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120mm fan with reverse fins? (optimal fan configuration for small case)

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Cattlepsy

New Member
Joined
Oct 18, 2018
Hello, I'm looking for a 120mm CPU fan with reverse fins, does anyone know if this exists? Basically when facing fan intake it should rotate counter-clockwise instead of clockwise. I have recently installed a Scythe Mugen 5 Rev B CPU cooler, its working well but I'm getting a weird noise at low RPMs and I'm pretty sure its coming from turbulence, I have an 80mm red case fan that was already existing before I bought this heatsink, I made sure to measure BUT I didnt think about the 80mm fan blowing in the opposite direction from 120mm CPU intake fan. Im guessing that this causes just enough turbulence to make an annoying noise, but not enough to cause problems, the 120mm seems to power through most of the time while gaming, its only while idle that I notice this noise, which is what leads me to the whole turbulence idea. But more than that I'm just kind of nitpicky and I would love for the 80mm fan to help speed up the 120 instead of fighting against it, the idea was to leave the fan so it has direct fresh air from close-by...
If I cant find a reverse CPU fan I might just unplug the 80mm red fan. I have inculded a picture of an extra thermaltake fan I have, these spin the opposite way as my Scythe CPU fan because fins are in the opposite direction, I need fins like the thermaltake but on a Mugen-quality fan if possible...

I was looking at this one, would it work?: https://www.newegg.com/Product/Prod...-gzxrMgRwZt7kPjWHHBoC6PoQAvD_BwE&gclsrc=aw.ds

...Also I had the idea to just take the Scythe fan and put it on the other side of this heatsink BUT its a really tight fit, and doesn't line up right with the exhaust fan so I'm not sure if that would be very efficient. Probably would only have 10-20mm between CPU fan and rear exhaust fan with the bottom half of the CPU fan pointing towards the metal case with no holes.

To break it down a little more I believe that air coming down from the 80mm fan is catching the edge of the CPU fan blades as they rotate upward from the Mobo, causing the CPU fan vibration/resistance... figure if I can get the CPU fan to spin in the opposite direction while not changing direction of air flow it might be a little more smooth. I could be very wrong it may just be that the fan is faulty and it doesn't matter. This whole build is secondhand parts so its to be expected that a few things won't work 100% here and there.

Gigabyte x58a-ud3r
i7-950+Mugen 5 Rev B cooler (stock speed)
GTX-570 (kfa2)
Samsung Evo 250GB

Thanks!
 

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OP
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Cattlepsy

New Member
Joined
Oct 18, 2018
Flip the fan over.

Unfortunately this would just blow air out toward the front of the case with my current CPU fan, my case is already set up with intakes across the front and exhaust at the back as well... I think it needs to either flip AND change direction, OR flip and move to other side of heat sink right?
 

trents

Senior Member
Joined
Dec 27, 2008
I fail to see the difference between reversing fain blades and flipping the fan over. You could do it with either the 12cm or the 8cm fan. Either way, all you are doing is changing the direction of the air flow. What difference would it make whether you did that by flipping the fan or reversing the blade pitch? What am I missing here?
 
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Cattlepsy

New Member
Joined
Oct 18, 2018
If you just do one, there is no difference, if you reverse fins and rotate in the other direction at same time you have an intake that spins in counter clockwise instead of clockwise.... so not just reverse or flip but both at same time.

to make it more simple:

Intake on my thermaltake fan turns counter clockwise,

Intake on my Scythe CPU fan turns clockwise.

If you put them blowing in the same direction, they would be turning in opposite directions.

I'm looking for a better fan that has counter-clockwise intake, like the Thermaltake. Does that make any more sense?

Also.. i believe this is true for ANY fan, so if you have a CPU fan with fins that look like this thermaltake from the front, then they should spin in the same direction by default. Fins should dictate direction from what I understand, like you said it would reverse the airflow otherwise.
 
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trents

Senior Member
Joined
Dec 27, 2008
So you think the direction of the rotation of the impellers being opposite of each other is causing the noise, even when the fans are flipped to cause the air to be flowing in the same direction? Am I understanding you now?

There could be exceptions to this but I've owned and installed a lot of PC fans over the years and all of them that I can remember are constructed such that the air flow is from the open side toward the side with the four spokes that radiate from the center to the rim. That would mean that if the direction of rotation is different from fan to another then the blade twist would have to be reversed as well in order to maintain that air flow pattern. Since I've never paid attention to the direction of blade spin I must take your word for it that some are turning clockwise and some counter clockwise.

The other thing you might look into would be changing the speed of one fan or the other. Those kind of noises are often very frequency specific.
 
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Cattlepsy

New Member
Joined
Oct 18, 2018
So you think the direction of the rotation of the impellers being opposite of each other is causing the noise, even when the fans are flipped to cause the air to be flowing in the same direction? Am I understanding you now?

There could be exceptions to this but I've owned and installed a lot of PC fans over the years and all of them that I can remember are constructed such that the air flow is from the open side toward the side with the four spokes that radiate from the center to the rim. That would mean that if the direction of rotation is different from fan to another then the blade twist would have to be reversed as well in order to maintain that air flow pattern. Since I've never paid attention to the direction of blade spin I must take your word for it that some are turning clockwise and some counter clockwise.

The other thing you might look into would be changing the speed of one fan or the other. Those kind of noises are often very frequency specific.

...PRECISELY, (this is my first pc build so there's a pretty good chance I'm wrong :p) what I think is happening is that air being pushed in toward the mobo from 80mm fan is catching the edge of those fan blades because its so ridiculously close and fairly strong. The 120mm CPU fan is shaped in such a way that its rotating AGAINST this downward current instead of working with it, so I figure if I can get a reverse-fin+direction then not only will the fins be turned down so they dont catch but also the fan will be spinning along with downward current instead of fighting it.... I'm probably just being paranoid tbh that was just my idea.

I REALLY LIKE THE IDEA OF RPM CONTROL!!!! thanks man I didnt even think about that, it may be very specific RPM since it does only seem to happen for a few secs at a time and then go away... typically when at low rpm and then ramping up for 1-2 secs while idling. I will definitely try to mess with that before spending money on anything as budget is the entire point of this build. lol
 

maxfly

Member
Joined
May 7, 2005
it does look as tho those fans spin in opposite directions? wtf, for some reason the scythe fan is built to spin in the opposite direction of pretty much all fans ive ever seen. that is truly odd. it spins to the right rather than with most fans which spin to the left(with the manny label facing out). the ninja fan spins the same way. those are the only two i could find that spin that way. well knowing that i would replace the thermaltake with a matching 120mm scythe kaze fbd fan. or if you prefer the thermaltake buy one of those instead.
https://www.amazon.com/Scythe-Sealed-Precision-120mm-300-1200/dp/B0763TSZ59

btw the noctua fan that you linked to spins the same way as the thermaltake. so if you were asking if that is a superior model then yes it is. i would go with the noctua all things, being, equal... lol.
 
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Cattlepsy

New Member
Joined
Oct 18, 2018
Sorry for the delay, and thanks! i figured this was the case, maybe its a Japanese thing? lol anyway I was going to spend a few bucks for a proper fan-mount on the font panel ( fan currently held in place with twisted cat5 pairs thru 5.25bay :p) I will probably just end up grabbing that Noctua fan while I'm at it since its only $12, then maybe I can use scythe fan for push/pull thru the fan bay.