Fans on motors and esc

[ghostdogg]

Hi all,
Daft question but what way round do you mount the fan?
Blow air onto the motor or esc or take hot air away from the motor or esc!!!!

Cheers

[mattr]

In theory it makes little to no difference, in practice, blowing on to the item will work best.

(As long as you have somewhere for cool air to get into your shell and through the fan!!)

[simoncrabb]

Yes, agreed, blowing tends to work better than sucking.

I think the reason for this is sucking pulls air from areas other than the heat source, as it's not a 'sealed' air source.

But by blowing the air kinda can't miss the hot bits.

[Cardnim]

Damn good question though Ghostdog - I had never thought about that before.
Interesting.

Good to know that ive got the fan on correctly though so it blows (even though I 'suck' at racing)

[Gunter]

During the national events this year in touring cars (sorry buggy boys) we found that sucking the air reduced the heat by between 5 and 10 deg more than blowing.

This dose depend on the position of everything of course, fan infront of the motor in the direction of travel needs to be blowing, fan behind the motor needs to be sucking.

Basically you want to move the air faster in the direction its already traveling, not try blow air back againt the direction of travel and stalling the hot air around the motor heating it up and making things worse.

[Cardnim]

a "touring" car?
Nope, thats a new one on me.

[kayce]

Originally Posted by Gunter

During the national events this year in touring cars (sorry buggy boys) we found that sucking the air reduced the heat by between 5 and 10 deg more than blowing.

This dose depend on the position of everything of course, fan infront of the motor in the direction of travel needs to be blowing, fan behind the motor needs to be sucking.

I'd like to see pics on how that was accomplished, but (like many such temp lowering propositions) it seems be a rather drastic change that seems rather unobtainable. 10 degrees just seems like a huge variation.
But, being as most rc company's fans are designed to blow on items, it makes sense they'd know what they're doing (maybe not ).

Yet it also seems that a lot of people use fans as a fix to address overheating, despite them being more of a bandage, as I was always taught to get your temps to an acceptable level before adding a fan.

[mattr]

Originally Posted by Gunter

During the national events this year in touring cars (sorry buggy boys) we found that sucking the air reduced the heat by between 5 and 10 deg more than blowing.

this is where theory and practise differs.

Best place for a fan, for maximum efficiency is in "clean air" so putting it in a position where it needs to suck (behind the motor) instantly puts it at a disadvantage due to the lack of clean air.

On the flip side, how "clean" is the air in front of the motor (in a blowing location)?
No-one knows, not without a wind tunnel anyway. And it will differ depending on car type, motor/ESC location, holes in the body shell (either sealing, cut holes, ducts, whatever). Then you have to consider packaging it all in as well, where do you have room for the fan, above, behind, in front (underneath!)? The difference between getting it wrong and getting it right could make 5-10 degrees performance difference depending on what temps you have in the first place (ambient, motor and/or ESC).

My specific example is on my buggy, with an ESC fan, where sucking thro all those fins on the heatsink really doesn't do it any favours, whereas blowing on to the heatsink fins, and consequently sucking the air from the intake above the ESC gives cleaner air flow (there is that damn theory again.......!) into the fan (and a more efficient fan, and more cooling)

Who knew that work would come in useful for RC cars