B-2:1 with Ratchet
C-2:1 Pulling Second Rope
This system is nothing more than a force multiplier turned around. One end of the line is attached to an anchor. The rope passes through a pulley and back in the direction of the anchor. The load is suspended from the pulley. The load is equally supported by both sides. When you pull up on the unanchored side you only need extend one half the force, but for twice the distance. Figure A portrays this in the simplest form. Note that this form is considered unsafe for live or critical loads.
Figure B is the preferred method for hauling a live or critical load. In this system we have added a ratchet cam. The ratchet cam is used to hold the load when sufficient force is not being exerted on the unanchored end.
Figure C shows how to use a 2:1 system to pull on a separate line. In this system we use an ascender (called the haul cam) to attach the traveling pulley to the load line. We place a second ascender (called the ratchet cam) below the haul cam. By placing the ratchet and haul cam on the load line the team can pull up the load line with the hauling system, set the weight on the ratchet cam, and then reset the haul cam to take another bite and haul up more of the load line. This same sequence is used with all other systems.Read More »