2x 120mm fan -> 4x CMP170HX/A100 PCIe intake plenum

Made a nice organic looking air intake to cool four Nvidia CMP 170HX PCIe cards with two high pressure 120mm fans. They move more air than 8x 40mm fans and are hell of a lot quieter.

Also compatible with the A100 PCIe and potentially other Nvidia cards with the same mounting interface*

I attached two Arctic S12038-4k fans. I think that's the minimum spec that will give enough airflow. Maybe the P12 pros might work at full RPMs, but the server spec fans have more aggressive blade pitch which improves static pressure at low speeds so hopefully it's net quieter overall.

Caveats:

• The screw boss on the short side is kind of close to the plenum. You will probably need a short Allen wrench to screw it in. I goofed that up in the design (didn't notice there isn't a sightline down the screw bore) but since my mobo will remain flat I'm too lazy to fix it. PRs accepted :)

• The other screw bosses are also somewhat obstructed by the rising plenum. A ball tip hex driver is ideal, but you can make do without.

• Quite a bit of cantilever load on the cards. If they are flat, you might want to prop the fans up a bit to relieve the load

• The plenum blocks the clips for the power connectors so you might need needlenose pliers (or to take the plenum off) to unplug a card.

• I haven't tested this for long-term stability/creep, especially when mounted vertically. I don't plan on doing so, so it wasn't a priority in this design. Print it in structural profile to increase layer adhesion just in case.

• Distance from front of cards to the fans is 15cm. It could possibly work with a shorter offset, or it might absolutely mess the geometry up Clone the Onshape project and tweak the variable to see if it works. No guarantees, and I apologize for the messy feature tree :P 

Required hardware:

• 6x M3 6mm (or 8mm maybe) bolts to attach frame to GPUs.

• 3x M3 8mm+ bolts to attach frame to plenum via 3x M3 nuts fit into the recesses on the screw bosses on the frame.

• 8x fan mounting screws (idk what they are, the self tapping kind) to attach fans to plenum.

• 2.5mm hex driver

• Philips driver (or whatever screws your fan uses

Assembly order:

• Put cards into every other PCIe slot.

• Press frame onto the cards. At default tolerances it should be somewhat snug. You might need to  loosen the card setscrews on the rail to even them out as you're putting the frame on, then retighten.

• Screw 6x m3 screws to attach frame to the two mounting holes on the cards.

• Screw fans to the plenum.

• Attach 2x PCIe power -> 1x EPS pigtails to the cards.

• Press plenum in place. It should be flush with no gaps.

• Supporting fans with something (thick book or something off the bottom of your case) put 3x m3 nuts into the recesses on the frame and screw the plenum to the frame.

*170hx_boilerplate.stl/stp is the reference part I cadded from measurements. Only the rear face (with the screw holes) is accurate. Length is not accurate

Clone and tweak at https://cad.onshape.com/documents/35e55c4f386d5d923c112115/w/cf63fc5346e4718dcd8400e1/e/e2d3d398c87ff1f16eb54af8?renderM