what to look for in a motor

[greenkarson]

going to the surplus store tomorow. Having trouble locating a local tape drive motor but surplus store carries lots of other motors. What other kinds of motors will work with out being modified. can any one let me know what to look for in layman's terms? for a low rpm 12v alt

what voltage motor?

what amps? anything else I should know

thanks love this site

[ghurd]

Start with a DC motor.

"Field: PM" on the tag means it is a permanet magnet motor.  The brush holders may or may not be exposed.

Low voltage and low RPM is like the Ametek etc tape drive motors.  Probably will not find one at the local junk store.

Best chance is finding a 90V DC PM motor.  13V / 90V X RPM = Charge Cut-In RPM.

So a 90V 1700RPM motor will start charging a 12V battery at about 250 RPM.

The name plate amps is about all the amps that can be safely get out of them.

A 1/4 HP 90V DC PM motor may be rated at 2.5A meaning it can make 40W, more if you push it.  A 1/2HP may be rated 6A.  Bigger is better.

Some people push them harder than others.

Look for motors with bearings instead of bushings.

Do not get anything with gear reduction, or a gear box on the end.

I doubt they will have anything great.  Never know.

G-

[greenkarson]

thanks alot appreciate the info any body else have anything to add? will be using a furnace cage fan for a water wheel if this helps

[Chuck]

For what it's worth, here's a link to some motor discussion I posted many years ago. It highlights some issues with using brush style motors as generators.

http://www.fieldlines.com/story/2003/10/13/155010/22

Chuck

[greenkarson]

there was a "PM 225 12v DC 88"  motor that was all they had for a PM motors would this work I beleive it was off some sort of fan. 3/8 shaft just curious if his will be able to make me any power can any body let me know roughly how much power it would be capable of producing if any?

[ghurd]

Most of the cheap and common 12VDC motors are fans or blowers.

The RPM required is too high to get much, if anything out of it at 12V.  Some won't even reach 12V open circuit at "very high" RPMs.

Your luck may be better than mine.

G-