An energy extraction system for a rotational surface including a drive mechanism having a rotational axis and configured to rotatably couple to the rotational surface and an energy extraction mechanism coupled to the drive mechanism. The drive mechanism includes a cam rotatable about the rotational axis and an eccentric mass coupled to the cam that offsets a center of mass of the drive mechanism from the rotational axis, the eccentric mass cooperatively formed by a first and a second section, the eccentric mass operable between a connected mode wherein the first and second sections are adjacent and a disconnected mode wherein the first and second sections are separated. The energy extraction mechanism is connected to the cam and is statically coupled to the rotating surface, wherein the energy extraction mechanism configured to extract energy from relative rotation between the energy extraction mechanism and the cam.