Building a mini cluster – Part 9: Drilling, tapping, building

Finally, the acrylic and aluminium have arrived. Of course, now that the software woes are behind me, this means only one thing: time to start building!

Because I asked the acrylic shop to send me all the “rest” material (the stuff that was cut out) as well, it all came stuck in large panels with sticky tape. I had 30 minutes of fun carefully prying all the different shapes out. The aluminium came is an open cardboard roll.


The individual acrylic components


The aluminium profiles


The acrylic left-over sheets

The acrylic has a protective plastic sheet on both sides, one side transparent blue, the other side white with publicity markings. This is why the arculic is not transparent at the moment. I removed the protection from a couple of small “rest” pieces, and it looks very nice.

I do see a difference in thickness between the colors: the blue and green are the same thickness, but the red is about a mm thicker. This will cause some problems with my measurements, but I hope it will not be too visible…

The aluminium is nice and shiny. I did fear that the edges would be very sharp, but they seem to have been sanded so no problem there. There is a problem with the brackets that will hold the fan assemblies in the housing: two thirds of those are not 2 mm, but only 1 mm thick. These will be mounted on the inside, so visually there is no problem, but these pieces feel very flimsy… I hope they will be able to carry the weight of the fans…

The Green and Blue compute housing

It took about three days to assemble the compute pods. All the screw holes in the arcylic are already cut out, but I need to drill the required holes in the aluminium profiles myself.

 

I am using an old Dremel multi-tool, attached to the Dremel drill stand for this. Sadly, this proves to be a very non-professional setup: it is pretty much impossible to drill the holes precisely. The stand is not rigid enough and very often, the drill bit slides around before catching the metal and going in. This causes a lot of the drill holes to be misaligned.

 

To solve this issue, I use the Dremel tool to make the holes in the acrylic larger so they line up and I am able to screw everything together. Since I will be using semi-transparent washers to protect the acrylic when I screw it all together, most of these adjustments will (hopefully) not be very visible. However, the end result is definitely not as nice as I want.

 

On the plus side, tapping thread in the drill holes turns out to be much easier then I had anticipated. The tapping bits I purchased are for “hard”metal because I could not find any “soft”metal ones and I was afraid this would cause problems, but apart from taking a lot of time, the taping itself is quit easy to do. This means that I will not be using any nuts to hold the case together and that mens it becomes a much easier task to assemble everything. Can you imagine having to hold the nut on hte inside of the cases while screwing the covers in place? Really happy with this!

 

After three days of drilling, tapping and re-aligning, the two housings are assembled. I am very happy it all came together in the end!










I have not yet removed the protective plastic sheets yet because I will need to disassemble the boxes when I install the hardware.

The Red Power Pod completed

The next challenge is the power pod. Drilling the holes in the aluminium was just as bad as for the compute pods, but in the end this case comes together reasonably nicely.

 

Next step is to install the power supply and the wiring. All wire connectors are crimped on the leads and then sleeved with shrink wrap. I am extremely paranoid when it comes to electricity, so shrink wrapping everything rules out any possibility for short circuits.


The back of the pod with the 220V in and three times 12V out connectors


The front of the pod with on the right the large red main power on/off switch and three switches for three 12V outputs




Top view with the 120 mm fan installed. This fan will be connected to the third 12V rail in the power supply. Whenever the power supply is on, this fan will be running, blowing cool air into the pod..


Side view where the brackets that hold the power supply to the bottom are visible. There is just enough room between the power supply and the sides to run the cables.




Side view


With flash, showing off the etching




Top 120 mm fan blowing air into the pod


Dust filter installed




Power test. The turbine fan visible behind the front


Rear side




With flash to show off the etching


The beauty shot


And some “beauty shots” of the power pod with the protective plastic removed and the fan filter installed.

The red acrylic looks very nice, allowing to see the inside of the pod. (Showing off the nicely sleeved cables.) The etching I put on the acrylic is barely visible unless you have to right lighting. But I knew this in advance and I like the fact that the writing is subtle.

Testing the power pod and all the switches was successful. The main red switch applies power to the power supply and that makes the fan spin. The three 12V outputs from the power supply are not available until the yellow switches are flipped over. This will allow me to power each compute pod separately. Since the power supply has three 12V outputs, I built three separate output circuits, even though I only need two for the two compute pods I am building.

Sadly, like the Red switch, the LEDs in the yellow switches only work when they get 220V, so they do not light up.

The power supply has a 35 mm turbine fan and that one is very loud so the goal for the 120 mm top fan is to make sure it never needs to spin up. Installing the top fan to turn at the highest rpm seems to do the trick for now, but without any load, that is not that surprising. I have to wait until the compute pods are done before I know if I will need to arrange further cooling.

Blue and Green Pod motherboard and fan install





Front and rear views of the motherboard assemblies installed in the housing. I am very happy with the alignment of the motherboard IO ports. (The measuring stick shows centimeters.)




A top view and detail view of the fixation of the motherboard assembly. The housing becomes very rigid with the motherboards installed, which is perfect!

Next step, mounting the fan assemblies:










Since I will not need to disassemble the cases one the fans are installed, I removed the protective plastic sheets. The acrylic now becomes transparent, showing off the innards of the case, as it is supposed to do. All in all, it’s looking very nice indeed!

Current Status of the cluster build

After four days of working on the cluster, this is the current result:

Power Pod: Fully functional
Blue Pod: Case assembled and fans installed
Green Pod: Case assembled

I have purchased a few bits and bobs, but not enough to warrant an update of the cost table. I will definitely put a cost table up when I am finished with the build.

Next time, the green pod will of course also get it’s fans and both pods will receive their disk+switch trays. Hopefully I will also be able to start with the cabling of the compute pods.

Jhon Masschelein

Author: Jhon Masschelein

Tackler of advanced Cloud and Hadoop challenges in a world of open-source technologies. – Impossible is merely a matter of time and effort. –

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