The benefits of Cams
Very few trad climbers leave the ground without some kind of camming device on their rack these days. The vast majority of protection opportunities on trad climbs come in the form of cracks, these either taper or are of a continuous width. Being able to make use of both types of crack keeps you safer.
For tapering cracks use Passive protection (diagram on left). Simply put: find an appropriately sized wedge and pull it into the narrowing until it lodges. For parallel sided cracks, a mechanism to transfer force away from the crack into the sides of the crack is needed (diagram on right).
Simple camming devices
Hexes can create the camming action, although limited in their range. They often require more than one free hand to set them in, and free them from, their cammed position. This makes them best suited to easier climbs, where cracks tend to be wide enough to manipulate protection inside, and a less steep angle may let you use both hands.
Camp’s Tricams are more suited to regular camming use and easier to handle. They also come in a large size range.
These are by far the cheapest way to protect parallel sided cracks.
Spring-loaded camming devices
The trad climbing scene was revolutionised when SLCDs were first sold. They could be placed quickly, with one hand, they held themselves in cracks and each size covered a large range of crack widths. These benefits explain why SLCDs still make up the vast majority of camming devices used, despite the higher price.
The basic design has changed little in thirty years, but refinements have come in the form of size, ergonomics and modern materials. While all SLCDs sold in the UK meet European safety standards, small design tweaks will change your experience when climbing.
Which stem design?
Cams either have a single stem (left) that runs from the axle to the sling or a double stem (right) in a U shape. Since Wild Country's Forged Friends were replaced by their Technical Friends all single stem cams use a stem which can flex in the direction of load which is applied. This is an advantage in horizontal cracks where the stem itself can be loaded over an edge.
On cams with a U shaped stem, the trigger bar is typically held captive between the two stems. This means that the trigger can be pulled with just one finger and the bottom of the U can be comfortably held with a palm. However the extra stem does create a wider cam, which limits the width of cracks that it can be used in. It also limits the ability of the unit to flex when placed in a vertical crack.
One axle or two?
For many years every cam had one axle and even when Black Diamond introduced the Camalot, the first twin axle cam, the design was patented and exclusive. As of 2010 there is now a competitor in the form of the DMM Dragon (left). The advantage of having one axle per pair of lobes is that the more the trigger is pulled, the more the lobes overlap. This allows them to fit into smaller cracks than single axle cams of the same lobe size. This increase in range means you are more likely to get the right size the first time.
However a second axle requires more metal, so these cams tend to be heavier. Some argue that this extra weight is offset by the fact that you are covering a wider range of crack sizes with less units. The other advantage is that the lobes are held captive within the axles so they cannot move beyond their intended range of use. When you stuff your rack into your pack or sit on a few cams when setting up a belay, the lobes can move into positions they were not designed to be in putting strain on the trigger cables.
Three lobes or four?
Due to refinement of the four lobed cams, the three lobed cams are becoming increasingly uncommon. However there are many still available, especially in the smallest sizes. The major advantage is the total head width reduced by approximately a quarter, increasing your placement options. This also translates into a weight reduction.
They are also less prone to 'walking' as the lobes are closer together. After placing a cam, you climb past it pulling the rope to the left and to the right. If the cam is under tension where it is attached to the rope, these movements turn the stem into a lever causing movement. Worst case scenario is having a cam move out of a placement, or moving so deep into a crack that it cannot be retrieved.
The disadvantage to such designs is that fewer lobes adapt less well to complex crack shapes.
Most manufacturers have a few little features to distinguish their designs from others. Here are a few of them and why you might consider them an advantage.
Two possible sling lengths are offered by extendable slings. slings can be used doubled up for racking, aiding and close to the ground, . For wandering pitches, pull the loop to give a single loop which is double the length. This can potentially save you having to use a quickdraw.
Metolius' Range Finder system gives a visual indication of how good your placement is with a 'traffic light' code. The colour of the dot where the lobe is touching the inside of the crack helps you to choose the right cam for the crack. This is especially useful to those who are new to placing cams.
Are the small protrusions which overlap on pairs of neighbouring lobes. They prevent the lobes from inverting. Relatively fragile trigger wires are less likely to be damaged if the lobes cannot move out of position. Some stops are rated to allow cams to be used as passive protection like a hex.
Metolius have started to use Kevlar cord in place of the traditional steel wire as the link between trigger and lobes. Flexible, very strong and abrasion resistant makes it very well suited to the job.
Camp Ball Nuts use a unique ball and groove system which mechanically is more akin to using a pair of standard nuts than a SLCD. In use however they operate very much like a cam. They are for relatively specialist uses and can offer protection in very thin cracks unlike anything else.
Nylon slings considered a bit old-fashioned now. Dyneema blends offer a better strength to weight ratio and are coming down in price. However short cam slings tend to suffer a lot of abrasion against rock (especially when aid climbing). Nylon deals better with abrasion than Dyneema and Black Diamond sew two layers of it for their cam slings so they last as long as possible.