This is my 3d-printed propeller that folds into a compact 16mm diameter semi-sphere. When rotated the two blades open up automatically by the centrifugal force. The blades will then fold back into the semi-sphere once the motor is stopped.
This is the drone concept that gave me the idea of trying to create the PCB motor and spherical folding propeller! Both of these projects need a lot more work and improvement to make this drone feasible but at least now I have a starting point :)
This is the thrust results of the first Spherical Folding Propeller prototype:
The results are not so bad considering the size of the propeller (1.6cm diameter when folded) and that no air-flow simulations were done during design. I'm going to conduct simulations for the next prototype, to try and make the propeller as efficient as possible.
This is the setup used to measure the thrust. The propeller was suspended around 15cm above the scale, to eliminate ground effect.