Eagle/Freya/EX/SX Counter Gear 18T - HI0404639 by Hirobo  [HI0404639]

Function and fitment of the counter gear

This Hirobo HI0404639 counter gear is an RC-scale service part designed for pipe drive configurations on Eagle-family rotorcraft. The part operates as an intermediate gear in the transmission train, transmitting rotation from the pipe drive to the main gearbox while keeping model-scale alignment.

Compatibility is determined by the gear's intended use in Eagle, Freya, EX and SX platform variants, so it is suitable as a spare when an original counter gear becomes worn. The 18T marking denotes the 18-tooth count required to match correct gear mesh and centre distances in the pipe drive set-up.

Installation notes: seat the gear onto the counter shaft with correct axial alignment, confirm engagement with the mating spur or intermediate gears, and refit retaining hardware to the specified torque where applicable. When replacing this gear, inspect surrounding bearings and shafts for endplay that can accelerate tooth wear.

Tuning and maintenance: aim for a light but fully engaged mesh pattern to prevent early wear, check tooth faces for chips after hard impacts, and apply lubricant suited to model gear trains. Regular checks and timely replacement of a worn counter gear will maintain drivetrain efficiency and reduce in-flight vibration.

Compatibility

• Eagle
• Freya
• EX
• SX