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Author Topic: How hot....  (Read 783 times)

Dwayne

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How hot....
« on: June 24, 2019, 01:33:10 PM »
....is to hot for a Eflite Power 32. After the first flight the motor was quite hot, not to the point that you couldn't touch it but almost, I put it up again with the top off and it's still very hot, there is plenty of room for the motor, there is a conventional opening under the spinner and I cut openings under the battery, so with the top off there is plenty of ventilation, it looks like it's always going to run hot, am I going to trash the motor?
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Offline Fred Underwood

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Re: How hot....
« Reply #1 on: June 24, 2019, 01:57:28 PM »
Eflite notes a maximum operating temperature of 220°F.  Other threads in this forum have noted that as a motor shuts off and sits immediately after the flight, the temperature without airflow my rise, so that you are feeling above operating temperature.  Not sure is sitting at over max operating temperature is ok for the motor as that is not specified. If you can stand to touch it without a fairly immediate burn, you are not at 220°F.  I have seen 140-160°F as the temperature for fairly immediate pain, depending you your finger/skin use.  And the Stator will be a fair bit hotter that the can and you didn't specify what you touched.
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Fred
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Offline Carl Cisneros

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Re: How hot....
« Reply #2 on: June 24, 2019, 02:55:55 PM »
If you do not already have one, get on down to your local (if you have one) Harbor Freight Tools and pick one of these up:

https://www.harborfreight.com/building-construction/measuring-marking-layout/thermometers-scales/121-infrared-laser-thermometer-63985.html

I use my older model all the time and not just on my boats and planes. Use it for cooking as well. Hot oil and such.

It lets me know what the motor (after shut down) as well as the batteries are doing temp wise.
It is a very nice and in-expensive tool that every one that runs electrics (cars, planes, boats, ect) should really have in their tool boxes
at their place of fun.

Carl
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Carl R Cisneros, Dist IV
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Offline Mike Alimov

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Re: How hot....
« Reply #3 on: June 24, 2019, 04:05:30 PM »
A couple of thoughts, as I did some pretty extensive testing on motors a couple of months ago, including measuring starting and ending temps using the laser thermometer...
Under "normal" or "average" loads, the motor should be finishing the flight not much hotter than 120-130 F, assuming it is well ventilated.  It will feel warm, but not uncomfortable for most people; definitely not burning hot.  If it is hotter than that, the prop load (pitch, diameter, RPM) is too high for the motor, which means you are trying to fly too much of an airplane on too small of a motor. Since you did not post any specifics, it is hard to evaluate that part.
Looking at the picture, the motor itself is not very well ventilated at all.  The oncoming air stream is being sliced by a large solid spinner, much larger in diameter than the motor.  The spinner leaves a certain area of low pressure air (a sort of vacuum) behind it, making it difficult to cool the motor.  Leaving the battery hatch off does help to evacuate the escaping air, but if the oncoming air is blocked (by spinner and motor mount bulkhead), then it doesn't help much.

Suggestions: (1) please post details of your setup - battery, motor, prop, RPM, airplane data - area and weight, line length, lap time; (2) consider using a vented spinner.
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Offline Fred Underwood

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Re: How hot....
« Reply #4 on: June 24, 2019, 04:37:33 PM »
It's hard to argue against more cooling, and that 130 is better than 160°.  But you have a built airplane and I think asking how hot is too hot.  I also have the HF non-contact thermometer, but as noted if you can remain in contact with the motor, not just swipe, you are probably in a safe range.  I can't tell about the mounting bulkhead hole, another place to move air.

More on the subject of rear mount ventilation by Igor
https://stunthanger.com/smf/gettin-all-amp'ed-up!/cooling-fan-using-rearthrough-the-bulkhead-rear-mount/msg557513/#new

Changing line length, prop, rpm may be helpful for temperature and make good trimming tools, if you want or are willing to change those characteristics. But, do you need to?
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Fred
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Dwayne

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Re: How hot....
« Reply #5 on: June 24, 2019, 05:28:40 PM »
Quote from: Fred Underwood on June 24, 2019, 04:37:33 PM
It's hard to argue against more cooling, and that 130 is better than 160°.  But you have a built airplane and I think asking how hot is too hot. 

Correct, how hot is to hot, seeing a 220 max is very reassuring there's no way it was that hot...lol I'll probably add some more cooling to be safe though.
Thanks every one
 y1 
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