On Sep 18, 6:55*pm, wrote:
Mark wrote:
Clarification: With regard to the cooling of a sealed brushless
motor, your concerns and comments about air density are
basically irrelevant. They cool differently than open typical
electric motors that rely on air circulation.

Yeah, how is that, magic?

There are only two ways to cool any motor, and it doesn't matter whether
it is an ICE or electric.

You either put a bunch of pipes in the motor, run a fluid through them,
and dump the heat with a radiator that has air flowing through it or you
put cooling fins on the motor and that have air flowing over them.

And air at altitude may be cold, but it is also thin which means you have
to move a lot more air at altitude than sea level to get the same cooling..

--
Jim Pennino

Correct. The higher you go, the harder it is to displace the heat.
I believe the topic of this post is..."How high *can* you go?"

This doesn't mean you cannot have electric airplanes, or that
at 20,000 ft. they aren't superior to internal combustion.

You say, "You'll play hell keeping it cool". Well, yes and no.
At 95,000ft...it very well may be impossible. IMHO, the motor at any
elevation needs to be cooled with circulating glycol through a
patented design that runs through the center. At what elevation
your radiator ceases to displace heat...I don't know.

So yes, the elevation is relevant to cooling as you said, but
I am asserting that for GA purposes between AGL and
20,000 ft., you won't "play hell keeping it cool". On the
other hand, try leaving the troposphere and you might
better pack dry ice.

---
Mark