A phenomenological model for chain transmission efficiency

This work deals with the development of a simplified and time-efficient phenomenological model for chain transmissions efficiency. Firstly, a complete multibody model for a final transmission of a motorcycle is developed in MSC Adams View environment, and is properly validated in terms of efficiency with experimental tests on a real chain system. Results from multibody simulations are used to develop a new analytical model, that relates all the main operating and geometry parameters of the transmission system to the transmission efficiency with simple relations. In particular, the influence of the polygonal effect on system efficiency is investigated, finding a relationship with the angle of the sprockets pitch polygon. A new parameter, called chain tension efficiency, is introduced to model the distribution of losses within the system. A linear relationship between this parameter and the number of sprockets teeth and with the system efficiency was assumed and validated, with good results. In addition, the dependence of slack span tension from several parameters, like speed, torque and number of teeth of sprockets, is investigated. In particular, it is highly dependent on the chain peripheral speed, both for a centrifugal tension and for a further linear component of tension, which might be originated by friction between links. The presented simple model can describe the chain system dynamics with low computational effort, allowing the designer to use a smart tool to select the proper transmission parameters. Due to its computational efficiency, the model is also useful for real-time and hardware-in-the-loop simulations.