Magnetic Capo?

[CES]

Cool thought, but I can't get past the idea of me trying to find all the loose individual magnets...I assume you were thinking about some form of a cross bar holding the magnets you'd set on top as the clamp, but the mental image I first got was of individual ones, and my son stealing them to use for various and sundry experiments of his own!

I can't believe no one has told you that capos for mandolins are "no part of nuthin'" yet!!

All kidding aside, I do think the idea is cool, and would be interested in seeing your results if you carry this out into an experiment, I just don't know that the idea has wings beyond just being cool...but, then, what do I know?

[Audio Artillery]

But is moving through a magnetic field the same as oscillating within one? Wouldn't each pass back and forth cancel out any current produced?

It doesn't matter that you change directions, the current is always opposing your movement, thus dampening the oscillation.

[foldedpath]

Use steel or magnet strips to replace normal binding at the edge of the fingerboard, and put your uber-powerful magnets at the ends of the capo bar, not the middle. There won't be any string damping, and it might be something you could retrofit without tearing out the whole fretboard.

I'm still thinking this is a solution in search of a problem, and this wouldn't allow partial capo'ing, but that's one way to do it.

Hmmm.... okay, here's the real way to do it. Build a very powerful series of electromagnets under the fingerboard, just behind the frets. Rig an AC cord to the instrument for power, with a small control panel on the side to trigger each electromagnet separately. Use steel wound strings. Then you can turn on whatever magnet you need to pull that string right down to the fret, without needing a capo bar at all. There is no damping effect on the strings from the electromagnets at other fret locations, because they're not powered up.

Add a Midi sequencer and the instrument will play itself.

[Pipeous]

how about producing the magnets in the fretboard with tiny electric coils under the fretboard. the magnetic field wouldn't be induced until electricity of some sort is applied to the coil. that would stop the string vibration issue when no capo is required. sure it would require wiring inside and a brain of some sort to engage the individual coils...

oops. had to go get a coffee before I typed and folded beat me to it

[Appalachia]

Have you tried talking to a physics professor there? ... Also, it's possible something like this could be used as a class project...

I've sent an email off to my old physics of sound and music professor who was head of the physics department at UNCA for some time. He wanted me to do an undergraduate research project with him when I was there, but it didn't happen because I transferred schools to study luthiery. I'm studying guitar repair and building next year and the classes are crammed to the brim already, though it still might interest some fellow classmates for out of class experimenting.

...retrofitting...

I had never thought of this as being something that would be retrofitted on existing instruments, because of the things that have been said. I saw it being implemented on new instruments while they're being built; that would drastically reduce the labor and material costs needed, perhaps even down to only marginally above that $20 range; that, and people often spend extra hundreds of dollars just for cosmetics.

...steel insterts...

The placement of ferrous metal in the fingerboard instead of magnets is a great idea, though I think the strength of the attraction between a magnet and ferrous metal is weaker than that between two magnets (I could be entirely wrong on this assumption though). This is definitely worth looking into.

...electromagnets...

Electromagnets would be one solution to this problem, but it's not a path I'm interested in taking; but if some else wants to, please keep us updated; it's definitely an interesting path.

...I can't get past the idea of me trying to find all the loose individual magnets...

There could be a place for them to stick on the headstock or similar. I figure if people are willing to carry around $50 picks they won't mind carrying a few $1.50 magnets.

[Appalachia]

Hmmm.... okay, here's the real way to do it. Build a very powerful series of electromagnets under the fingerboard, just behind the frets. Rig an AC cord to the instrument for power, with a small control panel on the side to trigger each electromagnet separately. Use steel wound strings. Then you can turn on whatever magnet you need to pull that string right down to the fret, without needing a capo bar at all. There is no damping effect on the strings from the electromagnets at other fret locations, because they're not powered up.

Add a Midi sequencer and the instrument will play itself.

Heck, just bump up the strength of the electromagnets to the max, and you can have a levitating-self-playing mando.

[CES]

There could be a place for them to stick on the headstock or similar. I figure if people are willing to carry around $50 picks they won't mind carrying a few $1.50 magnets.

True, but you'd have to fit them in an array around your Snark! I also thought of the cool in-case storage possibilities, but I have one friend who can't play a Wegen or BC because he'd go broke...looses picks like crazy...now imagining him finding them on his fridge holding up post it notes...OK, I'm quitting now

Again, not making fun of you at all. I think the concepts you're throwing out there are cool, and it's outstanding that you're actually THINKING, regardless of the practicality of it all...If this does turn into an experiment, please post some pics of the process and your results!

[Mandoviol]

What if you took the aluminum-instrument route and had a one-piece body and neck with a steel plate directly inside the neck? It would be tough, durable, and you wouldn't necessarily foul up the fretboard. Pop your rare-earth-magnet capo bar on top and be done.

[HoGo]

Attraction between magnet and steel will be probably half of what is between two magnets but with the strong magnets it may be enough for thinner strings with low action. The thick E of a guitar may require more power.
I don't know much about electornics but I guess the AC that will be induced in the string (especially wound, I believe current depends on length of wire in th emagnetic field) will be enough to cause unwanted hum in circuitry of electric pickup. I think strings are grounded on electric guitars to minimise ill efects. Just imagine how magnetic pickup works... the current in the coil reflects changes of magnetic field (of the permanent pickup magnet) caused by string vibrating in the field. But magnets under string probably won't dampen string all that much if not installed too close, well set-up electric guitars don't seem to have problem with dampening (bad bridge will probably have more effect...).
I still think this could be nice addition to the "stealth" banjo :-)

[Bertram Henze]

One of the major features of an acoustic instrument is its technological simplicity, IMHO. Covering it with space age tech immediately raises the question why the tech part can't do without the acoustic part in the first place. Why not skip this tedious evolution process, make some magnetic/electronic device and leave the mandolin out?

[Mike Bunting]

Anyone have any data on the pressure needed to press a string/course down to the fingerboard or any novel ways of finding out? From what I've found, two 1/8 inch by 1/8 inch cylindrical neodymium magnets can give you over a pound of force. I don't feel like I'm pressing down that hard when I'm playing on well set up instruments, but that is something that is hard to gauge so I could be way off.

And strong enough to resist the lateral pull when a flatpick is used in playing.

[Tom Wright]

I was kind of thinking like foldedpath about triggered electromagnets and such, but kept coming back to "why?" There is a need for a very thin and low-profile mechanical capo for mandolin, I would say. The Shubb and similar really get in my way, with no room between frets on mandolin scale. If one could keep the bar completely between the sides of the neck I might want one, and some way to fasten directly to the fingerboard might be a way to go.

As to permanent magnets, I have tinkered with strong neodyniums for purposes of pickup design, and if you bring them close you can see the vibration envelope changing. Stratocaster guitars were generally considered to have funky low-string harmonics because the pickups were in places that skewed those vibration nodes.

And the effect of induced eddy currents will always produce dissipated energy as heat, so the vibrational energy will get damped. You don't get a free lunch; electric guitars would sustain a bit longer without permanent magnets affecting the strings, although the effect it is slight and not a problem since one is not asking for mechanical strength from the magnet. And, yes, it would definitely yield artifacts in magnetic-pickup instruments. since that is how pickups work, inducing a field in the string which then excites the coil.

[Tommando]

Preliminary anecdotal data. I have two disc magnets that measure 15/32" diameter and 1/16" thick. These attract or repel each other beginning at a distance of 1.5" apart. I don't know how to measure the force, but they are very difficult to pull apart when they join. They were the clasp mechanism in a portfolio. Holding one on the fretboard of my guitar behind the third fret and the other on top of the high E string, they were approx. 1/32" apart and they did have enough force to join together with the string held between them. Similar result at the 5th fret. The string exhibited a somewhat muffled tone, indicating that it was not held securely in place probably due to the varying surfaces. I tried letting the magnets float together above the fretboard but they vibrated with the string, buzzing against the fret and the B string, and the tone was more muffled. I noticed that the magnets have very little attraction to phosphor bronze strings and no attraction to the frets on this guitar. I thought that a more ideal approach might be to magnetize the frets. I'm in the camp of not seeing this as a practical idea, but who knows what might come from this exercise. Now to unstick everything on my desk that these pesky little magnets have attracted.

[Appalachia]

So, I'm starting to formulate a plan for testing, and an ingredient list. I'm looking at trying to get a really cheap mandolin, and then drilling into the side of the fingerboard (parallel to the frets) to slide two small steel rods in at each position, just under the playing surface, for the magnets to be attracted to. The magnets that I'm looking at getting are a 1/4"x1/4"x1/16" (one per course), and the minimum order is 10, so if they aren't strong enough I can try doubling them up. I'm think of using craft foam or something similar on the bottom of the magnets to keep them from wobbling.

Thoughts?

[MikeEdgerton]

You need to get outside the box here. To test the concept you don't need a musical instrument, you need a flat board and some magnets and some strings. Nails will work for frets and screws will work for anchoring strings. Determine how big the magnets need to be before you put money into any instrument. Getting started is easy. Once you find out of you can do it then you move on to the next step, fitting it to an instrument. As there are more capos sold to guitar players in a day than will ever be sold to mandolin players in a year, I'd be tempted to try it on a guitar first. It's also a bigger platform.

[Appalachia]

You need to get outside the box here. To test the concept you don't need a musical instrument, you need a flat board and some magnets and some strings. Nails will work for frets and screws will work for anchoring strings. Determine how big the magnets need to be before you put money into any instrument. Getting started is easy.

I thought of that, but at this point, I'm confident enough that the magnets will hold the strings down; it's seeing how they interact on an instrument that I want to look into, and I feel as though making the kind of a setup you describe, so as to be accurate enough to a real instrument to get a useful output, would cost about the same as a really cheap mandolin or guitar (talking like $50 on craigslist).

As there are more capos sold to guitar players in a day than will ever be sold to mandolin players in a year, I'd be tempted to try it on a guitar first. It's also a bigger platform.

I chose mandolin first, because mandolin is what I'm most interested in seeing this implemented on (the fifth string of a banjo coming in just behind); though I might end up using a cheap guitar, just because they're easier to find.

[Michael Lewis]

Practical experience with electromagnetic pickups has shown that strong magnetic field dampens string vibration. This would tell me that you would not want magnets IN the fingerboard under vibrating strings.

[eadg145]

You might want to consider using stepped disc magnets as fret markers. In any case, this is a good source for powerful magnets.

NFI

[Appalachia]

In response to the past couple of posts: although the original question that started this thread related to having magnets in the fingerboard, this has since been ruled out as causing too much damping in the strings — though this could be used in a non-permenant for factor as an effect. The current thinking is to have steel or some other ferrous metal in the fingerboard for the external magnets to be attracted to, thus reducing the magnetic fields to a minimum.

[jesserules]

howzabout this:

- cover the entire fingerboard (or maybe just the first 5-7 frets' worth?) with a thin sheet of magnetic "German silver" (similar to the way old-time banjo players would fix worn-out fingerboards with copper sheeting)

- use strong small magnets to capo individual strings in various configurations.

bingo! (?)

[Dave Hanson]

Does anyone seriously think this is worth the effort ? when we already have have perfectly good capo's in plenty.

Dave H

[Bertram Henze]

Does anyone seriously think this is worth the effort ?

Compared to the musical benefit, probably not. But compared to one man's dream, it might be indispensable.
Plus, there are so many concepts that were never worth the effort but have stock indexes rising an NYSE today. All you've got to do is stick to the principle of completeness: you won't sell a solution unless you sold the problem first.

[mandolinlee]

Sorry if I'm hijacking this thread.
To Jim Rowland - I'm sending you a PM about your post #21 above.
Thanks,
Lee

[sunburst]

Does anyone seriously think this is worth the effort ? when we already have have perfectly good capo's in plenty.

I'm already on record as thinking it's a "solution in search of a problem" (and having that opinion remonstrated), but I don't think that's the point here. The point, I believe, is to give it a try, see how it works, and learn from the experience.

[mugbucket]

Not for nothing, but my mind works backwards - what about having an adjustable fret that acts like the nut? For the sake of the thread the actuating mechinism could be a magnet - I'm thinking the repulse affect when the like poles are aligned...

Ski