ESDU Mechanisms Series

This Series covers methods and data for the design and analysis of cams, gears, linkages and Geneva mechanisms, and also includes contact stress estimation.

A comprehensive set of inter-related Items in the cams area covers selection of cam and follower type, selection of cam laws, both trigonometrical and polynomial, kinematic analysis, estimation of basic dimensions and the blending of cam profiles. Blending is used to accommodate an intermediate cam displacement precision point or a constant velocity component of motion, or to achieve a cam design optimum such as a reduced segment angle, a reduced reference circle radius or an increase in follower lift. The cam methods also include selection of materials, manufacturing methods and lubricants and further provide an estimation of contact stress and lubricant film thickness.

Methods for the design of parallel axis straight spur and helical gears include the choice of materials, a preliminary estimate of major dimensions and geometric design. A method for the calculation of contact and root bending stress limitations, compatible with BS 436: Part 3 is also provided. The kinematic design of epicyclic gear trains, limited to a consideration of the kinematics and the efficiencies of the gear trains, is also included.

Linkage data includes the analysis and synthesis of the complete range of four-bar linkages, including crank-rocker, slider-crank, parallel-coupler and swinging-block. The force analysis of linkages presents analytical methods used to estimate numerical values of reaction forces at joints that connect links of single degree-of-freedom, planar, multibar linkage mechanisms. Other Items provide balancing procedures for planar linkages including comparison of the various techniques for force balancing, procedures for force-balancing using counterweights and rotating counterweights and methods for the reduction of torque fluctuation in drive shafts.

A complete analysis procedure for the design of internal and external Geneva mechanisms is provided, including a derivation of the basic relationships for kinematic and kinetostatic design, estimation of the forces and torques, evaluation of contact stress and calculation of the lubricant film thickness including identification of the lubrication regime.

Further Items provide estimation methods for the evaluation of contact stress for a general contact with purely normal loading or with combined normal and tangential loading for gross sliding conditions. The methods allow a complete map of the contours of contact stress within the contacting bodies to be constructed and apply strictly only to dry contacts but are valid for boundary lubrication and for the limiting case of very thin films in elastohydrodynamic lubrication.