physics

Spring-loaded camming device

Spring-loaded camming device is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Spring-loaded camming device rather than just read about it. In short: 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 axle forces the cams to spread further apart.

Key takeaways

Spring-loaded camming device belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Spring-loaded camming device to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Spring-loaded camming device from memory before moving on to harder problems.

Reference excerpt

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 axle forces the cams to spread further apart. It is then attached to a sling and carabiner 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 bore 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 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 pitons, SLCDs can be removed easily without causing damage to the rock, which made clean climbing (climbing without damaging the rock) practical on many more climbs. Since the invention of the Technical Friend (that replaces the original one-piece machined alloy shaft with a brazed assembly incorporating a length of thick stainless-steel 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 6–300 millimetres (0.2–10 in) wide, though devices of below about 10 millimetres (0.4 in) or above about 100 millimetres (4 in) 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 Engineering Principles Used in the Design of Camming Devices

Illustrations

Worked examples

Example 1 — a first encounter with Spring-loaded camming device

Start with the simplest possible case. Write down what Spring-loaded camming device claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Spring-loaded camming device before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Spring-loaded camming device ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Spring-loaded camming device

In research: Spring-loaded camming device appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Spring-loaded camming device in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Spring-loaded camming device is common in secondary-school and first-year university syllabi. It links to neighbouring topics Climbing equipment, Mountaineering equipment, Russian inventions, so understanding it makes those chapters shorter.
In everyday life: Look for Spring-loaded camming device outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Spring-loaded camming device in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Spring-loaded camming device means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Spring-loaded camming device out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Spring-loaded camming device in simple terms?

Why does Spring-loaded camming device matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Spring-loaded camming device?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Spring-loaded camming device.