Over and Under Cam
I’m not going into cams in this short piece, as I’ve covered other aspects about them before in this series, no - this piece is just about avoiding two typical mistakes that those new to cams often make - namely under and over camming.
The ‘ideal placement’
A text book cam is probably one where the lobes are set at about 50% retraction - the sweet spot. As you move away, theoretically they’re not so good, with the danger zone being around 5% open and 5% squeezed tight. Metolius goes so far as to have the ideal cam position marked on their units (making having a least one of their cams a good training tool for novices). In reality a cam is pretty much strong from super tight and over cammed (imagine hammering it home), to about 2% to 5% depending on the rock, as in most cases it will be the rock that fails you, not the unit.
Undercamming (AKA ‘tipped out’)
In very soft rock, loose rock, or expanding flakes (most flakes have some elasticity in them) the force applied to the rock will cause it to yield, either opening it up or compressing it (sandstone). If your cam is set at 50% and is medium sized (2 inch), then the loss of some small degree is OK, say the cam diggs into the crud by a few millimetres. A well placed cam has range to waste and will hold. On the other hand if your unit is tipped out (almost totally open), and you only have 3% range left, and the flake expands even just a millimetre the cam with open up and rip. By the way don’t put your hopes in cam stops (these stop the ‘umbrellaring’ - were they invert), because in the small cams the stops just snap off as the cam inverts, and in the bigger units, or the ones with double axles, nine times out of ten the open cam loses its stability and rips anyway.
Compression and deformation can take place, especially with soft cams like Totems and Aliens (the soft material also give it some ‘stick’ making the trade of worthwhile). In hard granite a medium cam made from aluminium (Camalot for example) you’re not going to get any real deformation in the lobes so in extremis you can have a little more confidence. If on the other hand it was a tiny black Alien with a range as big as a beaked bean, then you’re not going to get away with a tipped out unit. The danger comes with small and micro cams where the total contact surface area against the rock may be measured in square millimetres. Add rock that has a irregular shape, perhaps some lichen, and such a cam requires a safe cam margin in order to stay in place.
One thing to say about tipped out cams is that with some care you can often squeeze out a placement even in a crack that looks too wide, either by placing it deeper or just searching around. If you’re making a very delicate ‘surgical’ placement then extend the cam with a 60cm sling.
But again, for any novice climber you need to focus on the ideal, and work away from there - so cams half open (or half closed). A good tip here is to measure the crack with your finger(s), then get a cam a bit less than twice as big - so two fingers side by side would be a red Alien for example. After a few hundred placements you’ll pick up the sizes and just know by sight or by touch what will fit.
The best thing about a tipped out cam is that it’s easy to clean, in fact more often than not it will just fall out, the only danger being it may become inverted in the crack and look like it’s good when it’s not.
Overcoming (AKA: ‘It’s fooking stuck!’)
Over camming a unit, where it is stuffed in the crack so the cam are 99% retracted is not bad safety wise, as it will hold and has plenty of slack to take up - but it’s not good for the long life of your rack, or your climbing partnership if that cams belongs to your mate.
Cams tent to be stuffed in because of fear - the tighter it is the safer you are. Novices can place them like this for that reason, stuffed in so tight you can’t pull back the trigger, thinking that they’re playing it safe - when they’re not (they’re just too lazy to work out how to use the cam in the best way possible).
Like I said, a cam retracted all the way is still full strength in the real world, and the main problem is that you do this too much you will end up with fixed cams, and loosing even a single cam on a big route can make life tough.
The mean reason for leaving some slack, even as little as 5%, is that for the cams to be retracted by the trigger you need somewhere for them to go. Once the trigger does nothing you’re in trouble.
Dealing with stuck overcammed units
First off follow the number one rule of galactic hitchhiking and ‘Don’t panic!’. If cams really did get fixed then you’d see them everywhere, and you don’t , so it will come out.
Here are some ideas on what to do:
- First off don’t damage the trigger by pulling too hard or knocking it around. The trigger is vital for getting the cam out as well as using it again, but is also the most delicate part of a cam. Treat it with respect and as soon as you work out it won’t retract the cam them try something else.
- First check if you can move some of the cam lobes with your finger? Sometimes there will just be two lobes that are jammed (as it’s a cam, there must be an opposing force). If only two are wedged tight then very often you can rotate the cam so that the cams are originated so they can be pushed into a wider crack, opening the stuck lobes.
- If all the cam lobes are stuck tight, or there is no way to rotate the unit, then remember that a cam only cams in the direct of pull. This means that often you can yank it sideways with enough force to get it to budge. You can do this by hooking the hook of the nut tool and yanking the lobes ones by one (clip a draw or two to the nut to to give you something to yank it with).
Fool proof cams?
For my money the nearest you get to an unstick able cam is something like Camalot or DMM Dragon, as double axle cams are just so much harder to get stuck (yes in a test rig they’re not as good, but on the rock they don’t fail). The number one reason for me is that a double axle cam lobe is always locked in line with the stem, were on many single axle units its possible for the two loves to rotate around so they are at 90 or 180 degrees to the unit. If you use a double axle unit and tell the novice to alway keep the range around 80% (so no more than 90% closed or 10% open) they’ll be safe.
As for trusting them, stick a unit in a steep crack, back it up, and play around jumping onto it and see what happens.
Andrew Kirkpatrick is a British mountaineer, author, motivational speaker and monologist. He is best known as a big wall climber, having scaled Yosemite's El Capitan 30+ times, including five solo ascents, and two one day ascents, as well as climbing in Patagonia, Africa, Alaska, Antarctica and the Alps.Follow @ Instagram