Development of Test Facility for Interconnected Drivesystem of a Tandem Rotary Wing UAV

This work presents the development of an interconnected gearbox drive system for a tandem rotor unmanned aerial vehicle (UAV) designed for a power rating of 20 kW per rotor. Development of the facility for dynamic testing of the interconnecting drive system is also presented. Tandem rotor configurations offer superior payload capacity and aerodynamic efficiency but pose challenges in transmission design due to the need for synchronized power distribution between counter-rotating rotors. The proposed gearbox employs a simple two-stage reduction system combining bevel and planetary gears to achieve compactness, high torque transmission, and ease of fabrication. A dedicated test rig is concurrently being developed to evaluate gearbox performance under variable torque and speed conditions for the first stage with the mechanical interconnection. The test set-up integrates a variable-speed drive, torque and vibration sensors, and a data acquisition system to measure efficiency, losses, and thermal characteristics. While fabrication and assembly are ongoing, this work lays the foundation for experimental validation and optimization of drivetrain performance. The project contributes toward developing reliable, lightweight, and scalable transmission solutions for heavy payload multi-rotor vertical lift UAVs. The drive system dynamics, in particular, the torque transmission through the cross shaft during maneuvers will be the investigated using the current test rig configuration.