Bluefront's Monster 120mm Slot-fan DIY. Ver 2.

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Bluefront
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Post by Bluefront » Thu Feb 22, 2007 2:03 am

[F]bernZ.....I hate to tell you this, but you've cut the fan frame wrong according to my calculations. If you flip your fan over, the cut portion is exactly the same as my version. Essentially you have duplicated my first design......so it will blow out the slot opening if the intake hole is the same as mine.

Look....this is hard to describe in words. Imagine the cut on the opposite side of the slot opening. As the fan blades pass the opening, they in effect scoop in the air, attempting to carry it into the fan frame. As the blades get closer to the un-cut frame section, the air is forced outward through the normal axial opening, past the struts.

I still think this will work.....I'll try to make one this week-end, and post the results.
[size=75]"At the core of liberalism is the spoiled child - miserable, as all spoiled children are, unsatisfied, demanding, ill disciplined, despotic, and useless. Liberalism is the philosophy of sniveling brats." - P.J. O'Rourke[/size]

[F]bernZ
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Post by [F]bernZ » Thu Feb 22, 2007 7:38 am

Hmmmm.. I'll grab another fan to play around with.

Edit: Thanks Bluefront for tryin~
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@3.0 (300*10)load ~54-62[/size]

the_beast
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Post by the_beast » Fri Feb 23, 2007 1:45 pm

feel free to shout at me for being dumb if I am saying something stupid, but surely it makes no difference which corner of the fan you cut off, as, except for the wires, a fan is completely symmetrical.

Can't you just rotate the fan through 90 degrees?

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Post by McBanjo » Fri Feb 23, 2007 2:52 pm

the_beast wrote:feel free to shout at me for being dumb if I am saying something stupid, but surely it makes no difference which corner of the fan you cut off, as, except for the wires, a fan is completely symmetrical.

Can't you just rotate the fan through 90 degrees?
That would work if the correct piece was cut off but on the wrong side. As it is he cut off the wrong 50% of the side

It would be fixable with some glue or a piece of wood tho
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BrianE
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Post by BrianE » Fri Feb 23, 2007 11:40 pm

I think the_beast is right....

Conceptually you want the blades exposed at the trailing edge where they are scooping air away from the opening, rather than approaching the opening. I thought about it by looking at Bluefront's first picture and imagining to rotate the fan 90 degrees, then taking the housing off and putting it on top rather than underneath. I think that's what the final product should look like.

[F]bernZ, I don't know how you were testing to see if your fan sucked in any air, but try putting a ruler or other flat surface along the LEFT side of the fan in that first picture. That should seal up the side you don't want exposed and set up the intake as I described above (I think).

If that doesn't work, it may be that nici is right and there's just too much restriction. Either way, this is kind of interesting. :wink:

the_beast
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Post by the_beast » Sat Feb 24, 2007 3:14 am

As he only cuts off 1/4 of the fan, it can't possibly be the 'wrong' corner.

Each of a fan's 4 corners are the same, so how could he have cut the wrong bit?

He just needs to rotate the fan in it's current mounting. He may have to route the wires differently or something, but other than that he would be ok.

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Post by McBanjo » Sat Feb 24, 2007 5:40 am

the_beast wrote:As he only cuts off 1/4 of the fan, it can't possibly be the 'wrong' corner.

Each of a fan's 4 corners are the same, so how could he have cut the wrong bit?

He just needs to rotate the fan in it's current mounting. He may have to route the wires differently or something, but other than that he would be ok.
Since he is cutting of 50% of one side there is 8 pieces of 50%, 4 is wrong and 4 is right. Cutting of wrong piece can only be fixed by turning the fan itself around, ie changing the direction of how it blows. Not changing the frame then. Very hard and useless work :wink:

If he would cut of an whole corner then he can't cut of wrong one but since he isn't he can.

Image he is cutting of the top of a side and he wants the fan blowing towards him, then no mather how he turns it it will always be a top piece. Is that making more sence?
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the_beast
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Post by the_beast » Sat Feb 24, 2007 5:43 am

What you're saying makes perfect sense.

However, if you look at the pictures, he IS cutting off a whole quarter of a fan, not just half a side. If he only cuts off half a side it won't work at all.

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Post by McBanjo » Sat Feb 24, 2007 5:48 am

the_beast wrote:What you're saying makes perfect sense.

However, if you look at the pictures, he IS cutting off a whole quarter of a fan, not just half a side. If he only cuts off half a side it won't work at all.
Oops, I was sure he only cut of half the side. Just thought you where locked in a thought.
Guess my tiredness and bad memory played me a trick again :oops:
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Bluefront
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Post by Bluefront » Sat Feb 24, 2007 8:14 am

Ok.....here's the result of the reverse slot-fan design. The air is sucked into the slot, and blown out the normal fan hole. I cut this Scythe differently from the first design....necessary to get this version working. I also left part of the frame intact (not necessary). This leaves the fourth fan support strut in place, and makes the setup more rigid.....at the expense of some airflow.

This setup definitely needs some tweaking.....I don't think it performs as efficiently as the first setup. But it does work. Look at the last photo. You can see the small tissue strip being blown upward (the fan blades are stopped by the camera flash, they were spinning). Anybody want to tweak this design for better performance......please do so. I have no use for such a setup right now, but maybe in the future.

Image

Image

Image
[size=75]"At the core of liberalism is the spoiled child - miserable, as all spoiled children are, unsatisfied, demanding, ill disciplined, despotic, and useless. Liberalism is the philosophy of sniveling brats." - P.J. O'Rourke[/size]

the_beast
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Post by the_beast » Sat Feb 24, 2007 10:07 am

What would happen if you cut 2 opposite corners out of a fan, and sealed off both the front and back of the fan? In other words made a combination of the above 2 methods, to blow air along a narrow duct.

I reckon you'd get pretty poor airflow, but you might get more air for less noise than using small fans. You could fit a good 80mmx25mm fan plus wood panel top and bottom in the same area as 2 40mm fans without needing space above or below the duct.

Not quite sure what you'd use it for (air intake duct through a front bay maybe, or exhaust from a small htpc case?), but I'm interested as to what would happen and whether I'd work.

If I ever find the time/money to get myself a dremel then I'll give it a try.

[F]bernZ
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Post by [F]bernZ » Sat Feb 24, 2007 10:59 am

Well, I think I should elaborate on the problems that I faced with mine when I built it.

That's what I was wondering too - regardless of which quarter side I cut off, I can just rotate my orientation to fit my needs.

To clarify - I felt airflow being spit off the side of the the fan, where your tissue was. However, what I didn't feel was airflow directly above the fan, where it should have been directed towards - this was what I was hoping for.

Perhaps a redesign is in order for mine.
[size=59]Intel Core 2 Duo E4400 @ 3.0GHz (300 * 10) w/ Scythe Ninja revB + SCURK1
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Fans:
900RPM rear intake
900RPM front exhaust
600RPM CPU HS

Temperatures:
@1.8 (300*6) idle ~28-34
@3.0 (300*10)load ~54-62[/size]

[F]bernZ
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Post by [F]bernZ » Sat Feb 24, 2007 11:54 am

I just hacked up another fan, a GLobe B12025 12M this time.


I have to say, I'm getting some VERY odd results.

With a piece of tissue near the edges of the fan, I get the tissue being blown out like Bluefront''s.

However, the weird part is this - as the tissue approaches the hub of the fan, the airflow seems to get reversed! Here's two pictures.

http://img388.imageshack.us/img388/7227/dsc00049bf3.jpg

That one shows that, near the edge of the fan frame, the air is being blown out.

http://img70.imageshack.us/img70/5109/dsc00050gq4.jpg

And this one, the air being sucked in. Both my designs were identical to Bluefront's, but I guess I wasn't clear enough when I said I didn't feel any airflow - I felt loads of airflow at the sides but none directly above the fan - ie; how it should feel without the fan frame being cut.
[size=59]Intel Core 2 Duo E4400 @ 3.0GHz (300 * 10) w/ Scythe Ninja revB + SCURK1
Corsair XMS2 5400C4 @ 600 4-4-4-12
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Lian Li A05B

Fans:
900RPM rear intake
900RPM front exhaust
600RPM CPU HS

Temperatures:
@1.8 (300*6) idle ~28-34
@3.0 (300*10)load ~54-62[/size]

Bluefront
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Post by Bluefront » Sat Feb 24, 2007 12:16 pm

I think this is where the tweaking will help. Try to add a spacer on the back side of the fan frame.....where the intake would normally be....the side closed off now. I'd start off about 1/4". This will make the slot opening taller, and add space between the back of the blades and the closed panel.

There's no reason this thing won't work fairly well. The fan is designed to blow this direction anyway.....we just need to open up the intake slightly.

The spacer should be three-sided, with the open side at the slot.
[size=75]"At the core of liberalism is the spoiled child - miserable, as all spoiled children are, unsatisfied, demanding, ill disciplined, despotic, and useless. Liberalism is the philosophy of sniveling brats." - P.J. O'Rourke[/size]

spookmineer
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Post by spookmineer » Sat Feb 24, 2007 5:23 pm

For a slot cooler, sucking air in through the slot and blowing out where the fan is, wouldn't it be easier to make a box with a hole in it and place the fan outside of this box? (this would also work for the reverse direction)

This way, you get the most optimal airflow and you can re-use the fan for a normal application later.
It does get a bit bigger then the first setup though.

Image

Sorry for bad drawing, I never used paint before.

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Post by BrianE » Sat Feb 24, 2007 7:13 pm

Errr...... that's weird [F]bernZ.... O_o

In case anyone is still wondering, I got a close look at an Antec VCool today, and it appears that Antec "cheats" with the whole slot cooler concept. Not only is there a grille-covered opening directly below the fan intake, but the shroud around the fan that I saw earlier in a photo doesn't extend all the way to the bottom. It stops 1/4" above the lower surface, and so in reality it just boils down to a traditional fan mounted to the top of a rectangular box with enough gap that it can suck in air through the rear slots (it's a 2 slot device). Doesn't sound like anything someone here couldn't make himself... :?

Edit: It's also a pretty small fan... I think it looks like a 60x15mm.

[F]bernZ
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Post by [F]bernZ » Sat Feb 24, 2007 11:01 pm

Actually spook, I've tried that design already.

What I've found is that it cools worse than a fan in free air - I've tried it with my hard drive.
If I just put my fan beside my hard drive, HDD will be around 40C. [mind you, SFF case, extremely low airflow]
If the fan is ducted to suck in from the PCI slots, the HDD hangs around 45.

It seems that it does better by just taking in the air around it versus getting air ducted from a PCI slot.
[size=59]Intel Core 2 Duo E4400 @ 3.0GHz (300 * 10) w/ Scythe Ninja revB + SCURK1
Corsair XMS2 5400C4 @ 600 4-4-4-12
Abit IP35Pro
WD 2500AAKS
Pioneer 111-DVR
eVGA 7800GT w/ Accelero S1
Corsair 520HX
Lian Li A05B

Fans:
900RPM rear intake
900RPM front exhaust
600RPM CPU HS

Temperatures:
@1.8 (300*6) idle ~28-34
@3.0 (300*10)load ~54-62[/size]

[F]bernZ
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Post by [F]bernZ » Sun Feb 25, 2007 2:44 am

Alright.. more results, since I strangely have SO much time to tweak with a fan when midterms are so damn close.. Oo.

The fan doesn't do very well even with an INCH of space above it. Compared to how much air it blows with no restrictions.. Right now even with an inch of space above it, it feels the same amount of air is being blown out compared to when there was no space above it. Of course, this may be because I'm using a rather high CFM fan. If I use a fan with a lower fan rating, perhaps this ducting system will work better. As it stands now however, with a high CFM fan, air doesn't get sucked out from the duct effectively.

I'm not sure if my problem lies in the fact that I'm using a high CFM fan or not. :S
[size=59]Intel Core 2 Duo E4400 @ 3.0GHz (300 * 10) w/ Scythe Ninja revB + SCURK1
Corsair XMS2 5400C4 @ 600 4-4-4-12
Abit IP35Pro
WD 2500AAKS
Pioneer 111-DVR
eVGA 7800GT w/ Accelero S1
Corsair 520HX
Lian Li A05B

Fans:
900RPM rear intake
900RPM front exhaust
600RPM CPU HS

Temperatures:
@1.8 (300*6) idle ~28-34
@3.0 (300*10)load ~54-62[/size]

Fawlters
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Post by Fawlters » Thu Mar 19, 2009 8:40 am

Prodding a sleeping thread may not help anyone much, but I'm pretty sure I know why the modded axial fan will only blow out the side.

For BlueFront's original set-up it works because of the centrifugal effect of the fan, the air coming into the middle is thrown outwards by the blades. This also means that fans with straighter blades should work better for this mod, though I can't say how much.

For [F]Bernz steup, it's pretty much impossible to work for the same reason, the centrifugal effect of the fan stops it being able to pull air in. The reason it blows at the edges and sucks in the middle is the same effect again, just the air is pulled in the middle then can't get blown out the gap in the frame so its blown out by the fan blades and the pressure. The fan is acting like an uncut fan with the intake side blocked off, so a circular air current is set up blowing out the edges and sucking in the middle.

To make a fan to blow from the duct is probably easiest by using a thin (~10mm) fan and making the duct big enough to allow enough air to the intake side. Depending on how many sides of the fan can be left open changes the height needed, with the least height needed for all four sides.

Assuming a 120mm fan, the area the fan moves air through is roughly 118^2/4*pi or 109cm^2.

1 sides = 109/12 = 9cm height
2 sides = 109/24 = 4.5cm height
3 sides = 3 cm
4 sides = 2.25cm

These heights should be from the top face of the fan, so if the fan is inside the duct the fan thickness should be added to these heights. Any ducting would also have to have an area around 100-110cm^2 to ensure even airflow.

If anyone wants further explanation I can make some models of what I mean and post pics.

-Fawlters
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xev
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Post by xev » Thu Mar 19, 2009 9:29 am

I would love some pics of your explanations

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