Peak Rescue Institute: Twin Tension Rope System 1 | Block and Tackle

Written By: Lance Piatt

Two Rope System The Two Rope System is used as an alternative to deflection lines or Tyrolean traverses when spanning large gaps. It incorporates two main lines and two belay lines that work together. While one system lowers, the other raises. When the haul becomes to difficult for the hauling team, the lowering team simply lowers more rope. The has the effect of naturally limiting the angle between opposite anchors and limits over system forces. The main and belay lines are rigged on the same sides. The use of high change of directions are very beneficial. Initially rig a lowering system on the departure side and a MA system on the opposite site. Two systems work together in sync. Do not exceed 120 degrees. The two rope system is used as an alternative to deflection lines or Tyrolean traverses when spanning large gaps. It incorporates two main lines and two belay lines that work together. While one system lowers, the other system raises. When the haul becomes to difficult for the hauling team, the lowering team simply lowers more rope. This has the effect of naturally limiting the angle between opposite anchors and limits overall system forces. The use of high directionals on one or both sides may assist in the edge transition. The two belay lines and one of the main lines are attached to the rigging ring with a direct tie-in. The second main line is attached with a long tail bowline and becomes the litter handler working line. Keep the angle at 120 degrees or less between the two systems. The two rope system is a variation of the Tyrolean traverse and uses two standard main and belay systems on opposite anchors instead of a track line and control line between the anchors. For the purpose of lifting or moving heavy loads a block and tackle system consists of two or more pulleys connected by one common cord or rope that is threaded between the pulleys. As most know, pulleys are simply wheels on axles designed to assist or direct movement of the rope along the grooved circumference of the wheel. One pulley alone can be utilized to lift loads and apply forces to transmit power, but incorporating multiple pulleys into a system decreases the amount of applied force required to transmit the power to move the load. A pulley, also known as a sheave or drum, most commonly has a groove on the wheel’s outside edge along the perimeter of the wheel between two flanges around the pulley’s circumference. The cord or rope is the drive element of the pulley or pulley system. When the rope in a pulley is pulled upon, the force applied to the rope compresses it against and into the V groove between the flanges of the pulley wheel creating sufficient friction to move the wheel, rotating the pulley wheel around its axle. Multiple pulleys can be configured to form a block and tackle system for the purpose of providing a mechanical advantage to apply large forces in order to lift or move the heavy load more easily than with one pulley. Two pulleys together in a system form blocks. Blocks are arranged in such fashion that one moves with the load while the other is in a fixed position. The assembly of a set of two blocks with the rope threaded around the respective pulleys is called tackle. The rope threaded around the pulleys is referred to as reeving. The rope or cord that is reeved through the pulleys provides mechanical advantage. Mechanical advantage amplifies the force applied to the rope allowing for the moving or lifting of the load with less initial, original force. The end result is a system of pulleys that moves and lifts loads more easily while less force is applied when pulling upon the cord or rope.

About The Author:

Lance Piatt

Beginning his career in the rescue and rigging world as a “blue collar” SAR member with Deschutes and Jefferson County teams. Lance Piatt owns and operates Red Ibex Solutions, a sales and marketing wheelhouse blending rope rigging education and exquisite imagery with equipment knowledge and understanding; housing Rigging Lab Academy and Rescue Response Gear… Lance is producing high-end video education, working with several experts and instructors to produce unique series of “how to videos” and courses for rope rigging: Such as; the first ever full-length rescue training DVD, 'Tower Rescue', released in fall of 2005. As well as a series of scenario-based rescues ranging from cave rescue to cliff rescue.