Shaft Power Equation
The power of a shaft is its ability to rotate a load at a certain speed. The faster the shaft rotates, the more power it has. To calculate the power of a shaft, you need to multiply the torque of the shaft by its angular velocity.

Average Shaft Power
The average power is calculated by applying average values for the shaft power equation.

Shaft Bending Stress
The largest alternating and mean bending stresses are at the outside surface.

Shaft Torsional Stress
Shaft torsional stress is derived from the shaft bending stress.

Torsion Equation of a Shaft

Torque and the Diameter Equation for a Solid Shaft
To calculate the diameter of the shaft we can, derive a equation from the torsion equation. And the equation below also can be used for calculating the bearable twisting moment of a give shaft.

Torque and the Diameter Equation for a Hollow Shaft
Even we most commonly use solid shafts, in some cases, we have to use hollow shaft. Since the polar moment inertia of a hallow shaft is kind of different,
