Wednesday, July 3, 2019

Very Large Raspberry Pi Cluster - Part IV

So I've had a couple weeks here without much of a progress update. A lot of work has gone on. So here's a quick update before the holiday. First some photos. The first one is of the original prototype 3D printed out with some Pi in it.

This is a very nice design. The Pi just snap in place, there's room in the back to get to the micro USB power plug. But there are three problems:

1. I can only print half a 2U, so things had to be designed in such a way that once side is put into place, slid over, the other side goes in and is slid over and bolted, the first one slide over bolted, then the two remaining Pi on the ends are put in. And it requires two people.

2. It takes 50 hours to print one 2U holding 21 Pi.

3. It requires access to the rear of the rack. Without those rear bolts it wouldn't survive shipping.

So back to the drawing board. And here is the new design.

It's difficult to see what's going on here but there are 23 individually 3D printed pieces; one for each Pi and one for each end cap. They connect together by sliding on a piece of series 10 80/20 1"x.5"x10" long that has had about 3/4" milled off and the ends tapped. These are at the machine shop now so I will show some photos when I get them back.

One thing that's really nice about 3D printing is the RepRap; or the ability to rapidly prototype and revision. 3D printing is slow, but it's faster enough to do this. Here are some of my tests.

The one in the middle is close to the final design. You can see that two of the bolt hols of the Pi have a post and the last one has a threaded insert for a bolt.

Next post I will go into these two parts in detail. They have been designed for strength, speed of 3D printing and ease of assembly.

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