Bolts
A bolt is understood to be a rock hook that is anchored in a hole drilled in the rock, in contrast to the normal hook, which is designed for existing natural rock cracks. Bolts are mainly used in sport climbing , mountaineering and related sports. Drilling is done either with a hand chisel and hammer or with a cordless drill.
Construction forms
Bolts are often categorized according to the way they are anchored. They are divided into mechanical systems and chemical anchors, the chemical systems. Further possible distinctions are the design of the eyelet (e.g. ring, tab) or intended use (intermediate securing, diversion or for abseiling).
Mechanical systems
In a mechanical system, the hook is inserted into the borehole and a frictional fit or form fit is created by mechanical deformation alone , which creates the holding force. Mechanical systems have the great advantage that they can be loaded immediately after insertion. This makes them the only sensible system for first ascents from below.
Frictional systems
Frictionally engaged systems generate an explosive effect and increase the static friction through the expansion pressure.
A simple system forms the impact anchor consisting of a hollow cylinder and a spreading pin. For anchoring, the cylinder is placed in the hole and the expanding pin is driven into it. This spreads the cylinder and creates the holding force. This type of anchor requires a high expansion pressure for adequate static friction, which means that it is not suitable for cracked or splintered rocks due to the explosive effect. Its strength values are also in the limit range of the norm.
The bolt most widely used at the moment (as of 2007) is the express anchor . This consists of a threaded shaft and a cone around which an expanding clip rests. If the nut is tightened on the thread, the cone slides under the expansion clip and presses it against the wall of the hole.
Occasionally you can still find old hooks that do not meet the standard, such as B. pin or bolt bolts . They have a shaft with a rectangular cross-section and are driven into a small, round borehole. The holding forces are very low. The first crown bolts were set in the 1970s . Since the shaft of this system has to be made of hardened steel, it is not corrosion-resistant and therefore problematic.
Form-fitting systems
In positive-locking systems, the shape of the shaft and the bore are adapted to one another in such a way that they hook into one another.
The screw anchor , which has a thread, follows a simple principle . It is screwed into a slightly smaller borehole and also cuts a thread in the rock. This system works without expansion pressure and offers a very good form fit. However, the high turning resistance has a disadvantage, so that the system can only be used in medium-hard rock, such as B. lime can be used. In harder rock (e.g. granite) the resistance is too great and the screw can break off. If the rock is too soft (e.g. sandstone), the strength is not sufficient for the form fit.
The undercut anchor has, similar to the express anchor, an expanding clip which is expanded by tightening a nut. However, this sits at the end of the shaft and does not serve to exert pressure on the borehole wall, but to thicken the end of the shaft. To set the borehole, a special tool is required which creates a borehole that is larger at the bottom. If the anchor is inserted and spread, it fills the widened hole and wedges itself.
Composite hook
Composite hooks belong to the chemical form-locking systems. They create the form fit using a mortar that adapts to the shape of the shaft and the drill hole. In the climbing scene, the term adhesive hook is very common, although it is not an adhesive, but a two-component mortar or quick-setting cement. To set the anchor , the mortar is placed in a drill hole approx. 1 to 2 mm larger. The mortar seals the borehole against moisture and thus prevents erosion.
The " Bühler hook " is the first hook to be set in this way. It was invented by Oskar Bühler and its basic shape has hardly changed since then.
If properly set, standard-compliant adhesive hooks are considered the safest rock hooks today. The processing of the composite material, however, harbors many sources of error.
Norms
Bolts sold in Europe for mountain sports must meet the EN 959 standard. This places the following requirements on the hook:
- axial tensile strength at least 15 kN
- radial tensile strength at least 25 kN
- Anchoring must be independent of the bottom of the hole
- Materials must be corrosion-resistant
The greatest possible fall load when climbing is around 16 kN.
use
Alpinism and climbing
In connection with mountaineering and climbing, especially modern sport climbing , bolts serve as a fixed point in order to be able to secure one's climbing partner and oneself. In the Alpine region, the first bolts were set in the Wilder Kaiser in 1944 . These were so-called pin or prick hooks . In the Elbe Sandstone Mountains , ring hooks were drilled long before.
Already since its development there has been a dispute about the ethical climbing permissibility of the bolt use.
Many well-known mountaineers, including Reinhold Messner , completely reject the use of bolts as a "murder of the impossible". According to this, only the use of so-called mobile securing devices ( clamping wedge , friend etc.) and classic rock hooks should be permitted. Securing with mobile security devices has a long tradition, especially in Great Britain and the USA. The advocates of this climbing style point to the great adventure and experience value.
On the other hand, it was the bolts that made safe and sporty climbing possible for a large number of people. What was once reserved for courageous and experienced lead climbers is now possible for everyone with the help of bolts. In this sense, the bolt is of great importance for popular and top-class sport.
In Europe, and increasingly also in other continents, the frequent use of bolts has therefore generally prevailed. Of course, it must always be legally clarified whether the use or setting of bolts requires the consent of the landowner or other authorized person. There are different regulations for each country.
Other areas of application
In speleology , bolts only allow safe exploration of cave parts in many cases , and they are often the only means of making such areas accessible, since the walls in caves, due to their formation, usually only offer few options for classic securing techniques (Friends , Rock hooks etc.). In addition, a fall into the rope cannot be tolerated for safety reasons, as even small injuries underground can quickly become fatal.
In addition, bolts are also used in other related sports, such as canyoning .
literature
- Chris Semmel: 1 × 1 of the mechanical bolts . In: Berg & Steigen . No. 1 , 2007, p. 70–75 ( bergundstieg.at [PDF; 414 kB ] Presentation of the various drill hook systems (without compound anchors).
- DAV (Ed.): Bolts . November 2007 ( alpenverein.de [PDF; 1.7 MB ; accessed on August 21, 2017]).
Individual evidence
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↑ Chris Semmel: 15: 2 adhesive hooks against expansion anchors . In: mountaineering . No. 2 , 2006, p. 24–29 ( bergundstieg.at [PDF; 1.8 MB ; accessed on July 22, 2015]). Dieter Stopper: Broken hooks when climbing . In: DAV Panorama . No.
2 , 2001, p. 78 f . ( bergundstieg.at [PDF; 713 kB ; accessed on July 22, 2015]). - ↑ Jürgen Kollert: Infoscript Bohrhaken. (PDF) Retrieved July 22, 2015 .
- ↑ Jan Gürke: Striving for the best style when climbing. Interview with Robert Jasper in: Wildernews 39, 2005, p. 3 ( PDF ) Accessed: September 29, 2012.
- ↑ Känel, Jürg von: For drilling and rehabilitation of Plaisierrouten. Thoughts and tips about bolts ( http://www.filidor.ch/uploads/bohren_sanieren_juerg.pdf ) Accessed: September 29, 2012.
- ↑ Cf. u. a. Michael Malaniuk "Austrian Mountain Sports Law" (2000), p. 89.