For Hirobo Helicopters: HI2521054 9x11x5 Blade Holder Collar  [HI2521054]

Main rotor bearing collar for Hirobo helicopters

This RC blade holder bearing collar is intended for use with Hirobo helicopter blade holder assemblies. The 9x11x5 mm collar serves as a locating and retention sleeve around the main rotor bearing, securing the blade hub while permitting free bearing rotation.

Builders and pilots use this collar when precise bearing seating impacts blade tracking and pitch response. It is a simple replacement option for worn collars that lead to excess play or inconsistent blade runout.

Installation notes: verify the bearing is fully seated before fitting the collar, ensure mating surfaces are clean, and slide the collar into place without forcing it to prevent damage to the bearing races. After fitting, perform checks for axial and radial play and confirm blade tracking at low throttle before flight.

Tuning role: when fitted correctly the collar helps maintain blade alignment, which produces more consistent pitch changes and smoother cyclic feel, lowering the need for continuous trim adjustments during tuning.