wind - magnets

[g reif]

hi

instaed of just epoxying magnets to the steel plate how about milling pockets into the plate so they hold in better? is this a good idea or will it create problems?

[Flux]

Depends on your take on a good idea. To hold the magnets on it is an excellent idea. Unless you want to spend at least 50% more on extra magnet size it is a stupid idea as the leakage flux will be dreadful.

If you are worried about the magnets staying on then just skim a shallow groove in the disc less than 1/8" deep and this will prevent any chance of the magnets sliding outwards. If you just epoxy them without casting them in a block then this may be a good idea but Dan's stainless band round the disc is possibly even better. If you cast them in epoxy for weather protection then they won't be going anywhere but the groove, stainless band or a few screws sticking out of the steel disc to key the cast block gives you added security. The cast block will hold them together, the only possibility is that the cast block could slip as a unit. With epoxy this is virtually inconceivable but it can happen with polyester.

Forget milling pockets it's a waste of time, magnet and performance. If you feel that you really have to do it then do it with an aluminium ring for the magnets but sit them on the steel not in it.You will need to fix the aluminium retainer to the steel discs for complete security if you do it this way.

Flux

[hamitduk]

Flux

Can you elaborate a little more on the Flux loss here? Where is the loss going to occur? Maybe why?

Hami

[Janne]

If you put a magnet in a steel pot, the pot around the magnet will efficiently short the magnet flux from one pole to another.. the magned flux always takes the easy route, so in this case the easiest route is through the steel pot. Without the pot the easiest route is through air to the magnet in the opposing rotor.

I hope this makes sense.

[hamitduk]

Ok, a little conflict in my only Brain cell, all of the graphics I have seen shows field going down into the plate and back up into the next Mag, crossing to the stator and then back into the sister Mag, and it dose it again? So the steel speed bump between the Mags would disrupt the field?

Hami

[Flux]

You are correct in that the flux should link through the steel plates and pass from one magnet to the other through the air gap.

If you fit the magnets in pockets then there is a direct flux path from the front pole right to the back one and there is no incentive for any flux to cross the air gap when it has a very much easier path directly through the surrounding iron. All the flux that you get crossing the gap will be leakage flux that doesn't manage to get back directly through the iron. If the iron round the pockets is thin and saturates early you may get some useful gap flux but if there is s good thick lump of iron in the pocket then only those flux lines originating from the centre face of the magnet have any chance of crossing the air gap. If the magnets have large surface area then you may see 50% active but if the magnets are of small surface area then you may only use 10%.

You need to take all available steps to force the flux through the desired path and stop it trying to link directly back from front face to back face.

Flux