In
rock climbing, an anchor can be any device or method for attaching a climber, a rope, or a load above or onto a climbing surfacetypically rock, ice, steep dirt, or a buildingeither permanently or temporarily. The intention of an anchor is case-specific but is usually for
fall protection, primarily
fall arrest
Fall arrest is the form of fall protection which involves the safe stopping of a person already falling. It is one of several forms of fall protection, forms which also include fall guarding (general protection that prevents persons from enteri ...
and fall restraint. Climbing anchors are also used for
hoisting, holding static loads, or redirecting (also called deviating) a rope.
Types of anchors
![Climing anchor](https://upload.wikimedia.org/wikipedia/commons/9/96/Climing_anchor.JPG)
Depending on the surface being climbed, there are many types of
protection
Protection is any measure taken to guard a thing against damage caused by outside forces. Protection can be provided to physical objects, including organisms, to systems, and to intangible things like civil and political rights. Although th ...
that can be used to construct an anchor, including natural protection such as boulders and trees, or artificial protection such as
cams,
nuts,
bolts or
pitons.
Natural anchor
A natural anchor is a secure natural feature which can serve as a climbing anchor by attaching a sling, lanyard, or cordelette and a carabiner. Examples of natural anchors include trees, boulders, lodged chockstones, horns, icicles, and protrusions.
Artificial anchor
An artificial anchor consists of man-made climbing gear placed in the rock. Such gear includes
spring-loaded camming device
A spring-loaded camming device (also SLCD, cam or friend) is a piece of rock climbing or mountaineering protection equipment. It consists of two, three, or four cams mounted on a common axle or two adjacent axles, so that pulling on the ax ...
s,
aluminum nuts used like chockstones, steel expansion bolts, and
pitons. Artificial anchors may be permanent or removable.
Belay anchor
A
belay
Belaying is a variety of techniques climbers use to create friction within a climbing system, particularly on a climbing rope, so that a falling climber does not fall very far. A climbing partner typically applies tension at the other end of t ...
anchor is used as a sole attachment to the cliff face, to support a belay or
top rope
Top rope climbing (or top roping) is a style in climbing in which the climber is securely attached to a rope which then passes up, through an anchor system at the top of the climb, and down to a belayer at the foot of the climb. The belayer takes ...
. Ideally, it should consist of multiple redundant components (natural and/or artificial), none of which are likely to fail, and none of which in the event of failure would cause the entire anchor to fail. Any one component of a good anchor should be able to support the entire system by itself.
Running belay anchor
A
running belay anchor is used as a safeguard in the event of a fall while
lead climbing
Lead climbing is a climbing style, predominantly used in rock climbing. In a roped party one climber has to take the lead while the other climbers follow. The ''lead climber'' wears a harness attached to a climbing rope, which in turn is connected ...
. The leader and follower climb simultaneously with protection placed in between. When the two climbers advance using a running belay, the belay is almost as secure as using a belay device and anchors because if the leader falls, all the slack is already out of the rope and the follower acts as a counterweight to catch the fall. A running belay is used as a faster alternative to pitch climbing when the risk, consequences, and likelihood of a leader fall are deemed to be acceptable.
Ice anchors
The snow picket is used as an anchor in
mountaineering. It is driven into the snow and used to arrest falls.
Snow pickets
Snow protection (snow pro) is a type of natural or artificial protection used in mountaineering as an anchor. Two common artificial devices are the snow fluke and snow picket. It is used both for climbing and for securing tents and other camping ...
can also be placed horizontally in snow as a
deadman
Deadman or Deadman's may refer to:
* "Deadman" or "dead man", are alternative terms for a dead man's switch
* "Deadman's foot" is another name for a Salamander in metallurgy
* "Deadman anchor" is a buried object (log, concrete, block, etc.) used ...
, which provides a secure anchor to abseil on.
Ice screw
An ice screw is a threaded tubular screw used as a running belay or anchor by climbers on steep ice surface such as steep waterfall ice or alpine ice during ice climbing or crevasse rescue, to hold the climber in the event of a fall, and at bel ...
s can be hand-driven into solid ice and are the equivalent of cams or nuts when
ice climbing. Ice can also be protected using an
Abalakov thread
250px, Abseiling at an Abalakov thread
The Abalakov thread, also known as a V-thread, A-thread, or 0-thread (zero thread), is an ice protection technique named after its innovator, Soviet climber Vitaly Abalakov. The Abalakov thread is a commo ...
or v-thread. Because of the uncertain holding power of ice protection, it is sometimes attached to the rope using a load-absorbing sling or
quickdraw
A quickdraw (also known as an extender) is a piece of climbing equipment used by rock and ice climbers to allow the climbing rope to run freely through protection such as a bolt anchors or other traditional gear while leading.
A quickdr ...
, designed to reduce the load on protection by extending in case of a fall.
Attachment to the anchor
Indirect
When the rope goes from the climber to the belayer. Most often used under controlled circumstances at climbing walls or when the climber doesn't have the weight advantage on the belayer during bottom roped climbs. It is impossible to escape from the system.
Semi-direct
When the rope comes from the climber to the belayer, but the belayer is attached separately to an anchor. Often used when multi pitching and the belayer is on a stance. Or when top roping and it is possible that if the climber falls the belayer will be pulled from the stance above the climber. The belayer can, with a little effort then remove themselves from the system if required.
It is essential that the belayer is attached to the anchor via the belay loop at the front of the harness. Attaching the belayers harness to the anchor via the back of the harness can cause the harness, when placed under strain, to constrict inwards elongating front to back, rather than side to side. This can result in crushed pelvis and serious harm to the belayer.
Direct
When the rope comes from the climber to an anchor. A hanging belay device may be used, although it is common in this instance to just use an
Italian hitch. The belayer is totally free of the system.
Considerations
Force multipliers
The force on an anchor may be much greater than the weight of the climber. There are various mechanisms which contribute to excess force, including
* Direction of pull, or vector pulling
*
Fall factor
In lead climbing using a dynamic rope, the fall factor (''f'') is the ratio of the height (''h'') a climber falls before the climber's rope begins to stretch and the rope length (''L'') available to absorb the energy of the fall,
:f = \frac.
It ...
(if a fall occurs)
* Stiffness (reduced elasticity) of the climbing rope and anchor materials
* improper slippage through the belay device
* A swinging climber, or load.
* Cam-action type anchors (including nuts, and hexes)
Load-sharing anchor
A load-sharing (or load-distributing) anchor is a system consisting of two or more individual anchors which join together at a main anchor point to form an anchoring system. This configuration is a way to introduce redundancy and increase strength, typically for a belay anchor. If assembled correctly, the load will be distributed to each individual anchor, rather than placing all the load on a single anchor point. This decreases the chance that any single anchor point will fail, and, if a point does fail, the other(s) should still be able to hold.
Best practices
To ensure proper redundancy and effectiveness of a load-sharing anchor, some
best practices
A best practice is a method or technique that has been generally accepted as superior to other known alternatives because it often produces results that are superior to those achieved by other means or because it has become a standard way of doing ...
are commonly observed.
Redundancy
Anchors should be redundant, meaning that the overall anchor will still be sufficiently strong if any individual anchor were to fail. Selecting ''independent'' locations for the individual anchors would make an anchor redundant. This may mean using distinct boulders, crack systems, or objects for the placement location of each individual anchor. That being said, redundancy is not necessary in all climbing anchors. A living tree that is at least 6 inches in diameter will surely hold up several kN of force in any direction, and so is sufficient as being the sole anchor for any climbing anchor.
Equalization
In a load-sharing anchor, each individual anchor is connected to a main anchor point. The load-sharing anchor is said to be ''equalized'' if the load force is distributed equally to each individual anchor. This is accomplished by adjusting the length of each connecting member (between the main anchor point and an individual anchor) while pulling the main anchor in the anticipated direction of the load. Anchors can be either pre-equalized, in which the anchor is statically equalized between anchor points during rigging, or self-equalizing, in which the anchor system dynamically adjusts tension between anchor points during use.
Non-extension
A load-sharing anchor which does not extend in the event of an individual anchor failure has the property of non-extension. This important feature reduces the potential for shock-loading the remaining individual anchors during a failure. Non-extension can be accomplished by tying an appropriate knot in the interconnecting cordelette, or by using individual slings for the equalization. The principle of non-extension refers to the mitigation of shock-loading, rather than the elongation of materials under an increased load.
The principle of minimum swing is related to non-extension. The main anchor point in a well constructed load-sharing anchor will neither extend nor swing in the event of an individual anchor failure. Reducing swing can be accomplished by minimizing the inner angle between individual anchors, and by increasing the number of individual anchors. An additional technique is to place a directional anchor a short distance below the main anchor point.
Inner angle
When constructing a load-sharing anchor, it is important to take into consideration the angle formed between each individual anchor – the ''V-angle''. Climbers typically try to minimize this angle, because a greater V-angle will produce more force at each individual anchor.
If the V-angle is greater than 120 degrees, the load on each individual anchor will be greater than the load on the rope. Angles in excess of 120 degrees can create a hazardous situation which compromises the safety of the anchor, and should generally be avoided.
The sum of forces on all the individual anchors will commonly exceed 100%, and in some cases, the force on an individual anchor will be greater than the load. This may seem contradictory when only the magnitudes are summed. However, if the forces on the individual anchors are
added as vectors, the resultant force on the anchor system is equal to the load. In simpler terms, the forces in the ''vertical'' direction are equal to the load force, but there are lateral forces as well – which increase as the V-angle increases.
The force on ''each'' individual anchor is given by:
:
.
where,
*
is the overall load force.
*
represents the V-angle.
This equation is a special case representation of the more general
anchor force equation,
[*"Non-Load Sharing Anchors." Ratref. Web. 11 February 2012. .] in which the load-sharing anchor is constructed from two symmetrically placed anchors.
From this expression, the anchor forces can be calculated for selected angles in a two-element, symmetrical, load-sharing anchor.
*At a V-angle of 30 degrees, each of the two anchors will bear a force of about 52% of the original load.
*At 45 degrees, each anchor bears 54% of the load.
*At 60 degrees, each anchor bears 58% of the load.
*At 90 degrees, each anchor bears 71% of the load.
*At 120 degrees, each anchor bears a force equivalent to 100% of the original load. An angle this large should be avoided for safe climbing.
In
trad climbing
Traditional climbing (or Trad climbing) is a style of rock climbing in which the climber places all the necessary protection gear required to arrest any falls as they are climbing, and then removes it when the pitch is complete (often done b ...
belay stations, load-sharing anchor are often constructed from more than two individual anchors, which are rarely co-planar. In these cases, each individual anchor would feel a reduced force from the above values, but best practice is to reduce the angle between the two outermost elements, and avoid angles in excess of 120 degrees.
References
* Long, John (1993). ''How to Rock Climb: Climbing Anchors''. Chockstone Press, Evergreen, Colorado.
* Graydon, Don, and Kurt Hansen, eds. (1997). ''Mountaineering: The Freedom of the Hills'', 6th edn., pp. 143–152. The Mountaineers, Seattle.
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