This article explains some of the benefits of reversing your motor and propeller rotation for quadcopter and mini quad flying.
One of the most significant benefit of inverting your motor/prop rotation is Aerodynamics. This video explains this very clearly and here is my personal understanding of it.
Center of thrust
When propeller spins at a stationary spot, the centre of thrust (COT) is right in the middle (i.e. prop hub). But when the quadcopter begins to fly forward, force from air resistance is applied on the the propeller and thus shifting the centre of the thrust to the advancing blade (the red circles in the last image).
This means the advancing blade will tend to generate more thrust and pull more air than the retrieving blade.
On the front two propellers, the COT is located outward, and that of the back props are inward. The faster the copter is flying, the further the COT is away from the hub. That implies the back propellers would be working less efficient than the front propellers due to principle of moment.
Furthermore, the air turbulence from the front propellers can make the back propellers work even less efficiently. (That’s one reason why “stretch X” frame was designed to combat this issue by moving front motors further away from the rear motors)
By reversing the prop rotation, the centre of thrust of the front propellers are now inward while that of the rear props are outward, and it compensates the penalty we get with the dirty air disturbance from the front props.
Better yaw turns
With inverted rotations, back motors are less likely to go into “stall” at tight yaw turns.
These benefits would not make much a difference during a hover or 3D aerobatics flying.
One of these reasons might be enough to make you adapt to this idea.
Since your front props are not spinning toward the FPV camera but rather outward, your camera lens won’t collect dirt from the props such as grass or water. (However your FC will :) )
With reversed rotation you are also less likely to get caught by gates or branches (in theory).
Another positive thing in changing prop rotation is that most of us often get into situations where we have no CW props left but many CCW, or the other way round. That happens because we are left or right handed and tend to make more corners to one specific direction instinctively. Now we can just change rotation and keep flying.
How to reverse motor rotation in a quadcopter
Here is how to apply the custom mix for a pure X quad in boards using Baseflight / Cleanflight or Betaflight
- Remove all propellers
- Change motor direction with ESC, BLHeliSuite
- Go to BetaFlight CLI, type
set yaw_motor_direction = -1(command name changed in newer Betaflight version) set yaw_motors_reversed = on save
(by the way the option is also available in the Configurator with the latest Betaflight firmware)
And now install your props in the reversed order, CW instead of CCW and vice versa, not flipping it upside down. :)
And make sure you check it every time you flash/update firmware in case that setting gets reset, since this is not the traditional way of doing it.
- Jun 2017 – Article Crated
- Aug 2017 – Added one more benefit to reversed rotation