Hirobo HI2521072 COLLAR 3 x 4 x 4.1F shaft collar for helicopter parts  [HI2521072]

Shaft collar for helicopter parts

This HI2521072 collar is an RC-scale shaft collar intended for helicopter general parts under the Hirobo lineup. The part name carries its sizing as 3 x 4 x 4.1F, which is the reference used when matching the collar to shafts and adjacent components in a model rotor assembly.

Functionally the collar serves to locate and retain components along a shaft, helping control axial position and reduce unwanted end-play. It is a small mechanical spacer and locating piece used where precise spacing matters, such as between gears, bearings, or linkages in helicopter drivetrains.

Installation notes for model use: inspect the shaft for burrs or debris, slide the collar into the required position, and secure it according to the model's original fastening method. For tuning, move the collar incrementally to adjust blade linkage geometry or to correct minor axial misalignment, verifying movement under low-speed bench checks before flight.