The precision steel spindle on which a deflection or secondary sheave is mounted and supported by bearings.
Full Definition
The elevator sheave shaft is the precision-machined steel shaft (spindle) that forms the rotational axis of a deflection sheave or secondary sheave assembly. The sheave shaft transmits the resultant bearing reaction forces from the rope loads to the machine bedplate or structural support frame via the bearing housings. In deflection sheave assemblies the shaft is typically non-rotating (dead shaft configuration), with the sheave hub rotating on bearings mounted on the shaft; in some designs the shaft rotates with the sheave (live shaft) and is supported in fixed bearing housings. Sheave shaft material is medium-carbon steel (e.g., C45 per EN 10083) or alloy steel (e.g., 42CrMo4) heat-treated to the specified hardness and surface finish to ensure bearing seat dimensional stability over the design life. The shaft is dimensioned to limit the maximum combined bending and torsional stress to below the material fatigue limit, incorporating an adequate safety factor per the relevant machinery directive design calculation. Shaft deflection at the bearing mid-span is calculated to not exceed the allowable bearing misalignment, typically 0.001 radians for deep-groove ball bearings. Shaft inspection at overhaul includes magnetic particle testing of the fillet radii at bearing seat steps, which are the highest-stress regions susceptible to fatigue crack initiation.
