Large Heatsink with Case

I wanted to extend my approach to the possibility of attaching the NVME carrier.
Since I don’t own this extension I wanted to ask, if anyone can provide the dimensions of the carrier pcb and the other parts (including ribbon cable). A 3d model would be even better :slight_smile:
thanks a lot

The M.2 extender board is 87 mm long X 55 mm wide.

BTW, ALLNET says they have started production of an aluminum case, but I haven’t seen it yet.

The following is what I came up with after much thought, searching the web for suitable project boxes, and metalwork. Unfortunately, I am unable to upload the document as an attachment, so formatting is lost, but I hope the information is helpful for others.

Aluminum Rock Pi 4B Case

First, you see the typical Raspberry Pi arrangement of connectors on the top half of the aluminum case, while the bottom half has been expanded to accommodate the Rock Pi 4B’s large heatsink and SSD.

The SSD is mounted beneath the heatsink, but separated from the heatsink with standoffs. This positions the SSD it at the lowest level inside the case to avoid whatever ambient heat may be rising from the heatsink.
Beneath the ethernet and USB ports, the heatsink is in direct physical contact with the aluminum case, which effectively creates an extended heatsink.
The FPC cable for the M.2 extender board requires extra room beyond the end of the main board and heatsink, which means the microSD slot is located further inside the case, making it more difficult to access, plus microSD cards are more easily dropped inside the case.

A short length of ½” diameter PVC pipe, cut lengthwise, and mounted horizontally solves this issue by forming a catch tray and precise guide for accessing the slot. Tweezers are still required for insertion and removal, which is less frequent when booting the Rock Pi 4B from the eMMC module.

With the catch tray’s white color, it is much easier to see the microSD slot. A hole located near the power LED illuminates the interior of the catch tray creating a nice soft green glow when power is on.

The aluminum case is cooled with dual internal Raspberry Pi fans, with protective grills that make the Rock Pi 4B ready to roll. Junior can carelessly grab it up and stuff it into a backpack, with no worries.
The dual fans are positioned to force air directly into the space between the large heatsink and the M.2 extender board. The hot air is pushed out through connector ports and vent holes.
The fans are powered from GPIO pins 4 & 6. A custom ribbon cable extends the 5 VDC & ground wires to compatible connectors and splitters for powering both fans while the GPIO header is being utilized by a ribbon cable during project development.
The top panel of the case can slide away from the fans, creating a gap for either the GPIO extender cable or a standard 40 pin ribbon cable to slip through for communicating with the external world. By using the optional GPIO extender ribbon, the top panel can remain in place to protect the Rock Pi 4B board and to maintain consistent airflow. It is no longer necessary to get inside the case, just to disconnect the ribbon cable.
There’s also less risk of breaking the breakout ‘T’ on the solderless breadboard because all the connect/disconnect stresses are at the middle of the ribbon cable, not at the more fragile endpoints. The female 40 pin mid-cable connector also allows for ‘hot-plugging’ of projects, without powering down.

Above are similar configurations of the Rock Pi 4B aluminum case and the ($14.90) Raspberry Pi 3B+ aluminum case, both utilizing GPIO extender ribbon cables connected to solderless breadboards.
My objective was to make the case as small as possible, without losing functionality. But, the previously illustrated Rock Pi 4B aluminum case is less than half the size of the original aluminum project box from which it was made.

The unused portion of the original box can be a 100mm extension of the Rock Pi 4 case along the side of the cooling fans to include additional components and their electrical connections. No more grommets with silicone sealant.

The GPIO extender cable could be used for stacking RPi HATS or omitted if it is more desirable to connect devices directly to a few GPIO pins. Either way, M-F patch wires can be used to extend the 5 VDC power to the dual cooling fans, which have moved the far end of the extended aluminum case. With it being fully enclosed the airflow is forced onto the Rock Pi 4B, just as before. The air simply travels a little further to get there.
With the Rock Pi 4B being fully contained inside this case, the cutouts (except for the USB-C power connector and fans) could be omitted entirely for an outdoor headless configuration, safe from the elements.
Parts List:

BusBoard Prototype Systems BOX3-1455N-BK Black Aluminum Box, for 3U Sized PCBs, with 11 Card Guide Slots, Box = 6.30 x 4.06 x 2.10 in
$22.55

Raspberry Pi Fan, iUniker Raspberry Pi Cooling Fan 30x30x7mm Brushless CPU Cooling Fan for Raspberry Pi 3 B+, Pi 3, Pi 2, Pi 1 B+, RetroFlag NESPI Case(2-Pack)
$7.99

30mm Black Fan Finger Grill (4 Packs)
$7.99

2.5mm X 0.45 HSS Taper and Plug Tap M2.5 X 0.45mm Pitch
$11.99

Connectors Pro Pc Accessories 10-PACK 2X20 40P Dual Rows 2.54mm SHROUDED IDC Male HEADER, 40 Pins IDC Crimp Connectors
$16.45

Pc Accessories - Connectors Pro 1.27mm 0.05" Pitch Mini Dual Rows IDC FC Female Sockets or FD Male Transition Connector Terminates to 0.635mm 0.025mm Flat Ribbon Cable (FC-40P-10PK)
$7.45


$43.64 Parts Total (aluminum case, dual fans, dual grills, 1 x Male + 1 x Female 40 pin IDC connectors for GPIO extender ribbon cable)

Issues
• The M2.5 mounting holes on the large heatsink were only threaded on one side. In order to use them to securely mount the M.2 extender board, it was necessary to purchase M2.5 taper and plug taps, which are smaller than those being sold in most American hardware stores. I could only order them from Amazon.
I am an experienced machinist and knew to be extra careful to avoid breaking them off because they are so small (I suspect this is the reason the holes have not been tapped all the way through by the mfr.) I also took extra care to clean out the aluminum particles afterwards, which could lead to shorted circuits.

For the convenience of others, I have requested that Radxa extend the M2.5 threads completely through the heat sink’s mounting holes so that they can be utilized from both sides.

• I could not have built this case without the new, shorter M.2 extender board. Thanks to Radxa for making that modification. However, instead of the end of the board being in line with the USB and ethernet connectors, it needs to be in line with the board and heatsink. The RPi connectors are intentionally designed to extend beyond the SBC in order to fit through cutouts in a case. This specific aluminum project case has a ribbed interior for mounting circuit boards. The connectors were only able to be flush with the case’s interior by filing away the ribs around them.

Then, I used a Dremel tool to modify the mounting holes on the M.2 extender board into slots to allow the M.2 extender board to slide back in line with the heatsink. This also permitted the heatsink to be in direct contact with the aluminum case, improving heat loss.

I have requested that Radxa shift the mounting holes by 2mm away from the end with the M.2 connector on future M.2 extender boards for better heat loss and appearance.

2 Likes

This looks pretty nice. A bit to fiddly for me, but might be an option depending upon what allnet comes up with, hopefully they take into account fan and M2 in their solution.

BTW, even with the large heatsink, the fans are very much needed; Have loaded up a 1TB M2 card with a music collection in MP3 and FLAC formats, have been running python-rgain’s collectiongain utility on the library…the script is multi-thread smart and sees all six cores and spawns all of them at once, the big heatsink gets HOT and it starts to throttle within a minute. So thermally-activated fans would be a complete win…bursty CPU load will never start the fans, but sustained processes would.

1 Like

Thanks for the feedback.
GPIO pin #5 is also extended for thermal control of fans, but haven’t crossed that bridge yet. Someday. :sunglasses:

Hmm, you really think it is a good idea to enclose a RK3399 and heatsink inside a flammable insulator, w/o airflow from cooling fans? You might want to keep a fire extinguisher handy :wink: