Build a 9:1 pulley system with a Jigger

by | Feb 28, 2017 | Rope Rescue, Technical Rope | 4 comments

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?

  1. Attach a rope to the load.
  2. With the rope build a progress capture on your anchor ­– something efficient, your choice.
  3. Attach a rope grab onto your load line and another on the line coming out of the progress capture.
  4. Attach the Jigger in between the two rope grabs and you are ready to haul.

Notes

  • In effect, you will 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.

 

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Grant Prattley

Grant Prattley

Manager, consultant, designer

Founder and consultant at Over The Edge Rescue. Rescuer, instructor, guide, author, designer, and adventurer.

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