contra-rotating fans
 

There'd been a thread here a month or two ago about axial fan units with dual blades, rotating in opposite directions.
I just ran across some of these (probably for Dell) at american science and surplus for $3.95 each
http://www.sciplus.com/itm_photos/35535.jpg .
At 1.5"x2" they're probably too small to be immediately useful, but it might be interesting to have one or two in hand just to check 'em out - and $3.95 isn't going to break the bank...

Damn. They aren't even metric.

Yeh those are used quite a bit in Dell 1U and 2U cases for cooling or moving air from the CPU area in the rack cases.

At full speed, loud doesn't even begin to describe these beasts.

Ear bleeding, piercing jet engine at 5 feet would be a start... but only a start.

For those interested:
http://www.sciplus.com/singleItem.cf...LogFrom=Search

How are these different from the ones I mentioned?
Oh, wait - I get it now - folks don't realize that that thumbnail I posted is also a link(?)
Should I also have put a "click on thumbnail for link" note on there? Not have combined image and link? Something else?

I missed the link, so I dug it up.

Any progress on that conformal stuff? ;)

If you mean, have I made it to the UPS or FedEx shipping depots? No.
If anything, it's gotten worse - crunch at two employers (I contract) and I've just put my back out. Sigh. in the "every dark cloud has a silver lining" dept, one of those employers is about to run out of money if they don't find second round capital soon so my workload (and wallet) might be suddenly lighter.
How about if I just send it whenever I get there and it's a "gift from Santa" if/when it shows up. It is sitting right next to my desk to remind me of that to-do item.

57.5dBA

Tail wagging the dog. Fix the radiator, not the fan.

well... yeah.
For those folks interested in contra-rotating fans, here's a way to play with the technology for $4US.
Meanwhile, I'm still trying to find a heater core in the 6"x6" to 6.5".6.5" by 1" range with inlet/outlet on the "front" of the header tank (or tanks) single or double pass not a big issue for me given the low flows I'm using.
My two leading candidates are the

fedco 2-524: 6.25x6.375x1
http://koure.org:800/temp/fedco2-524.jpg

and the fedco 2-761: 6.625x6.188x1.625
http://koure.org:800/temp/fedco2-761.jpg
Both are too thick for really quiet operation. The second one, given no bottom tank, is probably even more restrictive than I'd like.
I'd just buy cases that better fit the BI Pro II or III if I weren't trying to retrofit a number of boxes that were already nicely set up for the "big momma" 6.125x6.125x2 heater core.

It ought to have some more pressure, which might make it interesting. I'm sure it won't beat a blower...

Let me see if I can dig up some specs.

(bk: sounds good, no rush, but I might have to send you a new shipping address, I'll let you know).

http://www.delta.com.tw/products/dcf.../GFBseries.pdf

It's the GFB0412SHE in that PDF listing.

57 db my ass! I should have clarified - I have a bunch of Dell 2U rack mount servers with these fans. They are, by far, the loudest fans I have EVER heard in a rack. I had one of the cases in my cube for repair and I literally could not turn it on outside of one of the equipment rooms because it would disturb the entire floor.

Once I put it in the case in one of our equipment rooms, my boss walked by and asked what the hell that wracket was coming from behind a solid wooden door, and STILL disturbing the whole floor.

Really, words just can't describe the piercing whine these things make. They are tolerable at lower speeds, but at full blast, they are just simply unusable if you have to be within 100 feet of them (even if there's walls between you and them - walls don't stop this frequency apparently).

Look for the Suzuki Sidekick/geo tracker core. It has dimensions like that.

db rating scale expodentially...57 dBa might actually be possible...
OT whoa, who can take such noisy servers...

A datacenter where no one is on a day to day basis?
;)

57db is a low estimate IMHO. I'd say it's closer to 75 - 90db, but maybe that's just the frequency they whine at that makes them seem louder.

Thank you!

The pressure is impressive (0.63 in/H2O), but the airflow really, really bites: max 22.25 cfm.

At least it can run undervolted. If they were cheaper, I'd try an array of these, over my 6*8 core (I'd need 12).

I think at 90 dB you get temporary hearing loss within a few minutes. A few hours would cause permanent damage. Put it like this, at 200 dB, humans spontaneously combust as the transmitted vibrational energy is so great. Remember, the dB scale is exponential, even a small rise produces a significant change :dome:

Its actually logarithmic, exponetial would mean huge changes in dB would equal small changes in intensity.

whoopeedo, my bad. got mixed up :X