A fixed grooved wheel in the machine room that redirects suspension ropes from the drive sheave down into the hoistway at the correct geometry.
Full Definition
When the drive sheave and the car/counterweight attachment points are not in perfect vertical alignment, a deflector sheave is installed to change the rope angle. It is a passive, non-driven wheel with grooves matching the rope diameter. The wrap angle between rope and drive sheave — critical for traction — is maintained by the deflector sheave position. Bearings must be lubricated and periodically inspected. EN 81-20 recommends that the pitch diameter of any secondary sheave is not less than the drive sheave diameter to limit rope bending fatigue.
