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heynow999
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Joined: 15/02/2009
Location: Canada
Posts: 13

Posted: 03:53pm 08 Nov 2009

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I tried a search but found nothing.

I was at a local hobby show and I picked up a couple small brushless hobby motors. I think they are meant for RC planes. Here are the specs.

http://www.imexrc.com/servlet/the-1175/Brushless-Motor/Detai l

Dimensions: 28x26 mm
Size: 370 mm
RPM/Volt: 1210
Resistance: 289
IO (A): 0.5
Max Loading: 9 A/S
Weight w/ Connectors: 44 g
Shaft Dia.: 3.17 mm
Voltage Range: 6-12v
ESC: 18A / 25A
Continues Amps: 7A

I am wondering it it could be used to build a really small windmill. I suspect it would have the same problem as an F&P in that it is wound wrong to put out much usable energy. Specifically, the rpm/volts is 1210 which I guess means it would have to spin 14,520 rpm's to put out 12v! Perhaps it could be rewired like an F&P. It can be easily taken apart so that is my next step(I did buy two!) I would imagine it puts out 3 phase AC so I would have to rectify it. I will make a trip to the local electronics store and buy some bridge rectifiers

I realize that it would only put out tiny amounts of power but I want to practice a bit before I tackle my real F&P projectEdited by heynow999 2009-11-10

heynow999
Newbie

Joined: 15/02/2009
Location: Canada
Posts: 13

Posted: 07:30pm 08 Nov 2009

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Just an update

I spun the motor with my cordless drill and the most I could get out of any two wires was .7V AC

I took it apart to take a look and it has 12 coils and 14 magnets. It may be tough to get at the coils as it looks like the whole assembly (stator?) is pressed onto the shaft and the back half of the motor blocks access. Oh well, I bought two just in case

Dinges
Senior Member

Joined: 04/01/2008
Location: Albania
Posts: 510

Posted: 10:04pm 08 Nov 2009

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These are motors intended to run at high RPMs. In your case, 1210 RPM/V, so at 12V about 14.000 RPM. Electrical input power is about 84W (12V@7A cont.)

You could try rewinding it to lower the RPM/V and make it usable as a low-speed alternator. But by doing so, you will also lower the available output power: by rewinding with 10x as many turns (and using thinner wire to make all those extra turns fit in the same slot space), you'll lower power by about 1/10th (roughly), so 8W.

That's the price one pays for low RPM generators: they are physically large for relatively little power.

If you intend to play with rewinding (I would, if I had such a motor), then this is *the* website on small RC brushless motors ('outrunners'). Only available in German though, unless you can read google translations without all your neckhairs standing up....:

http://www.powercroco.de/

The 12 coils/14 magnets configuration is pretty common: http://www.powercroco.de/motorespeed.html
http://www.powercroco.de/12N.html

...for a boat:
http://www.powercroco.de/12N14Pbootsvomo.html
...for a bicycle:
http://www.powercroco.de/24N28P6530.html

Keep in mind that not all coils are wound in the same direction! That's the trick to those 'strange' stator/rotor pole combinations. Some coils are wound CW, others CCW. The croco site also explains it all:

http://www.powercroco.de/schemalesen.html
http://www.powercroco.de/tools.html

That site provides for many evenings of educative reading. And you'll be brush-ing (<-- pun!) up on your German as well.

Peter.

Tinker

Guru

Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 02:54pm 09 Nov 2009

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Thanks for these links Peter. I think my German needs brushing up too - 41 years in Australia does that to one

Klaus

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