How hot is too hot?

[BHChieftain]

Hi,
Did a test run on my syncron the other day, after 5min brought her back in. Lipos and ESC were cool to the touch. The motor *can* was warm, but not hot. However, the rotor shaft that sticks out the back of the can was very hot-- had to pull my finger away. So with a warm can and hot shaft, is that running "hot", or "normal"? I don't have a temp gauge...

Thanks
-Chief

[m4a1usr]

You my friend have demonstrated why I put little faith in shell cooling, like water jackets. The rotor can be much, much hotter then the windings, yet most assume that the heat is uniform or equally distributed in an electrical motor. Truth is the rotor sees most of the heat and without air flow its going to cool much slower then the rest of the motor. Now I will not state ever to dump or get rid of the water cooling shells we use. Heck I would be a hypocrite as most of my builds include a water jacket. But as an additional cooling method. Not the main method. Proper motor sizing and or load is key to that part of a build.

But if some of you honestly believe that shell cooling is going to solve your motor cooling issues you need to do some basic research and understand where heat is being generated and where it will stay.


Now that I have stated all of that you may have a bearing problem so you might check them, both the front and rear bearings as friction from bearings can conduct heat to the rotor too.

John

[Flying Scotsman]

John, on the button as usual. Motor incurred heat will take time to soak though to reach the outer surfaces and can cooling will have no affect on interior surfaces that are really toasty due to abuse, the damage has already occured.

Douggie

[BHChieftain]

You my friend have demonstrated why I put little faith in shell cooling, like water jackets. The rotor can be much, much hotter then the windings, yet most assume that the heat is uniform or equally distributed in an electrical motor. Truth is the rotor sees most of the heat and without air flow its going to cool much slower then the rest of the motor. Now I will not state ever to dump or get rid of the water cooling shells we use. Heck I would be a hypocrite as most of my builds include a water jacket. But as an additional cooling method. Not the main method. Proper motor sizing and or load is key to that part of a build.

But if some of you honestly believe that shell cooling is going to solve your motor cooling issues you need to do some basic research and understand where heat is being generated and where it will stay.


Now that I have stated all of that you may have a bearing problem so you might check them, both the front and rear bearings as friction from bearings can conduct heat to the rotor too.

John

Thanks, John.

The config in question is a feigao 540 8XL , Hydra 240 ESC, 4S1P 35C lipo (two 2S in serial), and a graupner 45mm prop. Would dropping back to a 43mm prop make a significant difference? The other prop I have is an octura x440/3-- is this a higher or lower load inducing prop than a graupner 45mm?

bye
-Chief

[Flying Scotsman]

That is a too much motor and prop combination IMO for a sport setup. What are your goals.

Douggie

[BHChieftain]

That is a too much motor and prop combination IMO for a sport setup. What are your goals.

Douggie

Mostly sport, but I'd like to race it now and then. But I'm more interested in reliability vs. all out speed...

-Chief

[Flying Scotsman]

I might suggest an X640 but I still think your motor is too hot for the application

Douggie

[LiPo Power]

Good suggestion....
My is:
Get the temp gauge and use it often before you get to the right set-up or

I might suggest an X640 but I still think your motor is too hot for the application

Douggie

[BHChieftain]

I'm trying to compare the octura vs. graupner props--

Would the x440/3 (I have one of these) cause a higher or lower load than a graupner 45mm (which seems to be too hot)?

-Chief