a rotor for a propulsive thrust device comprises a hub having a peripheral surface ; a plurality of rotor blades received at the peripheral surface of the hub ; a first bearing assembly located in the hub and around a shank of a respective rotor blade to support the rotor blade in the hub under centrifugal loading and to allow the rotor blade to rotate about a longitudinal axis ; and a second bearing assembly located in the hub and around a shank of a respective rotor blade and inward of the first bearing assembly to preload the first bearing assembly . a preload bearing assembly comprises an outer race ; a plurality of rolling elements located therein ; and a plurality of studs located in communication with the outer race . adjustment of the studs distributes a tensile load around the outer race to exert a preload force on a bearing assembly supporting the rotor blade .