Here are some results, they may be useful for designing a Nipkow disc device.

Theory

- The wattage needed to rotate a disc is proportional to its speed in the power of three (cube). Example: we increase speed x2, hence the power increase should be x2, but because also the aerodynamic resistance forse (and torque required for rotation) increases proportionally to the square of speed, we have the 2x2x2 increase required.

The torque needed to rotate a disc is proportional to its diameter in the power of five (!!!) Why? Example: we increase diameter x2. The speed of the disc surface relative to air increases x2, and aerodinamic forses increases x2 in the power of 2 (x4). But the area on which these forses are acting increases x2 in the power of 2, as well. And this is not all! The torque increases additionally x2 because the points to which aerodynamic forses are applied are twice as far from the disc center. This all gives 2x2x2x2x2 (x32) increase in torque (and wattage) required.

Sorry for maybe unclear explanation, but I tried this out and it's very close to theory...