Clamping device

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Clamping device in a rock crack, the load is directed to the left

A clamping device is an active, mobile securing device that is used when rock climbing to attach a fixed point . In contrast to the clamping wedge, it has a spring mechanism.

Working principle

Sketch of a friend in a crack

Clamping devices create a frictional connection to the rock using the toggle principle . In the event of a fall, this creates a frictional force on the rock that is proportionally a multiple of the fall force. The arc shape of the segments follows a logarithmic spiral so that the contact angle on the rock faces always remains the same, regardless of the crack width. Due to the high frictional connection, no form fit is necessary and a clamping device holds even in cracks with parallel or even slightly opening walls.

Spring mechanism

The spring mechanism allows insertion into cracks of different widths. It keeps the device in the rock when it is not stressed. In the event of a fall, the spring force is negligible. To insert and remove the clamping device, the segments are relieved of the spring via the so-called trigger.


The first clamping devices were designed by climber Greg Lowe in 1967 and distributed on a small scale with his brother Mike. These had two opposing segments and were operated via a cable. Lowe probably took the arc shape of the logarithmic spiral from the braking mechanism of ascenders .

In the early 1970s, space engineer Ray Jardine, who had also been experimenting with clamping devices since 1971, visited his climbing friend Mike Lowe for dinner. His brothers were also present and they showed Jardine their invention after Jardine had signed a confidentiality agreement. Jardine recognized the potential of the special arch shape and bought three copies. In the years that followed, he built further prototypes for his own use and improved the system with a spring mechanism and four segments that were much more stable in the crack and less likely to fall out.

In 1977 Mark Vallance became aware of the new safety device and was convinced of the market potential. He invited Jardine to England and founded Wild Country, which offered Jardine's devices to a wide audience under the name "Friends". Jardine was only able to patent the spring mechanism. Even if the arc shape is the crux of the invention, as a mathematical curve, the logarithmic spiral, it does not have the necessary inventiveness. That is why the Lowe brothers did not get the economic benefit of their invention.

It is only since the introduction of the clamping devices that it has become possible to walk some routes in a clean style . These include the many routes in Yosemite National Park with their parallel cracks.


To place a clamping device, the lead climber pulls the segments using the spring mechanism and places them in the crack. In contrast to clamping wedges, a clamping device can cover a larger range of crack widths. It should be noted, however, that the segments are not completely open or completely compressed in the gap. In addition, all segments must have contact with the rock.

The climber attaches an express set to the loop . In order to decouple the device from the movement of the rope as much as possible, choose a slightly longer quickdraw.

The contact pressure of the device can be very high in the event of a fall. The rock must be robust enough to withstand this explosive effect. Caution is therefore required, especially when placing it behind rocky sheds. The surface (contact surface) should be free of dust and vegetation. To remove the device, pull the trigger that applies the segments so that they no longer touch the rock. The climber needs some experience to safely assess the reliability of the placed clamping device.

Clamping range and sizes

Crack width ranges of different sizes

In order to be able to secure crack widths of different widths, all clamping devices are offered in different sizes. The different sizes are numbered consecutively by the manufacturers for the sake of simplicity. For example, a size # 2 friend covers the range 29 to 44 mm. A size # 2 Camalot covers 37 to 65mm. The sizes given by the various manufacturers have different clamping ranges. This must be taken into account when size information about required friends is given in climbing guides.

Brands, manufacturers and types

  • The name Friend is a product name of the Wild Country company . With the Friend, a clamping device was brought onto the market for the first time at the end of the 1970s.
  • Camalot brand clamping devices come from the manufacturer Black Diamond . In the newer generation of Camalots, the pivot points of the clamping jaws are distributed on two axes instead of one, as in other comparable clamping devices. This is intended to achieve a better clamping effect and thus security.
  • Link Cams are clamping devices similar to Camalots, Friends or Aliens. With a basic angle of 13.5 °, Link Cams ensure that the entire span can be used without great effort of the hand. There are four jaws divided into three segments. These three segments in different sizes can be unwound and rewound. The span of the clamping device can thus be significantly expanded in a simple manner.

Clamping devices from different manufacturers and their sizes in comparison

Friends in different sizes
DMM Dragon Cam 00 = 13.6 - 22.5 mm 0 = 16 - 26.7 mm 1 = 20 - 33 mm 2 = 24 - 41 mm 3 = 29 - 50 mm 4 = 38 - 64 mm 5 = 50 - 85 mm 6 = 68 - 114 mm
Black Diamond Camalot 0.3 = 13.8 - 23.4 mm 0.4 = 15.5 - 26.7 mm 0.5 = 19.6 - 33.5 mm 0.75 = 23.9 - 41.2 mm 1 = 30.2-52.1 mm 2 = 37.2-64.9 mm 3 = 50.7 - 87.9 mm 4 = 66 - 114.7 mm 5 = 85.4 - 148.5 mm
Wild Country Technical Friends 0 + 0.5 0.5 + 1 1 + 1.25 1.75 2 + 2.5 2.5 + 3 3.5 4 + (5) * 5 + (6)
Rock empire 0.5 + (0.75) 0.75 + (1) 1 + (2) 2 (2) + 3 3 + 4 4 + 5 5 + 6 6 + 7
  • The sizes in brackets indicate that another clamping device is needed for the specified area of ​​application. If two sizes are given without brackets, then both sizes are required in approximately equal parts in order to achieve the intended use of the Camalot.


The original friend has an axis on which there are four segments, with two segments pointing to the left and two to the right. Friends of the new generation have two axes and are therefore more stable in the rock and have a larger clamping area than their predecessors.

The Camalot has two axes, each with two segments. On the left axis are the segments that are aligned to the right and vice versa. With this design, a larger clamping area can be covered than with the first Friends. The second axis, however, also leads to a higher weight.

The Link Cam has an axis on which, like the Friend, there are four segments. The segments are in turn composed of smaller segments. This allows the segments to be wound up and down. This design leads to a particularly large clamping area.

The BigBro has a completely different design without an axis or segments and is similar to a tube that is jammed at an angle. With BigBros, cracks up to a width of 467 mm can be secured.

Individual evidence

  1. Pit Schubert: terminal equipment . In: mountaineering . No. 2 , 2005, p. 76–81 ( PDF [accessed January 21, 2016]).
  2. ^ A b Matt Samet: The Climbing Dictionary . The Mountaineers Books, 2011, ISBN 978-1-59485-502-3 , pp. 44–46 ( limited preview in Google Book Search [accessed January 21, 2016]).
  3. ^ A b Ray Jardine: The History of Friends. Retrieved January 21, 2016 .
  4. Patent US4184657A : Climbing aids. Registered May 30, 1978 , published January 22, 1980 , applicant: Ray Jardine, inventor: Ray Jardine.
  5. ^ Andi Dick: Aim high - with a head . In: Panorama . No. 2 , 2010, p. 62–63 ( PDF [accessed January 20, 2016]).

Web links

Commons : Clamping devices  - collection of images, videos and audio files
Wikibooks: Information on Friends and other intermediate  backups - learning and teaching materials