Ok, so hi guys and welcome back! My goal for the build which I want to show you today was to assemble the smallest and most lightweight quadcopter possible, which still supports 4” props and uses only off the shelf budget components. Additionally I wanted it to be able to carry my RunCam 2, in order to create beautiful full HD videos. This was quite a challenge, and today I want to show you the build and of course how it flies.
Build Log & Videos
After researching for some time, I decided to go with the Diatone Grasshopper as a frame for this build. This is a very small 160-size frame which still supports 4” props. Its bottom plate is 2.5mm strong, which is sufficient given the low weight which I planned to build it up to. The bare frame is also only 28g heavy, which is awesome!
So, let’s start the build. Here you can see the first step of it. I’m using the very lightweight 1306 motors with 3100 kv, together with DYS XM20A ESCS. I have cut the motor wires short, and soldered them directly to the ESCs. Here I’m using a little trick which works well. At the ESC side, I do not desolder the existing wires, but simply cut them off at their origin and then solder the motor wires directly on top of the old solder points. This way I only have to get my solder iron close to the ESC once, which lowers the risk of potential damage from the hot solder iron.
You can also see the very small and light-weight Diatone PDB here at the center. I like it for its low weight and nice layout – they have been working great so far. The ESC wires are already soldered as well as the power connector. Both the 5v and 12v outputs are pre-tinned already, and thus we can continue with step two – the flight controller.
Let’s start from the top. Here you see the buzzer connected already and on the left of it, you can see two more wires. They go to the battery voltage sensor of the Naze, and are not connected to the battery yet, that comes a bit later. That way the Naze knows the voltage of the battery and can react to it, for example to turn on the buzzer if the battery is low.
On the right side we see our cheap FrSky AC-401 reciever connected to the Naze. That reciever is still pretty new and very cheap. It is full range. I like to use them on flying machines which I keep closeby, for everything else I use original FrSky recievers. That reciever is connected to the minus & plus (for powering the reciever) and the PPM pad of the Naze, so that the Naze can recieve its instructions.
On the bottom, from left to right, the 4 ESCs are connected, so that the Naze can steer the motors. Additionally, we use the plus and minus connector of motor 6 to supply the Naze with 5v from the PDB below it.
Next comes the reciever. This is simply put on top of the Naze, separated by standoffs. I’ve 3d-printed a little plattform for it, but you can just use an old plastic card or something similar as plattform, if you do not have access to a 3D printer.
Finally, there is the video transmitter on top. Noteable here is that I have detached the SMA connector from it, I have simply cut it away using a strong cutter, and directly soldered a lightweight cloverleaf antenna to it.
Here you can see some photos of the completed setup so far. Note that I do try to put everything between the plates in order to have the upper plate completely empty. The reason for this is that I want to optionally put a RunCam 2 there for recording. That means of course that I had to use longer standoffs for the upper plate to fit everything in.
Here you can already see the mini camera mounted to the frame and connected to the VTX which supplies it with 5v. The camera holder is simply glued to the frame.
Here you can see the last part of the wiring. As you can see I’m using a balance plug to also use the balance connector of the battery for power. The balance connector is connected to the voltage sensor of the Naze, the power input of the video transmitter and additionally to the RunCam 2 USB cable which you see on top. That allows me to directly power the RunCam 2 from the flight battery, which saves weight, because I do not need a separate battery for the RunCam 2. You can also see the regular 4045 bullnose props in the picture. and also the buzzer which is already glued in place.
And here we are. We arrive at 156g for the complete 4” prop quadcopter, including FPV and including RunCam USB connector (without lipo!). I believe that is a pretty great weight and will allow for very long flight times. Just as comaprison here is the empty weight for my ZMR180, which was already a very lightweight build, as you can see in the referenced video. It’s around 70g more light weight than it – pretty awesome.
Here you can see the weight including a 850mAh 3s lipo, which I like to use with this build and which gives me more than 11 minutes of flight time, as shown in the video.
And here you can see the weight including the RunCam 2. This will still give me around 9 minutes of flight time, but will push me over the 250g limit. Using a more light-weight lipo, maybe something in the 600-700mAh range should get me below 250g weight with a still decent flight time in this configuration.
Check out the full build video here, if you like, including the 11 minute flight & a video of it carrying the RunCam 2:
Here comes the full parts list for you.
That’s it, guys! Hope you liked this article and I do look forward to see more sub 250g quadcopters in the air