Thanks for the youtube link Bob;
    That was interesting. It's quite unlikely that I'd reach anywhere near 300F, so it should be fine.

Todd       
C-FSTB

On Mon, 2009-05-04 at 07:46 -0600, Bob White wrote:

You are looking for Curie temperature.  For Neodymium magnets, they
start loosing strength at around 300F and the curie temperature is 590F
(according to a web site).
http://www.matchrockets.com/ether/magfaqs.html

Here is an interesting YouTube video of the phenomenon.
http://www.youtube.com/watch?v=X8ZHQQUusGo

Bob W.

On Mon, 4 May 2009 19:40:21 +1000
"George Lendich" <lendich@aanet.com.au> wrote:

> Todd,
> The heat actually affects the rare earth magnets, a search on the internet should confirm this. I just can't remember the details. I guess the glue is another matter.
> George (down under)
>   Hi Ernest;
>       From Georges comment, I gather that the heat sensitivity would likely be due to the glue that bonds the magnets to the inside of the rotor. This makes sense and also means that I shouldn't have much of an issue if no air blows under the rotor and onto the stator. Air movement around the rotor should be enough.
>        I really am a lot less satisfied with "should" than I used to be.
> 
>   Todd
>   C-FSTB
> 
>        
> 
>   On Sun, 2009-05-03 at 21:01 -0400, Ernest Christley wrote: 
> Todd Bartrim wrote:
> > I'm thinking about the cooling issue that you are addressing with fan 
> > blades. How much heat do you think it will generate? I'm 
> > thinking/hoping not much. I don't know about the original Harley 
> > install, but as this is commonly used source of power, I got to 
> > looking at my Ski-Doo, ATV and dirt bike. In everyone of them the 
> > stator/rotor is completely sealed up and is not liquid or oil cooled. 
> > And I've never had issues with them. It would be a simple matter for 
> > me to put a small baffle at the exit of one of the evap cores that I 
> > use for cooling and direct some of the air over the rotor, but due to 
> > the tight fit, not much air would find it's way under to the stator.
> I don't know what sort of heat load it'll generate, but it is almost 
> immaterial to my installation.  For me, he intake air will be flowing 
> over it regardless.  I've been told that PM alternators are only 50% 
> efficient.  I find that hard to believe;  that would be a 500W heat 
> source for a 40A generator.  But even at that worst case, it isn't an 
> issue for me.
> 
>