A spring-loaded camming device (also SLCD, cam or friend) is a piece of

rock climbing Rock climbing is a climbing sports discipline that involves ascending climbing routes, routes consisting of natural rock in an outdoor environment, or on artificial resin climbing walls in a mostly indoor environment. Routes are documented in c ...

mountaineering Mountaineering, mountain climbing, or alpinism is a set of outdoor activities that involves ascending mountains. Mountaineering-related activities include traditional outdoor climbing, skiing, and traversing via ferratas that have become mounta ...

protection Protection is any measure taken to guard something 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 ...

equipment Equipment most commonly refers to a set of tool A tool is an Physical object, object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many Tool use by ...

. It consists of two, three, or four

cam Cam or CAM may refer to: Science and technology * Cam (mechanism), a mechanical linkage which translates motion * Camshaft, a shaft with a cam * Camera or webcam, a device that records images or video In computing * Computer-aided manufacturin ...

s mounted on a common

axle An axle or axletree is a central shaft for a rotation, rotating wheel and axle, wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In ...

or two adjacent axles, so that pulling on the axle forces the cams to spread further apart. It is then attached to a sling and

carabiner A carabiner or karabiner (), often shortened to biner or to crab, colloquially known as a (climbing) clip, is a specialized type of shackle, a metal loop with a spring-loaded gate used to quickly and reversibly connect components, most notabl ...

at the end of the stem. The SLCD is used by pulling on the "trigger" (a small handle) so that the cams retract together, then inserting it into a crack or pocket in the rock and releasing the trigger to allow the cams to expand. A pull on the rope, such as that generated by a climber falling, will cause a properly placed SLCD to convert the pulling force along the stem of the unit into outwards pressure on the rock, producing massive amounts of friction and preventing the removal of the unit from the rock. Due to the large forces exerted on the rock when an SLCD is fallen on, it is very important that SLCDs are only placed in solid, strong rock.

History

Vitaly Abalakov's invention of the Abalakov Cam was the first application to climbing of the principle of a cam to climbing equipment. His cams were sections cut out of a pulley wheel and bear a remarkable resemblance to today's tricams. Since these shapes were eccentric, the intercept angle of the cam changed as the cam rotates and expands. In 1973, Greg Lowe filed for a patent for a cam that had a "constant intercept" angle. Using a

logarithmic spiral A logarithmic spiral, equiangular spiral, or growth spiral is a self-similarity, self-similar spiral curve that often appears in nature. The first to describe a logarithmic spiral was Albrecht Dürer (1525) who called it an "eternal line" ("ewi ...

shape resulted in a uniform angle between the rock and each lobe of the cam; this constant angle is designed to always provide the necessary friction to hold a cam in equilibrium. Designed so that a load produces a rotational force, the logarithmic cam shape allowed for a single device to fit securely in a range of crack sizes. Modern SLCDs were invented by Ray Jardine in 1978 (US patent 4,184,657) and sold under the brand name of "Friends". Ray designed a spring-loaded opposing multiple cam unit with a more stable 13.75 degree camming angle and an innovative triggering mechanism. (The term ''friend'' is widely used by climbers to refer to SLCDs in general, but properly speaking it refers to the brand popularized by Mark Vallance and manufactured by Wild Country). Other popular brands include Black Diamond Camalots, Metolius Power Cams, DMM 4CUs, Trango FlexCams, and CCH Aliens.

Modern use

The invention of SLCDs revolutionized rock climbing because it meant that parallel and flaring cracks could be easily protected. Furthermore, unlike

piton A piton (; also called ''pin'' or ''peg'') in big wall climbing and in aid climbing is a metal spike (usually steel) that is driven into a crack or seam in the climbing surface using a Rock climbing hammer, climbing hammer, and which acts as an ...

s, SLCDs can be removed easily without causing damage to the rock, which made

clean climbing Clean climbing is rock climbing techniques and equipment which climbers use in order to avoid damage to the rock. These techniques date at least in part from the 1920s and earlier in England, but the term itself may have emerged in about 1970 dur ...

(climbing without damaging the rock) practical on many more climbs. Since the invention of the Technical Friend (that replaces the original one-piece

machined Machining is a manufacturing process where a desired shape or part is created using the controlled removal of material, most often metal, from a larger piece of raw material by cutting. Machining is a form of subtractive manufacturing, which util ...

alloy shaft with a

brazed Brazing is a metal-joining process in which two or more metal items are joined by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal. Brazing differs from welding in ...

assembly incorporating a length of thick

stainless-steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chr ...

cable, which is better able to cope with loading over an edge), there has been a great deal of development of the SLCD by a variety of manufacturers. For example, the adoption of the dual axle design by Black Diamond, the invention of three-lobed camming units to fit smaller cracks, and the more recent invention of the Link Cam by Omega Pacific, a design that allows one SLCD to span an even larger range of crack sizes. SLCDs are sold in various sizes to fit a diverse range of cracks from about wide, though devices of below about or above about are not often seen. To fit non-parallel cracks, there are SLCDs with asymmetrical "offset" cams and devices that expand the lobes independently (Totem Cam). Traditional climbers frequently climb with numerous and variously sized SLCDs to cover a wide range of crack sizes, often having multiples of the same size, depending on the protection requirements of the climb. Some popular climbing areas like Indian Creek, UT have extremely consistent feature sizes that require climbers to carry double-digit numbers of the same size SLCDs to properly protect a route.

References

External links

Elastic Model of SLCD Holding Power
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