An apparatus using differential gearboxes to collect, combine, and transmit torque generated by multiple, interconnected rotor systems. The rotor systems are connected via a driveshaft. The driveshaft is connected to a generator gearbox, and the generator box drives an electrical generator. The torque may be converted to mechanical power by replacing the electrical generator with a mechanical power device. The rotors are activated by fluid currents such as wind or water.