Below is a picture of 2 small brushed motors.

The one on the right is what I am used to seeing (permanent magnet)

What's up with the one on the left

1) motor on left has s 2 piece magnet with very little magnetizm, plus a much larger rotor

kv is around 1500 wjile motor on right is around 200 kv

Both are rated at similar torque, and neither has true brushes.

TIA

Wierd! one on the left looks like a CD-ROM style motor where the magnet is just polarised on either side. Doubt it would be very powerful at all as a result, but not too sure really.
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Actually, they were bioth supposed to have almost identical characteristics, but it turns out that the wierd one has the same torque, but different kv

Motor on left is around 1500 kv while the other is 2200kv

left one is simpler to make at the expense of more material.
in *theory* the left one should have *more* magnetic power, theory and china often differ even more than theory and practise ;->

Oh as for which to use, if its in robots, the one on the left would probably have less of an issue with the magnets smashing out of them.
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Mechanical engineers build weapons, civil engineers build targets

So, you have seen this type of full circle magnet before?

yeah, not common. the ring itself is harder to make, in theory it needs to be heated and magnetised as one piece.
I don't know why but I'm feeling its an older school way of making them.
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Mechanical engineers build weapons, civil engineers build targets

the only real reason that I am liking it is that I've had magnets break or come loose before (rare), and this seemd a bit more robust than 2 magnets