Abstract: The machines of the present invention are adapted to brake a rotor or pulley by the action of centrifugal weights or units which are arranged to produce a reactive braking action on the rotor or pulley. In one application, the machine constitutes a fire escape pulley device including a pulley on which a cable is wound to rotate the pulley under the load of a person suspended by the cable. A rotor bodily rotates with the pulley, a stationary annular cam is arranged around the rotor and defines a radially undulating cam surface facing radially inward toward the rotor, and one or more centrifugally responsive units are radially displaceable on the rotor to be centrifugally biased into rotation reactive engagement with the undulating cam surface.