Fellow Propnutter Dan recently built a 130mm quad and it’s seriously impressive. Really it is, and I knew I had to build something similar myself. Enter the Realacc RX130.
For the build I went with the following parts:
Frame – Realacc RX130 carbon frame kit with PDB
Motors – Emax RS13-6 3300KV Race Spec Motors
ESCs – Chaos BLHeli_S Dshot 20A ESC
Flight Controller – Steak F4 (AirbotF4)
Receiver – FrSky XSR
VTX – Team Blacksheep Unify Pro HV – Race
Camera – Foxeer HS1177
Antenna – Realacc RHCP SMA Pagoda
With all the above parts received it was time to crack on with the build. First up was to inspect the frame carry out a dry build. That is to say build up the frame without any other components just to get a feel for how it goes together, and more importantly how much space you have for wiring etc. At 130mm in size the build is going to be tight but not ridiculously hard.
Once I had a plan in my head of how everything would go together I wanted to try something a little different.
To give the frame a nicer finish I decided to round of the edges of the carbon. This is easily done with a diamond file and a running tap. Keep the frame under the running water to remove the carbon dust and file off the desired amount round all the edges. The results are pretty good and it doesn’t take long to finish.
Motors and ESCs
Next up is to get the motors and ESCs in place and soldered up.
I’ve been using the 25A version Chaos ESCs from Unmanned Tech on my 180 and 210 quads for a little while now and I’ve been really impressed. Out of curiosity I wanted to see just how small the 20A version was and if I could make them fit. As you can see they ‘just’ fit on the bottom of each arm with room to slot the motor wires through the frame.
I realise that 20A is overkill in terms of ESC for the motors I’m using. I picked these more out of curiosity than requirement and they’re nice and cheap too.
Check out how small these motors are, the mounting screws look so tiny when compared to a normal 2204 motor screw:
All wired up now. The motor wires pass neatly through the hole in the frame with just enough room to twist back on themself and solder back to the ESC.
Power distribution & flight controller
Now onto the PDB. It needs the slightest of rise to allow the battery strap to slot underneath, nylon nuts come in handy for this I find. Then it’s a simple case of running each pair of ESC wires around and over the top to keep it nice and neat.
The ESC signal wires folder neatly up in the same way and are soldered on the underside of the FC. The red, black and white wires poking out the bottom here are for the LED. At this point I hadn’t realised but I’d wired up the white signal wire incorrectly (it should go to slot 5 to be able to be picked up in BetaFlight). Easily fixed once I plugged it in to test but I forgot to take another picture.
I also added the received at this point which in the final build is affixed to the carbon plate which sits on top of the purple standoffs in the pic below.
Now the quad is ready for an initial set up and check over. I was able to run through the usual configurations in BetaFlight and BLHeli suite to make sure the rx is working, check motor directions and set up the arm switch and any modes required.
A quick test flight and I’m happy to say everything work and it hovers quite nicely.
FPV camera and VTX
So, onto finishing up the build, which unfortunately I forgot to take pictures of each step!
It’s fairly straight forward however. The camera is sandwiched nicely between the vertical carbon plate.
There’s a really handy slow behind the camera for the VTX to be attached to and the choice of antenna mounts at the top or to the side. I opted for the side as it should give the antenna better protection. I believe if the antenna were mounted to the top, the SMA would likely break on the first crash in that area.
The below picture of the finished build shows the VTX in place with the LED bar placed over it.
Complete build and initial impressions
Overall I’m very pleased with the build. Everything went together really nicely and it was easy to work on.
If I were to build this over again I might consider a 4in1 ESC although the separate ESCs under each arm aren’t really a problem. I probably would however swap the XT60 PDB for a normal PDB and run an XT30 off on a wire. The XT60 feels like overkill.
For the initial test flight I had to try out the new Racekraft 3076 props I got. I mean they look ridiculous!
It was fairly windy outside for the initial flights and on 3S you do feel it. It lacked a certain punch to help deal with any sudden gusts of wind. Swap over to 4S however and it’s another story. Plenty of punch and the quadcopter feels like it’s got plenty of speed in it.
The real test will of course be over the winter when we move back to primarily flying indoors. Who knows, perhaps we’ll add a micro race league to any upcoming events…