I’ve built my first 7” mini quad few months ago. First flights were pretty rough when it comes to performance and fight times. Ever since I built it I tested numerous motors, props and battery combinations and finally found the good solution that gave me smooth footage. One of my colleagues – Kamil Bujniewicz (kbfpv – well known smooth freestyle pilot and absolute genius when it comes to PID tuning) commented my recent video recorded on 7incher „awesome and smooth as far as 7” prop can go goes”. His words mean business 🙂
In this write up I will explain the steps that I took to achieve the satisfying footage smoothness from 7” machine.
My initial 7” setup
InIn the past I was flying 6” Alien frame with 7” arms. It was just my modified favourite 6incher I used for about 2 years.
This machine was my first 7” experience. I’ve put TBS FPVision with Colibri FC on it + Crossfire micro RX. Motors of choice were ZMX X40 2608 1500kv prototypes I had around for testing.
Prop of choice was HQ 7×4.5 and HQ 7×4 because these two were the only ones available back then. First few test flights was pretty much bumpy ride and it didnt go well.
In the meantime my quad configuration changed few times. Nothing proved to work properly to be honest. There was always some oscillations but also weird yaw twitches I was getting.
I was never happy about how it flew, it seemed like a constant work in progress.
My current setup
After changing pretty much all bits apart from FPVision+Colibri+Crossfire I ended up with this:
- Frame: ImpulseRC Reverb + 7” arms
- Motors: ZMX X40 2608 1500kv
- ESC: Spedix 35A blheli32 2-6S
- FC: TBS Colibri Race v2 (hard mounted)
- VTX: TBS FPVision
- RX: TBS Crossfire
- FPV Camera: RunCam Swift V2
- Lipo: 5S between 1500 to 3000mah
- Prop: Gemfan 7042 (for now)
Let me take you through the choice of components.
I have chosen Reverb because it was a little bit lighter than Alien but also it is very robust and stiff construction. Flex is kept to absolute minimum. Reverb has definitely lower profile than Alien but still plenty space inside and easy for upgrades. I have been using ImpulseRC frames for years and I am huge fan of their design work work.
I was lucky enough to be able to test X40 motors ever since they appeared on the market. Huge beasts @ 40g per motor. They are massive compared to typical 2207 motor. 26mm diameter and 8mm stator hight means business. Those motors deliver a lot of power even at low throttle. I also used some 2206 1400kv motors (TBS Endurance and BrotherHobby ones) for comparison but they were lacking power on my, rather heavy quad. This was not a case with X40s. I can’t back up my choice by any science but they just felt right on my quad and lack of power was the least of my concerns here.
Let’s face it, most current ESC on the market are very similar. I went with well priced Spedix. 35Amps seemed all right. Blheli32 is also very smooth, so my choice was simple. Good performers ? Hell yes. No need for a change.
Colibri wasn’t actually my choice but it came bundled with TBS FPVision. It is TBS own FC running F3. It integrates very well with power cube/FPVision, so I couldn’t choose anything else really. Solid performer despite F3 processor (old tech? nah…).
As a long term TBS Unify user I didnt change that. FPVision has Unify under the hood with add on of TBS integrated OSD etc. Great piece of kit. Current sensor comes calibrated out fo the box (yeah!) and it also allows for connecting external GPS to get flight info in OSD. Its my favourite piece of kit recently. Worth every penny.
This machine was meant to fly far so I could either choose FrSky R9 or Crossfire. I personally prefer Crossfire because its trusted and simply more reliable system. Choice was simple. Crossfire win here for me.
Camera doesn’t help with smooth footage but helps with how you see where you fly. I always used Runcams and Swift V2 is my choice and has been for a long time.
After using 4S and 5S on the same setup I came to a conclusion that 5S handles heavier quad better. I am getting around 8 minutes on 5S 1500mah and 13-15 on 3000mah. All depends of course how I fly. Those times are for fast cruise @ around 60-70km/h and around 10A current.
I have tried new Gemfans Flash 7042 after recommendation and looked no further. Those are twin blades (easier to carry), super quiet, almost like a stealth mode when flying around and give best footage. I may try different props and probably will, but for now gemfans blown me away. Can you imaging I am still on their first set and been for over 3-4 months now ? 🙂 I have never ever balanced those props. They even have few chips on them!
Tricks for smooth footage?
There is few things that made my quad flying smooth and improved the footage.
1./ ND filter
It’s not a secret that ND filter helps with jello on the flight cameras. It simply worked in my case too. I get very little jello in the footage. Because of my 3D printed GoPro mount I could only use stick on filter and I ordered few ND4 and ND8 from GetFPV. I use ND8 at the moment.
2./ Hard mount FC
It is hard to believe but that made the biggest difference actually. I can’t back it up with anything other than my flying experience, so don’t expect me to explain you why it made an improvement on my machine. I honestly don’t know. I’ve replaced soft mounts under the FPV vision with just nylon standoffs. No more weird yaw twitches and usual oscillations. All gone.
ButterFlight is known for a smooth performance it gives. I tried it as well and it made huge difference to my quad too. Pretty much stock PIDs, all filters OFF and adjusted rates. I have set 8K/4K and Q at 1400. That’s all. The feel is different compared to BetaFlight – pleasure to cruise.
4./ 48Khz PWM frequency
This setting made a difference in flying. In blheli32 suite I’ve changed it from 24Khz. Much smoother performance.
5./ Smooth fingers 🙂
That helps too. If you’re notoric jumpy racer or someone who change flight direction every half second you would never get a smooth lines. Patience is a key here. Don’t over compensate the quad, let it go, be gentle and just feel the flow. It helps. Maybe I am talking bullshit here, who knows. It works for me 🙂
When higher throttle is applied (above 50-60%) my quad still gets some oscillations. I set TPU at 0.4 but oscillations are still there. It doesn’t actually affects me that much because during my cruising I never go above 50% throttle to save some battery juice. Low end throttle on 7″ has plenty of speed too.
Jello is no more. I have tested my setup in cloudy and sunny conditions. Jell is not present there!
Also no more yaw twitch and any of the shakes I had in the past on 7″ props. Now it’s time to conquer some hills in Scottish Highlands this summer!
Video from the cloudy day:
Video from sunny day:
UPDATE Summer 2018Since the article was originally written I don’t actually own this particular 7″ Reverb any more.
I’ve had to downsize my quad fleet since I move onto wings recently.
I still have 7″ Cruiser but it’s is TBS Source Once with the following specs:
– BrotherHobby SpeedShield 2207.5 1750kv
– KISS FC V1
– KISS 32A ESC
– TBS FPVision
– TBS Crossfire
This machine flies even better smoother than my old Reverb.