[rad2014]

Build Name: Acroquad 400
Flight Controller: CC3D clone
LibrePilot version: "Next" (originally 16.09 Black Rhino)
Frame: DIY - 2mm carbon plates, 10x10x1mm aluminium arms
Motors: XXD A2208-1100KV / Racerstar BR2208-1100KV
ESCs: Multistar 20A Slim V2 (BLHeli 14.9 - Oneshot125 and damping light enabled)
BEC: generic eBay Mini DC-DC Converter Step Down Module Adjustable
Props: Gemfan 8x4.5 or Aeronaut CAMcarbon Light Prop 8x4.5
Battery: Power X6 3S 3300mAh 35C/70C
Telemetry: FrSky Battery Voltage Sensor FBVS-01 via S.Port
Rx: FrSky X4RSB
Tx: Taranis X9D +
AUW: 720g


My first multirotor larger than 250. Built for LOS acro flying only.
I had flashed the CC3D with Betaflight 3.1.7 and it had flied very good. Now I switched to Librepilot and after some tuning it flies great, too. The copter flight characteristics with Librepilot differs to Betaflight to my surprise. The most difficult tuning was to get good expo response within my 800degs/sec rates.

XXD A2208-1100KV motors are not well built. I bought 6 of them, 2pcs didnt work. One motor destroyed during a crash. Now one motor replaced with Racerstar BR2208-1100KV. The Racerstar motor looks better than XXD, it has all edges chamfered and runs smoothly.

[AerialPerPlexity]

Have you tried acro+ flighmode?  If not i definitely recommend you looking into it. I personally like it the best,  for flipping and corkscrews

[rad2014]

I have tried the acro+ flight mode. I am fully satisfied with the rate mode. My rate mode response and max rate limit are 800 degs/sec with 15% expo. The acro+ moves it to the complete madness 

[TheOtherCliff]

But you can control the amount of madness you want. 

Fast Rate mode with expo should feel similar to Acro+, but I hear that Acro+ acts better in fast flips, because it has some "anti wind-up" code in it.

[rad2014]

During last flying session I tried to acro+ again. I let the 800degs/s rates and lowered acro+ factor to 1. Maybe is acro+ better in handling during extreme maneuvers, but I can't feel the difference. I tested my new Runcam 3 attached to the top of the quadcopter, you can see short video

[ernstock]

Hi
Well I think that's really nice video with great rolls n flips.
Suggest you experiment further with lower rates and higher acro+ factor -maybe 300 to 500 degrees/s and anything from 60 to 90 acro+ factor.

[TheOtherCliff]

None of those flips looked like 800 degrees per second.  That is a little more than 2 whole flips per second.

Are you aware that there is an overall max rotation rate (Max Rate Limit) and a separate rate for Rate mode (Rate Mode Response)?

Stabilization -> Advanced -> Bank# -> ...

[rad2014]

Thats a piece of "smooth" flying , max rate limits and rate mode response set to 800degs/s. Thanks to attached camera I know now, there are wobbles at the and of fast rolls or flips. I must do some fine tuning. It is quite difficult now, because the wobbles are hardly visible during LOS flying.

[Mateusz]

Regarding wobbles, I haven't tried this but there is TPS (throttle scaled PIDs) curve. You can set any shape you want and scale PIDs accordingly. Maybe that helps boost PIDs at high throttle? Just a thought. It's in advanced tab.

[TheOtherCliff]

I understand that a "normally configured" Acro+ may handle that better.

Normal being a lower (than 800) max rotation rate but a higher (than 1) insanity factor?  I'm not an expert...

[TheOtherCliff]

I think you want to set up TPS to boost PIDs at low throttle and decrease it at high throttle... 

[rad2014]

I think you want to set up TPS to boost PIDs at low throttle and decrease it at high throttle... 

Just like that. After some fine tuning I got very high PIDs. I combined them with TPS (lowered at high throttle) and smoothed throttle curve with expo ca. 20 it flies best ever, but still not perfect. As I heard the quad during flight, motor bearing becoming noisier and I should replace that cheapass motors 

[mr_w]

What are your motor temperatures after flight? Considering these are low 1100KV motors and you use it with 3S, how much throttle you need to give it usually?

I have flown recently my older tricopter build, using similarly looking motors (A2212, 1000KV) also with 3S, using 8" props too - and while I might be a bit biased towards my other more recent "racer" builds - that one (tricopter) seemed quite sluggish and not really as fun as doing 4S, 2300KV and good 5" props. One thing that I have noticed that even after 3 minutes of flying, those motors were really hot..

[rad2014]

What are your motor temperatures after flight? Considering these are low 1100KV motors and you use it with 3S, how much throttle you need to give it usually?

I have flown recently my older tricopter build, using similarly looking motors (A2212, 1000KV) also with 3S, using 8" props too - and while I might be a bit biased towards my other more recent "racer" builds - that one (tricopter) seemed quite sluggish and not really as fun as doing 4S, 2300KV and good 5" props. One thing that I have noticed that even after 3 minutes of flying, those motors were really hot..

Motor temperatures depend on a flying style and AUW. With 3S 3300mAh battery is AUW 720g and I am pushing the copter, that I reach 100% throttle often, motors are very warm (when touching them, I don't burn myself). With 3S 1550mAh battery and AUW 600g I dont need to throttle 100% and motors are on human body temperature (36°C-37°C). Motors XXD A2212 1000Kv are not 4S rated. Maybe you should use some 4S rated motors to getter better performance.

Racing copters have much higher power-to-weight ratio, motors with higher KV (faster responsivness) and smaller props (less inertia to move) and 4S batteries, so racing copters are much more responsive compared my LOS Acroquad.

The weakiest point of tricopter is IMO the servo. Even digital servos are slower compared to Oneshot125 (and newer). Some high quality servo with feedback wire and triflight can improve a tricopter's tuning and responsivness (see rcexplorer.se to get more info). I got a Trifecta frame from hobbyking in last sale for €4, my tricopter build will follow   

[mr_w]

I haven't had problems with yaw servo. My biggest concern was 3S + 1000kv + 8" props = sluggish performance. I have to check if escs support 4S, to see if that makes difference, although the motors were already uncomfortably hot at 3S.