ROTATIONAL CONTROL APPARATUS

rotational control apparatus in the form of fan clutches (C) are disclosed including a first, fric- tion disc portion (12) splined on a hub (20) in turn rotatably mounted on a shaft (24). The friction disc portion (12) is reciprocal between a first position ro- tatably related to the facing (52) of a sheave (50) ro- tatably mounted on the hub (20) and a second posi- tion rotatably independent of the sheave (50). In a preferred form, a second friction disc paction (212) is splined on the hub (20) and is reciprocal between a first position rotatably related to the facing (252) of a second sheave (250) rotatably mounted on the hub (20) and rotating at a different rotational speed than sheave (50). By the selective engagement of the fric- tion disc portions (12, 212), the hub (20) will be rotat- ed on the shaft (24) at either the rotational speed of the first sheave (50) or the second sheave (250). In a further preferred form, a second, friction-disc por- tion (112) is rotatably mounted on a reciprocal piston (100) and rotatable relative to the hub (20). Planetary gears (114) are rotated intermediate and in gearing relation between a sun gear (96) fixed on the shaft (24) and an annulus (124 ) fixed to the hub (20). The second, friction disc por- tion (112) is reciprocal between a first position rotatabty related to a facing (152) secured to the sheave (50) opposite to the facing (52). By the selective engagement of the friction disc portions (12, 112), t he hub (20) will be rotated on the shaft (24) at either the rotational speed of the sheave (50) or at a rotational speed different than the sheave (50) and'specifically at a rotational speed de- pendent on the ratio of the planetary drive.