Drum 2 rotates about fixed axis B. Cam 1 turns about fixed axis A and its working surface a is designed so that the cam is jammed between its axis and the rim of drum 2, braking the drum when it starts to rotate clockwise. When the drum rotates counterclockwise, its rim slides freely along surface a of cam 1. Cam 1 is held in contact with drum 2 by flat spring 3.
$3384$SmF,Br$