Custom frame settings
If your frame is not a standard X or H frame, here you find the basics on how to configure your flight controller for this custom frame. There are two methods about getting the right values for your controller. The first one is by using the angles between the arms and the Roll and Pitch axes. The second one is by getting the distance from every motor to the Roll and Pitch axes. I used the first one for setting the mixer editor on my KK2.0 board about two months ago, because I saw this method on YouTube.
Although I will use the second one in the future because it is more accurate. Why?
Using the first method you take the angles between the line from the motor-shaft to the flight controller center and the Roll and Pitch axes. Then use the sinus of this angles to get the value we need for our flight controller. But its almost the same as method two:
For the angle α, the sinus function gives you the ratio of the length of the opposite side (distance from the motor shaft to Roll/Pitch) to the length of the hypotenuse (this is the distance from motor shaft to the center of the flight controller). The flight controller uses only the ratio between these two sinus functions. So it also knows the ratio between the distances to Roll and Pitch and where the motors in space are.
Using the method with the sinus of the angles would be 100% ok, if all 4 arms have the same length and are mounted in the same distance from the flight controller. On my SG Adventure Mini Quad the distance from the front two motors to the FC are 135.3mm and the distance from the rear motors is 136.2mm. That is less than 1mm. Using the method with the angles would be no problem at all. But to be 1000% accurate, I am using the second method.
Here is how to do this:
Measure all the distance from every motor to the Roll and Pitch axes. Take the biggest nominal value and divide all the distances by it. In that case every distance is a ratio of the biggest one.
In my case this is the distance from Motor 1 (Rear right) to the Pitch = 108mm. Dividing:
Pitch 108/108 = 1 (KK2.0 or KK2.1.5 Mixer Settings value – 100).
Roll 83/108 = 0.768 (KK boards 77)
Pitch 83/108 = 0.768
Roll 106,9/108 = 0,989
And so on for every motor. That is the way I did it for my Naze32 custom motor mix. Note that the motor layout differs for every flight controller.
As said both methods work well, but the second one is more accurate when using arms with different length. I hope it is more clear for you now.