A software engineer who’s also into drones and 3D printing has shared a single-motor drone that they built inside their home and tested on their bed. Joshua Bird shared a video of how they created it on YouTube, highlighting the unique technique they used to maintain controllability and stability. The design used a combination of a hinged propeller, rapid changes to the motor’s rotation speed, and a custom flight controller and motor controller firmware that allowed the motor to react to necessary changes in under 0.2 milliseconds.

Most rotary wing aircraft require a mechanism to counteract the torque generated by the motor or engine and to change its flight direction, typically with the use of a swash plate to change rotor disk attitude and a secondary propeller. While this method has been effective for decades, it has made rotary-wing aircraft heavier and more complex. This single-motor drone cut the need for a secondary mechanism by constantly adjusting the speed of the motor — speeding it up produces more reaction torque while slowing it down applies opposite reaction torque. This essentially turns into a balancing act between these two forces to reduce the torque on the drone body to a more manageable level.

The hinged rotor also relies on the same mechanism for directional control instead of relying on a swashplate. Each rotor blade sits on a 45-degree hinge that makes it pivot when the motor accelerates. As this happens, one blade pitches up to produce more lift, while the other blade pitches down, reducing lift.

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