A Computer Aided Design for Internal Spur and Helical Gears


This research describes an interactive program to design internal gear pairs. From a specification, the program first performs a kinematic analysis to determine tooth numbers and to satisfy centre distance requirements, and then proceeds to calculate the face width. It is possible to call up any design standard in order to stress the gears; that used here is the British standard. Calculated face widths are compared with practical design and, if outside accepted bounds, the program will alter tooth numbers, or module or request a change in gear material.
A complete design is provided, which includes all the necessary information for manufacture. The design specification places tight tolerances on centre distances and/or gear ratios; the program automatically makes the required centre distance arid tooth profile corrections. On every occasion the program will find a satisfactory solution, or guide the user towards one. The program is flexible and allows the experienced designer maximum freedom to direct the design. The program contains many built-in databases, such as standard tooth cutters and material properties, and will draw the gear pair if required.
The research describes the design method and the structure of the program and a sample design is given and compared with a manual design to the same requirement