RC Helicopter Shaft Collar 2 x 4 x 12 HI2521131 by Hirobo  [HI2521131]

Shaft collar for model helicopter assemblies

This Hirobo collar is a compact RC-scale component intended for use in helicopter general parts where small axial retention is required. The part is identified as HI2521131 and referenced by the 2 x 4 x 12 marking; it serves to locate and hold components on short shafts in model rotor systems.

Fitting usually involves sliding the collar to the chosen axial position on the shaft, aligning adjacent parts, and securing with the model's chosen retention method. Ensure the mating surfaces are clean so the collar seats correctly and avoids any unnecessary play.

For routine checks and tuning the collar provides a simple positional reference to keep blade grips, gears, and spacers aligned. If you experience end play or abnormal vibration, inspect the collar seating and the clamp or screw method during your diagnostic process.