Textbook cam placements can pull in smooth stone

Cams in perfect placement can pull if the rock is smooth enough PERIOD.
That is a simple statement, and it is 100% true. Let's stop arguing the obvious, please. If the friction coefficient of the cam lobe material on the rock is less than the tangent of the camming angle, the cam will pull out. Physics 101.

It is why I minimize my use of cams at Eldorado for example. I have pulled cams out of perfect parallel placements by hand there before.

mattm wrote:Also a good example of why Totem Cams can be superior. They were made to address just such an issue.

What issue are you referring to, and how are totem cams made to address it?

I'm baffled that some are calling this close to ideal placement. From the photo is looks fairly clear that the crack tapers down and gets more narrow up to about 2 inches above the cam lobes. Then, the crack begins to taper wider where the cam is. Add the fact that it appears most people jam their sweaty, chalked hands right where the cam is adds some grease and polish right there.

Over cammed is not an issue. Cams exert the same outward force at 10% retraction as they do at 50% retraction as they do at 90% retraction. (logarithmic spiral)

I'm with Tim. Nut in the tapper in the back freeing up that nice hand jam.

sanz wrote: What issue are you referring to, and how are totem cams made to address it?

It gets pretty technical, but basically, Totem cams apply the load to the cams in a completely different way (which is also why they are a bit more complicated), which in a sense decreases the effective camming angle, which makes the cam apply a higher outward force to the rock for the same vertical force. This allows the cam to hold at lower friction coefficients than a traditional cam.

BTW, this applies ONLY to their "TOTEM cams", and NOT to their (otherwise excellent) version of the Alien, which they call the "basic cam".

TBrumme wrote: This was my first thought as well. Not an inherently bad placement, but simply a poor choice of cam for that rock. Not all cams are for all rock types, and the metolius tcu in the video was probably the last type of cam I would choose for that placement; much less surface area on a tcu when compared to a C4, Mastercam, or Totem.

I am sorry, but surface area is - to first order - irrelevant here. One might even argue (without proof) that in slick rock, a cam with lower contact area may be preferable because it will apply higher pressure (force per unit area) on the rock and might therefore "bite" better.

The key parameter IN SLICK ROCK is camming Angle. You should favor cams with lower camming angles in such conditions (e.g. avoid Aliens in slick rock)

If you are climbing SOFT rock, on the other hand (desert sandstone for example), you need to consider contact surface, because the failure mechanism is ENTIRELY different: lobes can "track" into the rock, resulting in pulling and opening of the cam. For the same reason, you may also want to place deeper in soft rock than usual.

I've had cams slide out of very polished quartzite before, but the circumstances were so rare that I had to go 2-3" to either side of that spot in the crack and got better friction. Certainly gives you pause.
The ultimate metric of a cam placement is the friction between the rock and the lobe. And (to the surprise of no one), when that friction is too low, the cam will not hold at any appreciable load. The only reason you'll get a cam to stick at all in the scenario described is because dust, humidity, etc, can provide a little boost in friction, but that simply does not matter when your load exceeds the weight of the cam.

Dylan B. wrote: We're talking past one another.

No, we are not.

Dylan B. wrote: What you're saying is not that this is a bad placement,

Wrong again. This is not a good placement. Downward flare. Some hand grease. Possible polished by all the hands. Hello!

Dylan B. wrote: but that there's a better placement right above it.

Yes, there is.

Dylan B. wrote: What I'm saying is that irrespective of whether there is a better placement elsewhere in the crack, this placement is pretty excellent.

God no! It is not.

Dylan B. wrote: Of course, Metolius cams (like the one in the video) are known for having a lower camming angle than most. It's one of their selling points.

Sure. That simply reinforces the point that no matter what cam you use, if the rock is slick enough, it will pull out.

Greg D.: you're missing the point and/or changing the topic. This thread is meant to remind us all that cams can and do pull out when placed in slick rock. That is true whether the placement is textbook perfect or not.

Sure, if you have options a textbook placement is more likely to hold than an inferior one, but again, you're hijacking this thread by making it about this particular placement, when it is not.

I think a lot of us are having trouble accepting that what looks like a fairly reasonable placement can pull out so easily. Thanks to the OP for starting this discussion. If nothing else, it has brought the issue to my attention. I climb on quartzite a good bit, and will keep this in mind when I'm pumping out on finger buckets, trying to stuff a blue metolius in a horizontal that feels slick.

I wonder how many of the people who are saying this placement is "not textbook" actually fall on their cams and/or aid very much ( I'm sure Healyje will tell me otherwise). 'Cause I can tell you for sure that I have fallen on or jumped up and down on a lot of cams that looked much worse than this without them failing. And in all my time, I've only had a couple of cams pull, and those were obviously suspect. From a geometric perspective (ignoring friction) that cam looks fine.

csproul wrote:I wonder how many of the people who are saying this placement is "not textbook" actually fall on their cams and/or aid very much ( I'm sure Healyje will tell me otherwise). 'Cause I can tell you for sure that I have fallen on or jumped up and down on a lot of cams that looked much worse than this without them failing. And in all my time, I've only had a couple of cams pull, and those were obviously suspect. From a geometric perspective (ignoring friction) that cam looks fine.

Seconded. I would've whipped on that without hesitation.

For those who would like to understand the physics behind all this, here is a nice description of the function of traditional cams and Totem cams: totemcams.com/files/galeria…

[edited for clarity]
Among other things, it shows that Totem cams increase their holding power compared to classic cams built with the same geometric camming angle (i.e. the same lobes) by a factor that varies from 1.59 (when fully closed) to 1.67 (when fully open). In other words, in theory, a Totem cam would hold in rock that is ~60% slicker than a traditional cam that would be made from the same material and with the same lobes. However, noone makes classic cams with a geometric camming angle that steep (20 degrees); instead the Totem cam was designed to provide holding power similar to most cams on the market, but a wider range.

Yet another way of thinking about it is that a Totem cam will give you a wide camming range (due to its steep "geometric" camming angle of 20.35 degrees), yet simultaneously provide the holding power of a cam with a much lower camming angle (the "effective" camming angle of a Totem cam is about 13 degrees).

csproul wrote:I wonder how many of the people who are saying this placement is "not textbook" actually fall on their cams and/or aid very much ( I'm sure Healyje will tell me otherwise). 'Cause I can tell you for sure that I have fallen on or jumped up and down on a lot of cams that looked much worse than this without them failing. And in all my time, I've only had a couple of cams pull, and those were obviously suspect. From a geometric perspective (ignoring friction) that cam looks fine.

Well let me clarify on the text book I personally learned from. You see, these words were stored away in the half rotten brains of a couple crusty, old, trading salts(& well worth theirs). They once told me, that "ifya can't get a nut or hex to stay, then ain't no reason to expect a cam to" & at the "shit hole" 30 foot cliff I was climbing here in Columbia sc, this advice would save your life. See the few exposed areas of rock around the lake here are mostly a super slippery quartzite or a soft, flaky and even more slippery schist. I've watched( guess what in aiders), as a cam compressed & pulled through a constriction that would have held something passive all day long. Sure, if the rock was coarse those placements would have been bomber, & the one in the video probably would have too, even though I still see it as a bad placement in a slight flare. But that's a different text book, this is a different class. When I saw a cam pull in my class, I took note of what EXACT attributes constitute a good placement.

The question for me isn't whether the cam is good or suspect (but it's the latter on just looking at it); no, the real question is if you came upon this spot and were going to place a cam in that vicinity would you place it as shown? If so, really?

As a couple of old guys who've both been around the block, I don't usually find much to disagree with RGold about (other than the efficacy of hip belaying even in high fall factor falls), but this is another instance where we definitely part ways. I would never make that placement at that spot and there is no shortage of reasons for that conclusion.

RGold and I started on pins and nuts - no cams - and I (don't know about him) happen to do a lot of reasonably hard free climbing over the years above a LOT of small yet mostly solid passive placements and, as csproul recokons, I've also fallen a lot on all manner of gear and placements. And to further set the stage, about 50-80% of my free multipitch leads over forty years have been roped-solo pretty consistently at just slightly under my partner grade. In that, I always second my own pitches and am 'dogfooding' the placements in the sense of cleaning my own gear.

The outcome of all those experiences is I learned to let the geometry of the placements do the bulk of the work and - because I'm also doing the cleaning - rarely if ever 'set' gear and even then it's no more than a slight, steady pull until I feel some friction engage with the rock. From my perspective the key to any placement is looking - no, really looking - down to a micro-topology/terrain level where millimeters count. And those millimeter differences in placement topology really do count if you might be staring at 30-60 footer onto a #4 HB brass offset stopper, #3 Crack 'N Up, #2-3 ball nut, or a #0 (Metolius) cam. I've taken solid dives on to all of those; one day even taking six successive 30 footers on to a #3 Lowe/Byrne ball nut (utterly bomb - came right out when cleaned). Again, it's super important to really study and optimize your placements and even tiny adjustments can yield the difference between a piece holding or not.

A big issue with folks today favoring cams over passive pro from what I've seen is that it's a very similar situation with regard to their perceptions of grigris - "hey, they always work and you don't have to put much thought into it"; just place / thread and go and 98% of the time you're good. The result of the fact the grigris and cams do work the majority of the time (and people being people), is they come to think of grigris as autolockers instead of autoblockers and cams as generally being solid without much [inspection/placement] effort on their part. In other words, it's all 'automagical' and folks develop an entirely unwarranted over-confidence in both with the downside of that over-confidence being those 2% edge cases are always lurking out there and can kill or maim you anytime you either let your guard down or misinterpret what's going down. Hell, it's basically raining people dropped by belayers using grigris on a planetary basis every day; ditto on the plethora of people unable to imagine why their cams zippered. And don't even get me started on sport climbing on gear without re-checking and possibly resetting a piece every-single-time after you rest on it.

And all that's not to say I haven't had cams pull on me either - I have. But I can count on my hands and feet the number that have over my climbing career and half of those I knew were potentially marginal placements. The other half are still basically complete mysteries, but then I once had what I thought was a solid tricam in a roof get shot out of it's placement and then somehow came winging off the biner and shot into outer space never to be seen again in the process - go friggin' figure.

The take away should be that cams need the same care of placement and slinging as passive pro. Hell, for that matter I'll take a solid nut over a cam every time because I consider cams sketch until I convince / prove myself otherwise on every placement where I use one (btw, that goes double for really big cams).

Bottom line is you just can't get overly detail-oriented with placements, especially marginal placements, 'double-up' placements before cruxes, or in rock which is suspect for any of a variety of reasons - e.g.:

Dylan B. wrote:The video reinforces what every Devil's Lake leader already knows: that even very good cam placements in low-friction rock are suspect.

It's amazing you can even climb that shit. I mean chalk doesn't even stick to it. Anytime us SoILL sandstone folk would go to DL or vice-versa, it was always an occasion for high hilarity as we'd be pounding our knees into their glass-like rock totally unable to figure out what your feet might or might not stick to and they'd be on their bellies looking for micro-edges on high-angle slabs we'd casually walk up no hands, barefoot free-solo.

Personally I'd advise against selling passive pro short and over-estimating how solid cam placements are.

My mind is blowing up. I think I just read that slick really means, like, slidey and, uh, slippery. Slip-pery.
How did I miss it for so many years??

SLIQ Slabs, bro.
Hey man, that's SLIQ!

Healyje wrote:...I'll take a solid nut over a cam every time...

^ +1!

rgold wrote:Really, there is nothing terribly the matter with that cam placement. It isn't ideal; the crack is slightly flared downward at the placement, but to a degree within what cams can usually handle. The crack variations wouldn't matter in most climbing areas. The entire point of the logarithmic spiral curve is that holding power is independent of the cam position. "Overcamming" should mean cams retracted so tightly that there is no room to retract them further for removal. People use the term incorrectly to refer to a placement in which the lobes are highly contracted but still have more room to be compressed for removal---those placements are actually the best from the point of view of security. I'd call the placement in the video close to ideal. Cams depend on coefficient of friction. If it isn't high enough, they will pull, and the effect will be the same if you jerk them by hand or fall on them, because they press on the crack walls with a force proportional to the load. (Actually, well-placed cams in appropriate rock fail for a completely different reason having to do with the deformation of of the lobes and shearing of the lobe material.) I'd take the post at face value and be extremely cautious about cam use in that area. I've read and heard a number of reports that certain limestone and basalt areas also have low enough rock friction to produce cam failures for what seem to be ordinary placements. Moreover, rock friction can vary locally from crack to crack and also within a particular crack. Water-polishing might make certain crack sections slick.

I agree 100%. I have fallen on cams in similar placements for almost 20 years and never seen one slide out like that. I wonder if a 6061 alloy cam (like an alien) would hold better in slippery rock.

I dont think many people posting here have spent much time plugging cams into quartzite.

Greg D wrote: No, we are not. Wrong again. This is not a good placement. Downward flare. Some hand grease. Possible polished by all the hands. Hello! Yes, there is. God no! It is not.

I can pretty much guarantee from the above post that you rarely to never fall on your gear and never climb on gear at your limit.