Selection of gearbox for rotating a solid shaft

[Amre]

Hello
Being practical I have been stuck in one question like if I have a 320 mm diameter and 805 mm long shaft which is suppose to rotate through gearbox how do I need to select a gearbox.
As per I think I need to calculate the torque of shaft and find the torque of gearbox and based on that I will select gearbox.
I just want to know the basic formula to calculate torque of shaft and torque of gearbox assuming that it has a flange mounted motor so again how much power we need for that perticular gearbox

 

[Hysteresis]

Without seeing the question it's hard to determine what the actual answer is. Because you are talking about angular velocity and given the values you have provided you most likely need to calculate the moment of inertia which for a cylinder is 1/2mr^2. However you still need parameters such as mass, power output from the motor, angular velocity of the motor. You must have additional parameters in the question