Abstract: A centrifuge includes a frame, a hollow spindle supported by the frame for rotation about an axis, a bowl including a shell fixed to the spindle for rotation with the spindle, a shaft situated within and movable with respect to the hollow spindle, and a conveyor fixed to the shaft including a scroll situated adjacent an inner surface of the bowl shell. A harmonic drive unit including a housing is fixed to an end of the hollow spindle, the housing containing a circular spline fixed to the housing. The harmonic drive unit also includes a flexspline gear ring situated within and engaged with the circular spline, the flexspline gear ring being fixed to the shaft situated within the hollow spindle. The harmonic drive unit also includes a wave generator positioned within the flexspline gear ring for displacing the flexspline gear ring with respect to the circular spline. A brake rotor is coupled to the wave generator.