The machined groove profile on the drive sheave surface that grips the elevator wire ropes through friction to transmit drive force.
Full Definition
The traction sheave groove is the interface between the drive machine and the wire ropes — it must generate sufficient traction (friction) to drive the car and counterweight without rope slippage. Three groove profiles are used: semi-circular (U-groove) gives the lowest contact pressure and longest rope life but least traction; undercut U-groove increases traction by reducing the rope contact area; and V-groove provides the highest traction but greatest contact pressure and fastest rope wear. The groove material (typically cast iron or hardened steel) and surface finish are critical. As grooves wear with rope movement, the traction coefficient changes; EN 81-20 requires traction calculations to verify adequate grip across all loading conditions. Grooves are periodically recut or the sheave replaced when wear exceeds permitted limits.
