Stratux Nano Case w/ GPS Shield, Fan Mount, Suction Mount Port

This is my take at a Stratux case remix. I wanted something better than the plastic injection case sold on Amazon (https://amzn.to/2VFRRFG). My goals are: to shorten overall height, have it easy to mount and unmount (portability), and to improve and make consistent GPS accuracy.

I like to mount on the left rear seat window on the C172. The plastic injection molded case with the antennas were too tall. I also wanted a no-fuss mounting solution. Since I rent, it needs to be easy-on, easy-off.

Going to test to see how this set up compares with the injection molded case set up with an in-flight test. If I still don't get accuracy I want, might just go back to the external GPS and figure out another mounting solution.

Update: I've been using this for a while in a C172. GPS tracking shows good accuracy in Foreflight but the track log still looks like crap. In traffic pattern/touch-and-gos, it shows that I'm landing consistently in the grass adjacent to the runway. When I find some time, I'm going to design a brand new case specifically for mounting in the rear C172 window for better sky visibility and using the external GPS unit.

Background

I had printed mistertech's Stratux case earlier and assembled my Stratux with a GPYes (https://amzn.to/2Wf6Aob). I experienced GPS accuracy and reception issues with the internal GPYes unit like many other Stratux users have also experienced.

Later, I found Kevintjuh's GPS shield design and printed just the shield portion to see if it would improve the horrible accuracy (30M as measured by Foreflight). But it did not fit in mistertech's original case so here we are with a freshly designed GPS shield.

Component Features

• Bottom of case is no change from mistertech's design.
• Top of case is modified to include a fan mount similar to the popular Stratux box. (https://amzn.to/2XTkAob) No screws, just two built-in clips.
• Top of case is also modified to have an inset for the screw head that will allow me to mount the entire enclosure to a suction mount I have already purchased previously for Stratux. (https://amzn.to/2VHQWF6)
• GPS Shield is inspired by Kevintjuh's shield design. But I wasn't able to remix it or make it work/fit so I made a new one from scratch. Used CyberCyclist's RJ-45 cap and flintol's USB Cap to mount the shield so it's not just floating around in the case. A few prints for the scrapper before I got the alignment right.

Shield Grounding

The shield should be snug to the GPYes unit. The bottom of the GPYes unit has a metal casing that is already connected to ground on the Raspberry Pi. (Tested with a multimeter) When you wrap the shield in double-side conductive copper tape (https://amzn.to/2ZO2RA4), make sure it has good contact to the bottom side of that casing! Doesn't hurt to test again after mounting with a multimeter.

Performance Testing

Control: Tested with the Stratux plastic injected molded case. GPYes antenna side facing directly up clear view of the sky, 30m accuracy on ForeFlight. Same accuracy indication when oriented vertically, as if mounted onto a C172 window.

Test: Tested with this setup with conductive GPS Shield grounded to the Raspberry Pi. GPYes antenna side facing directly up clear view of the sky, 3m accuracy on ForeFlight. When oriented vertically, 10m accuracy.

Will test to see if improvements exist in track log while in-flight.

How Designed

Top Cover

• Grabbed mistertech's original .123dx file. Loaded up 123Design and exported with coarse tessellation.
• Imported into Sketchup, my tool of choice. Modeled the fan and inset it 1mm into the grills. Designed two clips around it and subtracted it from the resultant solid.
• Took two cylinders, one 7.5mm in radius, one 3.25mm in radius to create the bolt inset for the suction mount.

This top cover took me hours because of the number of faces/edges in the original model. Also I was watching Netflix on my second monitor. :)

GPYes Shield

• Grabbed mistertech's original .123dx file. Loaded up 123Design and exported with coarse tessellation.
• Loaded up a Raspberry Pi 3 from the 3D Warehouse. (Not an exact model, in turns out later.)
• Imported the USB and RJ-45 plug caps. Slowly but surely with my micrometer, the actual Pi, and my already printed bottom portion of the case, drew lines until the shield/plug appeared.
• Printed it, turns out it didn't fit right. Use my tiny clippers to trim off the excess and to make the appropriate changes on the model as I made the changes and tested fit.

Print instructions

Print Tips

• The shield will need supports.
• Top cover supports shouldn't be needed.

Assembly

Everything is pretty straightforward except:

• If you have the pigtail cables that go with the antennas, you'll need to arrange them in such a way that it'll fit snugly before you finish tightening the end onto the case. Mine had an L shape end and I had to ensure each pigtail cable can make one complete loop while still being able to connect to the SDRs. They came as a set, I got the NooElec's and took the plastic casing off (https://amzn.to/2GSBlJ4).
• The shield will fit snugly as designed. It will take some finesse to get the GPS Shield + Pi combo into the case without breaking anything. TAKE THE SD CARD OUT BEFORE ASSEMBLY. That will give you a few more millimeters on one side to push it in under the screw mounts on the wider end of the case and prevent you from damaging it.