Light-Weight, Non-Contact Magnetic Transmission for UAV and Rotorcraft Applications

Speed reducing units consisting of mechanical gears are widely used in applications to match high speed prime movers to low speed loads. All aerospace applications of gearboxes require lubrication, maintenance, and overhaul; and are subject to eventually wearing out due to tooth surface wear and gear tooth fatigue. In many cases the requirements for gearbox lubrication, maintenance/overhaul and service life limits are acceptable; but in some extreme applications these requirements become a severe performance limitation. For example, high altitude long endurance missions (HALE) typically operate at an altitude greater than 60,000 feet and stay in flight for durations longer than 24 hours. HALE vehicles need a lightweight, highly efficient solution to operate slow moving propellers maintenance free for an extended period of time in an extreme environment. We are proposing to develop a magnetic gearbox technology that can meet the needs of these extreme applications. A magnetic gearbox has many advantages over a traditional mechanical gearbox. The different rotating components in the magnetic gearbox will never touch so the only lubrication required is in the bearing systems. The magnetic gearbox will be essentially maintenance-free except for periodic bearing lubrication/inspection. Vibrations that do not exceed the pull-out torque of the magnetic teeth do not add measurably to the mechanical stresses in the magnetic gearbox so fatigue issues will be minimal. If the pull-out (maximum) torque is exceeded the magnetic gearbox will simply skip a tooth and re-engage when the overload situation is resolved. In the present research we have demonstrated an experimental magnetic gearbox that achieves much higher specific torque than any previously demonstrated design.