This is my 7-inch TBS Source One

This is my 7-inch version of TBS Source One quadcopter frame. So far, so good, Source One is really tough and stiff frame so all the problems with resonance and oscillations in flight should be over. And looks like they are over.

It might sound like a good old V8 engine but flies smooth. And after all, that was my ultimate goal. So let’s say “bye, bye” to wobbly-wobbly iFlight XL7 v2 and say “hello” to 7-inch Source One! 6mm thick arms are the way to go!

iFlight ION Raaange/ION Drive 2506 1250KV Motors

220x motors are the workhorse on the RC hobby right now when it comes down to mini quads. Sometimes they are joined by 230x too. But 2205 and 2206 brushless outrunners have a serious problem that limits their use with propellers bigger than 5 inches. They might still be fine with 6-inch props, but on 7-inches problems begins. What 220x lack is torque! They are just too small to have enough copper wire and diameter to deliver enough torque to drive much heavier 7-inch propellers.

Let’s welcome something much more powerful: ION Drive / ION Raaange 2506 1250KV!

Betaflight 4.0 – improved dynamic filtering on 7 inch quad

The next major release of Betaflight will be 4.0 with new and improved Dynamic Filtering. For now, today I only did a quick test of Betaflight 4.0 running on my TBS Source One 7-inch FPV drone. No tuning, no playing with settings. I only flashed, set modes and radio and that’s all. I pretty much like how it feels. This quadcopter was mainly doing cruising, no freestyle, and it felt good to put those props into more demanding use. Yes, Betaflight 4.0 has a good chance to be just awesome…

Hardware

A note about the sound. It indeed sounds like a V8 engine. Bear in mind, that those are default settings and Gemfan FLASH 7042 props are light and do not like to have too much D gain.

Smooth 7-inch FPV drone – motor soft mounts, part 1

I have a theory that 7-inch FPV quadcopters fly “below expectations” due to frame resonance, I did not expect, so many pilots agree with it. We had nice talks in comments, I’ve learned a lot about stiffness and moment of inertia (that you Pierre-Louis). Many of you shared some of their tricks and ideas on how to solve that. Let’s start testing some ideas how to fix that!

7 inch quadcopters fly like shit? Well, kind of, yes…

So, you got yourself a 7-inch quadcopter drone, you try to tune it, and you finally discovered that something is bloody wrong? Whatever you do, no matter how long you tune the PID gains and filtering, you can not get rid of jello and some strange vibrations? Welcome to the club mate!

Apparently, scaling 5-inch frames to 7-inch ones in XY axes does not work! Longer arms equal lower modal frequencies. Bigger propellers equal lower vibration frequency. After combining both factors, we have frame oscillations that are happening on the hardware level. No way you can tune that thing out. To make thing worse, 2205 and 2206 (even 2207) motors does not have enough torque to quickly change 7-inch propeller rotation speed.

For the details, watch the video.