Pulley systems — mechanical advantage
| System | Mechanical advantage |
|---|---|
| 1:1 | Single fixed pulley — no advantage, only redirects the load. |
| 2:1 | One moving pulley at the load — pull twice the distance for each metre of load lifted. |
| 3:1 | One fixed + one moving pulley — pull three times the distance. |
| 6:1 | Compound system — pull six times the distance. |
| 9:1 | Compound system with additional redirect — pull nine times the distance. |
The higher the mechanical advantage, the less force the operator applies — but the more rope must be pulled through the system.
Block-and-tackle — one third the force, three times the rope
Theoretical MA
3: 1
Real MA
2.77: 1
92% efficient
Input force
0.36kN
to lift 1 kN
Rope per metre
3m
pulled / lifted
For a 10 m lift: pull 30.0 m of rope through the system; budget ≈ 33.0 m of working line (incl. 10% overhead for tails and progress capture).
Good efficiency