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 Post subject: frameless and suspended (opinions pls.)
PostPosted: Mon Nov 25, 2002 5:42 pm 
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I hacked the frame off my NMB 18cfm fans and attached elastic string instead. Do you think this is going too far?

With an ear test, I could hear a reduction in noise, but 12V F&F is still not as quiet as 7.5V w/ frame. I'm going to change all of my fans to this sort of setup and do some noise measurements soon.

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PostPosted: Mon Nov 25, 2002 8:42 pm 
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PG, you and I and Intel are on the same track. I did that to a Panaflo and a few other fans some months back, tried using them in various apps -- in a PSU, as a case fan, over a CPU. My findings then were

    1.Air turbulence noise is reduced...
    2. but if fan speed is already low, the gain is not huge
    3. directionality of air flow is reduced, it is more diffuse
    4. ie, CPU temps rose a bit, as did PSU temps
What Intel has done is develop a frameless fan with extra long and tall blades. They showed some prototype versions at IDF in San Jose. It is intended to decrease noise & improved airflow without loss of directionality.

Will see if I can find the paper for this and post a link.


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 Post subject:
PostPosted: Mon Nov 25, 2002 10:51 pm 
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powergyoza,

what size heat shrink tubing do you use, and how do you get it over the connector?


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PostPosted: Tue Nov 26, 2002 12:52 am 
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Quote:
what size heat shrink tubing do you use, and how do you get it over the connector?


The tubing came stock with the fan, but it would be pretty simple to fit the heatshrink on. Just remove the plug from the leads by pushing down on the exposed part of the metal leads and pull. Then you can slide on the tubing. Push the leads back into the plug and voila! Just make sure you plug each lead back in the right place.

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 Post subject:
PostPosted: Sat Dec 07, 2002 11:36 am 
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UPDATE

I've modified all my fans to be frameless and suspended and the results are not very good. Here's some pics:

Image
Image
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The fans on the HS have a 1" x 1" x .5" rectangle of camera foam underneath. The PSU fan is @ 12V and the other 4 are @ 7V.

The noise has gone down a bit, but my temps are way up. I'm betting it's party because this setup is all NMB 18cfm'ers while my old setup was Panaflo L1A's for case and HS and NMB for PSU. It's also probably 'cuz the fans are, like you said mike, moving air more diffusely.

HD: old 55/55C, new 58/58C
CPU: old 66/61C, new 82+/76C+ and stable
PSU: warmer!

I'm ripping this mod out right away, thank you. My nerves are frayed. Chaulk this one up to experience.

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PostPosted: Sat Dec 07, 2002 11:44 am 
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Ouch, that's pretty hot...

I get scared when my harddrives exceed 40C, last one that did died a horrible death.

Do you think 120 mm. fans would exhibit the same kind of behaviour, or would they cope with free-air suspension quite well (considering their size)?


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PostPosted: Sat Dec 07, 2002 12:08 pm 
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I'd think a single 120mm fan would behave the same way, but not as badly as 2 - 80mm fans. Sorry for the ugly math below. My logic tells me this (calculations based on Panaflo series of fans):

total circumference of fan blade assembly of 2 - 80mm fans = 2 * 75 * 3.14 = ~470mm

effective fan blades surface area (ex rotor) = 2 * [ (75/2)^2*3.14 ] - [ (37.5/2)^2*3.14 ] = ~6600sq.mm

---

total circumference of fan blade assembly of 1 - 120 mm fan = 1 * 110 * 3.14 = ~350mm

effective fan blades surface area (ex rotor) = [110/2)^2*3.14] - [(55/2)^2*3.14] = ~7100sq.mm

-----

The 120mm has more surface area to move air than 2 - 80 mm's and it's circumference is smaller, so that less air is lost at the sides...

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 Post subject:
PostPosted: Sat Dec 07, 2002 12:19 pm 
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What benefit did you expect from taking the frame off the fans ? (apart from looking a bit cooler ?)


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 Post subject:
PostPosted: Sat Dec 07, 2002 4:59 pm 
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Quote:
What benefit did you expect from taking the frame off the fans?


I was trying to cut down on noise from wind turbulence caused by the moving air interacting with the frame.

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 Post subject:
PostPosted: Sat Dec 07, 2002 9:27 pm 
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UPDATE #2
I ripped out that frameless and suspended mod, but I just didn't simply return to rigidly mounting the fans. The case fans and PSU fan now attached to the case with camera foam in the same way as those fan isolators are used.

Result: No more vibration noise, just the sound of bearing chatter and air turbulence (and maybe the faint whine of the HD).

Thanks to cutting away the rear grills, I've also decreased my CPU temps by 2C/1C. I'm ready to undervolt my fans some more, now that I know I can run stable at 82C/76C from my previous experiment!!!

UPDATE #3
Here's a diagram of how I did it.
Image

It's a good idea to seal the gap with some tape. Electrical tape is nice because it's flexible.

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 Post subject:
PostPosted: Tue Jan 07, 2003 11:34 am 
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<bump>

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 Post subject:
PostPosted: Tue Jan 07, 2003 12:37 pm 
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lol omg that is the ugliest thing i have ever seen.


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 Post subject:
PostPosted: Wed Jan 08, 2003 6:51 pm 
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powergyoza wrote:
Thanks to cutting away the rear grills, I've also decreased my CPU temps by 2C/1C. I'm ready to undervolt my fans some more, now that I know I can run stable at 82C/76C from my previous experiment!!!


Wow, I am amazed at the temperture you can run it at, seems pretty high. But at the end of day if you have a quiet computer that is stable, there is not much to complain about.


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 Post subject: Temp problem solution
PostPosted: Thu Jan 09, 2003 12:09 pm 
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I see you found out the hard way about a classic and offend forgotten problem. The fan frame is there not just to support the motor, but it is also design to direct the air follow.

An easy solution is to use some round tubings around the fan to sub for the frame. You could either attach the rope (cord) to the tube or just place it around it fan on the side where it is pulling area in.

Good luck!

Ice


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