From The Ashes: Carbon Fiber Mini Quad

After a battery fire that claimed my entire tricopter, transmitter, and custom-cut case, I was essentially given the opportunity to start from scratch.  Seeing the Blackout Mini H-Quad and the BAH Mini H Foldable by RCgroups users Enforcement and Bayareaheli, I decided that my next build was going to be a portable mini H-quad that I could use for FPV.  

I had on hand a beautiful 12x12 sheet of .06" carbon fiber plate from Rock West Composites so I started with templating out the shapes for the frame and electronics tray.  Part of the size consideration came from the propeller size. Instead of the 5x3 propellers that a lot of other people are using for their mini or micro quads, I wanted to scale it to fly on a 6" prop. Once I was happy with the design, I taped out the measured shape onto the plate and got set to cut.

As always, when cutting carbon fiber, being safe with the dust is paramount.  Safety glasses are a must and I personally use an N95 mask to keep from breathing in the particulates. Blue nitrile gloves keep the shards out of your hands as well. 

I transferred my measurements to the carbon fiber plate and outlined where I needed to cut with blue masking tape.  Cutting out the frame took almost an hour with a diamond Dremel cutoff wheel but ended up with a matching pair of top and bottom plates and one longer electronics plate.  My design holds the electronics plate off on some vibration isolating mounts supprted by the bottom frame.

After cleaning up the edges, I taped both H-frame pieces together just to make sure through holes would be perfectly lined up. 

Three hours of drilling, cutting, and shaping later, the finished pieces were ready.  

I decided to base my Mini-H around the OpenPilot platform with a CC3D flight controller.  It's almost three times more expensive than a KK2 but the community support forums are awesome and the project has strong software support.  The flight controller board itself is offset from the electronics board sandwiched in between two layers of fuel line tubing on some M3 hex screws. 

McMaster-Carr is an awesome resource for all sorts of hardware and specialty tools and from their site, I was able to pick up some sandwiched rubber vibration isolators threaded for M4 screws.  In the next two pictures, you can see how I secured the isolator to the bottom plate and passed it up through the second level. 

Including the flight controller, the frame and hardware currently weighs just 207g.  Since I have the option of using some shorter screws, and will be needing to cut some through holes to carry cables through, that weight will continue to go down.  

In my next post, I'll be covering the build of a wiring harness and motor mounts!

I ended up going with some bare speed controllers flashed with SimonK firmware so I had to make up my wiring harness from scratch:

Since I wanted the wiring harness to be as modular and swappable as possible, I ended up soldering twenty bullett connectors overall.  Pictured below is the progresssion from set loosely on tinned lead up through soldered and heat-shrinked overall.  I found it easiest to extend the heat-shrink tubing past the end of the barrell and then trim it back with a hobby knife to get a clean, flush cover all the way to the end. 

While I ended up using nice T-Motors rather than the cheap Hobby King ones pictured below, all of the right pieces are here.  You can also see the cutout in the mid-tier plate for wire routing. 

With everything assembled the frame is actually quite stiff. 

Since I designed this one to be foldable, everything except for the batteries fits inside of a Pelican 1520 case. Tucked underneath the transmitter is a repurposed DeWalt bit case that folds up to hold spare nuts and screws as well as spare zip ties and allen wrenches. 

When you take it outside, all that needs to be done is to velcro the GoPro up front, battery to the bottom, put on four propellers, and head off. 

This build has been an awesome success and it's nice to be back up and flying after my tricopter battery fire.  The OpenPilot platform is incredibly powerful and as you can see in the first flight video below, reasonably stable right out of the box.  The next future tweaks will be around changing some of the PID/responsiveness values and learning how to fly FPV.   

First flight:

If you have any questions or want to see a particular part detailed with a better picture, please let me know in the comments!

 Update 7/14:

As commenters lynxstrife and gustavoxumbin requested, here's an annotated picture of my frame layout with some dimensions:

The parts list for this build:

Motors: 4x Tiger Motor MN2206

Speed Controllers: 4x iFlight 10a ESCs flashed with SimonK firmware

Flight Controller: OpenPilot CC3D from ReadyMade RC

Radio/Reciever: Spektrum Dx6i and Satellite reciever

Spektrum Satellite Adapter from reciever to CC3D sold by the OpenPilot store

Video TX/RX: FatShark Predator V2 and 250mw transmitter, stock antenna

Camera Mount: NoMoJello wire rope isolator

Vibration Isolators for flight controller board: Part # 9247K31 sold by McMaster Carr

All screws: 4mm socket head cap screw, various lengths

Update 8/7:

The OpenPilot Revo finally came back into stock and I've integrated the new controller into the quad.  A separate article/video will come soon!

If anyone has more questions or requests, please let me know in the comments below!