Abstract
High-ratio compound stepped planetary transmissions are typically characterised by poor overall efficiencies, even if the individual mesh efficiencies are high, because of the very high sliding velocities imposed by the kinematics of their topologies. Here, a parametric exploration of the design space is presented for a stepped transmission topology, which is assessed in terms of transmission ratio, efficiency, and power density. It is confirmed that high ratio per (compound) stage is accompanied by low mechanical efficiency and/or large volume for the most part of the parametric design space, as is also anticipated by prior research. At the same time, specific niche regions of particular importance are identified that combine high-ratio, high-efficiency, and good power density.