Hirobo HI2521123 Collar 4 x 5 x 4.3 shaft collar for RC helicopter assemblies  [HI2521123]

Shaft collar for helicopter assemblies

This HIROBO collar is an RC-scale shaft accessory named by its manufacturer code and dimensional mark-up, intended for locating and holding components along a model helicopter shaft. As a simple mechanical element, it provides a defined axial stop or spacer point so bearings, gears, linkages, or other small assemblies keep their intended positions during operation.

Installation is straightforward: position the collar on the model shaft where axial registration is required, then secure it using the model's existing retention method or a compatible fastener. Because designs vary between helicopter kits, verify fit against the shaft and mating parts before final tightening to avoid interference with rotating components.

In tuning and setup, collars like this are used to set endplay, maintain gear mesh alignment, and keep control linkages from shifting under load. Routine inspection for wear or loosening is recommended; replace the collar if you detect deformation or persistent slippage to retain reliable axial positioning.