Design space exploration of pericyclic transmission with counterbalance and bearing load analysis

The pericyclic transmission provides the opportunity to vastly impact transmission design in rotorcraft due to its ability to provide exceedingly high reduction ratios in a single stage that would normally require multiple gear stages. This could lead to lighter transmissions with fewer components, increased reliability, efficiency, speed and decreased cost to maintain. While many previous studies have focused upon the gearing within the pericyclic transmission, this work focused on what influences pericyclic geometry, and how changes in geometry impact bearing loads. Specifically, the loading of bearings that must deliver power from the input shaft to the nutating and rotating gears of the system were of primary concern. A comprehensive look at dynamic loads generated by nutating bodies was performed. Methods to address these dynamic loads via application of counterbalances, and deviation from conventional pericyclic transmission designs were utilized to negate the dynamic moment of concern. Counterbalances negating the dynamic moment were shown to weigh between 30-50% of the pericyclic motion converter gears in a 40:1 reduction ratio pericyclic design at 12,000 rpm input speed and reduced applied moments by three orders of magnitude. Finally, a static solver was used to determine the bearing loads with updated component geometries and mass moment of inertias that included the required counterbalances.