Hirobo HI2521072 Shaft Collar 3 x 4 x 4.1F for Helicopter Parts  [HI2521072]

Shaft collar overview

The HI2521072 is an RC-scale shaft collar listed among Hirobo helicopter general parts. Its sizing of 3 x 4 x 4.1F is the reference used to match shaft diameter and axial spacing when assembling a model rotor system.

The collar locates and retains components along a shaft, helping control axial position and minimizing unwanted end-play. It functions as a compact spacer and locator where precise spacing is important, such as between gears, bearings, or linkages in a helicopter drivetrain.

Installation notes for model use: check the shaft for burrs or debris, slide the collar into the required position, and secure it following the model's original fastening method. For tuning, move the collar in small steps to adjust blade linkage geometry or correct minor axial misalignment, verifying free rotation on low-speed bench checks before flying.