Drive Cage, Complete!

posted Mar 15, 2014, 8:12 PM by Andrew Stock
Looking more and more like my life is allowing for monthly updates... sorry for the long delay.  I've worked little bits and pieces each weekend for a few hours at a time... so while I haven't shared in a while, at least I saved it up and have a large bit to share now!  Anyway, on to the fun...

Last we left the drive cage, I had cut and shaped most of the pieces, but they were just leaning together... nothing solid yet, and pretty rough. I decided the best approach would be to glue it together first, then use my dremel, sandpaper, etc to clean up some of the edges. Here it is with the inside wall glued in place, and the two supporting beams glued as well.



The two clear beams will serve not only to strengthen the inside wall (without them, only the edges would be glued to the "U", not very much surface area for the kind of weight I would be putting on it...) but they will also be the mounting points that will attach the drive cage to my case... more on that later.

With everything glued in place, I had some excess scrap to cut off the "U" (I left it intentionally, to give myself lots of room, as the measurements pre-bending were a little too hard to figure out on paper. ). I used some simple masking tape to mark the line I wanted to cut, then decided my jigsaw would be the best tool to cut off that edge. My table saw was a little too risky given all the work I put into the piece so far, and using a manual hand frame scroll saw would take ages. 






I left just a bit of an edge, as I didn't want to accidentally cut into my support beams. I then went back over this edge with my dremel and a sanding drum attachment to grind it down nice and flush. Next, I moved on to drilling some holes in the support beams to seat more press-fit screw housings into, using the trusty old drill press:




Initial fit test, all screwed in and looking just fine!



And from the back side:



Now, it's all screwed in, but it's still not much of a drive cage yet... time to get to work on planning the most important piece... the backplane!



First, I did quite a bit of measuring. Hours and hours of it, in fact. To get the drives to slide in nicely, I needed "sub millimeter" precision... the slightest bit to the left or right, and the drive wouldn't seat correctly. 

I ended up taking the approach of measuring it all out on a scrap piece, and giving the cut a few attempts, tweaking the measurements and re-cutting as I iterated through attempts. A little archaic, but it guaranteed a reliable/reproduce-able result in the end. Here is my first go at measuring out the cut points. In this first iteration, I was cutting out a block large enough to allow room for the connectors to stick through, along with all the pins, some of which you can see stick out of the PCB a bit, requiring room. 




After measuring it out a bit, I cut it out using the drill press to create some pilot holes, and the jigsaw to finish it off. The result...



Not so pretty. Fail.  The Jigsaw proved too squirrely for these small parts, and the large cutout was not the look I was going for... I wanted something a bit cleaner looking. At this point, I decided to drop the old metal ruler, and go for my high precision digital calipers, with 'actual' sub-millimeter measurements!



... alas, I'll spare you the multiple additional iterations of attempts I made before I finally got the measurements and process right. 

Here's the final backplane, all measured and marked, with pilot holes cut, ready to finish the openings for the SATA passthrough ports:



The biggest challenge in getting all this measured out was that the bays are not exactly perfectly spaced... one millimeter off here and there... which makes very little difference as I gave myself about 20mm of space between drives for slack... but makes a huge difference for the backplane, which all four drives need to seat against simultaneously. I measured and re-measured these lines more than 20 times... partly because I wanted them to be exact, and partly because at this point, I wasn't exactly sure how I wanted to proceed...

I could use the hand scroll saw, which would take hours, but I would likely end up with a fairly accurate cut. A power scroll saw would be perfect, but I don't have one of them yet unfortunately...

I could use my dremel with a cut off wheel... but the chance of messing it up would be pretty high, and the cut wouldn't be perpendicular to the surface of the acrylic, which would be pretty important for this high precision piece. 

I could use a hand router, but I didn't have any bits that would make this small of a cut. and I felt like it would be too overpowered/not precise enough at making straight lines. 

I had a tiny router bit (a downward spiral bit) that came with my dremel, but I've never been able to get it to do a straight line correctly. Hmm...  If only I had some way of using the tiny dremel bit, with a big machine that will hold perfectly steady. Then I came up with a wacky idea... 



Put the dremel bit into my drill press, and use it as some kind of hybrid table router / scroll saw!  I cranked up the speed on my press to make sure that I was getting a very quick cut... the drill press wasn't made for this kind of "side to side" cutting, and my spiral bit has seen better days (not very sharp any more), so the extra speed helped make sure the lines were clean. 

Here it is after the first cut... works perfect! 



I went through and quickly finished the other four cuts, then broke out the hand file tools to clean up the edges and square everything out:



Perfect! Nice clean opening, just wide enough for the connections to fit through without exposing any of the underlying PCB. 

Here we are with all four drive bays populated and slotted in!



Again, perfect! SO glad it worked on the first try... would have been a lot of work lost if something got screwed up. 

After verifying everything roughly fit together, and using my filing tools for hours on end, I finally got to peel the backing off and assemble everything! I had to run down to the local hardware store and find some tiny washers and nuts that would fit the 6/32 MDPC screws I was using, then put it all together:



You can see in the closeup below, I had to put two tiny washers between the acrylic and the backplane PCB... this was due to those solder points sticking off the board, mostly. With these, it floated nicely in place. 




Here it is quickly put together, for a "quality / progress" check:






Getting closer! 

Next, I had to decide how I wanted to attach the backplane to the drive cage. My original thought was that I would glue it on... but I decided it would be way more useful if I could disassemble it when I needed to clean it or make modifications down the road. Well... disassembly means using screws, and the drive cage didn't have anywhere I could really seat my press-fit screw housings into... time to add a place!  




I used a few remaining scraps of my 1" thick clear acrylic to cut some wedges for along the inside top and bottom of the drive housing. These would allow me space to drill into, so that I could drop some press-fit screw housings into them and screw the backplane on. 

Here we are post gluing:




And with the screw housings drilled and pressed in:






Huzzaw! All screwed together!  







And back in the case, for a final look:









And finally, with the backing off of the drive plates:




That's almost it for v1 of the drive cage! That's right... v1. There will be more... later... but I think I am happy with the functional version for now... I just have one more step (adding a fan for airflow... it's in the mail right now...)

The flashy/added effect version will come in the future... hint... there's a reason the drive plates are made out of clear acrylic!  


Until next time! 
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