Analysis of ice screws in climbing
jjgeng.com
jjgeng.com
The first surprise was the size of the forces. Their initial fall test actually broke some carabiners! So they adjusted it to be a smaller load.
The big finding was that negative placement angles held higher loads. I remember being surprised at this, and I have a vague memory that it was major news in the climbing world. I believe that, to that point, the typical climber would try to place screws square or at a slight positive angle.
Incidentally the reason to carry short screws is for thin ice. A short screw placed fully tests stronger than a long screw, because if the long screw hits rock before going all the way in, the exposed tube creates a lever arm. In those situations the generally accepted practice is to use a webbing runner to tie off the ice screw at the ice, instead of using the hanger.
>This analysis is meant to show the relative stresses in the ice and ice screw placed at different angles and not to predict pullout loads.
would have invalidated the analysis but apparently not under a lot of circumstances. I suspect the positive angle comes from experience with nails and screws where pullout tends to be the dominant failure mode.
As an aside, ice is a really interesting material on all sorts of dimensions--solid usually being less dense than liquid, typically used near its melting point, etc. As the post notes, the US Army has done a lot of research on ice. My thesis advisor ended up establishing an ice lab partially funded by the Army CRREL and has a lot of papers on the topic. (I worked on high-temperature metallic alloys however.)
I'm surprised they didn't go by the UIAA standard of 80kg factor two falls; it's been in effect for a while and makes comparisons easier.
> if the long screw hits rock before going all the way in, the exposed tube creates a lever arm. In those situations the generally accepted practice is to use a webbing runner to tie off the ice screw at the ice, instead of using the hanger.
This goes for pitons as well. There's a nice illustration in "Mountaineering: The Freedom of the Hills" which I can recommend picking up as a good introduction to climbing and mountaineering. The supplemental resources listed also are good if you want to go into more detail.
... for testing dynamic ropes. That's because they weren't testing dynamic ropes. All the other UIAA standards—the ones for harnesses, nuts, camming devices, static ropes, and so on—tell you to apply a set force, usually 10kN, and see what breaks. To be pedantic, all this stuff is specified in the CE standards that the UIAA ones incorporate by reference.
If you're in a lab, you apply 10kN in a precise way that uses a whopping great hydraulic ram. If you want to avoid hauling a whopping great hydraulic ram halfway up an ice cliff, then you improvise, but the aim is still to control the force acting on the gear and measure what happens. I'm using "control" and "measure" in the technical sense here.
Dynamic ropes are different because they determine the forces that act on everything else. In a dynamic rope test, the conditions of a fall are controlled as well as possible, and the peak impact force it generates is one of the variables to be measured. If you did that in the ice screw tests, the results would depend on which rope you used, and that isn't what you want.
this is another: http://hmga.gr/storehouse/word-acrobat/Ice%20Climbing%20Anch...
I used to climb at the gym in Salt Lake adjacent to BD's headquarters, and remember meeting equipment designers and testers. They seemed pretty fanatical about testing and had rigged up all kinds of equipment to, among other things, destroy carabiners at different angles, which made me feel good about their climbing gear. The most important factor is that you always rigged to load biners along the length, never near or on the gate.
BTW self rescue is a critical skill for all climbers, but the years i lived in the Bay Area, i remember only a handful of clinics for this (the ones I went to were in Davis)
> Craig Luebben1 and Chris Harmston did some drop testing on ice screws and found poor results in aerated ice. Using a solid mass of 185 pounds of iron, Luebben reports having “pulled out entire lengths of ice screws” in some tests resulting in a ground fall from the top of the climb.
It appeared in the November 1997 issue of Climbing magazine.
The focus is geared more towards high performance racing machines rather than ice climbing but it's the bible amongst certain groups that like to stick two supercharged, fuel-injected nitromethane-burning blocks of metal together with a handful of threaded rods to produce 10,000 horsepower. It also covers more basic things like when you should use a washer and if so, what kind.
I also happen to particularly like the book as, at first glance, the subject matter looks dull but the author makes it...riveting.
I really like pragmatic books like this; do you have anything in a similar vein? Specifically, I'm looking for a book focused on the practical application of fluid mechanics (not just plumbing). I know how daunting a subject it is, but that doesn't deter me from learning just enough to be dangerous.
I've been eyeing Granger's "Fluid Mechanics" (and most of the Dover collection in fact.) [1] It's more academic, so I would like to pair it with something more practical.
Perhaps this textbook is better than others I've used but I wouldn't really expect it to be especially focused on practical applications. For really practical stuff you may look at Crane's (http://www.flowoffluids.com/). I used it a lot when I was designing piping systems.
https://www.amazon.com/Album-Fluid-Motion-Milton-Dyke/dp/091...
The great Alex Lowe had this to say about the report:
"Good work on the screw research. Having read it and thought about the mechanics of pulls along the axis of the screw as opposed to loading such that shearing through the ice plays a role, it makes intuitive sense that a screw placed at a positive angle should indeed hold better, but only in ideal ice conditions - that's the big qualifier. Of course determining what constitutes "ideal ice conditions" is the art and essence of placing ice gear. I felt you made this clear in your article. My personal conclusion from your tests is to place screws at a positive angle when I feel the ice is 'very solid'. Obviously some rather ill defined terms in that statement! 'Very solid' will remain an intuitive assessment."
Good work on the screw research. Having read it and thought about the mechanics of pulls along the axis of the screw as opposed to loading such that shearing through the ice plays a role, it makes intuitive sense that a screw placed at a positive angle should indeed hold better, but only in ideal ice conditions - that's the big qualifier. Of course determining what constitutes "ideal ice conditions" is the art and essence of placing ice gear. I felt you made this clear in your article. My personal conclusion from your tests is to place screws at a positive angle when I feel the ice is 'very solid'. Obviously some rather ill defined terms in that statement! 'Very solid' will remain an intuitive assessment.
In Europe, pitons may still be used in some limestone areas that don't take modern gear very well.
You may come across gear given another name - such as Hex, Micronut, Stopper, Chock, etc - but they're all variations of the two: either a lump of metal that wedges into a crack in the rockface, or a spring-loaded movable metal device, that wedges into a crack in the rockface.
Nuts and cams (as well as ice-screws) can be easily removed by the last person on the route (who is being belayed by someone higher up, so doesn't need the protective gear any more). In most cases, gear isn't left behind, unless something's gone wrong.
[1] https://en.wikipedia.org/wiki/Nut_(climbing)
[2] https://en.wikipedia.org/wiki/Spring-loaded_camming_device
Bolts (expansion or glue-ins) are heavily used for protection but the use is controversial in places. They are basically always left in permanently. Push here as been to limit use to areas where there's no other options and to place them carefully to minimize impact. There's a push to only use high-quality stainless (or Titanium for areas exposed to salt) for longest possible life.
The rest of the protections used, nuts, hexes, cams, ice screws, snow pickets, and some exotic devices are usually meant to be removed after use and minimize impact on rock. Although if someone needs to bail in a hurry, leaving expensive gear behind is normal.
Nuts and hexes are basically blocks of aluminium on a wire or webbing sling. Nuts being smaller solid chunks and hexes being larger and hollow. They have tapered shapes (sometime complex, curved, or even designed for a camming action) and you try to wedge them in place. They can be very secure in the right placement. After a good fall on one, it sometimes happen that it cannot be dislodged and it stays fixed for a few months or years.
Cams are mechanical devices designed to grip both sides of a crack and expand outward when loaded. They have two spiral shaped lobes to accomplish this. Very strong when well placed and they have a range of sizes to fit different cracks from tiny body weight only cams around for cracks of 1/4" or so to monsters that fit in cracks of 6" or more.
Ice screws are hollow threaded tubes, the article here does a good job showing how they function.
Snow pickets are T-shaped beams, about 2 feet in length or more that can be driven into hard snow or buried in a trench. Not that strong but workable.
There's a lot of special purpose "protection" that is usually barely able to hold body weight that gets used for aid climbing (when you use the gear to make progress) in situations where nothing else will work. Often to link sections (called pitches) of unaided climbing (called "free" climbing). Free climbing still uses protection in most case, unroped "free-solo" being the exception.
No. Ice screws are definitely something the follower cleans (just unscrew them) and pitons can generally be removed, either by hammering them back and forth, prying them out like a nail, or using a funkness device (a wire with a loop on each end) to yank them out. "Big Walls: Elite Technique" by Jared Ogden has some nice diagrams, but they didn't turn up online when I searched for them. Also, pitons generally aren't used any more (definitely not in sport or trad climbing), but I wouldn't say they are niche or rare. Many big walls in Yosemite still haven't been done "clean", they still require the use of pitons.
This is coming from someone who's only climbed clean aid and whose climbing partner really doesn't want to climb anything that requires a hammer, but I've still picked up a hammer and some old pitons to practice with.
Also, pitons are rarely used these days except for in some types of big wall climbing. Typically rock climbing protection uses cams and nuts, which don't mar the rocks the way pitons do.