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Question anyone make a 'squirrel cage' low profile rear slot fan?

GunsMadeAmericaFree

Senior member
Jan 23, 2007
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I would like to add a slight amount more airflow to my old Lenovo ThinkCentre M82 SFF (small form factor) system.
I have an extra SATA power connector available, but none of the old molex/IDE connectors.

This system is a pretty cramped desktop (not tower) pc. When I searched for rear slot fans,
I found a lot of squirrel cage blower type fans, but they all have the old molex/IDE power connectors,
and not SATA. Also, I'm not seeing any low profile types.

Can anyone direct me to solutions for a low profile PC with an additional rear slot or two?
This sort of 'squirrel cage' blower would seem to be a perfect solution, but after searching for a half
hour, I can't seem to find any low profile options.

Thanks!
 

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mindless1

Diamond Member
Aug 11, 2001
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TLDR; Easiest passive thing to do is keep looking. Otherwise you may end up forced to DIY, though that could get expensive and/or time consuming for what it is.

Frankly I wouldn't do any of the below, instead I'd cut a hole size for the largest (especially deepest for longer life and better flow:noise ratio) traditional axial fan that will fit, an intake fan so you are pushing more, rather than less air through the PSU than if you added an exhaust blower. This could make a significant difference in a SFF PSU's lifespan. I'd shoot for a 92mm x 25mm if it'll fit.

A cut hole on painted metal can be ugly (or not so bad if you have the right size hole saw and paint the cut edge to match) but you could finish it off with a filter panel over it, or cheap ~$2 pack of black automotive door edge guard molding from a local auto parts store. Power, get an adapter off ebay, or get a molex 4 pin splitter assuming the system has at least one but it's in use? Adding a small fan will be a negligible difference in current for this purpose. Heh, I don't know your past PC moddin' experience so whether this type of thing needs to be mentioned.

Other DIY options...

Take a low profile bracket with the typical two tabs 'n screws, cut a piece of circuit board (or aluminum, steel might be too heavy) large enough to mount the fan on, drill several well placed holes in the bracket till it looks like swiss cheese, then pick the size fan you want on it from Digikey, and while at Digikey get an SATA plug, or get an adapter plug off ebay cheap ($1?), or saw one off an old dead HDD/etc and solder it up.

Option 2, I can't tell how tall that fan is, but you might be able to just cut down the bracket on it to be short enough, or not, depending on how wide the airflow exit hole is.

Option 3, make your own bracket out of steel or aluminum, though you might need to heat the aluminum to get a sharp enough bend at the top w/o cracking it, and you'd at least need a bench vise and hammer or better still a metal brake to make that bend.

You do realize that this type of fan is quite loud for the amount of air moved? Granted any addt'l airflow beats nothing, but connected straight from PSU SATA, removes the opportunity to adjust the fan speed.

Well not entirely, through experimentation you could add a series of diodes or few tens of ohms 2W resistor in series on the positive (or negative) power lead to slow it down but like all the above, this requires some DIY rather than plug 'n play. Another option would be get an SATA adapter dongle of ebay and swap wire positions to get 5V powering the fan, if you pick one compatible and still retaining enough airflow at 5V which is sort of hit or miss unless you had a variety of fans to test.

Getting a pack of diodes and soldering on one after another as you test the resultant noise and flow rate is the surest way to a solution with the noise:airflow ratio you need, with a single purchase of diodes, unless you happened to have a variety of 2W resistors in roughly 22 ohm to 120 ohm range to experiment with.

The cool kids might 3D print a low profile bracket. Another option might be swapping a faster fan into the PSU, though it might require soldering and will definitely increase noise. If you have a particular hot zone you might be able to cut a hole, slap a filter panel on adjacent to that zone and let the existing exhaust fans pull air in there.

I've already written too much, do you have any willingness to go the DIY route with any of the above?
 
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fralexandr

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Apr 26, 2007
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There are molex to SATA power cables.
A low profile blower would probably be using a 50mm blower fan which would make it either provide almost no airflow or make it sound like a loaded laptop (noisy whirring sound).

Someone on ebay makes some low profile pci or pci-e fan for $40, though they're pricey and not blower styles and I don't think anandtech allows ebay links to small ebay stores.

If you have a dremel and drill you could always create a fan hole and use an IDE to fan cable. This would be a better option, since you could make an opening on the side panel over the CPU and/or GPU and mount a common fan size like 120mm/140mm/200mm and put a dust filter or something if required.

edit: I was too slow, doh!
 
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mindless1

Diamond Member
Aug 11, 2001
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^ Since I don't have a "wide" assortment of hole saws, I can use my door knob 2-1/8" for a 60mm fan but otherwise it's just a reciprocating saw after a hole drilled to start it.

Dremel, meh I own one and only use it for light/tight areas because the bits are just too expensive for their short lifespan. Recip saw does leave a rougher edge that I sand or file a bit, but that's where the filter panel or door edge molding over it comes in. If it's one of those flimsy-thin metal sheets (most prevalent on cheap aftermarket cases but even an OEM might go thinner on a smaller system's panels), you may need a pretty high tooth count blade to not leave ripples in the metal from the recip saw action, but if it's that thin you can make a larger starter hole and use tin snips.

I wasn't aware of the small store ebay linking rule! I must have broken that one a few times myself. I think it's a good idea to cut down on spam, as well as from Amazon, but of course it can have its down side too, like if I had tried to help by posting to an ebay fan adaper dongle. Hmm, I'll have to try to remember that rule.
 
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aigomorla

Cases and Cooling Mod PC Gaming Mod Elite Member
Super Moderator
Sep 28, 2005
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That is the inside of the M82.

From my impression a rear blower, which your are asking for won't do much merit as they are all underpowered.
And if your looking for a low profile version, that will be even more underpowered.

There are some solutions tho, the CPU is cooled by the top fan, the system is cooled by the front fan.
You can replace both fans with stronger PWM fans, however lenovo uses pretty decent OEM fans.

You can try to replace the front fan, but it will make the system louder.
You can also try to remove all your PCI-E slot covers and put a fan right up against it as well, but putting a single slot blower will probably not net you much that you are expecting.

The greatest gain i can see is replacing the front fan to draw more air in, and allow the cpu fan to get colder air.
 

HerrKaLeu

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Nov 23, 2016
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A centrifugal fan ("squirrel cage") provides high static pressure. There used to be some CPU coolers with centrifugal fans, but never made progress into the market. In a PC, even in a CPU cooler or radiator, the static pressure drop is relatively low. A typical application would be a HVAC air handler, with thick filters, coils, and a large duct system. For HVAC applications with low static pressure drop, we use axial fans (propeller). This include systems with some duct, dampers etc. I'm an HVAC engineer.. If you look at a PC case, you see it is a very open system with relatively low pressure drop. In HVAC applications we would call it a plenum. The 120mm fan feeds into a 350mm plenum instead of a 120mm duct. Almost no pressure drop if you have enough openings. The case filters are nothing compared to HVAC filters, and you don't have coils (which would be similar to a CPU cooler).

So what would a centrifugal fan do with all the static pressure it produces? Waste the energy and turn it into noise. Any energy (electricity) gets converted into air movement, heat, and noise. A quiet system is an energy-efficient system, since you convert less energy into noise. ... So for a case, you want to use a regular propeller fan. You discovered that there are not many centrifugal fans for PCs.... and now you know why.
 

GunsMadeAmericaFree

Senior member
Jan 23, 2007
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Wow, thanks for all of the thoughts, everyone. When I looked things over closer, I found that there was a CRAPLOAD of dust in the front of the PC, on the filter that led immediately to the propeller fan in the front. I used a brush to clean that off well, and now the airflow through the system works a heck of a lot better. I'm guessing that was probably the reason why everything inside felt hotter than expected, and why the hard drive was starting to fail.

Given that it is 8 years old, I think I'd like to replace the front fan as a form of preventative maintenance. It is 3" size.

Can anyone recommend a quiet replacement fan for the Lenovo ThinkCentre M82 SFF? We have two of these, and I think I'll have
my son replace these as part of his 4-H self guided project.
 
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VirtualLarry

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Aug 25, 2001
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Most fans are of a standard size, more or less, for different size classes, but Lenovo being as proprietary as they are, I would try to get the "FRU" (field-replacable Unit) number/code, and look for an exact replacement on ebay or Amazon. Saves the hassle of trying to find an exact equivalent replacement. Then again, the ones on ebay probably aren't new. So there's that.
 

mindless1

Diamond Member
Aug 11, 2001
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If the HDD is 8 years old too, it may be starting to fail merely from old age/wear. That's not a bad run at all.

Fans are measured in millimeters. At 3" it's probably 80mm. Next determine how it mounts, if using the conventional 4 corners with screw sized holes (whether Lenovo uses screws or clips or whatever), then a standard replacement should work, providing it has the same power connector. If you have soldering skills, or buy the connector and crimp pins (digkey.com et al), you can instead swap the connector if you prefer.

If it is 25mm thick, OR if a 25mm thick fan will fit (without being so close to the HDD that airflow is restricted (I'd give it at least 10mm clearance)) then use 25mm, not a thinner fan.

If the original fan is a major brand with dual ball bearings, odds are good that it has much life left in it and doesn't need replaced yet. Quality dual ball bearing fans tend to get louder, a whining sound when they still have thousands of hours of life left in them.

Note the current rating on the fan, or if you can find the manufacturer datasheet then you can determine the RPM to pick a new fan of similar RPM, or a little higher if you want to accept a little more noise for an airflow increase.

Yes filters need to be cleaned every so often. I check them every year. It still beats cleaning dust out of the whole system, especially heatsinks and PSU, if your filter has small enough particle effectiveness, but then it needs cleaned that much more often and needs a larger surface area to not restrict flow too much.
 
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GunsMadeAmericaFree

Senior member
Jan 23, 2007
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If the HDD is 8 years old too, it may be starting to fail merely from old age/wear. That's not a bad run at all.

It was a Seagate Constellation Es.2 drive from a server farm that I bought and installed about a year ago. Over the past week, we got messages on bootup that it was having problems. After seeing that a couple of times, I decided the hard drive must be starting to fail, so I cloned the drive to another one I had here, and no problems since then.
The original Constellation drive is now serving as an image backup only on my shelf.

Regarding the fan, I do like to replace things with moving parts that wear, especially since most of the cooling of the system depends on this single fan. I'll have to take a look at the power connector, and see what I can locate. Maybe I'll just buy 1 and have it on the shelf in case of a failure - ready to use.
 

mindless1

Diamond Member
Aug 11, 2001
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^ Depends on the quality of the replacement fan. If you're going to buy and store it anyway, I'd go ahead and swap it in, then keep the old fan as the backup, give it a drop of oil in the bearings if a sleeve bearing type.
 

aigomorla

Cases and Cooling Mod PC Gaming Mod Elite Member
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Sep 28, 2005
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I'm guessing it's an 80mmx25mm fan, so you could go with the noctua r8.
nah, that AVC is a better industrial fan with higher static pressure, its only crevet is its a bit noisier then a noctua.
 

mindless1

Diamond Member
Aug 11, 2001
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^ AVC? What is pictured looks like a Delta to me. One other factor is in the pic, as small and one-dimensional as it is, I still see case perforations below the fan, and inevitably that hinged design must have gaps around it too, that limit the effectiveness of pulling fresh air in rather than recirculating a significant % in a short loop there. I would see how much of that area I would block off with (any type really) foil duct tape without interfering too much with the ability to pull drives later, to make the only air passage in the front, through the fan.

The Noctua probably wouldn't give up much (if anything depending on what the RPM was of the stock fan), but we should just wait for some specs on the OEM fan, and go from there. I mean model #, a datasheet showing RPM, or at least current rating to infer the ballpark. Then there's the factor of buying a fan with higher 12V RPM rating and throttling it back to the noise:flow ratio that seems most appropriate.
 
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