There are power transmission shaft systems consisting of many belts and gears in automatic teller machines. In these systems, parts may be modeled by two-dimensional structures and may often be drawn by two-dimensional CAD systems. This paper presents an effective transmitted-torque analytical method for the power transmission shaft systems of drive-bill carrying machines. The main results are: (1) The driving-driven relationship of a power transmission system is introduced by a combination of motor, belts, pulleys, gears and shafts. (2) Using this relationship, a tree model is composed which defines the power transmission route. (3) Transmission torque and driving torque are calculated by adding the transmission torque of the lower layer in the tree model. The processing is carried out interactively in a two-dimensional CAD system.
