How to calculate engine power?

Question

Do it yourself

There is a round stand, diameter 3m. The stand has a 2.5m swivel, which should rotate a load weighing up to 400kg, at 4rpm. How to calculate the power of the electric motor and how to calculate the gearbox? What is the best way to make a transmission: belt or gears?

Answer 1

Friction is therefore unknown.
If we consider friction equal to zero, then an engine of any power will sooner or later spin any weight to any speed (except light).
If the application is real, that is, there is friction, then it is easier to pick up empirically.