Summary

https://youtu.be/gd3dIFpSpE8
Split flap clocks have been in use for some time in alarm clocks and in train stations.
The mechanisme is relatively simple. Moreover, if the rotationspeed is increased, it acts as a kinematoscope (zoetrope like result)(thanks Kongorilla). The movie is quick and dirty because I did not have the patience to make nice series of drawings. I'm sure you can do better :-).
The motor is a popular mini geared motor. The battery voltage should be choosen below the motor voltage, to reduce the rotation speed. The stop bar on top can be rotated to achieve a good synchronisation. The wheel is printed twice. At one side an M3 screw is inserted and fastened with a nut. The other side recieves the motor shaft. The two halves are connected with two M3 screws. The flaps are inserted by bending them a little.