would be - how will you measure success and will you define this, as you should, in advance.

Welcome again.

Dennis I remain fascinated by your design!!!

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Post by Serge » Mon Dec 10, 2007 9:57 am

Hi James and welcome here mate!

What the others have said makes a lot of sense, it all depends on what you want to achieve through experimentation, my first gitter cost me something like 25$ and produced sound for a 100$ so everything is possible! :lol:

Anyways, i'm on no 4 now and i encourage you to follow what your heart tells you, what will result is the learning curve so go ahead and don't forget the progress pics, we just love it here! :D

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Post by James Mc » Mon Dec 10, 2007 2:42 pm

Hi All… Thanks for the welcome and the thoughts. That’s an interesting guitar Dennis! Being one of those engineers who can’t look at a mousetrap without trying to figure out a way to build a better one, I suspect I’ll be experimenting for the rest of my life. After picking around the posts on this forum all I can say is there are some beautiful guitars being built by the participants. Amazing!

Serge, you have me reminiscing about my first guitar, what a mish mos of timber reject spruce top, kauri pine neck, silky oak sides, red gum back with tuners and fret board salvaged from a smashed guitar I found at the local dump. Didn’t cost anything and ugly as, but played ok and I was very proud. Second attempt was much better, steel string from rosewood from an old piano with a pepperwood top that I made from timber I salvaged from an old yacht I helped refit. The guy teaching me had an aversion to steel strings but when he played it he was very proud. At the time I didn’t know there was such a thing as cross bracing, wish I still had it so I could rebuild that top.

I don’t know how hard it is to find quartered pepperwood (Cinnamomum laubatii) wide enough for a top but I suspect I’m going to find out over the next couple of months. I’ve looked online but all I could find was the timber properties… www2.dpi.qld.gov.au/hardwoodsqld/8296.html for anyone interested in experimenting with native timber.

Cheers

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Post by Serge » Mon Dec 10, 2007 3:39 pm

Hey James, thanks for sharing that cool story about your first my friend, it just shows that when we're driven to accomplish something that everything falls into place at the right time and that the excitement was truly felt all along the way. Good to reminisce those first steps as humble as they were for the lessons learned the hard way! :D

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Post by Dennis Leahy » Tue Dec 11, 2007 8:11 am

bob wrote:...I think it is reasonably accepted that most of tone of our current guitar designs comes from the lower bout so the forces that are being exerted in modern guitar design are actually desirable to load the soundboard so that string vibration is efficiently transferred through the bridge into a light, yet still structurally stable soundboard.

This is the tone that we associate with modern steel/nylon instruments ( say the last 150 years.)

So yes, there are stresses that we have to deal with but they are part of what constitutes the currently accepted guitar sound...
I was surprised that my experimental guitar, with a radial bracing pattern and a single transverse "pivoting" brace beneath the saddle, and offset soundhole, sounded like a steelstring guitar of about that size and shape. One guitar of course is not "data", in any scientific sense, but it is a hint. My conclusion is that the shape and interior volume of the instrument produces the lion's share of the timbre or voice of the instrument.

I'm not sure what I expected. Having heard comments such as "piano-like" attributed to Kasha braced instruments, I kind of suspected my guitar might be in that realm. What I got was a pretty typical steelstring sound, but with bass and mid bass much richer than just about any steelstring I have ever played (admittedly, not hundreds of high-end, hand built guitars, but probably dozens.)

Because the windings on strings will grab the edges of the holes in the bridge at least a little bit, there may be some initial shear force, but I suspect most of it equalizes out after stretching the new strings or when playing. So, I have to conclude that string shear force does not contribute to the sound of the guitar.

My bridge does have torque force, so I cannot yet personally rule out the requirement of torque force to drive a guitar top. However, Ned Steinberger and Steve Grimes patented a "stress free" bridge as part of a system that basically keeps the string straight from the nut to the saddle to the tailpiece, but includes a bend down then back up behind the saddle (to achieve the break angle.) I only have Steinberger's and Grimes' word on it (I wrote to both of them), and both told me that the prototype guitars are loud, with lots of sustain, though both admitted the sound was somehow not *perfect*. The prototypes were good enough to convince Gibson Guitar to buy the patent. (You'd have to read about the history of Gibson management to know why it is no indictment against the stress free bridge that Gibson did nothing with the patent, and finally Steinberger bought it back. (Steinberger/Grimes only tried one bracing pattern, if I remember correctly.)

My next few guitars will have very little torque force, so I'll have a better idea whether the torque force at the bridge contributes much of anything to the overall sound (timbre/sustain/volume), but I suspect it does not. In one article I read, Steinberger talked about all the torque force still being present - it is simply "resolved" within the bridge, and therefore does not twist the bridge to torque to soundboard.

As for the reasons that I built this experimental guitar (that I call "Angelina"):

I have convinced myself that the X-brace, copied by and made popular by Martin, is a wonderful compromise between structural engineering and sonic engineering. However, I believe that it is a compromise, and I just cannot believe that it happens to provide the *best possible* sonic engineering, since it was first and foremost done to keep steelstring guitar tops from distorting under the force of the anchored strings.

The thinner the soundboard and the lighter the bracing on X-braced guitars, (theoretically), the more likely that the guitar's top will distort over time. I want to build a guitar that sounds as good as or better than the best guitars I have heard or played, but ensure that the top will not distort.

I have read that guitars are very inefficient, utilizing as little as 5% of the strings energy to yield sound. That made me wonder how to capture more of the string's energy, and I am guessing it requires a thin, flexible soundboard, braced to allow the plate to vibrate as naturally as possible.

So, the suspended bracing, the tunnel bridge, and some sort of a tailpiece are simply providing a starting point to experiment with bracing configurations, soundboard contouring, and sound hole placement.

Using these ideas, if I can enhance mid and treble frequencies in a guitar, and yet hold on to the enhanced bass and mid bass that I already know is possible, I think I will have a really musically inspiring guitar.

I think it is also possible that these engineering strategies will make it easier to make a really fine instrument. I say this because as a complete beginner on a first guitar I think I hit something remarkable in bass and mid bass (probably about average on the rest.) So, I suspect this engineering strategy may have a bigger "sweet spot", and more beginner and intermediate luthiers will be able to produce exceptional instruments without building hundreds of instruments or studying under a master X-brace tweaker like Somogyi. Of course, if I'm right, then it will also provide a tremendous potential for the extremely experienced luthiers to tweak the engineering to produce guitars with attributes that cannot physically occur in an X-braced guitar. (Yes, I'm a romantic! But, I have a very strong left-brained hunch that this is attainable.)

Confronted with these engineering concepts, and the possibility of creating a guitar that (at least some players would say) is beyond what the best X-braced guitars could ever do, Cumpiano wagged a finger and said something like, "why do you want to change the sound of the guitar. I like the sound of the guitar." Again, by keeping with the general shape and interior volume of current guitars while adding these engineering concepts, I don't think the unique timbre of that size guitar will be lost, I think it will be "more." I adore the sound of guitars. I want more.

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Post by Dave White » Tue Dec 11, 2007 9:06 pm

Dennis,

I think it's great that you want to explore new and different building avenues in your quest for your sound - it's a philosophy I endorse and follow. Just a few comments though.

First there is very little that hasn't been done before in the history of guitar making, it's usually just that people don't always follow down their original ideas. The tailpiece secured strings that are fed parallel to and through the bridge like on your guitar was - I'm pretty sure - done on some instruments made in the 1800's.

In your quest for trebles and mids you need to think where these ranges are going to come from. Personally I think you need tops that are thick in the centre working from there to get the basses blended in.

Also, although a very small percentage of the strings energy goes into end sound, on a steel string this is not a big deal - you can make some VERY loud guitars with the right tecqhniques. With nylon strings this is a bigger issue though, but then thinning the tops to get the response/volume leads to the Holy Grail search for good/balanced mids and trebles.

Also for steel strings, I think that tension/stressed systems are a good thing - pre-stressed systems when distrurbed release energy. Tap a thin floppy top and then tap one that you flex slightly into a dome and listen to the difference in sound and response. I want my tops to distort with time but not so that the guitar is in structural danger or so that playability is impacted.

Just some random thoughts.
Last edited by Dave White on Wed Dec 12, 2007 7:15 pm, edited 1 time in total.
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Post by Serge » Tue Dec 11, 2007 11:20 pm

An approach i love to guitar building is from both rationale and from instinct, understanding what we're doing and why is important but we're also dealing with many types of wood properties with tactile feelings that need to be developed just as much overtime and experience with soft and hardwoods, the fingers of the luthiers must develop that instinctual intelligence IMHO. Or if there is such a thing as instinctual intelligence of the fingers... :lol: :D
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Post by Hesh1956 » Tue Dec 11, 2007 11:43 pm

Angelina!!!!!

:evil: :evil: :evil:

Dennis you stay away from her mate - she's mine, mine, all mine...... :lol:

No wonder you shaped the lower bout as you did...... :lmao

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Post by Dennis Leahy » Wed Dec 12, 2007 6:29 am

Hi Dave,

Yeah, it's funny, what I thought were "innovations" in Angelina, I later found were mostly things that have been tried in one form or another. I was ignorant of the Tilton Improvement (from the 1800's) when I engineered the suspended bracing and tunnel bridge, and was ignorant of the Steinberger/Grime patent on the stress-free bridge when I engineered my (what I guess I would now call) "shear force-free bridge." I guess it is laughable that I had a bit of a struggle deciding if I would pursue patents on my "innovations", but that I decided that I would offer the ideas to anyone who wanted to utilize them. (As it turns out, the more I think about patents on guitar features, like Wechter's butt door, or Babicz's adjustable neck, the more pissed off I get.) I also put all my cards on the table hoping some other luthiers would try the concepts, design a different bracing pattern/method, and share their results.

Thanks for your intuition on keeping the center of the top plate thicker. That instantly *feels right* to me, because I have been struggling with the two-edged sword that the guitars with the best treble seem to have pretty stiff braces, and yet stiffening the pivoting brace beneath the bridge with braces would probably be counterproductive to bass. I want the bridge to mimic a "canoe in the water", and don't want outriggers. I think you'll see a larger elliptical bridge plate beneath my next bridge, lending stiffness and mass to the center of the top, without any braces tied to the pivoting brace. If that aids trebles without muting bass, I'll herald it as a Dave White Improvement. If it sucks, it's all mine!

You're right, I have heard X-braced guitars that were plenty loud - I don't need to get louder than that. And, I now realize that too much sustain can be detrimental to some styles of playing. So, it's not just a matter of making louder guitars, or guitars with more sustain that I'm after. Maybe the best way to explain my quest is to compare a junk plywood guitar with a decent factory guitar with a world class hand-built guitar. In each case, there is a leap in quality of the timbre - each progressive step supplying an instrument more melodious or sonorous, more musical, more inspiring, more magical. I may be full of shit, but I have a hunch that there is another leap that can be made, and that the key is in removing the X-brace and finding a way to brace the top strictly for sonic properties.

99.99% of the great guitars that I have ever played or that I have heard on professional recordings utilize the X-brace and anchor the strings at the bridge. There are also a lot of players deeply rooted in tradition that really want a big name brand guitar or a clone of a big name brand guitar with invisible modifications to make it sound better than the big name brand guitar. So, if I was going to try to pay the bills and support my family with lutherie, I'd build the best X-braced guitars I could. But, I'm just a beginner, an experimenter, and someone who derives no income from lutherie - so I can afford to experiment. I also realize that no matter what comes of my experimentation, some may like the results and some may not. There is no perfect guitar, and the variation between guitars is used by good musicians to help find a voice for some specific songs, or some style of playing, or maybe even a genre of music - but that same guitar that was *perfect* for that task may not be the right tool for another song, style, or genre.

A relatively floppy, un-stressed soundboard that is almost unaffected by the bridge and strings, until a string is plucked, is my understanding is of the Steinberger/Grimes guitar's design. I wish there was at least something recorded that I could hear with my own ears, so I'd know if it is a timbre that I would like, or dislike. But even then, if I heard something lacking, I would not know if the stress-free bridge is an unworkable concept, or if some different method of bracing the top could complete the system better.

I agree that stressing the top into a dome shape makes the tap tone "richer", and I might even explore slightly smaller radii on tops as another way to enhance mids and trebles.

Good food for thought, thanks Dave!

Serge, I admit that I want a shortcut to the results achieved by masters who have earned "instinctual intelligence of the fingers." I know I will never build that many guitars, but I want to make guitars that possess world-class sound. I have a hunch that my path will get me into an area with a wider margin for error, or bigger sweet spot, by sort of getting out of the way and allowing the soundboard and the body shape to more naturally provide the sound.

Hesh, don't even think about sleeping with Angelina. Her G-string is dangerous!

Yes, the lower bout was partly a whimsical homage to the female form, and partly because a normal length G string would not have fit from tailpiece to tuner unless the butt was drawn up into a crevasse.

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Post by Allen » Wed Dec 12, 2007 6:30 am

I hadn't really noticed before, but Angelina is a bit of a fat bottom girl. And I'll say so again. I really like her looks. :)
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Post by Serge » Wed Dec 12, 2007 10:56 am

Dennis, i hear you bro, we always enter the craft having in mind some definitive or specific goals that we want to achieve and i remember too well the sleepless nights that i had during my 2 first builds, i wanted everything perfect on the second one which was pretty ambitious but turned out very acceptable, i even had a thumbs up by Sergei De Yonge who apparently hates Dreads! :lol:

Nonetheless my friend, what i see when i look at your guitar is precision and outstanding creativity that yells to be released so may i suggest that if you are looking for all these varying aspects of the build that you get in that shop of yours that must be filled with nice toys to play with and have fun making sawdust like a maniac? :lol: :lol: :lol:

By the little experience that i have under the belt, ahem, the longer i stay away from the shop, the tougher it gets to get back in and i got this bunch of sweet folks reminding me to get back there so i'll be the one to tell you to get back in the shop quick, you still got mistakes to make and learn from, that you will only get that signature sound by playing instinctively with woods of all kinds and that we're all hungry to see the next one coming along my dear friend!

Challenge sent to you bro:

WE WANT PICS WE WANT PICS WE WANT PICS

Your pal Serge :D
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Post by Dennis Leahy » Wed Dec 12, 2007 12:12 pm

Serge,

Challenge accepted. (I've been saying the same thing to myself, but not listening.)

I need to finish one programming project, then I will re-start 5 experimental guitar builds just barely started:
  • 3 "Basia" (named for my daughter) stretched parlors: 25.4" scale, 12 fret to the body, double sound hole, and a tailpiece like an archtop
  • "Grace", (my wife's middle name), a new 25.4" scale, 14 fret to the body, compound Venetian cutaway with a bell-shaped soundhole on the treble side horn, and a tailpiece like an archtop
  • and a Grace 28.59" scale baritone
Soon, soon, soon...

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Post by Serge » Wed Dec 12, 2007 1:19 pm

WOOOOOOOOOOO HOOOOOOOOOOOOOOOO HOOOOOOOOOOOO!

:cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl :cl

Looking forward to the next amazing projects bro!

And you can count on my full support! :bh

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Post by James Mc » Thu Dec 13, 2007 2:14 am

On’ya Dennis… Get down n dusty and keep the innovations coming. It’s always great to see someone willing risk the time, money and effort required to take a new idea off the drawing board and make it real. I think that innovation in guitars isn’t about trying to make them sound like something else or better. For me it’s about finding ways to better control and blend the sound elements we love.

I realised after reading the posts that I missed something in my original description of the old guitar that would have supplied the some upward stress to the top. There was a brass bar screwed to the bridge that the strings went under. There wasn’t near as much string deflection as on yours (maybe a third) but I guess it was doing the same job. A picture’s worth a thousand words, so I’ve draw a mud map. Hmmm I didn’t have a sheet of steel and engineers chalk handy, so I’ve used the computer instead.

Image
Image

Old Vic was convinced that the clarity and richness? of the treble was being enhanced by the bone attachment points inside the guitar working like a tuning fork and supplying extra vibration to the bottom of the soundboard. He tried attaching the strings directly to the bar behind the saddle to see how it sounded, but according to him it made it sound like a “bad flamencoâ€

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Post by Dennis Leahy » Thu Dec 13, 2007 4:53 am

Hi James,

I like hearing that you'll start working on your design! Please post progress shots, and commentary.

Somewhat parallel thinking... Heheheheh! :lol:

I thought about brass, but decided against it. (A combination of the corrosion/patina, and thought it might be a bit sound damping.) I have some 1/8" aluminum rod ordered, and some 1/8" titanium samples on their way. I may get some 1/8" stainless steel as well. The pieces are so small, that the considerable density difference between the metals is probably moot. I'll probably opt for the sample that rings with the longest sustaining ring, but may need to modify that if I determine that the aluminum will too quickly be gouged by phosphor bronze wound strings.

I'm at the edge of the two-edged sword about using any metal on a bridge. On the one hand, virtually every bridge that ever included a metal contraption robbed the guitar of its sound, on the other hand, a small amount of a very acoustically resonant metal may not cause any damping problem and is the only practical solution I can see to some of the engineering issues.

I'm going with metal rods to assist the strings longitudinal movement (stretching, without catching on the bridge), and because without metal, it would take a huge mound of wood above the strings to keep the strings from ripping through the bridge. Using metal tubing to line the bridge's "tunnels" would result in an angle too sharp for strings (especially wound strings) to easily slide through.

The Angelina guitar I built does have issues with initial tuning, which I'm convinced is caused by that extra length of string between the bridge and tail, so I'm adding a floating tailpiece (like an archtop) and will actually have the ball ends of the strings closer to the bridge than a typical tailpiece.

I'll post my CAD scribble-sketches of my next bridges when I get to the computer where they are. You'll see that I'm planning on using 2 metal rods: one just as you are to supply the saddle's break angle, and a second one at the trailing edge of the bridge that will lift the strings high enough to greatly reduce the bridge's torque on the soundboard.

What are you doing to keep the string spacing at the saddle? Vertical pins? For me, Plan A is to rout some longitudinal (with respect to the guitar) troughs that will act as string guides. I'm also doing the opposite of what I did on Angelina: as the strings leave the back of the bridge, I'm going to converge rather than diverge them. My intent is to destabilize the bridge laterally, again thinking of the canoe in the water, trying to allow the bridge to move in that natural (secondary) lateral motion. If I find that the leading or trailing edges of the troughs do catch the strings, then I'll switch to vertical pins. In fact, the vertical pins make more sense, in terms of mechanical engineering, to allow the strings to slide. But, it adds even more metal to the bridge, and may promote the bridge splitting, which is why the pins are my fallback design.

Dennis
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James Mc
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Post by James Mc » Thu Dec 13, 2007 1:19 pm

We sometimes line engine boxes on boats with aluminium because it acts as a sound deadener… so maybe some issues there, it also chews out very easily. Most importantly, aluminium and brass are dissimilar metals so they react, a brass fishing swivel can rot through an aluminium boat in a couple of months. I’d recommend you avoid brass strings in direct contact with aluminium.

I think hard brass would work well but soft brass would wear. Stainless steel could be good depending on the grade. 3CR12 is a low grade that they use for wear plates on bulldozer treads but it is kind dull sounding and doesn’t polish well. 304 to 316 is what they use for kitchen benches pots and pans etc and could be a good middle of the range choice. However I’d be leaning towards high tensile verities, this is the stuff they make steel rulers and other tools from. A cheap and easy option worth considering would be to try a 3mm TIG welding electrode (tungsten) available at any welding supply shop. To line holes in timber it may be worth seeing what you could find in ceramic insulators. They are using ceramic for valve stems etc in racecars because it is almost impervious to wear.

The old guitar had a thicker than normal bone saddle with grooves cut in it to keep the strings in place. It seemed to have held up well enough over a great many years. Buffalo bone is easy to get hold of, just find a waterhole in the Northern Territory with a good sized croc in it then wade around in the shallows feeling with your feet, they don’t tend to swallow the larger bones. Alternately, you could contact one of the cheap luthier supply places in Thailand and buy a few large pieces or have what you want made to order.

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Post by Dennis Leahy » Thu Dec 13, 2007 3:33 pm

James Mc wrote:... just find a waterhole in the Northern Territory with a good sized croc in it then wade around in the shallows feeling with your feet, they don’t tend to swallow the larger bones.
I once saw a nature special where they filmed a croc spinning its body 180°, in super slow motion, then calculated the speed with which it had made the turn. 250 miles per hour is what I remember, if memory serves me. You know, that's faster than the pee can run down my legs. I'm going to leave the waterhole bone hunting to you, mate.


If you look at many of the windchimes available (even the really expensive ones) they are often made from aluminum. Whatever alloy that is, it sure seems to resonate for a long time. I'm familiar with dissimilar metals corrosion, and have wondered just how much will occur with dry contact (no seawater!) Thanks for making me actually look it up! Galvanic Compatibility Chart OK, that does it, aluminum is out! Looks like stainless steel and especially titanium pass the "anodic index" galvanic test. As you mentioned, brass would also pass with flying colors.

304 stainless is available in small quantities, cheaply. When you get to the more exotic alloys, you need a friend in the business to get small quantities, or a big wallet to place a minimum order. I have been looking for readily available metals, that would not deaden sound any more than Ebony.

Titanium (Ti-6al-4v) is available in small quantities. Abrasion resistant, apparently no galvanic problem with phosphor bronze or steel strings... as long as isn't sound damping. I have never worked with titanium, but based on other properties like hardness and density, I suspect it would not deaden sound any more than 304 stainless steel (probably less.)

And that brings us back to your suggestion of brass. It's really cheap, and readily available in small quantities in a variety of sizes. It would also allow me to consider brass for the tailpiece, which I think I could make lighter and stronger in brass than in wood. Hmmmmm....

Dennis
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Post by James Mc » Thu Dec 13, 2007 4:23 pm

I’ll be using brass because it is cheap, can be forged with a little heat and a hammer, is a piece of cake to silver solder and it looks nice against timber.

I did give a lot of consideration to tungsten. It is much harder to work with, any bends would need to be cut and silver soldered. But it's easy to get in small lots and doesn’t cost much (guy in the US selling Tungsten rod electrode on ebay, $0.77 per inch for1/8 diameter) which brings it into my budgetary range for experimentation.

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Post by Dennis Leahy » Thu Dec 13, 2007 4:47 pm

Image
Here's a couple of CAD scribble sections of my new bridge, working out the placement of the rods and string tunnels.

Note that the saddle (in this case, 1/4" wide) will be slanted somewhere between 4° and 6° for intonation compensation, so the rod needs to parallel that angle to keep the break angle approximately the same across all six strings. It also has to dive down on the treble side, due to string gauge change plus action change, to keep that approximate break angle consistent across all six strings. (Only the break angle vector is drawn - not the entire string path.)

The numbers 70...16 are gauges for a baritone.

As I have thought about this more today, I am trying to envision the vertical pins that would take the place of the tunnel walls, for string alignment.

Dennis
Another damn Yank!

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