Hirobo HI0301041 Lower Hub L=125 for XRB SR  [HI0301041]

Lower hub assembly suitable for XRB SR

This lower rotor head assembly is an RC-scale replacement part designated by Hirobo as HI0301041 and identified for use with XRB SR series helicopters at length L=125. The component acts as the lower hub where blade grips and the lower swash linkage meet, so its condition directly influences rotor tracking and cyclic response.

Installation guidance: check fit against both upper and lower linkages before final tightening, ensure blade grip alignment matches the original geometry, and inspect surrounding ball bearings and link pins for any wear. Follow the helicopter maker’s recommended fastener torque and, if required, apply a medium-strength threadlocker to secure fasteners.

Tuning role: fitting a new lower rotor head can reduce play in the rotor system and make pitch commands more immediate, aiding trimming and cyclic adjustments during test flights. Once installed, carry out static tracking and a low-throttle hover test to confirm correct assembly and rotor balance.