Attempting something a bit unconventional.

5" quads usually carry 2204 size motors and weight upwards of 400g with HD cam and battery.
3" quads can fit under 250g but can't carry HD cams (exceptions exist, read on) but the real issue is they can't match good flight characteristics of 5" unless good motors / 4S batteries are involved and that becomes expensive.

Manufacturers are continuously putting out smaller components that match the performance of larger ones available in the past. Runcam split mini is one such example, full HD video at <20g. I have this on 5" and I've seen builds of these on 3".

So, the idea is a lightweight <= 5" frame with lightweight + cheapest components, a combined FPV/HD camera and GPS module (because I just don't like any of my quads without them).

Candidates for components so far:

Frame - GGT150 160mm 
Motors - EAGLEPOWER SA1306 3100KV
FC - FULL SPEED F3 2S Flight Tower with OSD 20 x 20 Mounting Hole 20A ESC Support Dshot600
VTX - Some VTX03 equivalent
FPV/HD cam - Runcam split mini eventually but intermediate tests with the cheaper alternative Turbowing 720p FPV CAM + DVR
GPS - mini M8N

The unconventional part of this build is the motor kv, it's way high for a 5" prop, but will see how this goes. I got 4 of those motors for $12 which is a steal. The FC+ESC combo was also under a flash sale and is light enough for this project.

Looks the frame I originally intended to use will not be here in time, so going ahead with an old 5" frame, well not the frame but just the baseplate. This belonged to a Falcon210 quad.

Components put together weigh roughly 180g. This is using the Turbowing DVR so RCS mini adds 25g. Plus wires and spacers and props and battery strap etc. might add 40g more.  That comes to 245g.. might be a nail biting finish?

For some reason I got an urge to make this a Betaflight quad (as opposed to iNav which I'm more comfortable).
The board came flashed with Betaflight, and I updated it to the latest available at this time 3.5.1.

Unfortunately, realizing that GPS support had been dropped from F3 boards since 3.1.7, I'm now going to build by custom version of Betaflight with all unused protocols, features removed so that the code fits into F3. This is an unwanted digression, but can't seem to get my mind off loading Betaflight and adding GPS support.

For those of you looking to have the latest and greatest Betaflight, this repo contains regular custom builds for most F3 targets for the latest Betaflight version - https://github.com/spatzengr/betaflight/releases

I did notice support for my board present (OMNIBUS) and flashed it, but looks like some of the features I wanted to try out were missing, and vice-versa.

I'm following this link for the build process - https://hub.docker.com/r/betaflight/betaflight-build/

245gm. That's very neat I guess.
My 210 dry weight is 369gm, I have the bigger gps mounted on mast. That must taking some 40gm. Still mine is heavy.
What lipo you plan to use?
I am using 3300mah 35C 3s weighing 258gm, and getting around 10min flight time.(hovering only)
Is there a way to get more flight time out of this?
All the best for your new setup.

Quote from: sim_tcr on September 21, 2018, 10:02:10 AM
245gm. That's very neat I guess.
My 210 dry weight is 369gm, I have the bigger gps mounted on mast. That must taking some 40gm. Still mine is heavy.
What lipo you plan to use?
I am using 3300mah 35C 3s weighing 258gm, and getting around 10min flight time.(hovering only)
Is there a way to get more flight time out of this?
All the best for your new setup.

For a quad that's already built like your case, the one single change that affects flying time is LiPo. Bigger is not always better as motor efficiency have a non-linear curve, they might be drawing more current due to the higher battery weight, reducing flight time.

For a "typical" 210 quad, try to keep it within 350gm and LiPo within 200g. A 2200mah 3S with good C rating might be the best compromise between capacity and weight, but I don't have data to say this is the "best". I say typical assuming conventional 2300kv motors. This build attempt of mine (is still a 210 quad) violates this typical rule of 2300kv / 3~4S setup.

Second best thing you can try is a prop with lesser pitch. Experiment with 5030 and 5040, 5045 and above will provide more thrust and also drink more current.

The custom firmware build system is complete. Flashed firmware and the enabled features are working:
-ESC protocol - Multishot
-serial RX protocol iBUS
-sensors - MPU6000 over SPI, Baro MS6511 and compass AKM8963 over I2C
-No datalogging

I've made the source code changes as well as the HEX that can be flashed from Betaflight configurator here - https://drive.google.com/open?id=1ZrRXV9wkdpIdbey421uQeYsOylhTRDjO

Version is shown as Betaflight 3.5.8 to avoid confusion with current stable version.

The build begins.

Here are the components laid out, from left to right - FC, 4 in 1 ESC 20A (comes with the FC), Turbowing cyclops 3 FPV cam/DVR, VTX03, GPS, Compass/Baro module
Ignore the frame shown in the pic, this is just for a 210 frame size reference.

Forum crashes when I try to submit a long post 
Anyways,

Falcon210 frame with the motors mounted, these motors are tiny! Also the motors wires are too short, so had to extend the length with extra wires.






Wires lengthened and soldered to ESC pads-




ESC board mounted onto a 20mm to 30.5mm adapter, with some rubber vibration dampening washers installed




Battery lead (2pin JST) and some extra VBATT, GND wires soldered (for when I install Runcam split mini)-




Noticed late that the manufacturer missed out VBATT wire on the ESC to FC cable
One more set VBATT and GND wires soldered-




Connected to FC to ESC and did a quick power test. No magic smoke.

Time for things to start getting messy, VTX and CAM soldered.




Connections:




Another power test and checking if FPV is working. Setup Betaflight at this stage and configured OSD to show battery voltage and flight time.
FPV and OSD are primarily for PID tuning and other quick configuration without needing to connect to the PC.




Weight check with everything: 212g. Wow!

Here's the first flight test video. I should say, it flies very well, hovers at just 30% throttle and gives a flight time of 8 minutes. More details in the video.

Quote from: kn8alpha on September 22, 2018, 08:52:45 PM
Here's the first flight test video. I should say, it flies very well, hovers at just 30% throttle and gives a flight time of 8 minutes. More details in the video.

Good job.
Does this version of Betaflight you built has altitude hold (Baro) mode?

I've built the firmware with I2C baro support included, so yes altitude hold should work.

I'll mostly be using only GPS and no compass/baro for this build, mainly because there are no dedicated i2c pads on the FC.

Do u sell turbowing cyclops v3 ?