PiHotel - Modular Raspberry Pi Tower Cluster Case

A fair warning
This is my first model! I've marked these files as version 0.1, and fully expect there to be improvements to come. Feel free to leave comments or suggestions and I'll do my best to get working on them straight away! 

Bonus note: Pis are back in stock seemingly, I recommend https://rpilocator.com/ to find stock in your country :)

The what and the why

This project is intended to be an open-source spec for Raspberry Pi (and other microprocessors/controllers) tower cases.

I made this as I was struggling to arrange my PoE switch and Pis neatly, whilst also providing adequate/consistent cooling across all of the Pis.

From my testing, the Pi stack solution keeps my Pis comfortably around 30°C/86°F during idle. I did not enable any PWM/fan speed control during my tests, just the stock 5v speed from Noctua.

The base/shelf design 

The base of this project is simple 129mm x 105mm shelves, using 2mm notches at the top, and 2mm notch cutouts on the bottom to lock the shelves through friction - no glue required (on a well-calibrated print). The height of the shelf is dependent on the component being housed.

POE Switch

I used the TP-Link Poe Switch - TL-SG1005P. It was (and still is, in the UK) the cheapest big brand POE+ switch I could find on the market at the time, it cost roughly £40 and provides a maximum of 65w PoE power, enough for 4 Pis (although maybe not enough for 4 pis at parallel high load). 

SSD Bay 

The size of the stack can comfortably fit a standard-size 2.5”/Laptop SSD. In my example, I just added a 47mm by 12mm gap for the USB to SATA connector to fit through.

Fans aren’t intended to go through this section of the stack due to SSD size constraints. I would recommend putting SSD bays towards the top/bottom of your stack (or in the middle between fan sections if going for a 2x4Pi stack!

Raspberry Pi 4

The Pis just sit onto the spokes on the 3D print. If you’re using standoffs, I push the spokes into the standoff themselves for added security. The area to the left and right of the Pis is adequate space for desktop fans.

Recommendations:

• POE+hat + Standoffs - 10mm
• Heatsink - as shallow as you can find. Mount so that airflow from the fans has the most impact.
• Noctua Fans - PLA may start to struggle with hot electrical components. I wouldn’t recommend using the stack without fans as it’ll get hot fast.
  • If you think you’re going to be operating consistently at 70°C+, try printing in a more heat-resistant filament 

USB hub/Power bank holder

To power my USB Noctua fans, I made a shelf to store a USB hub. My USB hub was relatively large, so I made a taller version. There is a 28mm height version for those wishing to keep their USB hub section the same height as their Pi/switch sections.

Printing advice

• Use heat-resistant filament if you’re not using fans (although I strongly recommend against not using fans!)
• Excessive corner warping will make the notches unusable - calibrate your printer, use a quality filament, and use a brim.
• Use tree supports on any gaps - they should snap off quite cleanly with the brim

Suggested implementation/build

• Switch: TP-Link Poe Switch - TL-SG1005P
• 1-4 x Raspberry Pi 4s, POE hats & Memory cards
• Some form of cluster management, if desired (K3s worked in testing).
• USB Hub
• 2x 92mm x 92mm x 25mm fans - I recommend Noctua NF-A9 5V. 
  • Do not get 12-volt fans, they’re unlikely to spin on a 5v USB power supply (as I found out with Noctuas 12v fans)
• Think about airflow, have one side pushing cool air in, and one side pulling the cold air back out. Similarly, think about fan orientation - make sure the air can move and isn't hitting a wall :) 

A few improvements already on my mind:

• Allow for USB-C power - Add a USB-C socket at the back of the Pi Shelf, such that the PoE switch isn't necessary.
  • Although, for less power cables purposes, I strongly recommend a PoE switch :)