IIci exhaust fan duct thingy

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KennyPowers

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I don't know how useful this'll be for others since it's a pretty specific use-case, but I have a couple extra toasty full-length cards in my IIci, and I was trying to come up with a way to get some air moving through that walled-off part of the case. Since these particular cards don't require mounting brackets, I removed them and came up with this little snap-on duct thing for a 40mm fan that spans two adjacent NuBus slots:

-8132048643815677397.jpg PXL_20250821_133922804.jpg PXL_20250821_222317101.jpg PXL_20250821_222400977.jpg

It's not perfect, but what I found neat is that this model was almost entirely generated by ChatGPT 5. I took some measurements, and then told it roughly what I wanted and gave it the measurements, and it spit out a downloadable STL (along with some configurable Python code to create that STL). It took a couple back-and-forths and some minor manual tweaks to arrive at the final model. I particularly had to help it with the snap-on mounting tabs, but everything else is completely LLM-generated. One tiny step closer to a Star Trek replicator :LOL:

It does seem to work pretty well too. A sheet of paper is now pulled against the vents at the front and top of the case, so I know fresh air is now being drawn in to that area of the case and spit out the back. The fan wires can be tucked under the duct and routed into the case, or the fan can just be powered externally.
 

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JDW

JDW

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Wow! What a nice idea! Pretty nice how ChatGPT was able to create something usable for you. I too am not adept at 3D design, so having a digital friend who can assist with that is handy!

Noctua fans blow out the sticker side though...

1755826639825.png


And because your main PSU fan also blows outward, are the two fans competing for air since they both blow outward?

If the main PSU fan is sucking away some of the air flow from your cards, would it be better to flip the fan so you blow cooler outside air on the cards, which in turn will become warm air that would route outside the machine via the PSU's fan?

Not sure what's best. Just throwing out some thoughts.
 
Stinkerton18

Stinkerton18

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JDW said:
Wow! What a nice idea! Pretty nice how ChatGPT was able to create something usable for you. I too am not adept at 3D design, so having a digital friend who can assist with that is handy!

Noctua fans blow out the sticker side though...

View attachment 22965

And because your main PSU fan also blows outward, are the two fans competing for air since they both blow outward?

If the main PSU fan is sucking away some of the air flow from your cards, would it be better to flip the fan so you blow cooler outside air on the cards, which in turn will become warm air that would route outside the machine via the PSU's fan?

Not sure what's best. Just throwing out some thoughts.
Click to expand...
In this case probably not. Flipping the fan would likely conflict with the power supply's fan. By having the fan set to pull and exhaust, you're building a wind tunnel effect via negative pressure in the case, a lot like how server chassis are setup.
 
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KennyPowers

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Stinkerton18 said:
In this case probably not. Flipping the fan would likely conflict with the power supply's fan. By having the fan set to pull and exhaust, you're building a wind tunnel effect via negative pressure in the case, a lot like how server chassis are setup.
Click to expand...
That was my thinking. With the particular cards I have installed, the section of the case exhausted by the 40mm fan is mostly walled-off from the rest of the case interior, so the PSU fan probably wasn't that involved in ventilating that area. There are slits in the case lid above the NuBus cards and slits in the case front in front of them. After adding the fan, a strip of paper is now drawn against both of those vents. I suspect that this is getting more heat away from the cards than just the heat supposedly rising out of the vents in the case lid. I could never feel any appreciable heat when placing my hand over the lid vents without the fan, but the temperature of the air expelled by the fan is noticeably above ambient.
 
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JDW

JDW

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If you have a thermal camera, you could leave it running with the top case on for about 1 hour, then pull it off and quickly measure the temps on your cards. You could repeat with that test with fan add-on. And if it is easy to flip the fan, you could do a third test. Those 3 temp. measurements would be the final proof of what keeps the cards coolest.

But for now, more air flow across those cards is better than without the 40mm fan. Of course, keeping the A/C on during the summer months to keep your room cool is also very helpful.

Again, I love the novel idea!
 
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KennyPowers

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JDW said:
If you have a thermal camera, you could leave it running with the top case on for about 1 hour, then pull it off and quickly measure the temps on your cards. You could repeat with that test with fan add-on. And if it is easy to flip the fan, you could do a third test. Those 3 temp. measurements would be the final proof of what keeps the cards coolest.

But for now, more air flow across those cards is better than without the 40mm fan. Of course, keeping the A/C on during the summer months to keep your room cool is also very helpful.

Again, I love the novel idea!
Click to expand...
I...do not have a thermal camera 😕
 
JDW

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Good thermal cameras (what they call high-resolution types) are rather pricey, which is why excessively frugal penny-pinchers like me tend to hold out for what seems to be like an eternity before buying such gizmos. The same was true of my Hakko FR-301 desoldering gun. I held off for YEARS, hoping to avoid that big spend. But after buying it, it has now become one of my most versatile soldering tools.

You can see me use my thermal camera in my latest video checking Color Classic temps. here and here.

That thing was pricey even though I bought it straight from China a couple years prior to all the tariff madness. But boy, it sure is nice when you need it.

As you can see in the first video clip, I also have a meter which has a Type-K wired thermal measurement, but those are much more fiddly to tape to your device under test (mine kept coming off in that test), and you really would need to add a good thermal paste to make sure it's contact with a hot chip is sufficient. Even then, it's only a local test to whatever it's affixed too. In contrast, a thermal camera can show multiple chips or even multiple cards all at once. Much too expensive, in my opinion, but they do come in handy.

Anyway, kudos on your fan mod. I really like it!
 
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