Gear 1 is keyed to shaft a, rotates about fixed axis A-A and meshes with planet gear 2 which is keyed, together with planet gears 5 and 6, to a stud. Planet gears 2, 5 and 6 are connected, through the stud, by a turning pair to carrier 3 which rotates about axis A-A. Planet gear 5 meshes with gear 8 which is keyed to shaft b. Planet gear 6 meshes with gear 7 of brake drum 4 which rotates freely about shaft b. Forward rotation is transmitted from shaft b to shaft a by braking carrier 3, and reverse rotation by braking drum 4. For shafts a and b to be coaxial, the numbers of teeth of gears 1, 2, 5, 6, 7 and 8 should satisfy the conditions (if the gears have the same module): z₁+z₂=z₅+z₈=z₆+z₇. The speeds n₁ and n₈ of shafts a and b (in rpm) are related in forward rotation by the equation n₈=n₁(z₁z₅)/(z₂z₈) and in reverse rotation by the equation n₈=-n₁(z₁/z₈)((z₆z₈-z₅z₇)/(z₂z₇-z₁z₈)) where z₁, z₂, z₅, z₆, z₇ and z₈ are the numbers of teeth of gears 1, 2, 5, 6, 7 and 8.
$2909$CxG,DR$