Hirobo HI2521052 4 x 8 x 4 Collar Replacement for Helicopters  [HI2521052]

Replacement Collar Compatible with Hirobo

This RC-scale collar is catalogued under Hirobo helicopter general parts as HI2521052. It is intended as a small retention and spacer piece where a 4 x 8 x 4 collar is specified, used for routine replacement and servicing on compatible Hirobo units.

In rotor and tail systems the collar maintains the axial position of shafts and limits lateral movement when combined with the appropriate shaft section and set-screw arrangement. When replacing the collar, examine nearby bearings and gears so the new collar can restore correct alignment rather than masking other wear.

Fitting is a standard maintenance operation: remove retaining hardware, inspect the shaft and adjacent parts for wear, place the collar on the required shaft segment, and secure according to the original fastening method. Carry out a slow bench test to ensure free spin and proper axial placement prior to flight.

Use collars like this during setup to fine-tune axial spacing for correct gear mesh and blade grip alignment. Make measured adjustments and keep notes so setups can be repeated accurately.