Farmcopter Build: Part 2

Now on to Part 2: the parts list and build.

In post number 1 I listed my goals for the quadcopter and what I wanted to get out of the build. This is very important as this will determine what parts you buy and there are infinite options from which to choose.

In this post I will detail all of the parts of the quadcopter and how to assemble them.


Here are the parts I decided on:

Frame:

I decided on the Hobbyking S500 Glass Frame. It is a good size and has a good number of mounting options for accessories. The arms have a carbon rod in the center making them very strong. At this price I would recommend ordering two frames for spare parts. On my first day flying I broke one of the arms (this was my fault and not the fault of the frame).

Motors:

The selection of motors requires some calculations to select the amount of thrust needed to fly. Total thrust required equals the total weight times two. You divide this by four to calculate the thrust per motor.

                                                 Total weight of the quad x 2

                                                 ----------------------------------     = Thrust Per motor

                                                                       4

I bought the Turnigy D2830-11 1000kV motor. These have worked very well and provide plenty of lift. 

Speed Controllers:

Initially I was planning to purchase the Turnigy 30 Amp ESC's but they were out of stock when I placed my order. I ended up purchasing the Afro 30 Amp ESC's. I am glad that I did because these come flashed with the SimonK firmware. This firmware has a much higher refresh rate, around 400 Mhz, than other speed controllers.  This also have bullet connectors already soldered on which is handy.

Flight Controller:

There are tons of good options when it comes to a flight controller. The kk2.1.5 is a good beginner board. It has an LCD screen on board and can be programmed on the fly without a laptop. It is also inexpensive.  There are also a number of open source boards including the cc3d and the APM powered boards. The APM powered board is more expensive but is autonomous with GPS and a barometer. I am starting with the kk board and will plan to upgrade down the road.

Radio:

I bought the OrangeRX 6 channel radio. It is compatible with spektrum dsm2 receiver modules and is working well. The Turnigy 9x radio is also a good option and has transmitter modules that can be exchanged for compatibility with different receivers. You will also need a receiver. I ordered this one.

Props: 

The props are very important for the proper configuration of the quad. I chose simple plastic props but will probably buy carbon props in the future. I would recommend buying a few sets especially when starting out as they are the first to break in a rough landing.

Here is what I bought:
Right hand rotation
Left hand rotation

They are fairly inexpensive but break easily. You will need a simple prop balancer to ensure that they are weighted correctly. I have had to balance them by sanding the underside of the heavier blade.

Here is a useful graphic used to tell which prop is right or left:

Miscellaneous Items:

Power breakout cable: For power distribution you have the option of soldering your own or purchasing a premade set. I purchased this and it made assembly very easy. Make sure the connectors match your battery and ESC's.

Battery straps: These hold the battery to the frame. Order a few of these.

Battery alarm: With LiPo batteries it is important to not let the individual cell voltage drop below 3.3v.  If the voltage drops below this point the battery could be permanently damaged and no longer hold a charge. This alarm connects directly to the balancing plug on the battery. When the battery is depleted it flashes red for the specific cell that is depleted and emits a loud alarm.

Battery:

The battery I chose was the Zippy 4000 mah batter. It is a 3 cell 25c battery. I have been getting around 15 minutes of flight time with this battery. One recommendation: if you are in the US order from a US warehouse. Ordering from overseas can take a long time as LiPO's cannot be shipped by plane. They can also get caught up in customs and take a long time to arrive.

Servo leads: Here. These are used to connect the receiver to the flight controller.

Battery charger: I already had a nice LiPO charger but if you don't you will need a charger and battery balancer.


Building the Quad:

After a few weeks I received all of my items. No problems ordering from China and everything came as expected.

The first step is to install the motors on the arms. I used blue loctite on all of the bolts to ensure that they didn't loosen during flight. I had to use longer screws because of the thickness of the arms.

Here are all of the arms fully assembled.

After installing the motors I built the frame. I put loctite everywhere just to be sure. 

I should have taken more pictures of the wiring but really the process wasn't too exciting. Everything went together easily with the wiring harness. I zip tied the ESC's to the bottom of the arms to protect them from damage. 

Routing the wires to the flight controller was a bit of a challenge but everything eventually fit. In this picture the flight controller is mounted in the box it came in just to check the fit. This frame has a really nice mount on the bottom and keeps the battery low in the center of gravity.

I puzzled for a while on how to mount the flight controller. There is lots of discussion on how to vibration damp the board. I bought a pack of ear plugs from the hardware store and cut the tips off. I then hot glued them to the bottom of a small piece of wood and zip tied this to the quad frame. The zip ties keep it pretty tight but it does have some flex because of all of the little ear plugs. So far I have had pretty good results with this setup. 

This frame does not have the mounting holes to mount this flight controller directly. I am not sure if the board has odd mounting holes or the frame doesn't support the FC configuration. I may look for other options to mount the flight controller depending on the flight characteristics. 

So, after all of this I figured out that I had forgotten to order the receiver for my radio. I had to place another order that took three weeks to arrive. But it all worked out and I am happy with the way it flies.

Stay tuned for post number 3. I will take some video of the flight and provide some tuning information for the kk board.