Asymmetrical frames like Dead Cat or Spider type have many advantages. Big central plate to put all the electronics, front view not obscured by arms and motors. And they look cool. Way cooler than traditional X frames. But there is a price. Because they are asymmetrical, flight controller has to put much more effort into stabilizing them. Motors are not in equal distance from center of weight, and because of this require different force applied when performing stabilization. Quad will fly even when standard X configuration is programmed into flight controller, but will not archive best performance. For example, when FC wants to roll, different motor distance from COG might induce also pitch rotation. Of curse FC will compensate in next cycle for that unwanted pitch movement, but what if it would have to do that? Less corrections, lower power usage, higher stability, better control.
This is why most flight controller software allows to program almost any motor configuration and tell it how far any motor from rotation axis is to match applied force for each motor separately. General rule: motors closer to rotation axis require more force than those further away (torque and stuff). This is called custom mixing.
I own a quadcopter based on Reptile 500 frame in spider configuration. And from unknown reasons internet does not tell much about proper mixer settings for that frame and Cleanflight software. Why? No idea, but I’m going to change that now and publish mixer configuration for Reptile 500 with Cleanflight 1.9 and 1.10.
Why two different configuration? Well, since release 1.10 there is different command for setting motor mixer (cmix vs mmix). Also, numbering of motors changed. In CF 1.9 it starts from 1, while in 1.10 and newer it starts from 0. So, here we go…
Cleanflight 1.9 Reptile 500 mixer configuration
cmix 1 1.000 -0.819 0.717 -1.000
cmix 2 1.000 -1.000 -0.717 1.000
cmix 3 1.000 0.819 0.717 1.000
cmix 4 1.000 1.000 -0.717 -1.000
Cleanflight 1.10 (also Betaflight) Reptile 500 mixer configuration
mmix 0 1.000 -0.819 0.717 -1.000
mmix 1 1.000 -1.000 -0.717 1.000
mmix 2 1.000 0.819 0.717 1.000
mmix 3 1.000 1.000 -0.717 -1.000
In both cases do the following:
- open Cleanflight Configurator,
- connect to flight controller
- open CLI tab
- copy/paste command from above. Or copy one by one. Does not really matter. Just remember to hit enter
After that, controller will reboot and you will be ready to fly!