Skills · skill
Rigging a Load with Pulleys
Rigging · Intermediate
- Difficulty
- Intermediate
- Done When
- The load rises smoothly at the calculated fraction of the pull, holds when you stop, and everything is within its rating.
- Tools
- Two or three pulley blocks rated above the load, rope, slings and shackles, a rated anchor point, gloves.
- Category
- Rigging
- Summary
- Lifting or pulling more than you can by hand by trading distance for force with blocks and rope.
Safety
Anything under load can fail explosively; stand clear of the line of pull. Rated hardware only, no home-made anchors. Rope burns are serious.
Steps
Rate everything: rope, blocks, shackles, anchor — the weakest is the limit, and it takes the load plus your pull.
Reeve a 3:1: anchor a block, run the rope from the load's block up and back; count the segments holding the load.
Haul; the load moves a third as far as your hand.
Add a redirect at the anchor to pull downward if that is easier — it changes direction, not advantage.
Progress-capture with a prusik or a locking block before you let go.
Lower under control; never let the rope run.
The Science
A pulley changes the direction of a force; several of them, reeved so the load hangs from n rope segments, divide the force by n and multiply the distance by n — mechanical advantage, at the price of friction in every sheave (a few percent each). Newton's second law and the tension in the rope do the accounting: the load is shared equally by every segment supporting it. The anchor sees the load plus the pull.
How It Fails
An anchor that pulls out because it was sized for the load, not the load plus haul. Rope jumping a sheave. Losing the load when someone lets go without capture.
Open on the Skills shelf — the interactive card, the filters, and everything alongside it.