Pulley
A pulley is used to reduce friction losses in pulley blocks and cable cars .
Rope pulley when climbing
application
Rope pulleys are in the mountain rescue ( column recovery after a fall in a crevasse) and in the height rescue used for the construction of pulleys. Examples: single pulley block , double pulley block, Swiss pulley block , loose pulley . In outdoor training they are used to tension ropes for rope bridges and cable cars. In makeshift freight and passenger ropeways, double rollers are used as a sliding suspension for the load. When kayaking, capsized kayaks are rescued from the current. Pulleys also simply serve as a pulley to change the direction of pull.
material
- Load roller
Load rollers have been tested and achieve breaking loads of 3000 daN . They are usually used as the first pulley, as this is where the greatest loads occur. Since the friction losses are greatest at this point, load rollers are often designed with ball bearings or self-lubricating. The roller is usually made of aluminum or steel. Load rollers are often designed with a bar closed so that the rope is still secured in the event of an axle break.
- Auxiliary role
Auxiliary rollers are often used as a second role in the pulley block, as only half the force has to be mastered here. Typical breaking loads are 1000 daN. They usually run unlubricated. The roller is usually made of plastic (polyamide). The adjacent model can be opened so that the rope can be inserted particularly easily.
- Makeshift role
Makeshift rolls consist of a single loose plastic roll that can only be used in combination with a snap hook that functions as an axis. Since climbing carabiners are usually asymmetrical, the hole in the roller is adapted to the curvature so that the load is distributed over the entire width of the roller.
Backstop
Rope pulleys are often combined with a backstop - either with a structurally integrated ratchet , or additionally with an ascender , a garda loop , a Kara-eight loop or, particularly inexpensive, with a prusik loop , each on or with the piece of rope running out of the pulley.
See also
Web links
- Application of a loose role ( memo of November 2, 2004 in the Internet Archive )