A guide to spring loaded cams
08 November 2008
Note: Many of these articles are very old, and although the technical information is still relevant the equipment mentioned may not be (for example a Stormy cooker was state of that art in 1995, but not in 2021).
Spring loaded camming devices (SLCDs) have been saving climbers lives and calming jittery nerves for nearly three decades, bringing instant high strength protection to all rock types and at all grades. The beauty of the SLCD is not only that it gives a broader size range then fixed passive protection (nuts), and that it works in a wide variety of placements where such passive protection won’t (parallel cracks, pods, flares), but that it fires in with minimal fuss, saving arm power easily lost fiddling in wires. SLCD are also very forgiving piece of protection, very rarely ripping even when badly placed, and generally, if it ‘goes in’ it’ll stay in.
The problem is that deciding which SLCDs to buy when building a rack, or replacing those original solid stemmed 70’s Friends can prove a dizzying and confusing affair, as the shear range of SLCDs on the market makes the choice anything but simple. As with most things these days there is a mass of conflicting advice on what makes the ideal cam, with every manufacturer singing the praises of their own design. Another factor is the huge difference in cam prices, with budget models coming in at well under £20, with other retail of for £40, begging the question “how much better is a £40 cam over a bargain basement cam?”
The aim of this article is to make this choice simpler, by giving you a little more background when it comes to these choices.
Single flexible stem
Introduced by Wild Country with their single steel cabled flexi Friend, this design creates a stem that can adapt to the angle of pull, working even in horizontal shallow placements. The single stem is flexible in all directions, and generally flexes back to its original shape and orientation. One problem with this design is that when forced must be applied to the trigger (such as when trying to unstuck a unit), the cable can bend, making it harder to operate (a bit like brewers droop). This has been overcome on several models by either enclosing, or supporting the cable with a plastic frame or tube – making it both a rigid and flexible unit.
This style of frame is best demonstrated on the now defuncted HB Quadcam, with a steel cable forming a U shaped stem attached on either side of the cam head. This design gives an almost semi rigid design, aiding placements, and protecting the trigger wires (which are help along with the trigger with the stem itself), and using this system it’s possible to achieve a very low weight. The downside of the design is that the cable can interfere with some placements, and can become bent if loaded across the U-frame (where it is rigid).
These days there’s only Wild Country that produce rigid stemmed SLCD in the form of their forged friends. In the smaller sizes these units have several drawbacks, namely their lack of strength when placed in shallow placements (old school climbers would add a short tie off loop of dyneema to the stem to overcome this). Yet in their larger sizes (3 to 4) these cams come into their own, being very strong, cheap, robust and lightweight (they have a forged alloy Stem then a steel cable), and the 3.5 and 4 are highly recommended.
These days everything revolves around weight and it would be foolish if you where to ignore this when choosing your cams, as cams are probably the most weighty item on your harness, plus you will often be carrying over half a dozen units as well.
This means a weight saving of several grams on each unit may pay in the long run, especially if your climbs involve long approaches or take place in the high mountains. When looking at the relative weights of cams the biggest weight savings occur with the larger sizes, and you should also take into account practical details as well, such as benefit/weight of having a adjustable 30cm sling on a cam rather then a 10cm (this may save you some quick draws on a climb one).
Luckily most of the new and up-and-coming SLCD designs are built with a view to being lighter weight then the competition, but with some designs it needs to be excepted that in most cases the lower the weight the lower the lifespan, as lighter materials and bare bones design do have there drawbacks.
SLCD prices vary wildly, and this leads to a great deal on confusion, especially over security and strength, after all how can a £15 be a strong as one twice the price? Well the good news is that all cams pass the minimum CE tests for strength, and all the main cams on the market come from reputable factories, with many operating a 3 sigma rating (meaning they are far stronger then it says on the label). The difference in price are easy to see once placed side by side, as the budget models feature basic components and construction (no fancy colours, extendable dyneema tape, or plastic exoskeletons), generally being the sort of unsophisticated SLCD we where buying for twice the price 10 years ago. Never the less they are just as strong and reliable and should for many years, and if you never played around with a Metolius Powercam, BD Camalot or Wild Country Zero you’d probably never know the difference. This difference is an increased sophistication of design, that gives a smother or ergonomic cam action, colour coding, and more user friendly features (milled cam stops for example).
Head width (the sideways diameter of the unit rather then it’s maximum camming range) is one of the most important aspects of the cam, increasing the smaller the cam goes. In the large size to narrow a cam can lead to instability, as a broader size allows the cams to locate over a broader range of crack, yet this has to be offset by the fact that a wide head may not fit into a shallow crack. One the smaller units this isn’t quite so important as the cam lobe sizes are actually narrower so relatively speaking then still maintain stability. The ideal in the finger and lower sizes is a head width around the same as two fingers. This means in finger racks, pockets or scars, you know of you can stuff your fingers in, then you can also stuff a cam.
The vast majority of SLCDs on the market feature 4 cams, as these offer the best stability, contact surface area, and adaptability to variations in the placements shape. Three cammed devices, or TCUs (three cammed units) remove one of the cams to reduce the overall width of the head, making them easier to place in tight spots (shallow cracks, peg scars). TCUs are also generally lighter, but do suffer from a lower holding power when compared to a 4CU in an ideal placement, but the question is what if only a TCU will go?
Black Diamond was the first company to promote the passive strength of their cams, meaning that even when fully opened the cam would still be able to hold a fall – only in ‘nut’ mode rather then cam mode. This was due to their unique double axel design, and was rather more of a bonus rather then a real design purpose. Other single axle cams didn’t have this ability, as any ‘open’ loading would simple snap off the pins that stopped the cam from inverting. This changed when companies like wild country began forging cams rather then simply cutting them out of bar stock, allowing them to do away with the flimsy pins and replace them with beefy stops. Now most top end cams feature cam stops, but how important is this feature? Well most climbers would never consider placing a cam in a opened ‘umbrella’ mode, as it’s very unstable and prone to falling out, but it does offer far more security if the cam’s tipped out (meaning it’s barely camming at all). In such as position if it was to rip and be dragged through the crack, then there’s chance that it may catch. Even if this isn’t the case then at least the cam won’t be broken if it’s ripped out while tipped out.
SLCDs are very, very strong and I’ve never heard on one breaking (ignoring Russian titanium models) in action, but due to the nature of how they work they will fail miles before their cables break or spindles explode. Due to the nature of how SLCDs work they just don’t break, failing instead by ripping out of the rock long before the stems, slings or cam lobes have chance to fail. All cams sold in the UK pass CE minimum strength tests which means that you can rest assure that even if it wasn’t to rip out it would provide a huge degree of protection.
The greater the camming range the lower the strength, meaning a balance needs to be struck, because a cam that ranges from fingertip to fist would have the holding power of a strawberry, while at the opposite end a cam with the holding power of a bolt would require you to carry 50 units! Ray Jardine calculated the optimum caming angle to be 13.75 degrees, and this still seems to be the standard by most companies. Anything more then this is usually considered ‘greedy’ and the only cam the bucks this trend is Black Diamonds double axeled Camalot design (BD modified their cams several years ago swapping a more greedy camming angle for something with more holding power). This range question has always been one of the debate points between climbers, namely do you carry more lighter units (single axel units are generally lighter), or less double axel units that are heavier?
This question is set to expand further as Metolius, Trango and others bring advance cam designs that feature broader cam ranges without sacrificing holding power or weight. Make take on the whole business (based on using both types of cams regularly), is that the actual differences is marginal. The reality is that you may be able to cover the same size range with slightly less units, but often you end up doubling up on sizes because you don’t want just want one piece that goes in. The alternative is carrying more units, but which are typically lighter. The only real advantage I see is that double axle cams or new style designs is that it’s easier to place the right cam first go, making them good for those who haven’t (or can’t) developed an eye for this kind of thing. Also if you’re on terrain where cams aren’t vital you can cover all you bases with less (although the may weight the same as taking more units). The bottom line is once the debate leaves the pub or shop floor there’s little difference and it’s all down to a matter of choice.
The tapes that are sewn into your SLCD are one of the most important aspect of the units design. First off the reduce the risk of unsettling the cams position, possibly causing it to shift out of position and so fail. The sling also reduces the chance of the SLCD walking into a placement and becoming stuck. The tapes also help colour code and identify the unit. For anything but straight up pitches it’s still worth extending any camming unit to avoid any movement as the tape of most cams is still relatively short. The exception to this are the units that feature extendable slings (DMM units), that allow the tape to be lengthened or shortened – a great feature. One aspect that is often overlooked is the ability to clip into the cam itself rather then the tape, perhaps to gain or few inches while aiding, or to reduce your potential fall by 15cm!