Thursday, July 11, 2019

Very Large Raspberry Pi Cluster - Part V

Last week I said I'd talk more about this part. So here is what the main bracket of the Pi holder looks like and the two parts individually.

The print time for the Pi holder is 98 minutes. It's a lot but it's a lot of plastic too. I print 12 of them at time, at 15% infill, with a .8mm print head, no rafts or supports. I can print one rack in 24 hours. You can do the math from there how many days the printers will be running. I spent a few days optimizing the amount of filament and the print speed with the strength needed. It is over engineers and will not break when being shipped. It is easy to assembly and requires very few parts. The reason for the curves is because it prints faster since the print head doesn't have to slow down when it approaches a corner. I was going to make the front two exes that are square round but it only saved 30 seconds print time and looks better being square when fully assembled.

Here are some views of the models from different angles since these are two separate pieces. Here are two views with the two pieces combined. You will notice a square rod coming out of that slot.

That square rod is a piece of aluminum extrusion. Specifically it is 80/20 series 10 that is .5in x 1in x 18in. I had 16.35mm milled off the end and the ends tapped for 10-32 by a local machine shop (GSFAB in Santa Cruz).

So I print 21 of the Pi Holders and two of them end caps (mirror of one another). Bolt an end cap to one end. Add one plastic threaded insert to the top hole, bolt a Pi on (the bottom holes just sort of clip on), slide it on the 80/20, repeat. After 21 Pis, bolt the last end cap and it looks like this:

So, there's a 2U containing 21 Raspberry Pi in a 19in server rack. I've only got 48 more of these to print and assemble.

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