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Counter-rotation fans

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Do you think gutting an old 120mm x 25mm and bolting between the two fans would be enough of a shroud?

You need a shroud because counter rotating fans sometimes fixed fins between the fans to straighten the airflow. Engineered for the best pressure ect, by engineers. Your trying a hack that might work, but for sure you need a plenum chamber to straighten out the flow. I'd try with and without for science. I appreciate your curiosity, I'm way to pragmatic for these adventures.

Your gonna have a 75mm thick fan now, isn't just buying a good 38mm thick fan with high pressure ratings isn't easier? I'm pragmatic?

Still, give it a try, better than being at a comic book store with Sheldon.
 
Actually, the fans are 38mm, giving me, with the radiator, a 136mm thick cooling apparatus...time for some all-thread and some method of support inside the case... I guess what I'm trying to do is duplicate a Delta GFB on the cheap.
 
I've owned a couple of factory made compound fans. The Delta GFB had focusing vanes in between the rotors but the Sanyo Denki doesn't have them. The home made ones I've made did it both ways and having vanes between the rotors didn't seem to make much difference one way or the other.
 
The fans should be delivered tomorrow. I probably won't have a chance to really check them out until this weekend. I have been on several forums for different things and I just want to say that the folks I've have interacted with here so far have been great. Thanks to all of you for your thoughts and suggestions.
 
haha, we do have several FANatics here. I being one myself.

do let us know of your findings. :)
 
Oh well, the fans were delivered today and both rotate in a clockwise direction. One was mislabeled on the website...So I contacted Jameco, they verified my claim and are exchanging the louder of the two for one of the quieter ones. I am impressed with the customer service, they are shipping the replacement today and will credit me when they receive the other one. I will punt on the counter-rotation project. This order was the culmination of my search for a counter-clockwise fan so I was disappointed to say the least. On the bright side, I will have a set of rocking 120x38's in a push pull on my H80. Once again, thanks for all the interest, suggestions, and knowledge!
 
Hell laslo, don't give up. If you need some opposite rotation fans for your project, buy these Delta EFB fans off eBay right here. Those are the exact fans I bought to play the counter-rotating compound fan game with. I offered $28 for them and he accepted and shipped quickly. Might even go a little lower than that now, since those fans have been up for sale at least 2-3 months. They aren't new, but the assembly I received was in good shape, as were the fans.

Specs for those fans are as follows:

cfm - 141.96
static pressure - 0.52 in water
noise - 52.5 dB (A)
power - 9.6 watts
rpm - 3700
 
Thanks muddocktor! Right now my fan budget is tapped. I doubt if I could clear it through "The War Department" if'n ya know what I mean. I'll bookmark this page and check back when the dust settles and the smoke clears.
 
Yeah, I know what you mean.:D

You should have seen me trying to explain the $1500 I spent for the proc and mobo for my present main system (980X system).:chair:
 
I will be able to tell in a couple of days. It is advertised as a "Speed Sensor" fan and has an operating voltage range of 6v-13v. 128 CFM @ 3000 RPM, .32 inH2O pressure.
 
Well, here are the results. Even though I was unable to stack counter-rotating fans, I did test the Gryphon GDA1238-12BB 120x38 fans as replacement fans on my Corsair H80. I ran Sisoft Sandra CPU Processor Arithmetic and Cryptography benchmarks because they seem to stress the CPU the most. Stock fans on the Arithmetic bench kept it at 94F (Speedfan) and 32C (Aida64), Cryptography nudged 100F and 36C respectively. The Gryphons hit 90F and nudged 30C on Arithmetic, 94F and 32C on Cryptography. The Gryphons are much louder than the Corsairs (duh) and don't quiet down too much at idle. I have an Antec 300 with the 140mm in the top (sitting on the floor next to my desk) so the noise projects right out of the case. Since the results with the stock fans are very good, my conclusion is the amount improvement was not worth the noise.
 
Thanks for the update.

I had a Papst once that ran clockwise when normal fans run counter-clockwise (depends on what side you watch the fan from, I guess). Fun, and a five-blade fan. But too noisy. The Arctic Cooling cage fans also run opposite from normal fans.

According to a San Ace white paper I found, the counter-rotating fan doesn't so much add cfm as it does static pressure.
 
I'm truly sorry for necroing this thread,
but I'm quite on despair finding a CW + CCW rotating fan setup:

DSC_0763.JPG

as you can see on the rear is a PAPST 4112 N/31HHA, the fan was set at a tolerable noise according to my ears (the rpm sensor was useless on the mobo)
on the cpu, is a Sanyo Denki 9SG1212P1G03 I manually set at around 1k2 rpm.
the fans are actually spinning as a friend took the picture, so I think they running quite slow.


long story short,
I want to make my fan setup as efficient as possible so I removed the two ADDA AD1212UB-A73GL (both spinning around 700 rpm-ish) on top exhaust and have them replaced by a cardboard to seal the opening (I saw the cpu fan taking my cigarette's smoke, so I though it taking air from where it shouldn't)


now for the interesting part....
I'm really prepared to lower my current OC.
since the 1.5-ish of v-core is really pushing my system temps to its limits,
but surprisingly, the system temps only increased by 1C from the idle till I finished up 5 loops of IBT (the CPU temps was also lower than the usual).

thought it was due to the "top seal" innovation I made, I swapped the rear PAPST with another 9SG spinning around 650rpm-ish (for much simple fan control unit and cabling routing)...
and now everything messed up :bang head
system + cpu temps went crazy, and having constant failures on IBT after 3 loops.


so,
before I'm bringing back the PAPST to the rear exhaust, I wonder if anybody beside laslo9 ever did any similar experiment with Clock Wise + Counter Clock Wise setup on their PC would share their experience?
I don't familiar with the Sandra Benchmark, and more expecting something more conventional like Prime or the Intel Burn Test as comparison results.
or maybe laslo9, if you ever did a comparison between dual clock wise and counter clock wise setup under Prime or IBT could you confirm any significant drop in temps (despite the noise)?


I'm still in doubt, if the the results were just a placebo.
but since rerouting the cables is a real pain, maybe I can have some encouragements by reading your past results :bday:
 
These counter-rotating fan setups would primarily be for heatsinks right?
They wouldn't help much for exhaust or intake fans would they?
Can the factory designed CRF's run at lower RPM's to acheive the same
CFM and static pressure as an equivalent diameter 38mm thick single fan?
 
Most heatsinks and radiators are not restrictive enough to get much benefit from doubled fans, the main exception being long 1U heatsinks. As for case fans, they excel in small form factors where there is a lot of resistance to airflow. For most traditional cases, don't expect much improvement.
 
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