Hirobo HI2521107 Collar 3 x 5 x 5.1F shaft collar for RC helicopters  [HI2521107]

Shaft collar for small helicopter shafts

This Hirobo HI2521107 collar is presented as a compact RC-scale shaft collar intended for helicopter parts maintenance and tuning. The product is identified by the dimensional code 3 x 5 x 5.1F which serves as the reference size for matching shafts and components. The item functions as a location and retention element on a shaft where a collar is required to set axial position or to act as a spacer between components.

Practical use focuses on compatibility checks and installation behavior: confirm that the receiving shaft or assembly accepts a collar with the 3×5×5.1F footprint before fitting, slide the collar into place at the required axial location, and use the existing retaining method on your model to secure it. Because manufacturer material details are not specified in the source, inspect the part on receipt or consult the seller for material and hardness if that affects your setup.

The collar is useful during tuning when precise component spacing matters, for example when trimming shaft-end clearance, aligning gear meshes, or stabilizing small assemblies on helicopter rotor linkages. Keep replacements and spares labelled by dimension codes to avoid mixing sizes during repairs.