The method of motion of a planetary gear structure is different from traditional parallel gears. Combined with the electric motors are planetary gear sets. The planet carrier is the central part of a planetary gear set. The 3L80HD has a straight-cut planetary gear set. The robot's waist gyrated sexily using a planetary gear. It also possible to use double row planetary gear combinations. The planetary gear carrier is used as input. For reduction it had an integrated planetary gear. The efficiency loss in a planetary gear train is typically about 3% per stage. The Lepelletier gearbox is constructed by connecting a planetary gear to a Ravigneaux gear. The converter now incorporated two turbines and a planetary gear set, with a single stator. The RDS is a fully automatic planetary gear transmission with a lock-up torque converter. Its transmission was a planetary gear type billed as "three speed". The planetary gear and the torsional damper are incorporated into the main flywheel. One popular use of 3D printed planetary gear systems is as toys for children.