Swiss pulley

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Swiss pulley is a method of makeshift glacier rescue (crevasse rescue ). A person who has fallen into a crevasse and roped up is rescued without their help by a pulley from comrades.

properties

The Swiss pulley is a combination of a power and a factor pulley . This has a theoretical ratio of 1: 5; in practice, friction losses result in a ratio of around 1: 3 to 1: 4. One person alone can therefore muster the arm traction required to rescue the fallen victim. The Swiss pulley is therefore also suitable for two-person rope teams.

business

before stroke
after stroke

By pulling on the pull rope (here the loose end at the bottom right in the picture) the load rope is pulled over the pulley and the load (here on the far left) is lifted. With one stroke you can always pull until the carabiner on the long Prusik loop (purple) arrives at the backstop (top right). If the pull rope is released, the Garda backstop blocks and prevents the load from sliding down. Now the short Prusik (blue) can be pushed further until the long Prusik loop is stretched again. Then the next stroke begins.

The lifting height for a single lift is about half the length of the long Prusik loop, at most the entire length. It depends on the length of the long Prusik loop, the position of the fixed point of the long Prusik loop, the care (push the short Prusik as far forward as possible) and the rope stretch. The fixed point of the long Prusik loop should be as far away as possible from the backstop in the direction of the load, so that the long Prusik loop is used to its full length and is stretched after the stroke (now the other way around). Static ropes are used in height rescue because of lower losses due to rope stretching.

With the pulley system, a greater height can be overcome with multiple lifts, for example after falling into a deep crevasse.

Alternatives

Alternatives are the single pulley block , the double pulley block, and for crevasse rescue: the Münchhausentechnik , self-rope pulley , loose pulley and team hoist

Web links

Wikibooks: Swiss pulley system  - learning and teaching materials

Individual evidence

  1. Tina Czermin, Peter Dullnig, Leopold Mathelitsch, Werner B. Schneider: Mountaineering and climbing - what does physics say about it? In: Physics in Our Time . 2001, p. 62–68 ( PDF [accessed March 18, 2020]).