Mountain Project Logo

Gear failure (small cam)

Original Post
CSG · · Unknown Hometown · Joined Mar 2013 · Points: 0

While climbing the route "groovy" in the gunks on sunday my partner ripped a yellow totem basic, resulting in one of the inner lobes umbrella-ing. The fall was tiny (cam approx waist level) and he had a solid nut less than a foot below the cam so no injuries. The cam was placed by an inexperienced leader who insisted it was perfectly placed

Earlier in the day, on P1of MF , I placed a blue mastercam that appeared to be a textbook placement , only to rip the cam out with my hand when testing it. I have fallen many times on gear with no problems but these events have left me with some questions

First, what are others experiences with falling on totems? Ive whipped on the green and was impressed with it, now im not so sure.

Any general tips or experiences with small cams? Ie. Lobes should be cammed further in general than larger cams, etc.

Any gunks specific issues with cams and friction?

Thanks,
Chris

Malcolm Daly · · Hailey, ID · Joined Jan 2001 · Points: 380

Take home lesson #1: Never trust a single piece of gear.
Take home lesson #2: Tiny cams are sketchy at best.
Take home lesson #3: This was not gear failure, it was placement failure resulting in damaged gear. You should change the title of the thread. Totem Cams are as good as anything out there.

Climb safe,
Mal

Erik W · · Santa Cruz, CA · Joined Mar 2007 · Points: 280
Malcolm Daly wrote:You should change the title of the thread.
+1

... at least until you get more info. I'm w/Mal in suspecting placement failure.
Morgan Patterson · · NH · Joined Oct 2009 · Points: 8,945
JSH wrote:If it umbrella'd out ... it had room to umbrella.
+1 placement issue...
bearbreeder · · Unknown Hometown · Joined Mar 2009 · Points: 3,065

1. small nuts over small cams anyday if you can find a good placement

2. small cams "failures" are i suspect a large % of gear failures ... there is much less margin of error in terms of placement and walking ... even small cams that "look good" can pull

3. a cam that is rated passively can save your ass sometimes ... its not an excuse for not placing gear right, but people screw up ...

4. never trust a single piece ...

;)

thomas.w · · Denver, CO · Joined Jul 2011 · Points: 5

Sounds like user error. I wipped on that yellow totem basic on Sunday. The fall was decent and clean and presumably generated a sizeable force on that thing. It held, no worries. With that cam, you know if they aren't placed right they will umbrella and fail. That being said those cams are just bomber small pieces with the flexible stem, and the go to in the finger ranges.

Patrick Mulligan · · Reno, NV · Joined Oct 2011 · Points: 995

umbrella = placement or rock failure not gear failure

Larry S · · Easton, PA · Joined May 2010 · Points: 872

The small mastercams in shallow placements where the lobes are only slightly retracted can be pulled by flexing the cable the right way. Flexing the cam at the "coil" around the cable can push the trigger bar back, slightly retracting one set of lobes. It's a reproducible problem.

divnamite · · New York, NY · Joined Aug 2007 · Points: 90

What's everyone's definition of small cams?

Yellow Basic is the similar size as the C4 .4, no? That's pretty decent size cam.

bearbreeder · · Unknown Hometown · Joined Mar 2009 · Points: 3,065
divnamite wrote:What's everyone's definition of small cams? Yellow Basic is the similar size as the C4 .4, no? That's pretty decent size cam.
anything up to and including a purple C4 ... which is the same as the biggest red TCU incidentally

;)
rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526

Lots of people have already said it: this isn't a case of gear failure.

I almost agree with Bearbreeder about cam sizes: I think "small cam" means anything smaller than a purple camalot (he includes the purple camalot as a small cam). I totally agree with Bearbreeder about small nuts being a better option much of the time.

Here's the deal: there is no such thing as a bombproof small cam. Yes, they can hold big falls, but they can also blow unexpectedly, and even experienced leaders can be fooled.

Small cams have to be placed with as much cam compression as possible (without making it impossible to extract the cam), because there is very little play from ok to umbrella'd, and very small cam motions combined with rock irregularities can convert a good placement to a worthless one. For this reason, I don't think of small cams as really having a "range." They are more like a nut; there is a certain size crack that they fit (the almost maximal cam compression size), and any available play goes to keeping the cam solid if it moves.

If you are used to using cams in granite or sandstone, where the cracks are typically very uniform, then you'll find you have to pay more attention to placements in the Gunks, because the cracks are often irregular and even if not can have surface features (e.g. the embedded pebbles) that make for lots of internal size variation.

If you can, you should get your eyeballs up against the crack and try to see what happens to all four (or three) cams, while wiggling the unit back and forth a little to see what rope motions could do. Sometimes a placement can be improved by using the other cam orientation, and sometimes you have to try both orientations to see which seems best. This is especially true with BD C3's, which have one very wide cam which needs to be optimally situated.

Another problem with small cams (and not so small cams too) in irregular cracks is that sometimes one is forced to place the cam in a "pocket" in a vertical crack which makes it impossible to align the stem with the direction of the fall (the stem ends up being perpendicular to the rock face). With a flexible stem, the physics involved in the cam's holding power basically goes to hell in this situation, and it is hard to predict how much holding power you'll get. It may not be intuitive, but having a rigid stem actually increases the likelihood that the cam will function appropriately, and this is a reason why C3's are preferable to Aliens in such placements.

Of course, such pockets are sometimes, but not always, an excellent place to drop in a good nut.

slim · · Unknown Hometown · Joined Dec 2004 · Points: 1,103

i would define small cams as being in the silver or purple tcu range (ie black and blue aliens; silver, purple, and maybe green c3's; etc). once you get into the blue tcu/green alien size, there is a quite a bit more margin in terms of range that is used when the cam is loaded.

Noah Haber · · Unknown Hometown · Joined Aug 2010 · Points: 78
rgold wrote:It may not be intuitive, but having a rigid stem actually increases the likelihood that the cam will function appropriately, and this is a reason why C3's are preferable to Aliens in such placements.
Can you elaborate here? In my thinking, more rigidity increases the effective lever arm on the stem, causing rotational forces on the lobes (i.e. a higher ratio of outward force on the upper lobes:lower lobes). I would think that minimizing this lever arm (i.e. a more flexible stem) would be advantageous in a placement which is perpendicular to the fall direction.

Edit: also worth noting that I don't have a good intuitive grip on exactly how this works with the c3's weird u-stem system, as it also rotates when pulled on.
slim · · Unknown Hometown · Joined Dec 2004 · Points: 1,103

i completely disagree with rgold on that point.

jim.dangle · · Unknown Hometown · Joined Jul 2011 · Points: 5,882

Small cams are bomber when placed well but because there is less surface area on the cams they are less forgiving than larger cams. I don't regard any of the c4s as small cams.

One trick I would add is that it helps to set the cams so they don't pop without giving the lobes a chance to bite. I often try to place them in constrictions a bit like a nut (but obviously still camming). For this reason I think they work particularly well in thin granite cracks where are crystals and constrictions that help with bomber placements. Although I wouldn't say the walk more than larger cams because they are less forgiving walking is more problematic. Another reason to set in a constriction.

Also make sure to place them in the direction of potential falls. I often see people placing them straight in and such instances they will twist and can pop out pretty easily. This is especially true in shallow placements. I would almost rather fall on 2 lobes of micro cam than one shoved in perpendicular to the fall.

My 2 cents.

JIm

John Peters · · Unknown Hometown · Joined May 2013 · Points: 0
shoo wrote: Can you elaborate here? In my thinking, more rigidity increases the effective lever arm on the stem, causing rotational forces on the lobes (i.e. a higher ratio of outward force on the upper lobes:lower lobes). I would think that minimizing this lever arm (i.e. a more flexible stem) would be advantageous in a placement which is perpendicular to the fall direction. Edit: also worth noting that I don't have a good intuitive grip on exactly how this works with the c3's weird u-stem system, as it also rotates when pulled on.
I think it's similar to the sentiments expressed here:

alpineexposures.com/pages/b…

Further more one of the designers at Black Diamond had something quite interesting to say that hadnt actually occured to me that might help dispel some of the flexible vs stiff rumors out there:

Not only do we have tests to show that it (the ‘stiffness’ of the stem) is not a problem, but we have tests that show too much flexibility is a problem in certain placements. Think about how cams work in a perfect placement: you pull straight down on the cams, that force is converted to a rotational force on the cams, and the surface of the cams push against the rock surface. Now place a highly flexible cabled cam in a vertical bottoming crack (the stem is sticking out horizontally). Should be good right? Think again about how the cams need to work. Pull straight down on this placement and you’ll notice a large component of the downward force is acting parallel to the cam surfaces. This is not how the cam is designed to work. The cams will not push against the rock surface without a force perpendicular to the cams plane of movement. In short, it stops camming and acts like a nut placement. You need some torque on the placement to convert the parallel load to more of an outward one that can act on the cams. This torque is provided by the stiffness of the cable, or the length of the shank of head terminal, or some combination of both. In testing, the high flexible cables did not generate the torque necessary to hold the falls and the units slid sideways out of the placement at very low loads. We even made C3s proto types out of softer cable, only to watch them fail our bottoming crack test because of this issue.
ian watson · · Sandia park, NM · Joined Apr 2010 · Points: 235

When I think of pockets I think tri-cams not ridgid stems. maybe I am misunderstanding something.

MorganH · · Unknown Hometown · Joined Sep 2010 · Points: 197
rgold wrote: It may not be intuitive, but having a rigid stem actually increases the likelihood that the cam will function appropriately, and this is a reason why C3's are preferable to Aliens in such placements. Of course, such pockets are sometimes, but not always, an excellent place to drop in a good nut.
In many conditions, this is not at all true. In pin scars, the long/wide rigid stem of the C3 often forces the cam to be placed with the stem close to parallel to the ground. The added moment arm on the stem from even a small fall can be enough to break it. I've personally seen a C3 fail (snap) in this type of placement, where an alien/totem the same size holds perfectly.
Noah Haber · · Unknown Hometown · Joined Aug 2010 · Points: 78
John Peters wrote: I think it's similar to the sentiments expressed here: alpineexposures.com/pages/b…
That may be true of C3s with the U-stem, but I am not so convinced for single stems or as a general statement.

Think about a perpendicular placement with a solid stem vs. a perfectly flexible cable. The solid stem would simply want to rotate out of the placement and puts enormous stress loads on the axle. It is less clear what would happen with the super flexible stem, but the short lever arm would prevent this from happening.

Perhaps there is a happy medium depending on a number of factors, but I think that a blanket "stiffer is better for perpendicular placements" is probably inaccurate, unless I am missing something.
beccs · · Ontario Canada · Joined Mar 2012 · Points: 200
JSH wrote:If it umbrella'd out ... it had room to umbrella.
this
rgold · · Poughkeepsie, NY · Joined Feb 2008 · Points: 526

Folks who doubt my comment ought to read the BD engineering account just above posted by John Peters. Although theoretical in nature when I made them, there seems to be confirmation from testing.

I don't know if I can say it any better, but I think the BD comment about "needing torque" is a misleading. It is true that a more rigid stem creates torque, but it isn't the presence or absence of torque that affects the cam's resistance to extraction.

In order to function, cams have to be loaded along the axis defined by an unbent stem. With a rigid stem sticking straight out from the cliff face, you get a vector component along the stem as the stem is forced down off the horizontal, a component which grows as the stem moves further down. This vector component, although small, is nonetheless the load that activates the cams. The other component, perpendicular to the stem, rotates the cams but doesn't do anything to engage them. What happens then depends on the internal configuration of the crack. If it tapers as it gets deeper, then the rotation could also compress the cams. But if the crack is uniform or flares as it gets deeper, then the load necessary to keep the piece in may not be present.

If the crack tapers down very quickly or if it is shallow and the ability of the lower cams to pivot in is blocked, then the unit will pivot around the lower cams rather than around the upper cams, and, since the crack is shallow, this could force the upper cams entirely out of the crack. In this case, the increased torque from a rigid stem might be a disadvantage, although the entire situation presents nothing but bad outcomes: cams not loaded so as to engage and rotation popping upper cams out of the crack. (Note, by the way, that this could be a mechanism for perceived "umbrella'ing out" that doesn't involve some portion of the crack being too big for the cam expansion range.)

With a flexible stem, you get little or no loading in the direction needed to force the cams against the rock walls, which is why such cams pulled under low loads in the BD tests.

By the way, a tied-off rigid-stem cam in a horizontal crack is likely to be to be considerably stronger than a modern flexible-stem cam for analogous reasons.

An interesting question is whether Totem cams would be subject to the drawbacks of flexibility mentioned above. The Totem system transmits loads directly to the cams in a way which, it seems, would still function even with the stem in a bad position.

Guideline #1: Don't be a jerk.

Trad Climbing
Post a Reply to "Gear failure (small cam)"

Log In to Reply

Join the Community

Create your FREE account today!
Already have an account? Login to close this notice.

Get Started.