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Cohesive Air / Hoot Chute: Read this

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Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
If you are considering implementing a centrifugal blower, such as outlined in my article, http://www.overclockers.com/tips461/index.asp from a few weeks ago, read on. Ditto if you already have.

In my article, I had recommended the Dayton 170cfm DC blower, Model 2C646. Dayton also has a 130cfm AC version of this blower, Model 2C647. If you have not gotten the blower yet, get the AC model. If you have the DC version, don't panic. It works just fine.

I wanted to see how the AC version would work, so I bought just the motor. Upon hooking it up, it performed as well as the DC one, with the exception that it was stuck running at full speed and the vibration was hard to tolerate. Unlike DC motors, you can not regulate the speed of an AC motor as easily as lowering the voltage. They are synchronized to the 60Hz line frequency and that, combined with the number of poles, contributes to the speed.

So, I had written off the Ac motor as a failed experiment and put it on the shelf as a backup. In a post I read last night, it was tossed up whether an AC light dimmer would work. I took this reasoning one step further and picked up a Bathroom Fan speed control, which works on a similar principle. When I got home form work, I wired it in and the results are stunning. You can slow the fan down to almost a complete stall, or run it full tilt. No complex regulator circuits to build, no brush noise (DC version). As I type this, the only way I can tell the blower is running is to look at it and verify the cage is turning. It is quieter than the Northbridge and GPU fans combined with the HDDs. It still gets loud at full tilt mind you, but performs very well at lesser speeds, just like the DC model.

While I'm sure that those of you with the DC version have no desire to throw more money at the project than you already have. You can convert your unit for the cost of an AC motor (appx $20.00) and I got the speed control from Menards for $14.95. You may be able to source both pieces for less through a surplus dealer. I did not try a light dimmer, which cost considerably less than the fan speed control. The controller is rated for 3A of load and has EMI surpression built into it (unlike some cheap light dimmers).

One caveat. If you have read the article, You know that the original design was based upon using one air source to both cool the CPU and provide through-case ventilation. When you turn the AC speed control way far down, it still cools the CPU fine, but doesn't provide sufficient through-case airflow. Normally you would not run it that slow though.

I apologize for not researching this angle more when I was doing the original article. I failed to think far enough "outside the 9 dots". I will continue to work on the last segment of the original article, detailing the variable DC regulator construction.

Hoot
 
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OP
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Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
I didn't pick that nickname. ;D Someone else started it and it took root. If you're not kidding, you build it, not buy it. You can buy the components though. Or, did you mean where can you get the blower?

Hoot
 
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William

Guest
i want to know where to by the blower, sorry for the confusion ;-)
 
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William

Guest
i know what you are talking about, do they have a website?
 

Magistrate

Registered
Joined
May 20, 2001
One caveat. If you have read the article, You know that the original design was based upon using one air source to both cool the CPU and provide through-case ventilation. When you turn down the AC speed control to a certain point, it still cools the CPU fine, but doesn't provide sufficient through-case airflow.

Unfortunately, that is one huge caveat. The main attraction for me was that the blower could potentially replace all the other noise producing fans in my case.

Could you define "turn down the AC speed control to a certain point".

I'm assuming this point is where the noise is no longer audible. Can you turn it up in order to get better total case cooling? If so, how much more noise do you have to tolerate?
 
OP
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Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
Just got back from riding bikes with my 7 year old.

The AC version weigh about as much as the DC version, just under 4 pounds. You don't need to reinforce the side panel to use it. The majority of the weight is close to the surface.

Go to the Grainger Web page and up at the top is a search engine. Click on manufacturer part number and key in 2C646 (DC) or 2C647 (AC). If the company you work for has an account with them, you can get about 5-10% below the listed price.

I was sincere when I referred to how quiet it is. At 50% speed, it's about as loud as when the forced air furnace is running, as heard through the vents on the next floor. If I had a place to drop off some .wav files, I'd record it compared to several different sized case fans (80-92-120mm) and you could be the judge. It is as quiet as the DC fan without the crickety brush noise. When it is cranked wide open, there is a low frequency rumble that might be improvable with some deadening materials effort. I haven't tried yet. At 50% speed, running prime95, the CPU is only 2C warmer than at full tilt.

Hoot
 

mEKbOY

Member
Joined
May 27, 2001
Location
San Diego, CA
What kind of power do these units use or do i have to mod it to work with my computer cuz im not to famaliar with wiring and such.
 
OP
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Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
I just finished a lengthy benchmarking session and I'm bushed. MEK, it runs off of 110 AC.

Yet another revelation. At full speed it does not cool any better than at 80%, but it sure makes a lot more noise. I think this may be the result of backpressure from the duct underneath it. That's actually good news, because at 80% the sound is tolerable. So what did ole Hoot find? Here's some results.

First I want to qualify the term Inaudible as making less noise than the fans on the Northbridge and GPU, combined with the HDDs. You do need an 80mm circulation assist fan when running Inaudible, to keep the through-case flow satisfactory. I used a Sunon 36cfm (very quiet) to do the trick. Okay, now those results:

Speed--------80%--------50%--------Inaudible
1333 Mhz----32.1C-----32.9C------35.0C
1400 Mhz----34.8C-----35.8C------38.0C
1450 Mhz----36.9C-----38.2C------40.7C
1500 Mhz----39.4C-----40.5C------44.7C

In practical use, Inaudible is fine for email, surfing, forums, etc. 50% is fine for 3D gaming, CAD rendering, compiling, Scientific Modeling, just about anything that I could throw at it. 80% would be for chasing that elusive one more step faster, that we lie about and put in our signatures, like we run that all the time. ;D The majority of the noise at 80% is air rushing, which indeed it is doing. I have not tried any sound abatement techniques yet. That will be the "Icing on the Cake". I am running with the speed control set to the inaudible mark as I write this. My CPU temp is 25.8C :)

Hoot
 
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William

Guest
the price of the unit took me back, but I was expecting to spend that much in normal fans. I am think that I am going to have to mount this differently though. I think parallell to the case running a duct to an SK-6(for my celey) should work quite well. And with running an Intel chip I should get great temps running at a lower RPM. How do you have this sunon helper fan positioned Hoot?
 
OP
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Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
In my mid-tower, it is on the bottom of the front exhausting, like I'll feel in 5 hours when my alarm goes off. :D

ZZZZZ
 
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William

Guest
Hoot (Jul 06, 2001 12:13 a.m.):
In my mid-tower, it is on the bottom of the front exhausting, like I'll feel in 5 hours when my alarm goes off. :D

ZZZZZ

sleep tight hoot! You have had a busy day.
 

CalCoolage

Registered
Joined
Jun 30, 2001
Hoot (Jul 05, 2001 07:46 p.m.):
... I took this reasoning one step further and picked up a Bathroom Fan speed control, which works on a similar principle
Hoot

You can find this also called a Ceiling Fan Speed Control (3 amp). Since you can find ceiling fans everywhere, you might be able to find this type of control nearby.

http://www.mcmaster.com/ has one for $12.77, their number 2042K58.
 

Magistrate

Registered
Joined
May 20, 2001
Does the AC model still have the brush noise problems of the DC when running above the 'inaudible' level?
 
OP
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Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
No, the AC model (2C647) is brushless and very quiet when you are not running it at full speed.

Hoot
 

Magistrate

Registered
Joined
May 20, 2001
So Hoot, are you going to add a section to your electronics writeup for people buying the AC model?
 
OP
H

Hoot

Inactive Moderator
Joined
Feb 13, 2001
Location
Twin Cities
I am currently making the AC speed control mount and interface. I will probably submit it as an article. No time frame yet.

Hoot