Build Log - ZMR Mini quad

11:06 AM giovanni 0 Comments

Since the mini quad craze begun I have been watching countless youtube videos of skilled people zipping through forests, parking lots or urban parks at incredible speed and with great agility, and I knew I wanted to be part of this super fun movement.
So at the end of May 2014 I purchased a FPV250 frame from hobbyking. Two months after I am still waiting for it...

So in mid July I also ordered a ZMR 250 frame from Banggood, and I received it in a week. Talk about service! 

But let's start the build, with a picture of my working bench, messy as I like it.

This is how I do it, messy but neat at the same time!
All the components I used are shown in this short youtube video:

And can be purchased following this links: (the links are affiliate links, so purchasing from the links helps staying alive! Thanks for your support!)

- KK 2.1.5  EDIT: Now I am using a Naze 32

- GoPro H3+ Black / 808#16 HD Camera

- ZMR 1804-2400kv Motors EDIT: Now I am using the DYS 1806-2300v

- Afro 12A ESCs EDIT: now I am using the EMAX Simon K 12A

The first thing I did was to cut the motor wires off the Afro 12A ESCs and directly solder the motor wires to it. A quick test with the servo tester to verify the spinning direction and off I was.

Afro 12A ESC soldered to the ZMR 1804 2400kv motor
After all the four motors were soldered to their ESCs I installed the arms to the frame, leaving the power wires as long as I could, to trim them after to length.
I used some conical washers for aesthetic purposes, the added weight is negligible, but I find that the appearance is greatly improved.

The arms installed with M3 bolts to the frame
Instead of the stock spacers, which are made of red anodised aluminium, I preferred some nylon spacers, which weight less and look much better. To get to the proper length I had to add some nylon nuts, but in the end I got them to match perfectly the stock length.

The new spacers
This is how the four arms installed look like. It definitely looks like a quad now!

The four ESCs and arms installed
In the meantime I installed the FPV camera to the camera plate of the frame using some M2x8 bolts, spacing the camera with some rubber tubing, which also isolates it from some vibrations.

The rubber tubing spacers for the FPV camera
I also purchased a Simple PDB from RCGroups member OSO Grande. This board allows all wires to be cut very short, distributing the 12V all around, and also provides video traces to solder the FPV camera and the video TX to it, keeping all the wiring to a minimum, which I like a LOT!

The Simple PDB installed and soldered up
 All is looking pretty neat so far. I added an LC filter to the PDB, this way it taps the 12V from an ESC, filters it and provides clean power to both the video TX and the FPV camera.
Also, the KK board is installed. Being an older generation board the holes do not match up, so I used some double sided adhesive foam, but depending on how it flies, I might upgrade to a latest generation Naze 32, which is the preferred Flight Controller for this type of quads.

Note: only the signal wires, one + and one - wires are connecting the rx to the KK board, to keep weight down and to simplify the wiring. The wires are color coded to avoid confusion.

Almost there: the KK board is in place, together with the LC filter
 I then installed the top plate, the propellers, the VTX antenna, and the ZMR is complete.

the completed model. Hover tests are successful, now I only need to take it to the club!
Final consideration:

The quality of this model is remarkable. As noted by numerous users, the quality control on these chinese frames is sometimes lacking, but I guess I was lucky, and the machining was really up to scratch.
All the build was made with the objective of limiting weight, so I removed all the unnecessary parts, shortened all the wires and overall I am at 470 grams with battery and 808#16 V1 camera. Or 520 grams with battery and GoPro. I am pretty satisfied with the result.

Next steps:

After the first few flights with and without the GoPro I will be able to decide if the components are sufficient or if something needs to be upgraded.
My worry is mainly regarding two things: the KK board and the motors. If I will not be able to tune out vibrations I will go Naze 32, and if the flight with GoPro is sluggish I will see if some more powerful motors will help. Or maybe get a Mobius cam?

Stay tuned to see what happens next!