Anablep

Introduction:

I've been having loads of fun flying indoors learning LOS with the RS90. My original plan was to build a lot more RS90s and try to learn to fly fpv outdoors with them, but the 3d printed frame really wasn't as strong as I was hoping it to be. Repairs are easily done with a a soldering iron, but I'm finding that I'm now doing repairs after each session and it's starting to get old. Also, I don't feel that my RS90 is really efficient with the props that it has. I'm also limited to the size of props I can use since the frame is rather small. I do have a couple of LKTR120 frames lying around, so I figured why not build an outdoor fpv trainer with one and see how it compares. After all, nothing compares to the strength of carbon fiber and the LKTR120 can definitely sport some larger props which may in turn increase battery life.

Components (~$80) :

  • frsky micro D8 receiver
  • racerstar 6A 2in1 ESC x2
  • racerstar BR1103 6500kv motors x4
  • Piko blx flight controller
  • LKTR 120 frame & props
  • 3d printed motor guards
  • FPV camera & VTX (to be added later)

Conclusion:

The name anablep comes from the four eyed fish "anableps". The great thing about building something yourself is that you get to name it whatever you want. Yes, I can call it black doodoo too, but I guess a four eyed fish is probably nicer. I wanted to name it after something with eyes since this will be a fpv trainer, after all. ;)

I guess I don't build quads like normal people do by buying standard parts that fit the frames perfectly. I've always liked to improvise while doing scratch built wings and I find that I'm doing the same when building quads. Of course, there aren't really any standard parts that fit the lktr120 frame perfectly anyway, but it would definitely have been easier using a standard 16mm stack. Unfortunately, I didn't have a 16mm fc, so I had to improvise. In any case, I think it all came together in the end. The only catch was that I had to diverge from the piko blx instructions by keeping inversion to "on" for sbus.

Without any fpv equiment, the total weight came to around 50 grams. I figure once the fpv gear is on, it should be around 60grams without the battery. It's designed to fly with a 2s battery in a fairly tame manner, which will be perfect for fpv training outdoors. I fit everything in the frame by removing all heat shrink tubing from the electronics and coating everything with conformal coating which should allow the quad to take a splash or two without worries. In fact, the whole thing should still run fine even if it falls in a pond, but I see no reason to test that theory. :) I also do this with a lot of my fixed wing electronics which have seen some water to no ill effect.

The plan is to eventually put on a small osd/vtx/cam. I have the vtx/cam, but still waiting for the minimosd to arrive. It'd be nice to get a omnibus osd fc instead though and save some weight.

Update 1/22/18: So my suspicions were correct about the prop size and efficiency. The batteries lasted 30% longer with these larger props given roughly the same weight as compared to the rs90. I have also added a camera and vtx to anablep now that she is performing well indoors. With the fpv system in, the total weight is now at 57 grams without a battery. Removing the motor guards will bring it close to 50 and by using smaller components, I'm sure one can easily build a 40g version. I'm not going to fret about a few extra grams though. I would if it were a 20g quad.

Update 1/23/18: Took it for the first outdoor fpv session today. Everything went well except for the range. I left the antenna inside the body to better protect it since that was the first thing to break on the rs90. Unfortunately, outdoor flying requires much higher range and I'm going to have to move the antenna outside to see if the range improves. I'm getting rssi warnings once I move beyond the range of a baseball diamond. Not quite what I expected, but hopefully, it can be improved. The video range is pretty impressive though with no static and a pretty solid picture. However, I was not able to make it past the first battery or test it in anything other than angle mode since it started raining. The quad didn't get soaked, but did take a light misting (good thing it's waterproof). I learned that it's not possible to fly in rain since a single drop of water on the lens will pretty much kill your vision.

Update 1/18/18: Took it out for the first time in rate mode. It flew just like the fpv simulators except landing fpv was a little more challenging than expected. I was too used to flying LOS and without any stability assistance from the gyros, I came in for a few hard landings. I also got a bit reckless and flew into a tree which resulted in losing a front motor guard. On my next to last battery, I also landed upside down in a large puddle. I had no intentions of testing the waterproof conformal coating, but now I can confirm that it works as the flight controller was pretty much submerged in water. I picked it up and continued to fly it without issues. So glad that I took the extra time in waterproofing it!