The 3:1 Z-Rig is one of the quintessential mechanical advantage system used by rescuers. This system when offset requires 1/3 of the rope than the 4:1 block and tackle system.It can be converted easily to a 6:1 compound by the addition of a single pulley and is a powerhouse due to its ability to be modified while loaded if progress capture is in place.
With a few modifications the Z-Rig can give a Rescue Team as much as a 22:1 Mechanical Advantage. The Z-Rig is reasonably easy to rig, is easy to add a progress capture device and provides an appropriate amount of mechanical advantage to raise one or two people.
This system is paramount to a rescuer’s arsenal and will unlock true stroke advantage with minimal rope consumption while offering a multitude of benefits both vertically and horizontally.
Construction of the Z-Rig
1:1 Change Direction (CD)
When constructing a Z-Rig always start in the #2 Hole of the rigging plate. This will allow for additional mechanical advantage through the process of adding a 2:1 later if needed.
Start off by placing a carabiner attached to a prusik minding pulley in the #2 hole of a rigging plate.
Run a rope from the load or direction of the load through the pulley and back toward the load.
This creates a 1:1 CD
1:1 CD with "Progress Capture"
Add a "Progress Capture Device" such as a Tripple Wrapped Prusik in order to hold the load while resetting the system.
1:1 CD with Progress Capture and added pulley & carabiner
Add an additional pulley and carabiner in order to grab the load line. Run the rope through the pulley back toward the anchor. This will make a "Z" shape out of the rope. This is how the "Z-Rig" gets its name.
Add a Triple Wrapped Prussik to the load line and connect it to the carabiner attached to the lower pulley.
Ensure all carabiners are locked.
Tension Analysis (click to enlarge)