Magnetic levitation for a VAWT?

[skipinder]

Hello everyone,

now I'm sure this has already been asked and answered a few times but I've looked for a while without any luck.

I was wondering, for a reasonably light vawt, could the turbine be be sat on two ring magnets with similar poles facing - to decrease friction?

I've read that ceramic and ferrite magnets risk to be demagnetised, but don't know about neodymium.I found the magnet FAQ but they don't say...

Also, would the repulsive force be in fact double the strength of one of the pair?

(this would seem logic to me)

Cheers

[vawtman]

Hi Skip

 Here's a company that claims a Mag Lev alt

http://www.solwind.co.nz

 It can't be of the dual rotor type because it could'nt levitate.I just gave up trying to figure it out but maybe 1 of the 10,000 here now knows.

 Neos are powerfull but can't take the heat like the others.

 So for now i'd say hot air.

 Mark

[skipinder]

Hi, yes I get what you mean for the dual rotor system, do you think it would work with the alternator you are working on?  

I just wanted to know if it was theoretically possible, without them being de-magnetised, I suppose it is, thanks for the link :-)

Also the strength bit, repulsive force = double lifting strength of one?

cheers.

[vawtman]

 I use locking collars on the bearings,sure there are slight losses in them but it's negligable to the turbine size.

 If you tried to float a set of vertical blades magnetically against a horizontal force i don't comprehend how it could work.The word wobbly comes to mind.

 To be honest i don't think the trouble of lifting the turbine will gain much if it could work and blade design would be more crucial.

 You still have to keep it within itself so you need bearings anyhow.

 Mark

[wdyasq]

Get the VAWT working ..... then you can work in perfecting the device.

Ron

............Still looking for a working VAWT

[tecker]

I used some neo dougnuts as a thrust bearing on my latest drum Vawt turbine thing as the other folks around here have call it  .  I'll see how long they last .It'll be up soon at first I was trying to support the alternator too .Too too uch wieght .Now the alt is out of the middle and on the bottom with a loose coupling to the wind rotor .

[Volvo farmer]

Funny, worried about the friction of a couple bearings, drag from an actual alternator? That will be figured out after the levitation part. LOL.

 

[dinges]

What's so bad about the (roughly) 1% power loss in plain ball bearings that you feel the need to switch to magnetic bearings ? Wouldn't an easier solution be to simply make the VAWT 1 or 2% larger (more swept area) and use plain ball bearings ?

With 2 magnetic bearings you'd save at best 2% power. The complications you will be introducing would take the size of a small NASA project to solve.

Peter.

[Norm]

You can probably support a VAWT weighing a ton

on a steel bearing a 1/2 inch in diameter.

[thefinis]

I like Peter's line of thinking.

In most cases here cost is an important factor so if you can get that extra 100 watts by making it a foot bigger for $50 why spend $200 on special improvements to get the same 100 watts. Not sure why on turbines so many want perfection when imperfection made a little larger often gives the same results. I chased this rabbit of making it all perfect or as efficient as possible till I got into actually building turbines. It was a real eye opener both on what can be built and on how to build one. It usually boils down to what is easiest with the best results. With experience one can hopefully refine design so ease of build and efficiency go together.

You tend to learn more when building a turbine than months spent perfecting a design on paper. My advice (worth what it costs nothing) is pick a design, study build notes from someone who has built one, come up with ideas for improvement, build it then see if adding the improvements you want are worth doing.

Good luck

Finis

[skipinder]

Ok, then maybe you can answer my second question, is the repulsive force double the lifting strength of one of the pair?

[skipinder]

You guys are real helpful and all, I know how generally vawts are supported, I just wanted to know if it was possible without demagnetising the donuts and about what kind of strength to expect...

Lets just say I like the thought of things floating on magnets :-)

I doubt I'll ever build my vawt this way, as it's hard for me to get small quantity cheap magnets (as for anyone I suppose) and as we all know ball bearings are very efficient, but maybe if I were to build a bigger one it might be worth looking into. The fact that they are being commercially built with magnet bearings (see vawtman's link above) leads me to think I'm not all that mad. I mean, if the neodymium mags don't demagnetise themselves there will be no maintenance necessary for something expected to turn constantly (or as near to as possible, fingers crossed) with almost zero friction.

I know what you mean Volvo farmer, but alternator drag is another matter, I'm just taking it step by step here.

What's wrong with perfectioning things? What's wrong with tinkering with different concepts?

Maybe I'll build it one day and it won't work the way I want (highly probable!), so what, maybe I'll experiment and find a system that does work the way I want, or I'll learn a thing or two before giving up and using normal bearings, but I will have tried...

[windstuffnow]

  It's an interesting concept and a small model might be fun to build.  I tend to agree with dinges about being cost effective for a large unit.  Because of the nature of the wind I don't think it would be very practical to make it completely free floating.  

  Perfectionism is self limiting, these words from a recovering perfectionist.. I learned along time ago that instead of trying to design a perfect device you need to bank one together then work out the bugs, the second one is usually better than the first because you've seen its workings and worked through things you couldn't possibly think through during it's original conception... to many unknown's.  Finis mentioned this.

  I completely agree about building it, maybe it won't work, so what !  What you learn from it will be priceless.  I build lots of prototype's, unfortunately, alot of the unit as intended doesn't work but the knowledge gained from building usually leads to a successful unit.. so what if it takes 20 failures to get 1 good one, it's the good one that can change the world.  If we give up before we start, it is a failure.  If we build it and it fails it's not a failure because of the knowledge we gained.  I've found it's not the end result that matters as much as the journey itself.

  Build it, perfect it later... Have fun along the way !

[windstuffnow]

I forgot to mention... magnetic attraction is far more powerful than repulsion.  Here is a handy calculator that will give you force in lbs of a known magnet size and strength...

http://www.magnetsales.com/Design/Tools1.htm

Handy for other things as well...

.

[finnsawyer]

You would need to control the location in two directions, vertically and radially. It seems that would require two pairs of tapered magnets of opposite polarity (shaped like tapered roller bearings), such that they would stack nicely together if not magnetized.  Since they are magnetized two would repel when one is placed on another.  You use two opposing on the top of the VAWT and two on the bottom.  They would, of course, have to be made to mount in some sort of tube shaped holder.  You would also need some way to adjust the spacings to get to the most stable alignment, and the magnets must be strong to hold the weight.  It would be an interesting demonstration if one could get the magnets.  There might be an idea here for a novelty company that could afford to have the magnets made in quantity.  

[skipinder]

Yes I see what you mean, if I had it floating on two flat donuts I'd still need radial bearings and thus still have their friction, but I don't see why I'd need 2 magnets at the top, surely anything like a nut on the shaft from the top bar to hold a minimum downforce on the two mags at the bottom would do?

[skipinder]

Cheers windstuff, that's one handy calculator!

[paradigmdesign]

To me mag lev is only worth its salt on very high rpm, or very high friction apps, like trains, and 100,000 RPMS etc.  In the case of high RPM, I personally prefer the air bearing to the mag lev.  Not to mention, the only mag lev. bearing in production that I have seen utilizes electromagnets, and a magnetic shaft, not NEOs.

[tecker]

 Nope once you have a magnet locked on a smooth surface it's much stonger with bonding than repulsing .The neos are 2 7/8 od an 1" inner ; suported in the middle of the turbine and alittle below the bottom of the turbine.I'm thinking I could use the trust as a clutch With a little hard ware <adds to the wieght  though. I had some pics from last year I posted of a s rotor testing worked fine even badly out of balance .I'll put them back up .

[Stonebrain]

The problems of VAWTs is not the bearings.

The mainproblem of vawts is that either they need a topbearing like the old savonius or the early darius what is a very expensif and thus bad solution.It's almost impossible to mount them on a tower.

Either they are of the H-rotor type that actually can be mount on a tower.But in this case,if the rotor is somewhat bigger and high rpm,you have mechanical problems,speciale the problem of dynamic balancing but lack of structural stiffness too.

Most of the vawt designs you find for exemple on this board are low rpm and need a topbearing.which make them unsuitable for the production of electricity at reasonable cost.Some of the low to medium rpm designs can be mount on a tower but to scale these up to an economic level seems very problematic.

But these designs could be interesting for something like waterpumping.

For production of electricity what we need is a high speed H-rotor(darius type)

To come at this you have to

    * find a method for dynamic balancing

and/or

   * make very long arms and very short airfoils(bad for the speed but good for machanical stability

and/or

  ** make extremely stiff and light construction

After you find solutions for all these problems,start thinking about magnetic levitation.

cheers,

stonebrain

[skipinder]

Yup, I'm rapidly losing interest in maglev...for now :-)

Just thinking on what Stone said, is there any reason why the lenz2 can't be mounted like an H darreus?

I have an image of my 'wings' mounted halfway on a horizontal bicycle wheel on a post...

Think this one's for Ed :-P

[windstuffnow]

  I've built several of the Lenz2 units with a central mounting hub.  It takes a stronger bearing assembly but it can be done at a reasonable cost.  Trailer hubs will work well for this depending on the overall size of the machine.  The light duty hubs are rated at 1000 lbs which most turbines in the 50sq ft and smaller wouldn't ever see.. with the exception of a major storm.  Pole mounting them isn't a problem.

  Another approach would be to use a tapered bearing at the top to carry the load and 3 external bearings mounted to the lower portion of the turbine, A machined ring attatched to the pole for the bearings to ride on completes the lower bearing.  

  Not a big problem to solve, just a little creativity and a few bux worth of parts...

.

[finnsawyer]

What would the nut work against to hold the shaft?  You would need bearings there too.  There will be a torque tending to bend the VAWT sideways at the top.  One can use two regular tapered bearings such as you find on a front axle on a car to counteract such a torque with the bearings at the bottom, but you don't have such an effect with the magnetic bearings only at the bottom.  With magnetic bearings at the top and bottom that issue is taken care off as well, in principle, as the adjustment issue.  I'm not sure if it would be possible to actually make the magnets with the poles on the slanted faces, though.