A flywheel system including a rotor shaft. The rotor shaft includes an inner passage therethrough, and a dam with a central opening disposed on a first end of the inner passage. An outer passage surrounds the inner passage. The inner passage is open at a second end, and the outer passage is closed on an end surrounding the second end of the inner passage. The outer passage is open on an end surrounding the first end of the inner passage. Fluid flows into the inner passage at the first end, via the central opening of the dam. Rotation of the flywheel rotor causes the fluid to accumulate along a wall of the inner passage, and to propagate to the second end, where the fluid exits into the outer passage. The fluid propagates along the outer passage to the open end of the outer passage, where it is released.