Stainless Steel?

[Yianie123.]

Is it required to use Stainless Steel bolts or threaded rod for the stator mounting and the bearing housing rods for the magnet plate and wind blades?

[TDC]

No.  Any conductive material close to the magnets will cause eddy currents,  but the bolts a far enough from the magnets so they are not a problem. 

[kitestrings]

I think it depends a little on the layout, size and placement of the stator bolts/rod. If they are small and outside of the coil perimeter it will likely be of no effect. If they are between the legs of the coils you can feel some influence.  In this case SS makes sense to me.

By the time you get to the bearing hub you're well outside of the fringe field.

My preference is studs & spacers as opposed to threaded rod.  Unless you order hardened stock the hardware store variety is pretty soft & subject to corrosion IMO.

 ~ks

[Yianie123.]

Do most use stainless steel or carbon steel?

[joestue]

The only issue here is corrosion.

[kitestrings]

I dunno.  When we had our alternator assembled but laid back on shop floor, Albert, a neighbor/friend walked by a bit too close one day.  He had a long chain hanging from his pocket.  The end of a pair of magnets grabbed the thing as he went by and gave him quite a start.  It was probably within an inch, or two, but I don't think this was corrosion...

[electrondady1]

stainless or brass is non magnetic

[Flux]

If you make the stator with fixing ears so that the stator bolts are away from the magnets there is no big deal. If too close you get attraction forces that may hinder balancing, when running even then the losses would be tiny.

The spacers for the magnets are rotating with them so no problem there.

As Joe said the main reason to use stainless is to reduce corrosion, you know your environment and whether this is an issue, I seem to remember you thinking it was.

Flux

[kitestrings]

We used stainless for the reasons described.  Different grades of stainless have more -or less magnetic attraction, but it is much less than steel.  Stainless fasteners can have there own issues with galling, but if it is not something frequently disassembled likely not an issue.  I've seen some hardened blade bolts, for example, that have held up better long-term than stainless.

Some designs I've seen have pretty long lengths of threaded rod (or 'all-thread' depending on where you live) supporting the stator.  To me a spacer over a bolt, stud or all thread seems like a better method.  Time will tell but torqueing unsupported threaded rod especially with electrical braking in high winds, seems like inviting unnecessary problems.  Probably of no concern on the size your looking at.

Good luck, ~ks