Motor fans, 1 x 40mm or 2 x 30mm

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Fireblade

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Corally RC's
  1. Kagama
  2. Radix
I'm in the process of making a Kagama LE style fan mount for my Kagama, I can laser cut a plate to whatever size and shape I need. I don't appear to be able to get 2 x 40mm fans in so my question is, what would give more air flow? 2 x 30mm or 1 x 40mm? I'll be using the Rocket fans which appear to be what Corally rebranded for theirs.
 
The fans all pretty generic The smaller fans usually can run at higher rpm. I ordered couple these last night cheapest I found. You can squeeze 2x40mm fans if run them on opposite sides but if making your own mount this maybe not an option. 2x30mm gonna push more air than 1 40mm

I just found this on AliExpress: ￡23.61 | RCZIPROY RC 25mm 30mm 35mm 40mm 50mm Fan Cooling Fan RC Creeper 1/10 1/8 1/5 540 550 3650 Motor Brushless/Brushed ESC RC Car
https://a.aliexpress.com/_EGSZ688

IMG_9222.webp
 
That's a decent price on the fans. I've got some 12mm tube clamps coming and will laser a kydex flat bracket to take the fans I reckon
 
Fireblade said:
That's a decent price on the fans. I've got some 12mm tube clamps coming and will laser a kydex flat bracket to take the fans I reckon
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I like a sucker for a bargain can get plastic case fans even cheaper if don’t mind not being so fancy

I just found this on AliExpress: ￡29.00 | 5Pcs YSIDO Hight Speed 4010 3510 3010 Cooling Fan Heat Dissipation for Hobbywing Traxxas ARRMA 4268 4274 1/10 1/8 1/7 RC Car
https://a.aliexpress.com/_EHT0MWo
 
I have a Kagama LE. I ran dual 30mm fans at first with the mount they provided with my truck. I then moved to a single 40 mm. My 30mm fans were low performing high life fans meant for the electronics industry. My 40mm was a high speed rocket fan.

They both performed about the same. I have a temperature sensor on my motor can and can log temps on my phone with the car running. So I have the data to prove they are similar.

What I think is going on is, just moving air past the motor is the important part. That does 90% of the cooling. The higher flow setups just get you a few degrees lower temps. So instead of 140F you might be able to get down to 135F. Whereas without a fan temps would be 180-200F.

More important than fan type or flow is spreading the air across the length and diameter of the motor, to maximize the amount of heat that can be removed. Thus ducting becomes more important. This is what my data showed as I experimented with different fan mounts that I designed ducting into.

That’s a long way of saying, just run any fan. It’ll be good.
 
Simple math area covered by 2x30mm fans is 180mm squared 1x40mm fan 160mm squared.
 
Yeah but is it as simple as that? When I look at the 30mm fans v the 40mm the centre part is the same, so the area that air can flow past is disproportionally smaller on the 30mm, but then the 30mm spin faster.
 
Fireblade said:
Yeah but is it as simple as that? When I look at the 30mm fans v the 40mm the centre part is the same, so the area that air can flow past is disproportionally smaller on the 30mm, but then the 30mm spin faster.
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Say that area was 10x10mm on both take that area away from each the 2x30mm would be 160mm squared the 1x40mm would be 150mm squared. There’s very little in it. Fitting one fan be easier & less wires . 2x40mm if temps a real issue the best way to go that’ll cover way more area.
 
If you rotate your motor so wires out if the way you might be able to get 2x40mm on it 🤷
 
There's a saying that outdoor survivalists use.... 2 is 1, 1 is none.

Go for X2, at least if one fails you still have one.
 
Fireblade said:
I'm in the process of making a Kagama LE style fan mount for my Kagama, I can laser cut a plate to whatever size and shape I need. I don't appear to be able to get 2 x 40mm fans in so my question is, what would give more air flow? 2 x 30mm or 1 x 40mm? I'll be using the Rocket fans which appear to be what Corally rebranded for theirs.
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Personally I like the Castle fan shrouds. They have one for 40~42mm motors that has a 40mm fan that has worked well in my Shiroi. I especially like that it has a proper grill with a mesh fine enough to keep debris out.

A shrouded fan fitted to the cooling fins on the motor is much more efficient at removing heat than an open frame fan pointed at it.

shiroi_taurus_07.webp
 
Aerodynamics say that an air stream from a fan will follow the surface of the motor. Like the air that moves over a car, will also follow the surface, untill it reaches a sharp edge that cuts it off, like the spoiler on the back of the roof/trunk.
So, it's not that the air lets go at the widest point of the motor.
A shroud may be better, but the usual fan clamps are doing fine.
 
Atomic Skull said:
A shrouded fan fitted to the cooling fins on the motor is much more efficient at removing heat than an open frame fan pointed at it.
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I agree. My testing verifies that simply shrouding 180 degrees around the motor is worth over 10 degrees F lower temps compared with the same fan simply blowing at the motor from 5 mm away. All other things remaining the same. For reference, my temperature sensor is mounted on the motor can, opposite of where the fan is mounted.
 
danl said:
I agree. My testing verifies that simply shrouding 180 degrees around the motor is worth over 10 degrees F lower temps compared with the same fan simply blowing at the motor from 5 mm away. All other things remaining the same. For reference, my temperature sensor is mounted on the motor can, opposite of where the fan is mounted.
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I have seen similar results except that the temp sensor is integrated into the motor and temp reading was from the ESC log. A single shrouded fan is better than two non shrouded ones. Even better would be a shroud and a double high 12v server fan to really blast air with a 12v voltage booster inline with the fan lead. Small volrage boost PCBs can be had cheap from Ebay, aliexpress, sparkfun or wherever just make sure to not get a crap design because some of them are good and some are garbage.
 
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I think people need to compare apples with apples. What motor you use, surface you run on, gearing, tyres etc.

Running stock 6S electronics on Kagama/Kronos? You're going to need fan/fans even in Blighty.

No need for anything extraordinary. These motors are big enough for twin fans. They work. But then you need to ensure they don't get clogged - which is why you also need a shroud to keep debris out.

I run 2 fans on my 22X-4 Elite as well. My 5.5t should be ridiculously warm, but not so with 2 Protek fans - one blows - the other sucks....😝🤣

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PXL_20251025_101014884.webp

On my Kronos XTR - they both blow at the same time. 🤭🤯👀

IMG_20220915_123624.webp

These just keep on working. They don't need special ducting or 12 volts. They just blow air around the motor and prevent the 230° runs I first subjected too on those first couple of runs! 🤣

Now they run tidy, even during speed runs or bashing on grass.

Apparently brushless motors don't like running at Nitro temperatures. My bad. 🤭
 
BashingBrian said:
Sorry, totally disagree, my Kronos XTR has no extra fans, running Max6/4082 1750kv, never gets hot enough to warrant fans, and it's geared correctly (y) :cool:
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The way a car is driven is also a big factor.
When i run my cars on a track, they never get hot. But when i bash them in my usual spot on a beach, they get lots of full throttle and then they all get hot.
All motors get hot when ran at full throttle all the time. It's that simple.
 
I drain a 9200mah battery in 8 minutes. I’m down to 12t on my pinion. Fans needed. I don’t lift till I see Jesus…
 
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