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

Precision Collar for Rotor Assemblies

This item is an RC-scale replacement collar listed under Hirobo helicopter general parts, identified as HI2521052. It serves as a compact retention and spacing element where a 4 x 8 x 4 collar is specified and is suitable for routine part changeouts on compatible Hirobo machines.

In rotor and tail drive systems the collar maintains axial shaft position and reduces lateral play when paired with the proper shaft and set-screw setup. Replacing a worn collar should be accompanied by a quick check of nearby gears and bearings so the new collar can restore alignment without causing binding.

Fitting is simple for those experienced with RC helicopter work: remove the existing fasteners, inspect the shaft and adjacent components for wear or damage, slide the collar into place on the specified shaft section, and secure it using the original fastening arrangement. Conduct a low-speed bench spin to confirm free rotation and correct axial placement before flying.

Use collars like this during tuning to fine-tune axial spacing when setting gear mesh or blade grip locations. Even minor adjustments in collar position can change tracking and vibration, so proceed in small steps and document each setting for consistent results.