Looking for a Source of Low RPM High Output DC Generators

Might be a challenge... gear up the generator... you have .22 HP availabkle to you.

Have you tried HSC?

Dc Generator Low Rpm - Alibaba.com
Or, Search GlobalSpec?
Where have you looked so far?

Here's a neat homemade one:

http://otherpower.com/hamster.html

The first thing that comes to mind for me to get fair power at low RPMs is to use stepper motor as a generator. Granted you will get two or three phase output but with a set of rectifiers you can easily convert that back to DC.

Power = Τω, 20ft lbs ~ 27Nm: So, Power = 27Nm * 60RPM/60sec/min * 2π = 180W ie it's certainly possible.

As usual it's difficult to get much power from a slow generator can you gear it up at all.

The following link will take you to a site which supplies the smart drive (AC or converted to DC) These guys configure to your requirements. Although a New Zealand company its worth an email as they supply world wide.

www.powerspout.com or

www.ecoinnovation.co.nz

Here's some great plans:

http://www.re-energy.ca/docs/hydroelectric-generator-cp.pdf

Good luck with your quest.

Yeah I agree the F&P Smartdrive motor should work, they are good for about 1 watt per rpm, and you can easily adjust the output for less. They produce 3 phase AC, so feed that into a bridge and you'll have DC.

But I'm a little worried about your comment "treadmill permanent magnet motors (too much load)". Load is proportional to output, and the treadmill motor would be reasonably efficient, so the load you feel is the load thats got to be there to make 10 to 25 watts. 25 watts is pretty hard work, you try hand cranking out 25 watts for an hour or two and your arms would feel like they are going to fall off.

Glenn

You can use a permanent magnet DC motor as a generator. The output voltage will vary according to the input speed so using a higher voltage motor will allow you to run it at a lower speed while still delivering your required voltage. With a 180v ¼HP motor run at 240-300 rpm you should be in the correct ball park. You would need to talk to the motor manufacturer for exact figures as they will vary slightly. Use somewhere between 4:1 and 5:1 spur gears to lift the shaft speed. Spur gears are easier to contrive an exact ratio and will be more efficient (above 98% up to 6:1) than using a belt drive. For suppliers try Leeson DC motors.

Think on add a transmition, pulleys for instance, to get a better speed and adapt a engine alternator. A home made solution.

The use of gears should be of particular use to you. I agree with the posts of others. If your machine can produce 180 W mechanical, and you can gear up reasonably to several hundred rpm, the result will probably satisfy the load you have in mind.