5 - Shafts

Abstract

This chapter introduces the concepts of a shaft design. An overall shaft design procedure is presented, including consideration of bearing and component mounting and shaft dynamics. The chapter explains the general shaft arrangement, deflections and critical speeds, shaft dimensions for strength, and fluctuating load integrity. It outlines a shaft design procedure for a shaft experiencing constant loading. The chapter further gives an overview of shaft hub connection methods along with shaft to shaft connection methods, the determination of critical speeds, and the ASME equation for the design of transmission shafts. These analysis techniques for calculating the critical frequency require the determination of the shaft deflection. Moreover, the Macaulay method, which is suitable for calculating the deflection of a constant diameter shaft, and the strain energy method, which is suitable for more complex shafts with stepped diameters have been discussed in the chapter. Shaft design involves consideration of the layout of features and components to be mounted on the shaft, specific dimensions and allowable tolerances, materials, deflection, frequency response, life, and manufacturing constraints. The use of steps and shoulders, and miscellaneous devices to locate components, methods to calculate the deflection of a shaft and its critical speeds, and a method to determine the minimum safe diameter for a shaft experiencing torque and bending for a given life have also been elaborated in the chapter.