Rigging Physics in Technical Rope Rescue
In low-angle and high-angle rope rescue, mechanical advantage systems reduce the physical force required to haul a litter, rescuer, and patient up a vertical face. While Theoretical Mechanical Advantage (TMA) counts tension lines, friction across prusiks, edge rollers, and pulley sheaves introduces practical mechanical resistance.
Common Haul Rig Configurations
- 2:1 Simple System: Traveling pulley attached directly to the load anchor; rope anchored at the top. Haul force is half the load weight.
- 3:1 Z-Rig (Simple): Industry standard for wilderness and trench rescue. Traveling pulley grips the main haul line via a friction hitch (progress capture), creating a 3:1 force multiplier with minimal hardware.
- 4:1 Piggyback (Compound): A 2:1 system pulling another 2:1 system, reducing haul space requirements in tight industrial vaults.
- 5:1 Complex Rig: Ideal for deep well extractions with small team staffing (2 haulers instead of 6).