DC Motor Output

[partsman]

Is there any rule of thumb on how much power a PM DC motor will make?

1/? of the watts it uses as a motor maybe.

[ghurd]

What are you looking for?

Big, small, lawn art, 10W, 10KW...

I'm going out on the limb this time and say "No Rule of Thumb" for the power it will make, based only on the power it uses, and wind power.

The larger the watts, the better the chances it will do OK.

The cheaper the motors construction, the worse the chances are it will do OK.

The lower the rated RPM/volt, the better it will be.  Do not use that for geared motors.

Above 1/4 HP is better.  Below 300W is not so great.  Yea, I don't know either.

The resistance, RPM/volt, amps/volt, inductance (never listed), etc, is all a consideration.

The larger the windmill, the easier it is to figure a motor.

The smaller a windmill, the harder it is to even guess, because the available numbers don't make sense.

Sometimes rated amps, times are used to gauge the max output before the motor dies.

IIRC, up to 3X the rated amps is possible for before stuff melts.

G-

[partsman]

I really just wnat 100-200 watt to play with.

I live in town and can't get enuff wind for "real" power.

Read some where about induction motors as generators putting out a fraction of there useage. Just though there might be a rule of thumb for DCs also.

I do realise that it would have to it at low rpm for wind.

It's just hard to find bargans without a little knowhow.

[ghurd]

Might Google search the board (top right)for 'Ametek' and 'ECM'.

The right Ametek or a 1/4HP GE ECM may be close to what you want.

Don't expect over 100W in town.

[partsman]

Been looking for treadmill motors.

What should I look for on them.

I just want to charge a battery and run a few lights.

You know, do my part to save the world and have backup lighting.

[CmeBREW]

I know this treadmill motor makes a good mill for the money:(mine is still working fine)

http://cgi.ebay.com/2-25-HP-260V-treadmill-duty-DC-Motor_W0QQitemZ220045667384QQihZ012QQcategoryZ152

80. QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
    
12. volt cut-in is around 350rpm--so it makes most of its power from 400-800 rpm. Use 4.5 foot diameter blade rotor is best for easier start-ups. Cogging is fairly light.
    
    

If you HAVE to put it on your roof, then the higher above the roof point, the better.

[gotwind2]

Did a quick test, spinning my Ametek 30v DC motor by hand, gave me 15 volts, without any cogging.

The Greenmaster 180v DC Treadmill motor gave about 10 volts, with a bit of cogging.

Not very scientific, but indicates the Ametek 30 gives about 1/3 more volts per rpm.

Ben.

[ghurd]

What POs me about that is he paid $10, because I posted it.

[partsman]

Thank you guys.

Looks like no good rules or calculations.

Just good old experience.

I'm glad this site is here or I would have had to find out for myself.

PS not mounting on roof.

Here in Oklahoma we still have something called a yard.

I am accualy thinking about an old water mill style tower.

We still have those too. I have climbed many a time.