Predrilled magnets...

[Logyman]

I have been looking at some 1x2x0.5 inch magnets for my upcoming duel rotor wind generator and came across some pre-drilled magnets in this size. They have a 3/16" hole in the center.  If I were to mount these on my rotor plates (12"dia, 3/8" thick), with stainless steel bolts, and nuts, would there be any adverse effect? I was wondering specifically, if there would be any loss of magnetism, or would the fact that these magnets have a hole in them have a detrimental effect on performance?

Phil

[tecker]

You don't need stainless but I'm sure there will be electrolysis there eventually the stainless will be ok . You might want to shop for a nail head to keep the screws from rubbing you can do massive damage to the stator with the heads .  Bringing the epoxy up to keep it flat on top  might be a good idea.

[Countryboy]

zubbly used these magnets on his 7.5hp conversion.  I believe the 3/16 hole is a good match with 10-32 threaded screws with a tapered head.  Drill and tap your rotor plate.  No nuts required, and the 10-32 screw head should be about flush with the magnet surface.

[Logyman]

Great advice. I thing I'll drill and tap the plate. The magnets, screwed, glued and epoxied in place should hopefully resist flying off and destroying things. That was a big area of concern for me, since my location has a good average wind speed of about 20 km/h, and regular gusts to about 55 km/h, as it is today.

Thanks,

Phil

[Flux]

In theory for a given grade of magnet you loose flux in proportion to the area lost by the hole. This will be so small that you will not notice it and you will more than gain from the added security.

If they use the next better grade you may have a net gain in flux.

Flux

[SparWeb]

I am installing exactly this type of magnet on the rotor of my motor conversion.  I found an epoxy coated type that eliminates the need to paint and isolates the material from the stainless screw - which also prevents the galvanic corrosion issue.  The countersink fits an 80 degree or 100 degree head screw - use whichever you like.  These types are available from several E-bay sellers, and on this site's catalog, too.

(Please, guys, stop using the term "tapered hole" - in mech engineering terms, that's something completely different.)

[zubbly]

hello Logyman,

i did use those mags with the 2 holes in my 7.5hp conversion. the hole is 3/16 inch, with just the top portion of the hole being tapered to fit the angle of the screw head (82 degree if i remember correctly).

the loss in the magnet i expect is very little with respect to the rest of the magnet area as Flux mentioned.

what i did notice about the black epoxy coating on them was that it scratched very easy.  not to much to worry about though as they are also plated under the epoxy coating.

the screws i used were #8/32 stainless. the grade of stainless i am not sure of but they are very strong. i got the screws at Canadian Tire (canada). i really suggest using a good quality tap to thread the holes as those small taps will snap easy if they are dull. use cutting oil on threading each hole. the holes will tap easier and with less work if you drill the hole completely through the plate.

i honestly beleive epoxy or glue is not necessary at all under the mags. just be sure to use thread locker on each screw as you assemble them.  i also sprayed a couple coats of clear engine enamel on the mags after assembly.  it covers any scratches you may make.

personally, i think these mags are the greatest thing and make attachment at least for my methods much easier, less costly, and provide an excellent insurance against the mags flying off.  i also think the mags without any filler poured around them will also increase cooling air turbulance for the stator plate.

i have also drilled and tappered the top portion of the hole i drilled in some #29 magnets i have used in conversions, and also with great success.

zubbly

[nothing to lose]

Zubbly,

Did you post anything or was there anything specail about drilling and countersinking the holes in the Neos? I've read about everything you've posted but don't recall reading about drilling Neos.

I have 96 1X2X0.5" Knickle coated ones without holes sitting here for my daul rotors I'll be building.

Any specail advice, or just do it and be carefull? I was planing to bond and cast the rotors, but I'd rather screw them down.

Thanks

[Logyman]

Hi all. Thanks for the responses and advice. I am now going to go ahead with these magnets and I'll give an update as progress happens!

Phil

[zubbly]

hi Nothing to loose,

when i did my 7.5hp i was going to drill the mags i already had. some drill easier than the others. clean up after is a hell of a job. so i just decided to order the ones with the holes and be done with it.  glad i went that route.

if you do wish to drill, i used a glass and tile carbide bit. steady pressure and lots of cutting oil. they will catch fire if you don't use a lot of oil.  for the countersink, i took a cement drill and sharpened it to the proper angle.

i did do some of the #29's because i wanted to mount them that way. if i find them with the holes already in them, that is the way i will go.

i would only suggest drilling if you have no other way. i wanted to try it, i did it, but cursed the whole time.

we just need more mags available with the holes.  demand will eventually make more available.

zubbly

[nothing to lose]

Thanks Zubbly.

Ya, I kinda figured cleanup might be a bit rough. Hard enough cleaning metal filings off them sometimes. When you drill magnets have you tried wrapping them in masking tape first. It helps me clean off metal fillings at times, just peel off the tape.

I might not drill them then, but I might, probably do a couple smaller ones and see how they go first.