Tuesday, February 25, 2014

Turnigy Fiberglass Mini Quad: Sharky

Meet "Sharky", my first non-indoor quadcopter.   (Shown next to one of my brushed-motor nano quads for scale.)

I wanted to graduate to a larger quad, but not something huge, so I decided this 345mm span "mini" quad was the way to go.  I liked the size and design of this quad.

The "pseudo-airplane" shape on the frame looked more like a shark than an aircraft to me, hence the name.

We'll start with what I initially built:

I fly this with my existing OrangeRX T-Six DSM2 transmitter.
I run MultiWii 2.3 with some minor modifications on the 32U4 flight controller.

Side note:  I have made the following changes since the initial build:

  • Upgraded the flight controller to the MultiWii Pro (Atmega 2560 based)
  • Switched to 2-blade 8x4 props.  (Easier to balance.)
  • In the process of upgrading the motors to SunnySky motors - but that might require new ESCs.

As originally built, this is a pretty amazing and capable quad.  It's fast, responsive, and climbs like a bat out of hell.  It only took minor tuning to the original MultiWii PID settings to make it fly how I wanted.  With the 2200 mAh battery it can fly for 12 minutes in basic "normal" flight, or 6-7 minutes of "aggressive" / aerobatic flight.

There have been a few drawbacks to this design:

  1. The fiberglass frame is not very tolerant of crashes.  It breaks easily, particularly on the arms just inside from where the motors mount. 
  2. The fiberglass frame transmits vibration really well, so balancing the motors & props is important.  This is why I ended up switching to 2-blade props- they're much easier to balance than 3-blade ones.
  3. The Atmega 32U4 microcontroller has some hardware limitations that I eventually ran into with MultiWii.  More on that in a subsequent post.
  4. The Park300 motors damage easily.  I initially tried repairing them with new bearings / shafts, but had about a 25% success rate doing so.  A couple of motor failures caused catastrophic crashes.  This is why I'm switching to slightly larger motors.

Overall, though, this has been an amazing quad to learn on.  If you're building one:  Buy 2 frames, at least 3 complete sets of props (2 CW & 2 CCW), and 6 motors (2 spares.)  You'll be glad you did after your first crash, as you can get in the air again while you're waiting for replacements for your spares to come in the mail.  ;)

I strapped a really crappy "Redleaf" 720p camera (not recommended) on board and took this video the second time I took it out to fly it:

Later, I added a 200mw 5.8GHz video transmitter and a Gopro Hero2 camera...

... and tried my hand at some "First Person View" (FPV) aerobatics:

I decided that FPV flying is really fun, so I've been doing a lot more of that since.

More to come...

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