I tried one of the small printable quadcopters on here but the arms were constantly breaking and I couldn't get any real flight time. I live in Japan so space is a little limited. As soon as the thing starts to drift in the wind I would try to land, but since I have 0 skill I usually ended up crash landing. Then I:d have to fix it again, and I ended up flying it only 3 times in as many months. Each time it seemed to work a little better, but I finally decided I needed to design everything from scratch and prioritize durability. This is my initial result.
The non-printable parts (besides electronics) are: a 60mm x 60mm x 5mm aluminum block, a 1 meter T shaped aluminum rod cut into 4 equal lengths with a height of 15mm and a width of 13mm, a little double sided velcro strap, and various m2 10 and 15mm bolts and nuts. (fyi, I got all of this at Tokyu Hands)
The motor blocks should just slide right onto the rods, and the blocks are basically "full tang". I put a little superglue on the ends and they seem sturdy enough. I printed them solid for additional strength since I need durability more than mobility with my current flying skill. The battery tray sits over my electronics and I attached my multiwii flight controller to the raised platform in the middle of the main compartment. I put my radio, gps, and battery alarm on either side in the sunken areas. I just attached those things with a little hot glue since they're very light and hot glue sticks to PLA VERY well.
UPDATE: Be sure to rotate the motor block 90 deg so that the T slot is on the build plate.
I tend not to design parts with predrilled holes because printers tend to make them a little bigger or smaller depending on calibration, which typically results in redrilling them anyway. Additionally I like to plan things out, but leave room for last minute changes, so if you don't have access to a drill, my design is probably not the best one for you.
Also, I designed the motor blocks to take a little piece of wood between the motor and the block. My motors tend to run a little hot, and have custom axles. The wood acts as a heat buffer and I drill out a hole which allows for the slight protrusion of the axle.
Finally, I designed the parts with support in the design. If you see .5mm lines/surfaces/shells, those are meant to be removed after printing. I find that simply adding the support in the design helps in two big ways, The amount of plastic needed for support is greatly reduced, and this in turn reduces print time by about 25% on the main compartment and 10% on the motor blocks. Just use a hobby knife to remove it.