Ceramic Vs Hard Drive magnets

[esc]

I've done a few searches and found a lot of interesting info here on hard drive magnets, but nothing that speaks directly to my question.

For a (relatively) low power project how will they compare?

Since I already have ceramic magnets (and am slowly making progress on a dual rotor axial alternator based on them) and access to a big stack of old hard drives, I figure I might as well make a second set of rotors with the hard drive magnets, just for fun.

I'm mostly just curious how the smaller but more powerful hard drive magnets will stack up (figuratively not literally) against the ceramics.  I'm not talking about big stacks of hard drive magnets, just 1 or 2 deep.

My GUESS is that the uniform, larger size of the ceramics will almost make up for the stronger but smaller, thinner and irregular shaped hard drive magnets.  I don't expect to see a very big difference.

But if someone else has either already performed a similar experiment or is getting ready to do something similar, I would like to hear about it.

In any case, I'll post my results...one day... when I have some.  

So far, 2 of the 3 hard drives I have taken apart used separate, side by side magnets, so they do not need to be cut in half.   Here's hoping my luck holds....

BTW, I know my time would probably be better spent doing something I could get paid for and buying bigger magnets, but this seems like more fun today.

[ghurd]

It takes a LOT of HD magnets.  Because they are so thin.  A large air gap kills the output.

I never placed enough HD neos on my wobbly disks to get half-way to a extra-super-crappy output, because I decided the thin magnets were better used in motor conversions.

Will revisit it soon.  Have some Giant Disks (4.25" dia) being made.  

Have a plan for something with less wobble & wiggle.

Have a million feet of TV degaussing coils.

If it doesn't work, at least I will have cleaned out some storage space!  LOL

Not sure how to compare apples to apples without making a new stator.

Probably want to go from 12 pole to at least 24 pole or the coil resistance will kill it.

But whatever you try, be prepared to throw a lot of hard drives into the project.  Maybe 100.  Maybe more.  Older the better, like in the dozens of KBs, instead of GBs.  Full size SCSI, is better than 1/2 height, is better than PC, and laptop HDs are near useless.

You probably saw this little motor conversion with HD neos.

It took 32 HDs with average HD sized magnets to supply the magnets.

The grey motor's OD is 3.75".  Guessing the "magnet rotor" is about the size of a toilet paper tube.

Sure doesn't look like 32 HDs epoxied on there, does it?

http://www.otherpower.com/images/scimages/2050/3phHD.jpg

"Dastardly Dan" made a decent HD windmill a while ago?

G-

[esc]

Yep, it was "Dastardly Dan's" 500 watt project that got me to wondering about this in the first place.

I've got about 30 hard drives to dissect.  but now that I've opened a few, what I'm even more interested in is the little coils that drive the read/write heads.  They are  perfectly sized for these magnets and appear to have a lot of turn of hair thin wire.

I wonder if they could be combined with a few of these magnets to light  some LEDs?

I'll have to check their resistance...

As far as the air gap, I figured I could use 1 thick and just bring the rotors a little closer together to make up for the thinner rotors.  I'm planning on about a 1/4" thick stator and, if the mechanical tolerances will permit it, a 3/8" air gap.

BTW, speaking of degaussing coils, I dissected a couple of old computer monitors...but there didn't appear to be any degaussing coils.   Could they have been TOO old.  The only magnet wire I found was on the CRT its self and that was all glued in a funny shape making it impossible to take apart.

[ghurd]

Be VERY carefull with the voice coils.  They get ruined without much effort.

They will light an LED easy.  Reach 12V easy too, but not many ma.

The gap, from the front of one magnet to the front of the other, needs to be the same or less than the magnet measurement between disks.

Hard to explain if you don't understand it by now.

The iron disks are 1" apart.

The magnets are 1/4" thick (long) each.

The magnets on the disks are 1/2" apart.

The air gap is 1/2".

The stator needs to fit in that 1/2" space between.

The magnets and stator and bearing wiggle and clearance all must fit in that same space.

Might look at my VCR windmill.  The "bad motor" coils are neat, if they are carefully removed from the iron plate.

Tiny stuff? 12V is not a problem.  50ma is a problem.

The degaussing coils are around perimeter the entire screen!

Giant mess, wrapped in black tape.  Looks like a rope wrapped in tape, around the screen.

Big as a pencil?

Need a pic?

G-

[esc]

Thanks ghurd,

That description of the degaussing coil helped, I found it.

I never would have guessed that was a coil.

So a handful of those HD coils and a few HD magnets could make 12v?

Even 50ma could light a small LED.  I might try something like that with a $10.00 mole chaser from HF.  As if I didn't already have enough projects...

I have looked at the VCR windmill before.  Very interesting stuff.

As far as the gap; With the 3/8" thick ceramic magnets I was planning on a 1/4" thick stator and about 1/8" clearance on each side for a total air gap of 1/2".  Which would also be about right for 2 of the HD magnets stacked.

1/2" is a little less than "the formula" calls for but I figure it will help with the ceramics.

Now I just have to strip a couple more monitors and get started winding coils.

[ghurd]

Advice: Only unwrap the degaussing coil enough to see the wire size and estimate the length.  Don't unwrap it until ready to use it.

"Seemed like a good idea, at the time."  LOL

Big giant CRT TVs are a jackpot.  A 37" had a figure-8 coil, guessing 1600~2000' of #19.  Can make a lot of mistakes with one of those.

G-

[esc]

I can see how the size of the CRT would have an exponential effect on the amount of wire present.  The little 14" monitors I got, have enough for a couple of coils, but it does seem pretty thin.

Is there an easy way to guesstimate the gauge?  Pry out several strands and line them up, side by side, until I have a measurable sample?

[gotwind2]

Personally.

I can't see a problem simply buying the correct magnets for the job.

Here in the U.K. Neodymium magnets are not that expensive, even when bought over eBay, as compared to stripping down many hard drives for the very thin irregular shaped magnets.

I'm not a wealthy man by any means, but the right magnet dimension for the job seems to make sense to me.

Just my thoughts.

[ghurd]

A 14" monitor is probably about #22.

Strip the varnish and measure with vernier calipers.

Bigger means more turn of larger wire too.  Usually.

But yea, I'd buy some neos.  Cheaper than gas collecting free HDs 2 or 3 at a time.

G-

[esc]

I try to measure the wire soon.  Thanks.

Like I said in the first post

.

BTW, I know my time would probably be better spent doing something I could get paid for and buying bigger magnets, but this seems like more fun today.

[ghurd]

The funny thing?

I have magnets.  And still bought all those HDs!

Yes.  Big fun in small packages.

G-

[ghurd]

Every TV and monitor I ever took appart had a degaussing coil...

Until today.

Two TVs = 0 degaussing coils.

One is an old Sharp 13" made in Osaka, Japan.  And it has 7 tubes.

Doesn't look that old.  Still works!

Other is a 13" Magnavox (outside), Goldstar (inside), warranted by NAP, made in Korea, in 1986.

I do not know if it is because they are so small, cheap, old, or some combination.

People looking for degaussing coils will find this helpful if they can not locate it.

More so if they have a TV without a degaussing coil!

G-

[TomW]

G;

Not exactly sure when they started adding them as a matter of course but old tube type sets didn't have them so us old TV guys always carried a hand held degaussing coil in our kits for "fixing" the buggered color on the old sets when someone cycled the vacum too close to the things.

I sold that business in the late '70s and the built in degaussing coils were introduced after that some time I guess. Or I forgot if any of those dinosaurs had them.

Must have been your lucky day, I haven't recycled a CRT device in a long while that did not have one. They can be buried in the plastic front bezel, too. I suspect you knew that already.

Lots of fine enameled wire in a big one, too!

Tom

[ghurd]

I need to add I have seen a couple with the coil in a (white) plastic/rubber housing stuck to the screen IIRC, which looked like a very short wide triangle from the side.

I did not know that.  Just checked.  These bezels have no wires.

Did find some fossilized dinosaur poo.  Mostly around the tubes.

G-

[RP]

And of course only color CRTs will have a degaussing coil.  Black and white sets don't need one.

[DamonHD]

G: how did they train the dinos to do that?

Rgds

Damon