# Useful Equations for Shaft Design

## 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.

## 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,