Tape drive motor

[41south]

Hi all,

I found an old backup tape drive the other day at work that looks like an overgrown CDROM motor. It has 18 teeth/stators around the outside, with a rotating magnetic "band" in the inside - the black ring in the diagram (attached to the tape drive spindle). It's about 100cm (4 inches) accross.

Pulled it apart last night and it will make an excellent mini generator if I can get the magnet pattern sorted. I will take off the "band" and put Neo mags on in their place. I'm just not sure how many mags and in what position they need to be.

I've done a rough diagram of the coil layout below. Its 3 phase but not a layout I have come accross before. Any help with a magnet layout will be greatly appreciated.

[willib]

does the motor have a position sensor ?

a small IC on a little circuit board near the rotor?

if so you may want to keep that where it is

you could use that for RPM measurement

[Countryboy]

Typically, most tape drive motors don't have much improvement if you replace the magnetic band with neos.

Output is already limited by the wire size, and tape drive motors aren't known for being able to handle the most current.

What RPM is this motor designed for?  If it is a high rpm motor (thin output shaft), it will be difficult to get much power out of it unless you rewind it.

If it's a low rpm tape drive motor, I'd recommend you use it as it is.  Any further modification are probably more effort than they are worth.

If it's a high rpm tape drive motor, I wouldn't bother with it.

[41south]

I would say that it is very low rpm. From memory the spec sticker said 12V 3 Amp. The wire is around 24 gauge and its very easily rewindable. It will be well worth the experimentation if anyone can help with the magnet layout.

[41south]

Sorted it - I think. By my calculations it should be 24 mags - 15 deg per mag. But it does make things look a little strange in that (refering back the diagram above) at any one time there are 2 red, 2 green and 2 blue coils - 180 degrees apart - covered by a magnet at any one time.

Something in all I have read is telling me that it should be all 6 red (or blue or green)coils at any given point, not 2 from each phase ?

Or do I need to rewing this beastie ? - which isn't a big deal.

[RP]

Wait for Zubbly to chime in on this.  That's a weird winding to me.  It looks like it has some kind of 6 or 12 pole thing going on.  

In any case, first thing to do is spin it up and see what it produces now before taking it apart.  hook it to your hand drill or drill press and see what kind of unloaded AC volts you get on 1 phase at 200-600 rpm (with the built in electronics disconnected).

[41south]

RP - good advice, I'll run it up on the weekend. It sure will be interesting.

And just to add to the interest I ran a compass around it and it has 8 poles on the magnet ring - N S N S N S N S. So its an 18 and 8 combo :-/

Back to my picture.

[ghurd]

I've seen stranger than 18/8!

Did the compass give a good solid positive reading?

On smaller ones it didn't work for me.  I use a carbon steel knife, sharp part to the magnet ring, slowly slide it around, it jumps pole to pole.

G-

[41south]

I took a picture of the beast last night. I'm sure it will make a great mini-gen when I get it sorted.

[ghurd]

So what is it out of? Brand, model, etc.

G-

[41south]

It came out of a DLT tape drive (as used to backup computer systems), not sure of the manufacturer but I will have a look at the chassis and see if I can find out more. There are 2 of these per drive :-)

I haven't had a chance to look at the magnet ring any closer to see if it really is just 8 poles or there are others "hidden" that I missed.

[ghurd]

Not sure how the wires were connected, but I'd suggest trying it in the factory configuration.  

The other one is untouched?

I figure it is wired star. Disconnect the drive circuits, then try it like it is, maybe it will suprise you.

Keep us posted!

G-