Active climbing cam, 1st report

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Executive Summary

For the first stage of our design, we were able to do product dissections and perform some analysis. Because of a failure of our product is fatal to its users, we recognized some important requirements. The product must be able to withstand a big dynamic load, it must be long lasting and the signs of damage should be clear. We have identified a few customer needs in order to direct us to the right path in redesigning our product. Some of these needs are less weight, easy placement and removal, easy to handle harness, affordable, low maintenance and accommodates different hand sizes. Of all these are important when we are thinking of opportunities in redesigning our product. We were able to disassemble our product although it was a bit difficult to do so since part of the product was welded. There are 12 different parts and 24 parts in total. The weight of the cam that we dissected was 52.5g. The cam that we dissected was an old design cam and has been used many times. Even though the weight is small, climbers carry a few cams, carabiners, chalk and nuts. All of these equipments add up to the weight that they have to carry when climbing. This is why reducing weight of our product is important but of course safety comes first. We performed FMEA, DFMA and DFE. FMEA for this product is crucial as mentioned before, a failure is fatal. From our FMEA, failure of the main cable and trigger wires are the most hazardous. The parts that usually fail first are the sling and the trigger wires. Because of this, we are thinking of integrating signs of wear or a detector to show if the product should be retired. From our DFMA, it shows that most of our products are machined and there are a few welding. So, in our DFE analysis, we suggested casting instead of machining as this will result in reducing waste of material. The welding can also be replaced by either redesigning our product without the need to weld. The products may be recycled by sending the product back to companies that sell them. After finishing these analyses, we are moving on towards research on the product and ideas for redesigning the product to fulfill the requirements that we have set earlier.

Product Overview

The climbing cam is a rock climbing protection equipment. The main purpose of the camming device is to shorten the distance a climber could fall, and to anchor climbers to the rock.

Product Requirements

The primary product requirement is that it functions reliably during frequent and varied use. Failure during use of a climbing apparatus can result in death or serious injury. In order for the product to be useful in the mountains it must withstand the abuse of the harsh, exposed environment along with the impacts of frequent use. The climbing cam must function properly each time it is placed to protect against a fall. Furthermore, the cam must function to some extent even when placements are not completely ideal. The size, orientation, or shape of a fissure in the rock may not hold the cam in the ideal position, yet the product must still perform outside the bounds of its ideal use. The most salient concern for this product is that the device functions properly to mitigate the inherent dangers in climbing. A more inclusive inventory of product requirements is listed below:

• Reliable functioning in a fall
• Able to withstand the impacts of climbing
• Functions in diverse placements
• Durable and long lasting
• Easy to identify wear or deterioration

Customer Needs

Beyond the performance requirements of the product, the customer also has specialized needs in order for the product to be useful. The customer’s main concern is that the product enhances the climbing experience through safety, allowing people to travel beyond pervious limits. Climbing is typically pursued for sport or leisure, thus the primary goal may be personal enjoyment. The customer needs a product that's benefits outweigh its detractions. In order for the product to enhance the climbing experience it must be easy and efficient to use, and low in weight as not to impede progress. The customer must be able to quickly and easily place and remove the product from the rock. Often times a more experienced climber will place the gear into the rock while a less experienced climber must be able to remove it. This requires that the product's removal is intuitive for an unskilled climber who may be exeriencing many other stresses while trying to remove the product from the rock. In order for the product to enhance the experience it must be of minimal weight. An overly heavy device may impede and slow a climber to the point of it actually putting the climber in danger. The customer needs of this product rely on an increase in safety without seriously slowing a climber’s movement. A more inclusive inventory of customer needs is listed below:

• Low weight
• Quick and easy placement and removal
• Accommodates removal by less skilled climbers
• Easy to handle between harness and rock
• Fast differentiation between sizes
• Compatible with sizes of older models and other types of climbing protection
• Affordable to average climber
• Low maintenance that can be performed in-field
• Accommodates a variety of hand sizes

Analysis of components

Identification of individual parts

Active climbing cam after dissection, with parts labeled.

Manufacture of parts

The climbing cam is a mechanical device composed of 12 different parts.

Part No. Name Weight (g) Qty. Function Manufacture method Picture
1 spring 0.5 2 Creates force that pushes the lobes against the crack walls to maintain position until loaded in a fall or removed by climber purchased metal wire
2 cam lobes 7 3 Main source of friction and subsequent force holding the cam in place; provides the reaction force to the load. extruded shape cut into slices by saw and drilled, hole that holds trigger wire has specific shape
(body) 45 1
3 main cable 1 Holds the trigger and responsible for transmitting the strain of the weight. purchased cable
4 thin plastic tubes 2 Help the trigger to slide easily through main cable. purchased plastic tubing
5 sling; plastic tube (orange) 1 Sling (part of the main cable) is the main place where the hanging weight is loaded. The plastic tube protects the main cable from metal carabiners and protects nylon slings from the cable. The color of plastic indicates the size of the cam. purchased colored tubing
6 trigger 1 Pulls the trigger wires that action the device. extruded bar sliced and then textured for grip
7 axle 1 Holds the lobes in place, and holds the equilibrium between the load and the resistant force coming from the lobes. extruded form, hardened metal, sliced to desired length
8 axle ends 2 Keep the axle and the main cable together. welded metal
9 finger support 1 allows user to apply counter force to retract the trigger extruded metal rod stamped with "Metolius" and size number
10 spring pin 3 Keeps the spring attached to the lobes. rolled sheet metal
11 trigger wire 3 Transmits the triggering force from the trigger to the lobes. purchased narrow cable and wire. wire has nail head and is bent to fit around cam lobes
12 copper connector 3 holds the two pieces of the trigger wire together. bent around the two sections and welded together
TOTAL 52.5 24

Assembly Procedure

The climbing cam seems to have been assembled roughly using the following process. Most of the parts used in this assembly do not have any external fasteners/screws; this reduces the assembly time considerably. Some parts however require welding to be secured which will increase assembly time. Finally there are many very small parts which would produce handling difficulties during orientation and insertion.

A. Initial Base Assembly

1. Taking the thick cable (3) and inserting it into the thick plastic orange tube (5).
2. Bending the thick cable to form a ‘U’ shape.
3. The bent thick cable seems to have been inserted into the finger support (9) and then fused in place.
4. Two thin plastic tubes (4) were then inserted over the open side of the assembly.

B. Trigger Assembly

1. The three trigger wires (11) were connected and fused into the trigger (6).
2. Then the wires attaching the cam lobes (2) to the trigger assembly are joined and fused using the three copper connectors (12).
3. Spring pins (10) are then inserted into the three cam lobes.

C. Final Assembly

1. The initial base assembly is then inserted through the trigger base assembly.
2. Then the cam lobes along with the two springs (1) are aligned on the axle.
3. Axle ends (8) are then fused onto the initial base assembly.
4. Finally the axle is put through the axle ends and welded shut.

* Note: numbers in parentheses correspond to part number


Camming device during triggering process.
Camming device during triggering process.

On its initial position, the camming device starts with the three lobes aligned horizontally. The trigger [6] is pulled towards the sling [5] using the index and middle finger. This movement slides the trigger down pulling the trigger wires [11], which are attached to the trigger on one end, and to the lobes on the other end. The tension on the cables causes the lobes [2] to rotate around the axle [7]; the trigger must be pulled until the lobes are completely aligned vertically. During the triggering process, the springs [1] come into action, creating an opposite force that causes the lobes to resist to rotation (and at the same time trying to bring the lobes back to their initial position); the fingers in the trigger must therefore apply resistance to keep the lobes aligned vertically. At this time is when the cam is inserted in the crack. Once the cam is in place, the trigger must be released, causing the lobes to return to their normal position. Now, the springs are in charge of pushing the lobes against the rock walls inside the crack.

Watch a demonstration video on using a climbing cam that we did in the lab.


DFMA and DFE Analyses

The design for manufacture-assembly (DFMA) and the environment (DFE) analyses were performed for each individual component of the mechanism. The outcomes are arranged as follows:

Part number Parts DFMA DFE
1 spring attaching the spring onto the axle is no problem as there is only one way it can go on, attaching the springs to the pins are complicated due to their very small size spring may be made leaner, metal can be recycled
2 cam lobes Due to the partial symmetry of the cam lobes, orientation time during assembly is reduced casting instead of machining to reduce waste metal, recycle metal
3 main cable Fully symmetrical and large enough to manipulate it easily with bare hands increase durability to maximize first life, recycle material
4 thin plastic tubes Designed for easy alignment as they both have axial symmetry make plastic tube shorter, recycle plastic
5 sling; plastic tube (orange) Similar to the thin plastic tubes this tube has axial symmetry and thus orientation time during assembly is minimized less thick plastic, recycle plastic
6 trigger The trigger can be inserted both directions i.e. it only has one axis which it must be rotated upon insertion use less material, recycle material
7 axle The axle is made of extremely durable metal and is a simple cylinder construction which is easy to handle. Additionally the parts which have to be inserted on the axle can be done so easily as there is very little resistance to insertion use material efficiently, casting instead of machining, recycle metal
8 axle ends The ends have to be oriented over two axes upon insertion which increased the time of assembly this can be eliminated by making it symmetrical over one face use less material to weld, use a lower emission production like join/bend
9 finger support Simple part which only requires two forms of alignment on insertion, also it is large enough to handle with the hands easily reduce mass, casting instead of machining the holes, recycle material
10 spring pin the spring pins are symmetrical over one axis but they are extremely small and insertion into the cam lobes would require extra time use less metal, recycle material
11 trigger wire The wire is simple and large enough to install without the aid of other tools increase durability to maximize first life, recycle material
12 copper connector The copper connectors again are extremely small but they are symmetrical over two axes thus orientation is not a problem with them, insertion and securing though will take additional time as it needs to be welded use lighter material, recycle less material


The design for the environment is to analyze this climbing cam's environmental impact, increase its life cycle and reduce its impact. In order to reduce its environmental impact, the material can be made leaner. However, because this product is very hazardous if it fails, safety comes first as to not let the product fail. This product involves the life of the users. Instead of reducing the material for the product, the manufacturing of the components can be chosen so that there will be less waste generated during manufacturing. For example the cam lobes can be manufactured by casting instead of machining. The end of the axle appeared to be weld. The welding may be substituted to a joint or a bend but a test should be done to ensure the product will not fail. After its life cycle, the product should be recycled as most of the components are made of metal and plastic. Most of the companies that sell climbing cams more than welcome users to return their products once it fails. They are finding out the reasons why it fails so they need retired cams. For an example, Metolius Climbing Company invites users to send them retired cams. They will do a research on it and recycle the cams after that.


Two major areas of potential failure were identified in the product. Although several individual parts failures could result in a hazardous failure of the product, the failures are easy to detect and unlikely to occur. The product was designed as a safety device for use in demanding environments, thus the parts are typically reinforced where catastrophic failures could occur. The two parts with high failure RPN values were the main cable, and the trigger wires, both parts made of braided wire cable. In both cases, the cable could incur internal damage that would be difficult for the user to detect that could weaken the product and lead to complete failures. Complete failure of the main cable is very severe and would yield the product inoperable and hazardous. Complete failure of one of the trigger cables would seriously disrupt usage of the product, and failure of all three would yield the product nearly inoperable, yet still safe for climbing if placement is made. A complete failure of the main cable could occur during a climber fall, as the weight of the fall is transferred through the cable to the axle. Complete failure of the trigger cables would be unlikely during a climber fall as they are not impacted in the fall. Both of these weaknesses should be corrected through material selection, and possibly reinforcements surrounding the cables. The trigger cables could be designed to accommodate at home replacement, encouraging and easing maintenance. Below is a more complete FMEA of each part.
A failure of the product itself is significantly less likely than a user error that could result in a catastrophic failure. When examining the product, which appears to be roughly 20 years old and extensively used, we saw few sings of wear that could lead to a dangerous failure. The concern of a failure is thus less in the manufacture of the product itself but rather in a sub-ideal placement of the cam. The cam lobes may be inserted into the rock in an orientation that leaveas them retracted to differing degrees. Although this is covered in introductory climbing courses as an unreliable placement, the situations of real climbing sometimes force this type of usage. If each lobe is not engaged on the rock to the same degree the cam can spin when loaded and possibly come free from the rock. Another common unreliable placement of the cam is with the lobes retracted too far or not far enough. The ideal placement requires the lobes to be retracted within the middle 50% of the range of the device. A cam retracted beyond this range will be difficult to remove and a cam placed with very little retraction may not expand enough in a fall to support the load. This is generally the result of a climber not possesing the proper sized cam for a given placment, and rather than climb on with no protection a poorly placed cam may be used. Placements in poor quality rock can also result in failure as the rock may not be physically capable of supporting the forces of a fall. Active climbign cams, such as our product can be placed into the rock in both the active, typical manner, or as a passive piece of protection that is placed behind a constriction in the rock but does not rely on the spring tension of the device. Not all cams are specified for this type of placement, and due to the age of our product we are unsure if ti was originally intended for the passive use mode. Our confusion over the products specifications could also plague a climber using unfamiliar equipment. Some sort of marking on the product could easily mitigate this confusion, and possibly dangerous situation. Other human errors can occur in the time it takes to remove the cam from ones harness or sling and place it into the rock and secure it around the climbing rope. A climber will usually remove a cam from the harness loops once a possible placement has been located. If the particular piece of protection chosen does not fit into rock then it must be swapped for a different type or size. An experienced climber can usually do this with little trouble and the likelyhood of an experienced climber dropping a device while climbing under normal circumstances is rather small. Under unusual circumstances, such as unexpected weather or injury, when climbers are under exceptional stresses, the likelyhood of a dropped item may rise. This type of human failure is espeically dangerous as in an emergency extra gear my be need for a fast evacuation. A less experienced climber removing the cams from the rock does not greatly increase the chances of a dropped item. When the unskilled climber is removing the cams the climber is already on a secured belay from above and a personal fall would typically not be very dangerous. Thus, the climber can advance close enough to the cam to clip it directly into their harness before removing it from the rock. This does still leave a slim chance that climber could knock the device free from the rock while attempting to secure it to the harness but after removing it from the rope. This is however unlikely and not a major concern.

Part # Parts Failure Mode Effects of Failure S Causes of Failure O Design Controls D RPN
1 spring A spring detaches from the spring pin, or is somehow severed Failure of all 3 springs would result in complete failure of the cam in normal usage. The cam could still be partially functional with one or two failed springs but should not be used for climbing. cam could still function as passive protection without springs. 9 Overuse of spring, spring somehow slipping free from the pin 2 If spring is not properly attached the cam will not function 2 36
2 cam lobes A cam lobe is crushed or misshapen through use Failure of one cam lobe by serious deformation would reduce the friction provided by the cam it would also interfere with how the other lobes engaged within the rock. 7 Deformation from dropping or crushing in rock fall 3 Lobes are protected in design and able to withstand high impacts. Easy handling design reduces occurrence of dropping. 1 21
3 main cable Cable seriously deformed or bent. A severed cable would result in the cam no longer supporting the weight of a falling climber. Excessively worn or severely bent cables should be used with extreme caution. 9 Cable could become bent after impact on poorly placed cam. This type of impact could also fray or sever the cable. 5 Cable is thick and flexible. Internal damage could be difficult to detect. 6 270
4 thin plastic tubes Tubes dislodged or worn through failure of tubing would accelerate the deterioration of the main cable, thus reducing the lifespan of the product. Failure would also increase force needed to retract trigger. 5 After excessive use tubing can deteriorate 6 Primary wear to tubing is in visible regions. Regions with highest wear have minimal affect on performance 1 30
5 sling; plastic tube (orange) Tubing worn through Failure of tubing would result in faster wearing of main cable and also wearing on nylon slings often looped onto cam and clipped to rope. 5 Repeated clipping of metal on plastic causes deterioration 5 Thick, durable tubing used. Easy to identify 1 25
6 trigger Fracture of trigger or housing of trigger cables Failure of trigger would release trigger cables and make placement and retrieval of cam very difficult yet still possible 7 Fracture or serious deformation from impact 2 Metal trigger used, as opposed to plastic 1 14
7 axle Fracture of axle Failure of axle by complete fracture would result in a complete failure of the cam yielding it unsafe for use in climbing 9 Serious impact, probably from rock fall onto cam 1 Axle made from hardened metal, protected from impact by cam lobes 1 9
8 axle ends Axle end ripped from axle If both ends were to fail the cam would not support the weight of a falling climber. Failure of one end would result in an unbalanced force on the cam and the lobes would probably be spun free form the rock 9 Very strong impact in a direction difficult to apply during normal or even modified usage. 1 Force would be dissipated by trigger and finger support. Axle ends protected by lobes. 1 9
9 finger support Fracture or serious deformation Complete fracture of finger support would make retrieval and placement of cam difficult but still safe for climbing 7 Serious impact from rock fall or dropping 1 Finger support made from metal. 1 7
10 spring pin Crushing, bending, or fracture of pin failure of a spring pin would have the same effects as failure of the spring 9 Impact in an unusual direction over a small area 1 Spring pin shielded from impact by cam lobes. Difficult to view. 2 18
11 trigger wire Fraying or complete failure of wires Failure of all trigger wires would make placement and retrieval of cam extremely difficult, if not impossible in normal climbing situations. Partial failure of wires would make placement and retrieval difficult. 7 Impact, use in horizontal placements, or normal wearing on thin cables. 6 Wires replaceable in factory. Internal damage may not be dateable. 6 252
12 copper connector Connectors release trigger wire pieces Failure of the connectors would be very similar to failure of the trigger wires, making it difficult to place and remove the product 7 Direct impact onto connectors, wear on connectors. 2 Connections are welded. Failure obvious. 1 14
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