A 3D Multibody Model for the Investigation of the Chain Drive Derailment between Sprockets

The study carried out deals with a kinematic and dynamic multibody analysis of the motion of roller chain drive: the main novelty of our investigation is the possibility of studying the 3D chain motion. Although roller chains have been traditionally employed to transmit power, nevertheless only in the last decades their complex dynamical behaviour has been studied. There are several multibody dynamics models concerning chain drives, but most of the contributions regard planar motions of the links. The 3D multibody model allowed us to investigate the chain derailment between two sprockets with the aim of optimising the system throughout different design changes. The change time of the transmission ratio, due to the chain derailment between two sprockets, constituted the most relevant variable in the optimisation of the system. Particularly, we analysed the 3D derailment motion on the basis of the contact 3D study between different bodies. We applied Bullet Physics as the software of the implementation. It is an open source physics engine featuring 3D collision detection, soft body dynamics and rigid body dynamics. Although the software is usually applied to such fields as games and film visual effects, we adapted the program to engineering studies by changing the solver parameters. We applied an innovative approach for an accurate, fast and robust integration of the equations of mechanical systems motion: the sequential impulse solver [4]. In this respect, some authors have emphasised that the sequential impulse solver allows a quick and stable simulation for several bodies. Indeed, the sequential impulse strategy proved competitive with the other methods in terms of computational efficiency and accuracy of the results. In addition to other advantages, the sequential impulse solver offers a plain program structure, as well as the possibility of simulating complex models, like the chain systems that represent extremely complex instances of contact between different bodies, such as bushings and plates.