The Syma X5C is a very docile and sturdy flyer, a perfect beginner quadcopter. Since I moved on to acro flying and racing quads my old Symas have been collecting dust. A while ago I converted an X5C to acro mode and 2s, but that one did not last very long.

The powerboost was nice, the acro flying great, but the gears are not really designed for the added violence of 8.5mm motors and 2s batteries. I therefore started to think about a a more ambitious conversion: brushless and 3s or maybe 4s.

Let's start out with a photo of the finished product:

This is the quad as it was right after the build. It is shown here with 4045 bullnose propellors, but after some tests flying I settled with DYS 3545 bullnose propellors. The former were too heavy for the 1306 3100kv motors and the quad responded sluggish.

Build log

Basically the only parts I reused from the original Syma is the body shell. The body is built using two shells of very flimsy and thin plastic, but screwed together the whole thing is surprisingly rigid and tough.

Furthermore I used the following components for my build: * Noname 1306 3100kv motors. Cheapest motors I could find on Aliexpress.

• ZTW spider 12A ESC's. I flashed these with Blheli 14.6, originally they come with SimonK firmware.

• PDB: cheap and simple, but effective, provides 5V and 12V.

• F3 EVO flight controller, programmed with Cleanflight 1.13.0. I chose a 6DoF one because I intend to do only LoS flying or FPV.

• Batteries: 3s, Turnigy 700mAh or Zippy 850mAh.

I designed two shims which form a motor mount for the brushless motors and printed them on my 3D printer using PLA. There are two different discs, the higher ones fit snuggly into the recess holes where the original motor mounts were. The lower one goes below to form a sort of sandwich construction with the original housing. The two shims are also glued together with some epoxy.

The files for 3d printing can be found here

The holes are fit for 12mm diagonal M2 screws which is standard for 1306 motors.

(Bottom view of the motor mount. For some reason my printer did not do a complete 100% fill. Maybe nozzle is starting to get bad...)

(In this picture the 4 motors are installed as well as the mounting plate for the electronics.)

To mount the electronics plate I first got rid of the original flight controller mounts. This has the added benefits that the flight controller is mounted almost flush with the bottom plate. The battery compartment is not useful anymore, but since we are going to use batteries that are much bigger that the original ones that does not really matter.

The PDB fits nicely on the 30.5mm standoffs.

The ESC's fit nicely despite their size. Nowadays, 20A ESC's are much more compact, but these were lying around and are perfect for this build. Flushed with Blheli they can be easily configured using the F3 controller in passthrough mode.

The original batterydoor is glued shut to the bottom frame with some epoxy to provide some additional structural integrity.

Part 2 of the build log can be found here