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Raspberry Pi Rack

A 3d printed enclosure to house multiple Pis

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A 3d printed enclosure to house multiple Pis.

The original idea was somewhat like enterprise blade server - a chassis that takes care of power and network distribution, with processor modules that can be easily added and removed. The recently released Raspberry Pi 2 features a quad core ARM processor, so they're very capable little machines for $35. Low energy usage (compared to a regular linux server) and fanlessness make them ideal!

You can download the 3d models here, created with SketchUp. To print, you'll need the STL Plugin to export a format that most 3d-printing host software likes. All the pieces (along with some prototype and test models) are in the one document.

  • Base / Switch Details

    Dave Pedu04/26/2015 at 20:04 0 comments

    The bottom most layer of the Pi Rack mounts an ethernet switch and some simple connections to bring power up to the Pis.

    Wanting to keep things simple, I decided to use an ATX power supply for now, as they provide a steady 5v power source good enough for computers, so powering a Pi would be no effort. The 3d printed bottom piece has recesses for the molex connector and a piece of prototype board (it's oversized because I wanted space for future additions - maybe a simple fan controller if needed). All that's really here is a SIP socket that power/ground is connected to.

    To connect to the power-providing SIP socket, this little right angle breakout board provides a pin for each PI, the jumpers are simply plugged into this. I also cut the switch's original power supply cable and resoldered it here so its powered entirely from one supply.

    This connects to the bottom socket something like this:

    What's neat about this is I can experiment with different power sources in a fairly modular way - just need a 6 pick SIP socket.

    All that's left is to flip the base over and bolt it in place! An opening gives easy access to the ethernet connections, and spare ports for the uplink.

  • Hotswap enclosure details

    Dave Pedu04/26/2015 at 19:42 0 comments

    The core of this project is figuring out how the Pis will slide into place and have all the necessary ports line up and make contact. Designing the sled gave me a firm grip on the capabilities of my printer, so creating the backplane was next. Having little 3d modeling experience, I turned to the simplest tool available: SketchUp.

    I found a reasonable accurate model of the Pi B+ online, so I used that to mock up the enclosure. Label 1 is a housing for the ethernet plug. Originally I planned to epoxy these into place, but force-fitting them into the 3d printed model seems sufficient. My cheap printer tends to round corners but in this case it only helps hold the RJ45 connector in place. Label 2 is a U-shaped holder for two more breadboard jumper wires, the female end of which is glued in place. The power and ethernet wires all run down through the hole at Label 3, down to the layer where the ethernet switch sits and power will be distributed. The vertical back is fixed to the top/bottom layer with a tongue and groove.

    A keen observer would note that in the model pictured above the ethernet wires would have to run through separate holes in the back. I ended up printing the bottom layer first and forgot these holes! I compensated by adding new holes in the rear vertical piece. This is a little more clear when seen here, with a Pi inserted and the top removed:

    I think I like this routing of the ethernet wires, they're a little more protected than the original design. There's room for some simplification here - I could have omitted two twisted pairs of each ethernet run here too - the Raspberry Pi only supports 10/100 lan, which only needs 4 wires - only gigabit ethernet uses all 8. In fact, my switch is only 10/100 as well. But I left them in under the idea of futureproofing. I would LOVE to see a Pi with gigabit support someday.

    Assembled with some simple threaded rods, lock nuts, and wing nuts from my local hardware store, the Pi bay looks like this:

  • Sled details

    Dave Pedu04/26/2015 at 19:12 0 comments

    Each Raspberry Pi sits on a custom 3d-printed sled. The original model B/B+ and the Raspberry Pi 2 have an identical form factor, so it works for both!

    Leftover breadboard jumper wires are connected to the GPIO pins the Pi to provide power, with the other ends glued to the sled. Power and ethernet are really the only connections I care about in this project, as the Pis will be ran headless. The Pi can be powered by these GPIO pins using any 5v source, but it bypasses protections on the usb micro power supply port, so care must be taken that the power supply is within what the Pi accepts, and polarity is correct. The Pi wants between 4.75V and 5.25V (less than this, or drops, can trigger the B's brown out detector - details here: https://www.raspberrypi.org/forums/viewtopic.php?t=58151)

    The sleds are completely screwless - pegs printed into them fit the RasPi's mounting holes, and little clips hold the Pi in place.

    This is my first adventure into 3d printing, and getting the sled just right took literally a dozen iterations. To figure out what my very low end 3d printer was capable of, figure out the easiest way to mount a Pi, how to run the power, etc.

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Bill Robison wrote 01/25/2017 at 19:26 point

I was looking to build an RPI blade server when I found your project.  I like it!

How are the bays hot-swappable?  Do you implement a software shut-down in case of sled removal?  Have you considered additional circuitry on the sled to handle this and other functionality?

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gatkinso wrote 09/12/2015 at 21:12 point

This is excellent work!

Hmm I wish there were a 3D printer that you could toss your scraps into to reuse!  Anyway... I am planning on implementing this rack... once I fully understand it I would like to enhance it by designing and printing rear transition modules for the USB, as well as serial, camera, I2C and SPI connections (maybe plumb out the Ethernet to a USB connection as well).  

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Dylan Bleier wrote 04/26/2015 at 21:06 point

how does an ethernet switch even work...

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davedarko wrote 04/26/2015 at 20:16 point

Great pictures and cool write up, now I see the reason for 3D printing! It first looked like raspberrys clamped between plastic sheets. The hot swap adapter looks pretty nifty! Great project, instant skull :) 

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Dave Pedu wrote 04/26/2015 at 20:20 point

Thanks!

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davedarko wrote 04/26/2015 at 07:42 point

what's that on the bottom? Power supply? Or a switch/hub/router? Looks like it could also be made out of wood. What do you do with 5 raspis? Is one missing?

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Dylan Bleier wrote 04/26/2015 at 07:55 point

one does not simply 3D print trees

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davedarko wrote 04/26/2015 at 08:08 point

there is wood filament. Argument invalid. Plastic doesn't grow on trees. *micdrop*

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Dylan Bleier wrote 04/26/2015 at 08:16 point

what is that, sawdust mixed with plastic?

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davedarko wrote 04/26/2015 at 08:40 point

wood is a better rescource than plastics and the shape looks like 4 sheets of plastic bolted together, so I really do believe and would like it to be doable to be made out of wood. I wonder how many failed plastic prints are already swimming in the ocean, since this all started. Anyhow, we're getting rudely off topic, so place your last sentence well and let @Dave Pedu tell us more about his project :)

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Dave Pedu wrote 04/26/2015 at 18:13 point

The larger board on the bottom is a switch,  the smallest I could find - http://www.amazon.com/dp/B0034CL3MA/ . The smaller prototype board is just a junction for where power (Provided by an ATX power supply) is split off for the 6 PI slots, and the switch. You absolutely could use wood for the layers and sides, be it 3d printing (I've never heard of doing this with wood?) or traditional woodwork, if you have a router to cut the slots and square holes.

I'm a linux geek so I have handfuls of hardware of various age running around my house, doing various linuxy tasks. The new quad core Pis are very capable and a much more energy efficient host for software projects. I hope my use of plastic over wood is offset by the energy savings :)

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