Hirobo HI2521052 Collar 4 x 8 x 4 — Helicopter Spare  [HI2521052]

Maintenance Collar for Hirobo Helicopters

Listed as part of Hirobo helicopter general parts, this RC-scale collar is supplied as HI2521052 and fits assemblies that call for a 4 x 8 x 4 collar. It acts as a retention and spacing piece for service and replacement tasks on compatible Hirobo airframes.

Within rotor drivetrain or tail arrangements the collar secures axial positioning of shafts and reduces side-to-side movement when used with the correct shaft section and set-screw configuration. When installing a replacement, check nearby gears and bearings to make sure the new collar does not introduce binding or misalignment.

Installation is routine for experienced technicians: remove the retaining hardware, assess the shaft and neighbouring components for damage or play, position the collar on the specified shaft area, and secure it with the original fastening method. Always perform a low-speed bench test to confirm correct axial placement and free rotation before returning the model to service.

During setup and tuning, collars are a simple way to make small axial adjustments that affect gear engagement and blade grip alignment. Make changes incrementally and log settings to reproduce preferred behaviour.