The information presented in this blog post is for educational purposes only. It should not be used for engineering design or relied upon as engineering advice.
This EngineeringPaper.xyz sheet (see below or open in a new browser window) shows how to calculate the torque and shear stress in a power transmission shaft based on the input power in horsepower and the input velocity in revolutions per minute (rpm). This example also illustrates how to work with angular velocity units in EngineeringPaper.xyz, which require some special attention to eliminate the radians unit in the resulting quantities.
This example assumes a circular cross-section for the transmission shaft. See this blog post for an example that allows several different cross-section geometries to be evaluated.