XRB SR Lower Rotor Head Assembly L=125 - Hirobo HI0301041  [HI0301041]

Replacement lower rotor head for XRB SR models

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 serves as the lower hub where blade grips and the lower swash linkage interact, so its condition directly affects rotor tracking and cyclic response.

Installation guidance: verify fit against existing upper and lower linkages before final assembly, check that blade grip orientation matches the original geometry, and inspect nearby ball bearings and link pins for wear. Use the helicopter manufacturer’s recommended fastener torque and secure fasteners with the appropriate medium-strength threadlocker if needed.

Tuning role: replacing a worn lower rotor head can reduce slop in the rotor system and make pitch inputs more immediate, which assists in trimming and cyclic tuning during flight testing. After installation, perform static tracking and a hover test at low throttle to confirm correct assembly and rotor balance.