Building the DJI 550 Flame Wheel Hex with NAZA-M and GPS

September 3, 20120 Comments

With most of the parts finally delivered, my DJI 550 Flame Wheel hex build has begun. There is something very gratifying about having all the necessary components spread out on your work bench before assembly commences. Before I did anything I spent a great amount of time doing research and probably spent more money than I needed to but in my opinion this hex will be made up from “the right stuff”.

The frame is a DJI product and is made from high-quality components. The 550 Flame Wheel is nearly indestructible and based on the way I usually “fly” that feature will surely come in handy.

The ESCs are Hobby King 20 amp UBEC flashed with SimonK firmware and soldered directly to the bottom frame plate. The 550 Flame Wheel bottom plate has circuit board traces built in resulting in tidy wiring. I trimmed the ESC wires to the exact length required in an effort to keep the total weight down and also making for a cleaner appearance. The signal wires are braided wherever possible to avoid unnecessary RF noise which could potentially interfere with control system, video transmission, and GPS module.

Once assembled the frame has very little flex which is an important factor as I will be flying with 6 powerful 900kv 210 watt Tiger Motors. Each of the high-strength polymer arms are held in place by 6 aircraft-quality hex screws. The Dragon Link long-range system which will eventually be installed down the road.

Initially I had purchased six custom made G-10 landing gear legs which bolt directly below the motors without needing to drill any holes. It sure makes the hex mean looking!

The 6 landing gear legs have since been replaced with AeroXCraft’s fantastic DJI 550 landing gear and GoPro gimbal which attaches to the frame using existing holes. This lightweight landing gear is very well designed and allows for super easy CG balancing by sliding the battery carrier and gimbal back and forth on black anodized aluminum rails. Assembly took a couple of hours but I can’t say enough about how clear the included instruction booklet is. This is certainly a well thought out product.

I assembled the AeroXCraft 2-axis camera gimbal with HiTek high-speed metal gear mini-servos. Both axises rotate on flanged bearings and is super smooth. Rubber grommets hold the G-10 gimbal in place on aluminum rail mounts and combined with the foam padded lining on the inside of the camera box, the camera gimbal should dramatically reduce in-flight video “jello”. Again, assembly took some time but the included instruction booklet is excellent.

My mini FPV camera is placed directly above it between the mounting rails.

FPV is transmitted using a 900mHz 500mW transmitter mounted directly below the propeller tip on one of the arms for optimal cooling as video transmitters typically generate a fair amount of heat. To avoid RF interference, an in-line low-pass filter is installed where the antenna comes out of the transmitter.

The 900mHz dipole antenna for video transmission is mounted below the lipo battery carrier keeping it well away from the GPS module, thus reducing the potential for GPS interference.

The on-screen display is handled by an early version of the EasyOSD which is mounted on a different arm. The EasyOSD comes with a small GPS antenna (not plugged in here) which gives compass headings in the display but I haven’t tested it yet to see if it will interfere with the NAZA GPS module.

EasyOSD’s in-line current monitor module is conveniently mounted behind the battery carrier.

The NAZA GPS module comes with upper and lower aluminum mounting brackets and a CF post. There are several ways to assemble the GPS post including epoxy glues and velcro but it is important to retain the ability to rotate the module for slight magnetic declination adjustments based on where on the planet you might find yourself flying. I chose to drill and tap 2 set screw holes in each bracket (top and bottom) which do a great job of holding the CF post in place yet still allows for any adjustments if needed. I mounted the GPS module as far away from the camera gimbal as possible because it is known that GoPro cameras are guilty of being super noisy when it comes to RF interference. At some point in the near future I may look into building a thin copper-clad G-10 lining around the GoPro to shield any potential RF interference leaks.

The all-important NAZA V-SEN unit with built-in BEC and status LED is temporarily mounted on the back of the battery carrier. I intend to mount it in a more unobstructed area where it can easily be viewed from the ground no matter what direction the hex is flying. The V-SEN unit also has a USB port which enables programming by the Assistant Software I installed on a cheap little PC notebook.

And finally, the heartbeat of the beast: the NAZA-M flight controller. It is mounted in the center of the frame as close to the CG as possible. This unfortunately makes access to the ports a bit tedious but with long-nose pliers the job gets done. It certainly is well protected in there!

One of the early flights after the GPS module was installed. The hex did a pretty darn good job at pirouetting during an altitude hold, all without any fine tuning! Needless to say I was pretty impressed. Now for the fun stuff: tweaking! Stay tuned…

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About the Author ()

I'm a professional tinkerer. Supreme wonderer. I NEED to know how things work and often I find out how by destroying stuff. I built, flew and crashed my first r/c plane within 3 minutes when I was 12 years old. I then discovered that r/c nitro hydroplane racing was pretty fun. When boats flipped or quit in the middle of the pond all I had to do was swim! I often have recurring flying dreams and I found that FPV flying is the closest thing to dreaming while I'm awake.