Tower Safety Barber Lift

Math & Teaching Notes

Free-running equilibrium: Equal left/right static-line tension and load-side tension are solved simultaneously from ΣFx = 0 and ΣFy = 0.

Static-line compatibility: The model compares the prescribed loaded path with the entered installed rope length. A positive difference is required elongation; a negative difference indicates excess length or slack. The simulator does not assign rope properties—allowable elongation must come from the rope manufacturer or Qualified Person.

Pretension and anchors: Setup pretension is not added to the equilibrium tension. Anchor design demand is the greater of setup pretension or calculated loaded tension, representing separate setup and loaded conditions. Attachment direction, structure, sling configuration, connectors, soil and foundation capacity still require evaluation.

Model boundary: This is a two-dimensional static-equilibrium teaching model. Rope self-weight, true catenary curvature, rope stiffness, time-dependent constructional stretch, attachment movement, rolling resistance and dynamic trolley acceleration are not calculated. These effects require project-specific evaluation.

Friction: Top-pulley loss is applied first, followed by heel-pulley loss.

Fz: This is a coplanar model, so out-of-plane Fz is zero. A nonzero Fz requires lateral offset or azimuth geometry.

Tower Safety review triggers: The 2.00× static-line multiplier and 80% entered-WLL utilization levels prompt planning review. They are not ANSI force-ratio limits, manufacturer deratings, or substitutes for the Qualified Person's evaluation.

Wind: Wind above 30 mph at lift elevation is a stop-lift condition under the standard plan and requires the applicable ANSI/TIA-322-A evaluation and special engineered-lift parameters.