Rewiring 5-wire steppers?

I think this isn't possible, at least according to [reprap.org], but if someone knows different...
5-wire motors seem to be the only motors that it is impossible to make work as a bipolar stepper. True/False?

... depends on the internal wiring - I've opened an old stepper, separated the central conection of the 4 coils and reconnected two pairs, so it was wired as bipolar setup with 4 wires.

If the connection isn't accessible from the bottom lid, you'll get problems cutting the correct wire.

And be carfully with disassembling steppers - when pulling the rotor out of the magnets you can weaken the magnetisation, so the motor will loose torque ...

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Viktor
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Thanks Vik, that's what I had gathered. If I get what I'm bidding on on ebay, I'll see if I can do that.

Hello,

I rewired a 5 wire motor and posted some pictures here : http://forums.reprap.org/read.php?110,125036,156442#msg-156442

Didn't test it for now because I haven't got yet a sanguinololu.

Yes these KP4M2-008 motors are cheap ($4), small, light, have a small 24 teeth T2 drive gear and a single 16mm (L) x 5mm(dia.) shaft. The only problem with them is that they are unipolar 5 wire version with four 75 ohm coils. I noticed that there are two type of these motors. The 260 g and the 180 g versions. They can be identified by of course there weight but also by their look, the lighter version having an aluminium cast casing.
I opened both of these and noticed that the lighter one has 8 coils and the other one has 4. Both motors can be rewired back to 2 phase easily.
I plan to use the lighter one for my extruder because it's small and light.
I also noticed that the lighter 8 coil version has a lower final impedance of about 15 ohms so I probably overlooked that they had an initial impedance that was different from the 4 coil version.
Once finished the 4 coil version was now 2 phase and has a 37.5 ohm per phase impedance. The finished 8 coil version has, as previously mentioned, a 15 ohm per phase impedance.
I tested both version with a pololu A4988 and both turned smoothly but the lighter motor heated somewhat after a short time at 25% setting on the current trim at 12Volts.
I'm making a series of images detailing the conversion process.

RJ

Any update about rewiring those KP4M2 motors to bipolar? Photos would help a lot.