Big Magnet Rotor for VAWT

[MichelL]

Would it work to take the 'rim' of an old cast iron wheel off of an old farm implement.

 attach it to the bottom circumfrence of the VAWT

 mount the magnets on this rim

 mount the coils on a frame that is part of the base mount for the whole VAWT, put them in-line with the magnets

some of these wheels are 3 foot diameter, so the magnets would really be whipping by the coils.

if using flat magnets, would it be better to grind the spot on the rim the magnet is going to be placed flat, or can you build-up a flat spot with weld?(I have never welded- is 'weld' even magnetic?)

 How about it??

MichelL

[DanOpto]

Combines have numberous large pulleys that can be adapted for many uses.

They are not as unwieldy as tire rims as they are slim and balanced.

They are bored for large shafts so they are easily mounted.

Another place to find large pulley assemblies is at the TSC stores.

They have large repacement pulleys that use "weld on" centers.

You choose the size of the axle assembly and weld the hub onto the pulley.

I have seen v pulleys up to 24 inches across made from pressed steel for weld-on hubs.

If you mounted the magnets just before the V flare, the V flare would act as a stop to help retain the magnets in place. It would also assist lining up the magnets.

http://www.mytscstore.com/default.asp

I did not see the weldon pulleys listed on the website but I have seen them in the stores themselves.

Surplus yards for used industrial equipment would also be an excellent place to find cheap pulley assemblies.

Welding on the magnets will destroy the magnets.

 

[Radomike]

The welding rod is fusing & becoming one with the pulley/wheel if you are truly welding, so it follows that flux will travel through it--I don't know how well.

  Dan's right, heat + magnets = expensive scrap metal, but I don't think you meant that.  Neos will also give you a toxic present if you light 'em up...

  I'd love to see some homegrown VAWT pics--sounds cool.

 Mike

[tecker]

   Think really big and really light on the tubine size a large flywheel will require

  good bearings .  The load will slow a huge rotor down fast so that will usually mean

the your stuck with gearing the large flywheel down or you have to catch a lot of wind.

[KHB1]

Dont weld magnet get carbon block and weld a bead against the block to form a dam the shape of magnet in each position you want a magnet, then epoxy magnets in position.

KHB1

[Victor]

 A three foot diameter will appear nearly flat across one magnet width unless you are using really wide magnets. The small gaps on each side will add to your total air gap but not very much, so the reduction in flux will be small. I would be more concerned with the mechanical attachment than the extra gap.

 It would be much easier to just grind flats on the wheel than use any kind of build up.

Victor

[Ungrounded Lightning Rod]

I think he's talking about making a flat spot for mounting the magnet, rather than welding the magnet itslef.  Yes, you can build up a flat spot by welding some metal on then grinding it flat.

Don't heat the magnets - even momentarily.  Even if you don't light them off, once they get above their "curie temperature" the suddenly become completely demagnetized - and don't get it back when they cool off.

A very large wheel with a lot of magnets cutting a lot of coils is an excelent way (indeed, the classic way) to generate from a high-torque, low-speed shaft.  This is exactly what is done in the large machines used in, for instance, hydroelectric dams.

The large radius acts as a lever arm, trading force for speed just like a gearbox (but without the friction and wear).

The large number of poles takes advantage of the speed by providing a large number of edges where flux cuts conductor - incidentally raising the frequency.  This is like having a large number of generators attached to the "output shaft" of your "gearbox", alowing you to make each generator smaller, compensating for the increased number of magnets by reducing the size of each.  This might mitigate the increased cost for the larger number of magnets.

The main thing you need to deal with, if you build your genny on one of these wheels (assuming you can't get two of them adjacent for an axial flux design or two rims concentric for a concentric-dual-rotor radial flux design, is designing a flux return path that doesn't consume a bunch of your energy in eddy currents.  For an axial-flux machine a spiral of metal strip will serve.  For a radial flux machine a slinky-like wound strip, or a stack of thin disks like enormous washers, will do the job.

[MichelL]

Thanks all for the input!!!!  Since I don't have a welder, I guess I'll just grind off a small flat spot and epoxy or 'JB weld' the magnets on.

I was thinking of making a large laminated stator to lay the coils up against, would strips of that metal 'plumbers tape' laid on top of each other with an isulating layer between work for that?  Any ideas on what would work as the insulating layer??

Thanks, MichelL

[nack]

It's probably not the best stuff, but if you want to give it a try use tape to insulate and wind it like a clock spring, rather than strips laid flat.