Hirobo HI2521052 4 x 8 x 4 Shaft Collar for Helicopter Maintenance  [HI2521052]

Shaft Collar for Hirobo Models

This RC-scale replacement collar is listed under Hirobo helicopter general parts and is supplied as HI2521052. It functions as a small retention and spacing component for assemblies that require a 4 x 8 x 4 collar, intended for routine part replacement and maintenance on compatible Hirobo models.

The collar's purpose in a rotorcraft drivetrain or tail assembly is to keep shafts axially located and to reduce lateral play when used with the correct shaft and set-screw arrangement. When fitting a replacement collar, inspect adjacent components so the new collar restores intended alignment without introducing binding.

Installation is straightforward for technicians familiar with RC helicopter maintenance: remove the retaining hardware, inspect the shaft and neighbouring parts for scoring or looseness, fit the collar to the specified shaft section, and secure using the original fastener method. Verify free rotation and correct axial location during a low-speed bench test before flight.

For tuning and setup, collars like this permit fine axial spacing adjustments when aligning gear mesh or blade grips. Small changes in collar placement can affect tracking and vibration, so make incremental adjustments and record positions for repeatable setups.