Keyed to the driving shaft is hub 2 with radial vanes a. Drum 1 is keyed to the driven shaft and is filled to some extent with steel balls 3. Hub 2 and drum 1 rotate about fixed axis A. When the driving shaft rotates, balls 3 are held by inertia in an annular layer inside the drum which they rotate by friction. Lugs are provided on the inside surface of the drum to increase the frictional effect.
$3406$SmF,C$