The subject matter of this specification can be embodied in, among other things, an actuator that includes a worm drive assembly having a worm shaft, and a worm wheel configured as a ring having a radially outer perimeter comprising a first collection of gear teeth extending radially outward from the radially outer perimeter and at least partly engaged with the worm shaft, and a coaxial radially inner perimeter comprising a second collection of gear teeth extending radially inward from the inner perimeter, and an epicyclic gear assembly having a sun gear and a planet gear engaged with the sun gear and the second collection of gear teeth.