RS90 Quad

Introduction:

Having been busy with work, I haven't gotten around to building more planes. Since winter is already here, I decided to build something I can fly indoor for the winter. I've been eyeing the RS90 for a while since I really like the way it looks (I know it's not everyone's cup of tea tho...) and also how protected it is for indoor fpv. I bought an almost completed kit from a great guy on RCGroups, but after seeing what he did, I decided to build my own instead since I had most of the parts lying around anyway. 

Components (~$80):

• 3d printed frame (I used PETG)

• M2 x 10mm nylon standoffs x14

• M2 6mm screws x28

• hubsan tri props

• frsky micro D8 receiver

• racerstar 6A 2in1 ESC x2

• racerstar BR1103 6500kv motors x4

• mini cc3d flight controller

• 5v 3amp voltage regulator

• FPV camera & VTX (optional)

Conclusion:

Building a quad is nothing like building a plane. The only transferrable skills are mainly soldering, and being creative. The thing that determines success though is having the drive to complete what you started as there will be many obstacles in your way. I was rather ambitious in wanting to create my own from scratch, so quite a lot of time was devoted to first printing out the frame. I had printed lots of things in PETG before, so I decided to continue down that path. It is super flexible and hard to break, but at the same time, also very stringy and hard to print. My main issues with the frame were the motor mount areas. Even though I printed with support, there was still a big mess to be cleaned. In fact, I had to buy a drill press to be able to clean the inside of the motor mount in an even enough manner for mounting the motors. The other big problem with PETG is weight. With the medium bottom plate, the original frame is about 14 grams. With PETG, my frame came in at 20 grams. Quite a penalty there.

When this quad first came out, the components available back then were not as light as they are now. I was able to achieve significant weigh reduction by using the 2in1 escs. Without any FPV gear, the total weight was 54grams so far for the quad.  Had I not gone with PETG, it would've come in at 49grams, which is a really good weight. The only other major annoyances during the build process was mainly the learning curve. Flashing the mini cc3d with betaflight wasn't too bad, but figuring out the reason my receiver didn't work because betaflight had moved the cppm pin from 3 to 8 took quite a few hours of googling. Most people are hesitant in building micro quads because they're hard to solder, but since I had built my fair share of planes and cars before going into this, I was not really worried. 

Everything accounted for, it took me a month to finish this project. About half of that time was spent experimenting with how to print the frame and prepping it for use. The other half was spent learning everything else from configuring the taranis, betaflight, flight controller, etc... It was all good because I'm pretty sure I can do another quad in just a couple of days now if I really wanted to.

Lastly, the maiden flight...well, it was nothing short of amazing. I'm not able to fly it in anything other than horizon mode at this point, but it was very stable and level. With the lower kv motors, take off requires about 60% throttle. That was expected though and I plan on trying another build with 8000kv motors at some point in the future. I didn't put in any fpv gear yet as I want to learn how to fly this LOS before going FPV. 

2018-02-11

After using it to learn how to fly LOS, the frame requires repairs after nearly every flight. I have therefore retired it to build a new one.