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floodrod
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Joined: 08/07/2009
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Posted: 03:21am 13 Oct 2009

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I was messing around with a 1/4 HP 110v motor which I garbage picked. The same kind you use on a table saw or the likes..

I opened her up and started drilling the armature with 7/16" holes for the magnets.. No planning, I just hacked away.. Eyeballed the holes.. Hammered in the magnets, no epoxy, no nothing..

I missed a few magnet holes, and messed some up pretty bad. I didn't care because the mags were my extra cheap ones and I have a few of these motors lying around..

I tested it with a drill, and it reached 13 Volts easily and wouldn't go over 16V. Looking OK

Sanded the heck out of the armature and squeezed it back in.. Hooked up 2 rectifiers and ran it to a 12V 100 watt holegen spotlight.. She lit up nicely..

My multimeters crapped out on me and I couldn't measure amps, but I couldn't push more than 16 Volts and it lit up the 100 watt 12V bulb fully.

Can I assume this genny is pushing 8 amps at 12V?

video coming soon of construction

floodrod
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Joined: 08/07/2009
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Posted: 02:32pm 13 Oct 2009

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The construction video is uploaded and ready to view.

http://www.youtube.com/watch?v=B8izAtr9EWs

RicRock
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Joined: 10/10/2009
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Posted: 06:57pm 13 Oct 2009

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Very Nice

You've motivated me... I have something similar out in the shed.

floodrod
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Posted: 07:42pm 13 Oct 2009

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OK, So I got new amp meters and ran some tests to get more accurate numbers..

Hooked up to a 12V battery:

If I drill spin it real fast, I can peak it at 3 amps.. If I use my slower cordless drill, I can get 2 Amps.

1 Amp is pretty easy to hit. 2 Amps would take heavy winds, and 3 amps would require gearing..

But I used real thin magnets and missed a bunch of holes. I could definitely squeeze in a lot more magnets and align them better.. I think If I took my time, I could increase the amperage dramatically.

So it looks like this motor is much better than the ceiling fan kind, but I have not yet reached the real power zone.

oztules

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Joined: 26/07/2007
Location: Australia
Posts: 1686

Posted: 06:17am 14 Oct 2009

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Floodrod,

The picture of the magnets in place is very fuzzy... however, it looks like you have sunk the magnets into the rotor. This is not a good thing. The magnets will have terrible leakage from the top pole (just at surface level) to the bottom pole (buried in the steel rotor). This means that a lot of flux is running from top to bottom of the magnet via the the steel of the rotor, rather than jumping the air gap to the stator and back through the stator to the next pole on the rotor.

Put simply, unless the air gap is wickedly skinny, you will sacrifice a lot of power generating ability (due to the degraded flux), and will have lots of armature reactance, as the effective field is weaker than it should be, so the back MMF will interfere with the magnets remaining flux more than would be expected.

I suspect that the gap is very small, and that will help mitigate the mistake (the smaller the gap, the more likely that the flux will jump the airgap and go through the stator and back, rather than just running from N to S through the rotor steel). It does require a lot of rugged machining if you don't have a lathe though.

It will never be a slow speed killer alt,and it is always good fun to see them drive anything

, but I don't think you have made best use of your magnets yet.

............oztules

Village idiot...or... just another hack out of his depth

floodrod
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Joined: 08/07/2009
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Posts: 70

Posted: 03:08pm 14 Oct 2009

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oztules said Floodrod,

The picture of the magnets in place is very fuzzy... however, it looks like you have sunk the magnets into the rotor. This is not a good thing. The magnets will have terrible leakage from the top pole (just at surface level) to the bottom pole (buried in the steel rotor). This means that a lot of flux is running from top to bottom of the magnet via the the steel of the rotor, rather than jumping the air gap to the stator and back through the stator to the next pole on the rotor.

Put simply, unless the air gap is wickedly skinny, you will sacrifice a lot of power generating ability (due to the degraded flux), and will have lots of armature reactance, as the effective field is weaker than it should be, so the back MMF will interfere with the magnets remaining flux more than would be expected.

I suspect that the gap is very small, and that will help mitigate the mistake (the smaller the gap, the more likely that the flux will jump the airgap and go through the stator and back, rather than just running from N to S through the rotor steel). It does require a lot of rugged machining if you don't have a lathe though.

It will never be a slow speed killer alt,and it is always good fun to see them drive anything

, but I don't think you have made best use of your magnets yet.

............oztules

True True.. I remember reading that on this forum in the past.. The motor is now sitting by my 4 other projects in the closet. it will probably never be used, except for experiments...

I don't regret doing it tho. I wasted $10 in magnets, but was entertained for a night and learned a little bit more..

But I do think it's possible to squeeze 4+ amps from one of these if I had the right tools..

Thanks for the info and evaluation.. your info is valued

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