thanks , i might have a 5.25 half hight drive floating around somewhere.. think that might have them in there?

 

Eh WilliB,
I'm looking for some magnets aswell and I wonder if 15mm dia x 20mm thick would be suitable as www.oatleye.com have them under the general items page. These magnets are "Very strong NEODYMIUM IRON BORON RARE EARTH MAGNETS" quote from the webpage.
anyway I'll keep looking over here in Oz for them and if I find any I'll let ya know straight away.

Cheers Bryan1

 

Hi williB,

Not sure about one *that* old, I took a 5.25 inch HD apart once, had a very nice stepper motor (400 steps/rev iirc) for the head positioning instead of the magnets.

All the 3.5 inch HD's I've disassembled (about 10) have the magents, from old 120MB to new (dead) 40GB.

FoxyRick.

 

Only seriously OLD!! TV's had any magnets in them, only in B/W sets, and probably 1950's vintage.

They also weren't that strong!.

Magnetrons in microwaves have two strong magnets inside, but they are circular (as were the old TV magnets) - would they be any good?.

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.. due to the size and shape of the ones on that site , if you stacked three in a line , with the same polarity facing up that would work..

 

last night i ebay'd NEODYMIUM IRON BORON magnets and found a bunch
and i suppose that i should use them..but i went to home depot and fould some ceramic magnets , in the hardware section 1-7/8 x7/8x3/8" ..from what i was reading the rare earth magnets were 10 times stronger than the ones i bought.. but i could allways switch to NEODYMIUM IRON BORON

 

really? what shape are they?

 

when i was a kid we had a bunch of really strong magnets around the house , i thought they were from TV's .. maybe not..
it would be best if they were flat , for ease of construction .. the next time i see one thrown out, i will tear it apart and see whats inside..thanks for the info..

 

Bryan1 , if you put them like this it would probably work very well..

Hugh Piggots site says to alternate the poles of the magnets like in the picture. the otherpower Site says also to alternate the winding direction...
CCW to CW to CCW..ect... But Hugh Piggot says during testing ... if the winding isnt working properly to just switch the connections on the coil...

Attached Images

magnet_layout.jpg (13.4 KB, 1175 views)

 

I have seen two basic shapes of HD magnet. They are used in the head positioning assembly, together with a voice-coil on the arm.

The magnets are flat, about 3mm thick, with poles on the flat faces. The shape of most varies from an arc to an elbow, intended to follow the arced movement of the arm from its pivot. Approximate size is 20mm on the long arc/elbow side to 15 mm on the short side, the width is about 10 to 12 mm. Somehat like the sketch below (don't laugh, I'm not an artist, that's why I teach science!)

Usually there are two of these. Sometimes I have seen a magnet nearly twice the size, but just one.

FoxyRick.

Attached Images

hdmag.jpg (2.0 KB, 1167 views)

 

huh , i suppose as long as they are flat , we could use them..
i shall take one apart ..
what grade do ya teach?

 

this 5- 1/4 drive has lots of neat parts inside
its got
a mechanical actuator which when power is off it applies a Brake to the plattens..
also cylindrical , a platten speed indicator..
a linear mechanical slide with a little over 1 inch of travel ..
and like Foxy said it has a 400 steps/rev stepper moror driving the mechanical slide..
but alas no magnets..
oh it also has a platten drive motor which could be used as a mounting mechinism for our Permenent Magnet Generator..

 

Yes, old drives can yield some good mechanics. I've a collection of spindle motors and linear rails from them, most make good, light-use bearings for other things, some (especially older motors) have too much cogging. A shame they are generally tricky to drive, not having sense outputs. Also, they don't give a useful output as a generator unless spun at silly speeds!

Some of the spindle motors have the spinning centre exposed at both sides, with the physical mounting points on a fixed outer edge. These would be good for smaller PM generator-type uses, allowing the magnet/coil assembly to be on one side and allowing easy machanical coupling to the driving mechanism on the other side.

I am head of science at a small, independent school, teaching 11 to 16 year-olds up to GCSE level in the UK.

FoxyRick.

 

I decided to make a fixture for the Armatures. This will keep them the same thickness. I plan to pour Resin around them , so when they are done i can move them around individually till i like where they are , then i can fasten them properly..
i started with plaster around the shape of my magnet. took out the magnet , poured resin into the hole where the magnet was and what i got was picture 3 , after some sanding and fileing .. i tapered the fixture so it would come off when it was done..
I started with two squares of heavy sheet metal ( from an old computer case ).. cut it with a pair of sheers.. filed and bent the edges away from the inside.. then i bent some 10-24 threaded rod for the handle ..
so now the armatures will all come out the same thickness..

Picture 3 shows the molded resin which i'm going to wrap the wire around.. i had two tapered screws all set to use on the inside to attach the handle to but then i got the idea to use the threaded rod , so now i am hoping that the nuts dont interfere with winding ..

Attached Images

	armature_fixture.jpg (11.4 KB, 1127 views)
	armature_fixture_2.jpg (14.5 KB, 1125 views)
	armature_fixture_3.jpg (13.1 KB, 1125 views)

 

I have a 1.2GB hard drive(gone). It has a stepper motor, with three terminals. Can this be directly used for our purpose.

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