Cluster enclosure for 5 Rock 5B SBCs.

Built with modular sleds for each Rock 5B.

The enclosure is sized to fit nicely on top of a Hasivo 8 port 2.5gbe PoE switch.  With PoE powering the sleds the only cables you need are 5 short rj45 cables.  This gives a very tide look without a lot if cable mess, etc.  

There is plenty of room on each sled for the NVMe drive and a thin heatsink.  Beefy NVMe heatsinks are a no-go for this box.

You can use PoE power for each SBC or 12v power distributed from a barrel connector in the rear. PoE should be fine for the SoC and NVMe drive but won't leave a lot of power headroom if you plug in a lot of USB or make heavy use of the GPU/NPU. The PoE hat is good for 20w to the SoC (5v@4A). Stress testing the SoC at 100% CPU loads and continuous NVMe writes showed ~16-18w draw measured by the PoE switch. With PoE I used the 12v output from the PoE hats to power the fans - this part doesn't count towards the 20w power budget.

For the power brick version I just wired the fans to the input from the power jack.  The non-PoE version of the cluster is about $125 cheaper to build (cheaper switch, no PoE hats but you need more expensive heatsinks, a few more parts in the case and a power brick).  You should also have no problem fully utilizing the GPU/NPU and plugging in a lot of USB devices when powered this way.

There are zip-tie loops on the inside back wall to tie down and clean up any wiring you do inside the case.  They may be a bit fragile and probably need to be fixed up a bit.

Airflow/cooling is really good.  The SBCs get a lot of air from the PoE hats.  The fans on top really just need to get hot air out of the box so its probably OK if you want slow them/quiet them with a resistor mod.  4 of the 5 sleds get really good airflow over the NVMe drive - the one on the far left may run a bit hot if heavily loaded because it is sandwiched pretty close to the outside wall, which may limit how much air it gets.  I haven't been running this long enough to know if that is a problem or just something I worry about.

Print details:

• .4mm nozzle, .2mm layer height works great.  Larger nozzle/layers may work too but not tested.  Watch out for tolerances around the IO ports if you print the sled with larger nozzle or layers - its pretty tight as it is.
• 3 top bottom layers to make everything rigid enough.
• Infill can be pretty sparse.  I used 5% infill but you may need more depending on how well your printer/filament handles bridging.
• Sled should import in the right print alignment.  You'll need to flip the box onto its back. No supports should be needed if printed in this alignment.
• You can print the sled with the front face down.  This gives a really nice finished look to it, especially if printed on a textured bed.  If you do this you'll need supports for the mounting posts and possibly the back of the sled.  I'm working on making mods to make this alignment easier to print.
• I printed everything in PLA but any filament you are comfortable with should work.
• Filaments that shrink/warp (i.e., ABS) could be difficult for the box due to the large flat surfaces with long unbroken strands.  YMMV.
• If you print PLA use a lot of care setting the heat-set inserts - PLA melts fast and you risk deforming the posts the SBC sits on.

Requires:

• 25x m3 heat-set inserts.  Four for each sled and one to receive the thumbscrew.  They need to be small inserts, 4.6x3mm  
• 5x m3 thumbscrews.
• 20x M3x5 button head machine screws
• 2x 8010 12v fan

In addition, if you are using PoE:

• High power pi compatible PoE hat like this one from Waveshare
  note: with this PoE hat you have to move the fan to the opposite side of the board
• 15x M3x16 standoffs to support the PoE hat (the ones included with the PoE hat are m2)
• A thin heatsink.  You may need to improvise this.  I used some random ones I had in a parts drawer and had to cut the corner off of them to clear some of the components on the PoE hat. This SBC does not need much of a heatsink and the PoE hat moves a lot of air - you might be OK without it, just relying on the fan from the PoE hat.  Again, YMMV.

If you are distributing power from the inside:

• A 5.5x2.5mm barrel connector panel jack to fit an 11mm hole
• 5x USB-c power pigtails
• A suitable heatsink for each Rock5b.  I recommend Radxa's heatsink with fan, but any should work.  Even passive ones if they are less than ~27mm tall.
• A 12v power brick with 5.5x2.5mm barrel connector.   Allow for at least 30w per node, so aim for a 150w or higher power brick.
• 18gauge wire, solder and heat-shrink tubing to wire the pigtails and fans to the power jack.  And some type of connector for for the USB-C pigtail if you want to be able to remove them.  I haven't really worked out the best arrangement for that.