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

Component description and fit

This HI2521072 collar appears in the Hirobo helicopter general parts range and is sized 3 x 4 x 4.1F to help you match shaft diameter and spacing in a model rotor assembly. The size code is the key reference when checking fit.

Functionally the collar keeps components positioned along a shaft, reducing axial play and helping maintain consistent linkage geometry. It serves as a small locating spacer for precision placements between bearings, gears, or link joints in the drivetrain.

For installation, clear the shaft of any burrs or contaminants, slide the collar to the desired location, and fasten it as per the original method. When tuning, adjust the collar slightly and recheck link movement and rotation on the bench before any flight attempts.