Counter rotating fans, what makes it sooo good?

[warlock110]

Having said this, i've seen alot of "extreme" people on the forum likes the counter rotating fans, since then i've realized that we can also make a version of that using our normal fans to be specific here's what i think

1 X delta 3 blade (any size)
1 X fan 5 blade (any size) this might be hard because most of the fans i've seen in the 92mm and 120mm size are 7 blades but it should create the same effect isn't it?

we then control the speed with a fan control

but 1st up why is counter rotating fans so great?

 

[Electron Chaser]

Having said this, i've seen alot of "extreme" people on the forum likes the counter rotating fans, since then i've realized that we can also make a version of that using our normal fans to be specific here's what i think

1 X delta 3 blade (any size)
1 X fan 5 blade (any size) this might be hard because most of the fans i've seen in the 92mm and 120mm size are 7 blades but it should create the same effect isn't it?

we then control the speed with a fan control

but 1st up why is counter rotating fans so great?

because basicly they are just so cool looking. Do they have higher pressure then some of the other high end Delta fans? Nope
Do they move more air? No again

I have the biggest baddest Delta you can buy that puts out as much air and more pressure as the biggest Delta GFB series fan . But I would swap it out in a sec if I could get my hands on one.

The GFB series fan is quieter though. 59dBA versus 65dBA of the fan that I use.

 

[Bios24]

No, they are not just for looks. Counter-rotating fans generally produce more pressure than single fans. Same goes for deeper fans. a 38mm deep fan generally produces more pressure than a 25mm deep fan.

And I'm not sure you can just 'make' a counter-rotating fan by just putting 2 fans together. They are engineered to have each fan run at a certain speed, blade pitch, distance, etc.

 

[millhouse]

you could make one if you found a fan that rotates counterclockwise.

I dont know where to find a fan that rotates counterclockwise (dont regular fans rotate clockwise?) though. i also wish i could get my hands on one of those deltas just so that i could say i have one.

 

[Silversinksam]

because basicly they are just so cool looking. Do they have higher pressure then some of the other high end Delta fans? Nope
Do they move more air? No again

Counter-rotating fans produce more pressure and they produce more air. For example, The 40mm counter-rotating fans for their size pushes more air than any traditional 40mm fan, not to mention you have less dead spots on the heatsink due to the nature of the improved airflow.
This was best explained by this member:

All axial fans produce a conical, spiraling airflow in open air. Some fans have static outlet fins to tame this phenomina(sp?); making the flow more cylindrical and straight. A counter-rotating fan takes advantage of that spiraling inertia (wasted energy from the first fan). A properly designed counter rotating blade will look quite different (not just reversed) from the primary fan's blade. The end result is a much higher static pressure, and increased volume.

you could make one if you found a fan that rotates counterclockwise.

I dont know where to find a fan that rotates counterclockwise (dont regular fans rotate clockwise?) though. i also wish i could get my hands on one of those deltas just so that i could say i have one.

It's difficult to make them yourself since most fans are polarity protected. ;0

 

[Electron Chaser]

Counter-rotating fans produce more pressure and they produce more air. For example, The 40mm counter-rotating fans for their size pushes more air than any traditional 40mm fan
This was best explained by this member:

This is not always the case, especially when refering to Delta Fans. While I will agree that in most cases they do.

 

[Silversinksam]

This is not always the case, especially when referring to Delta Fans. While I will agree that in most cases they do.

I can make the case referring to Delta fans, Delta makes Counter-rotating fans from 40mm to 120mm, they are very hard to find in the States. The 120mm Delta counter-rotating fan will smoke that Delta you have for many reasons (provided you can find one to buy)

 

[millhouse]

It's difficult to make them yourself since most fans are polarity protected. ;0

hmm... i never knew that. I just learned something new today!

 

[Electron Chaser]

I can make the case referring to Delta fans, Delta makes Counter-rotating fans from 40mm to 120mm, they are very hard to find.

LOL don't I know it I have been trying to get a hold of one of the 120mm models for well over a year. If you look at the GFB series fans and then the TFB fans you can see that the TFB has nearly double the pressure of the GFB and puts out the same amount of air.

MODEL RPM CFM MAX PRESSURE dBA
TFB1212GHE 4600 220.01 26.44 mmH2O 65

GFB1212VHW 3400 220.29 15.04 mmH2O 59

So like I said while in general they will put out more pressure this is not always the case.

 

[Gavote]

Keep in mind, the TFB series are NOT contra-rotating fans! They are a fan backed by a static vane set. A full contra system will produce roughly 1/3 more pressure and 1/2 to 2/3s more flow. However this comes at the price of even more noise. The noise is the result of a combination of blade flutter (blade flex) and pressure spikes as the blades of the two fans pass each other.

 

[Bobnova]

Interesting data, seven year old thread.

 

[Automata]

Welcome to the forums, Gavote. That is good information for the thread, but please mind the post dates of the thread. It is generally considered taboo to bump old threads.