Tower Safety Rigging Lab • Lift #9

3:1 Mechanical Advantage with Change of Direction

NORMAL — Training Range
Rope path: Knot at load → Top Pulley #1 → Traveling Pulley → Top Pulley #2 → Heel Pulley → Capstan Winch. Three rope parts support the load; the heel pulley redirects only.
3 to 1 mechanical advantage with change of direction
1 Knot at Load → 2 Top #1 → 3 Traveling → 4 Top #2 → 5 Heel COD → 6 Winch
Rope tension Resultant Fx Fy

Main Inputs

Load Standoff Presets
Advanced Setup & Equipment Ratings
Ground Geometry
Optional Tag-Line Geometry
Arrow length is proportional to force and automatically capped to keep the diagram readable.

Primary Results

Required Capstan Pull0 lb
Top Pulley #1 Load0 lb
Top Pulley #2 Load0 lb
Heel Pulley Load0 lb
Geometry / MA RiskNORMAL
Load Side-Force RiskNORMAL
Equipment Utilization RiskNORMAL
Engineering Inspector
Geometry-Available MA0.00×
Actual MA after Loss0.00×
Dynamic Gross Load0 lb
Segment T1 — Knot to Top #10 lb
Segment T2 — Top #1 to Traveling0 lb
Segment T3 — Traveling to Top #20 lb
Segment T4 — Top #2 to Heel0 lb
Segment T5 — Heel to Winch0 lb
Traveling Pulley Load0 lb
Load Assembly Fx / Fy0 / 0 lb
Tag-Line Fx / Fy0 / 0 lb
Top #1 Fx / Fy0 / 0 lb
Top #2 Fx / Fy0 / 0 lb
Heel Fx / Fy0 / 0 lb
Rope Utilization0%
Top #1 Utilization0%
Top #2 Utilization0%
Traveling Connection Utilization0%
Heel Utilization0%

Live Teaching Warning

NORMAL — Forces are within selected training limits.

Verify the complete lift plan, equipment ratings, attachment points, load control, and field conditions.

Calculation Method

Geometry roles: load standoff controls the three load-supporting rope directions; heel-pulley height controls the Top #2-to-heel direction; heel-to-capstan distance controls the heel-pulley exit direction. An optional tag line is treated as an external load-control force and does not create mechanical advantage.

The load is supported by the rope termination at the load plus the two rope forces acting through the traveling pulley. The engine resolves each segment direction, distributes total system loss across the four pulley stages, solves load-side tension from vertical equilibrium, and calculates each pulley reaction from its incoming and outgoing rope vectors.

Teaching model: pulley losses are represented by equal stage efficiencies. Geometry and side-force warning bands are educational review thresholds, not equipment ratings or substitute engineering criteria. Manufacturer data and project-specific engineering govern actual field use.