It’s English name is CARABINER.
Early mountaineering shackles were made of steel or iron. The characteristics of steel are strong and durable, and the bearing capacity is large (some can withstand 4000-5000 kg of tensile force). The disadvantage is that it is heavy, which increases the load of climbers and cannot be carried in large quantities. Later, such shackles were gradually replaced by aluminum alloy shackles. Aluminum alloy shackles are light and strong. At present, some manufacturers are better than aluminum alloy shackles. The shackle is the most widely used, and the most indispensable and alternative equipment in climbing equipment. The main purpose of the shackle when climbing is to connect the climbing rope and the intermediate fulcrum.
A shackle can replace many complicated and cumbersome knots in climbing. The combination and use of many climbing equipment, such as safety harnesses, ascenders, descenders, etc., are connected by hooks and loops.
The shackle is a safety guarantee when exploring the river and climbing the rock wall, also known as the safety buckle.
When climbing, make sure that the main rope is connected to the middle fulcrum through the shackles. Any shackles must be able to withstand the impact and pull of the climber suddenly falling.
But what makes it sturdy enough? According to the drop test of the International Mountaineering
Alliance “UIAA”, the climbing rope can withstand at least 1200 kg of tension. Due to the braking friction of the rope on the shackle, the load of the shackle should be 1.33 times that of the rope in the UIAA drop test. Therefore, the shackle must be able to withstand at least 1500 kg of impact pull. That is, for maximum safety in a severe fall, the shackle should at least be able to withstand such loads.
The normal pulling force of the aluminum alloy shackle is generally 2000-3000 kg to ensure the safety of climbers.
The shackle is generally divided into 0 type, D type and modified D type.
The advantage of type 0 shackle is that the friction force is small, the range of use is wide, and the activity of hooking on rocks and blocks is better than that of type D shackle. When climbing, type 0 shackle is generally used for ascenders, The pulleys and other equipment are connected, and under normal circumstances, they will not bear the impact and pull force, and will not be stuck at acute angles, change directions or move suddenly. Its disadvantage is that the impact tensile force is small, its load is equally shared by both sides of the hook and loop, and it can generally withstand a tensile force of 1500-1800 kg.
D-type shackle is a kind of shackle that is used more often. It is stronger than 0-type shackle. Almost all the load is borne by the long side opposite to the opening, so it can bear large impact tension and has a safety factor. high. Now it has been improved, and the opening is larger and shaped like a cashew nut, which is convenient for climbers to operate with one hand.
There is also a hook and loop with a safety lock, mostly large triangle or large D type, which is used for complex connection of equipment. The most common use is to ensure the connection of the main rope and safety harness. Therefore, We also call this type of shackle a safety shackle.
The shackle has two basic states, open and closed. When the shackle is closed, the pulling force it can withstand is three times that of when it is opened.
Special attention should be paid to the use: after hanging the shackle, the opening should be turned downwards and outwards, or downwards towards the climber, to prevent entanglement and twisting. Before use, check whether there are cracks or cracks, and the opening and closing of the opening should be smooth (because its internal structure is based on a spring, it can be removed by dripping kerosene, solvent or lubricating oil into the gap.) In order to reduce the friction of the rope, double hooks are used. Rings are also available.
Finally, when choosing a shackle, it should be selected according to actual needs, because different uses and different types of shackles bear different tensile forces, weights and prices. I believe that when you think about which kind of hook and loop you like, you also include your trust and safety as a reference. In short, this is a feeling that is easy to realize but difficult to explain.