The most common form of protection on protected routes is steel cable, which is firmly anchored to the rock at intervals of approximately 3-5 m. The anchoring is mostly carried out in such a way that an iron rod is placed in the rock, fitted with an eyelet at the end through which the steel cable is threaded through. In order to keep the steel cable from moving around in the loop, the cable often has clamps on either side of the loop, which can’t slide through the loop of the iron rod due to their width. In principle, this is therefore a method of protection using a fixed rope. The hiker or climber is fastened to the steel cable using two slings and carabiners, which she pulls along with her, still clipped to the cable. In the event of a fall, the climber will fall until the carabiner slides down the steel cable with the sling connected to the climber until it jams against the nearest fixed anchoring of the steel cable below.
When passing an anchor point of the steel cable, the climber must first clip one carabiner to the new section of cable, and only once it has been safely fastened can she clip the second carabiner from the previous section of cable. As a result, she is always protected when transferring her anchor; whenever one carabiner is unclipped during this manoeuvre, she remains protected by the other.
Video: Transferring an anchor point on a klettersteig. First one carabiner is clipped to the new section of the cable; during the manoeuvre the climber is protected by the second carabiner on the previous segment of cable. After clipping the first carabiner the second is transferred; the climber is now protected by the carabiner attached to the new segment. During more demanding sections where risk of a fall is present, both carabiners are clipped in, and thereby back each other up.
Video: Watch out for this mistake! When transferring an anchor point on a steel cable, don’t run your carabiners and slings under the cable. While the carabiners are placed on the new section of rope, the slings are still wrapped around the anchor point, preventing further progress.
It might seem that everything is obvious as far as protection on a klettersteig is concerned, and that the substance of the protection is simple, and there’s nothing else to explain. But it’s not that simple.
The core of the problem of protection on a klettersteig, a significant source of danger, must not escape our attention. It can be concisely summarised by the following questions: Where in the system is there a dynamic (shock absorbing) element, which will absorb the energy of a fall? In order to understand the gravity of this danger, it is necessary to understand the meaning of impact force and fall factor. It is an important matter which is critical for safe protection on a klettersteig.
Impact force and fall factor on protected routes
Let’s briefly review the problem. The climber, when ascending a cliff (against gravity), accumulates (potential) energy depending on her location. During a fall, this energy is converted to kinetic energy. Upon catching a fall, this energy is converted to work. When catching a fall, the sling tenses and the amount of force in it increases, reaching its maximum when the fall is stopped. This force is called impact force, and it is measured in newtons (N).
In comparison, fall factor has no units, as it is not a physical value. Fall factor (f) is the ratio between the total length of the fall and the available length of the rope that catches the fall. Sometimes it is expressed by the fraction f = h / L, where h is the depth of the fall, and L is the available length of the rope that catches the fall. This reflects the level of hardness or softness of the jerk which will occur when the rope catches the fall. A greater fall factor means that a greater impact force will act on the falling climber, while a lower fall factor denotes the application of smaller impact force.
A climber on a klettersteig is at a great disadvantage in one sense. Her “rope” is actually the sling which is connected to the steel cable. This sling is very short. So short that in and of itself it has practically no shock-absorbing capabilities. It certainly does not have shock-absorbing capabilities for a fall as long as that which can occur on a klettersteig. After all, the distance between the individual anchorings of the steel cable can be around 5 metres. If a climber falls while fastened to the steel cable using a sling 1 metre long, she will fall from the upper anchor 5 metres downward toward the bottom anchor, and then an additional 1 metre of the length of the sling below the bottom anchor. In all, she will fall 6 metres. And she will be caught by a sling 1 metre long. In this case, f = 6 / 1 = 6. A fall factor of 6! That’s serious. In the tenths of a second in which the braking of the fall occurs, an enormous amount of force will act on the climber, which can exceed 2000 daN (the rough equivalent of 2 tons of weight!). The climber is therefore at great risk of serious injury.
In order to reduce the action of this force on the climber, it is absolutely necessary to include a shock-absorbing element in the protection chain. A fall absorber is used for this purpose, sometimes called a klettersteig brake. There are several types of such absorbers, but all of them work on essentially the same principle: the stretching of the rope sling through an opening in the fall absorber. This work absorbs most of the energy of the fall, and distributes it into a slightly longer time interval. All of which softens the effects of a fall to a bearable level. The fall absorber, most often a metal casting, has various openings in it, and a lanyard is pulled through it and left in the section between the fall absorber and the sling, which is fastened to the harness with about a 1 m length of slack. The absorber is also fastened to the harness. During a fall, the lanyard will begin to stretch the openings of the fall absorber, until the fall absorber takes up the entire 1 m loose section of rope within the absorber. The friction of the lanyard sliding through the openings of the fall absorber therefore absorbs part of the impact force and softens the fall.
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Mountaineering Methodology – Part 4 – The Mountains
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Mountaineering Methodology – Part 4 – The Mountains
Available for download from Google Play.