Ripping Cams

31 July 2019

Ripping Cams

What causes bomber cams to rip?

Category: Q&A

Hi Andy



This just might be a dumb ass question but I had a cam rip out yesterday which seemed to me to be perfectly solid. Now I’m having the jitters how good cams are? I was climbing on limestone.

GB

Oh God, this is one of those subjects you get on forums that make my head bleed, where people begin to go on about camming angles and coefficients of friction, all of which have no baring on leg-breaking reality (if you want that then John Middendorf’s CAMS-A Technical Review is the place to start).

I guess I’d say that cams are generally always far more bomber than they appear, in that even in really bad placements, placements outside of the ideal (under and over cammed, not all lobes in contact etc), they generally still somehow work, and so can be viewed as remarkably forgiving, that they never rip out… unless they do!

When they do rip out, generally (in my experience) it’s because the rock expanded or was loose (both of which are on the same spectrum of solid to not solid at all). The way I teach this is to imagine placing a cam between a bookcase and the wall and between a washing machine and a wall. With the bookcase, as soon as you begin to apply any pressure on the cam it will just pull out, and may well make the bookshelf fall over, while a washing machine feels more secure, it doesn’t move, but if you put 8 kN of force through it, it will rip (it only takes a very small expansion for a cam to fail). Now imagine if you found a crack in the brickwork in the house, yes the cam will feel much more solid, and there will be no expansion or looseness, as you have five hundred bricks on either side, but apply 8 kN again and the brick will just disintegrate under the load and again the cam will rip (this is the issue you find when climbing on really soft sandstone). This is easy to get your head around, but now think about how friction affects this, think of a cam placed in a wooded crack, a steel crack, a glass crack, or rough concrete. The cam can sometimes have nothing that allows it to get that initial ‘stick’ that allows the cam to grip against the contact surface, allowing it to begin to cam. Instead, it just gets yanked out before it can deploy its incredible superpowers. The ability to ‘stick’ is what makes some micro cams the best on the market, such as a soft alloy black Totem, and others, that use hard alloy, less good. But both soft and hard cams still need something to prime the camming pump.

This is the problem you will encounter with very hard or smooth (or both) rock, such as limestone, slate, quartz, diorite, basalt, or very worn, smooth and polished placements in rock that is traditionally ideal for cams, such as granite. Even here, the hard rock type and/or polish are only a component that can lead to failure (like a plane crash you generally need more than one thing, not in your favour). Another element is the nature of the placement. Is it flared or parallel? Is the interior of the crack uniform, or is it knobbly and bumpy?

In the opening scenes of Psycho Vertical you see me take a fall off the first pitch of Tempest on El Cap, a pitch I’d heard Alex Lowe had had the same problems on, namely you have bomber cams that just shift under load. When I fell I had one bomber cam in and was clipped to a second, and all just ripped out! Although granite, the rock here seemed very hard and smooth, almost like slate, and the cams just didn’t seem to engage, and just skittered around. Scary!

So what do you do on such rock? Well on this kind of rock you need to focus on using nuts as much as you can, which also means digging out your big nuts, Rockcentrics, hexes and Torque nuts. On rock styles such as limestone, you can cut down your cam rack to the bone, and go for triple wires and more draws (tricams are also often more effective, as they can fit into pockets that cams won’t).

If you do have to use cams on less than ideal for cam placements rock, then how do you make sure they don’t rip? Well, again this is down to rock type, cam and rock hardness, friction, and the nature of the placement. You cannot change the rock type, but looking for higher friction spots makes a big difference, as well as avoiding parallel-sided placements, the ideal placement more like a nut, with a slight constriction below the placement, or a pod or flare. Once you’ve found the best placement then give it a hard tug to see if it’s sticking, and always use a long extender to stop it falling out (another problem with smooth placements).

Lastly, when climbing at your limit on rock types that can provide questionable gear (the kind of rock that tends to be bolted), then always go for strength in numbers, placing gear often, so that if something does rip it won’t be R.I.P!

Note: If you'd like to ask a question - no matter how dumb - then email me and I'll try and help.

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Andy Kirkpatrick
Andy Kirkpatrick

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.

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