Build a 9:1 pulley system with a Jigger
Something I am always looking to do is find new ways to make gear more useful.
For rescue one of the great tools in the toolkit is the jigger (aka set-of-fours). This is a pre-constructed pulley system made, in this instance, with two double pulleys. It has a set mechanical advantage of 4:1 simple(s) with a change of direction (CD) or a 5:1s.
A 4:1sCD (left) or 5:1s (right) can be useful pulley systems for various tasks. For example, we could use the Jigger as a bolt-on pulley system (shown above). However, the Jigger used for rescue hauling in a backcountry context may not be enough as you have a small number of haulers and limited equipment. In other words, you need a bit more work out of the pulley system.
Making the Jigger more useful
So how can we convert this tool into a 9:1 so it’s more valuable for backcountry rescue?
- Attach a rope to the load.
- With the rope build a progress capture on your anchor – something efficient, your choice.
- Attach a rope grab onto your load line and another on the line coming out of the progress capture.
- Attach the Jigger in between the two rope grabs and you are ready to haul.
Notes
- In effect, you are pulling the rope grabs together.
- You can rig the Jigger in either direction and it will still be a 9:1.
- One end is a 4:1, the other is a 5:1 and they join at the load end Prusik to become a 9:1 (i.e. the mechanical advantages are added together).
- The pulley system is a 9:1 complex (cx) i.e. it’s not a simple or compound, therefore it’s a complex.
