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Power Systems Talk about motors, ESC speed controllers, gear drives, propellers, power system simulators and all power system related topics

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Old 08-09-2012, 11:10 AM   #1
HugoW
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Default Cooling EF-1 motor?

Hi,

I fly a RBC kits Polecat in EF1 competition, but it's not going to plan. The plane is up and flying, finally trimmed out, should be OK. The motor is a Turnigy AerodriveXp 25 SK Series 35-42 1250Kv, as allowed by the rules. I fly an APC 8x8 thin electric, also per the rules. But I fear I have to prop down to 8x6, because the motor gets very hot. I have not measured yet (just ordered a motor temp sensor for the datalogger), but I can smell the motor if I land quickly after a speedrun. Any ideas on how to cool this motor better?

Here's some pics:
During build:




After maiden (with a nose stand landing, hence the prop...):




I would like to keep the spinner on, but modding the cowl is certainly an option.

Cheers,

Hugo

There´s always room for one more plane...
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Old 08-09-2012, 01:12 PM   #2
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You need to get some air moving through the cowl. That needs an exit hole for the warm air to get out, this is usually in the bottom rear of the cowl and should be larger than the combined area of the inlets. I'd open up the inlets a bit too, they look like no more than slits at the moment; make them larger and maybe consider putting some form of deflector behind the inlets to push the cool air that toward the motor.

I'd also take a sneaky peak at the set-ups that the fast guys are using.. See what motors they are running and how they have their cooling configured.

Steve
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Old 08-09-2012, 01:19 PM   #3
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I'd guess this is kind of obvious, but how about larger openings in the cowl to improve the air flow. The other question is how large an opening do you have in the aft for air to exit. If the air flow through the fuse is insufficient, then you will not get enough cooling. Just something to think about.

Steve P.
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Old 08-09-2012, 02:19 PM   #4
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Well, all may be obvious, but the air flow doesn't reach the motor when I increase the openings in the cowl. Even without cowl, the spinner blocks air going to the motor. And air passing over the motor only cools the can. The stator is the part that runs hot. And I know, I run 66A through a motor raited at 40A max, but since it's the recommended / approved motor and prop combo, I cannot understand why I couldn't do it.

So, my idea is to make some sort of aluminium cooling body to attach to the base of the motor, tha sticks out to the sides to be in the airflow. Any experiences with that anyone is willing to share?

Originally Posted by JetPlaneFlyer View Post
I'd also take a sneaky peak at the set-ups that the fast guys are using.. See what motors they are running and how they have their cooling configured.
That would be great, but here in the Netherlands I'm one of only three competitors. And I cannot find much details of what the US racers are doing.

Cheers,

Hugo

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Old 08-09-2012, 02:39 PM   #5
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All you need to do is get more air in (and out) of there then add baffles in the cowl that channel the air toward the motor.. that works fine. I vac formed a 'scoop' that fits in the cowl behind the opening and ducts air over the motor. I put the scoop on one side only with intention of creating a cross flow of cooling air. Balsa or ply deflectors would probably work just as well as the vac formed scoop.

I have seen people make oversize finned cross-mounts to cool the stator but it would only be worth considering that if the motor was still overheating after you improved the cooling airflow.. As it is right now there is probably zero air flow through the cowl, so hardly any wonder it overheats.
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Old 08-10-2012, 12:50 PM   #6
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Well, the problem has solved itself, sort-of. I read in a dedicated EF1 topic the Turnigy actually isn't up to the job. Fun motor for leisure flight, but not for racing. They overheat and burn out. So, to underline this fact, the motor burned out yesterday on the testbench.

All EF1 racers run this minimal cowl openings, but almost everyone has gone to the E-Flite or OS motors, newly added to the rulebook. Only in the Netherlands, they didn't update the rulebook, yet. So I just ordered the OS motor!

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Hugo

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