
Analysis of ice screws in climbing - Phithagoras
http://www.jjgeng.com/html/body_ice_screw.html
======
snowwrestler
A bunch of years ago, one of the climbing magazines (I think it was Rock &
Ice) did a practical test of ice screw strength. They went to the ice park in
Ouray, Colorado, placed a bunch of screws of different sizes and orientations
in solid ice, and then dropped a standard load onto them.

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.

~~~
npsimons
> Their initial fall test actually broke some carabiners! So they adjusted it
> to be a smaller load.

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.

~~~
amaks
I'm surprised "Mountaineering: The Freedom of the Hills" even mentions pitons
as it's all about the non-destructive ethics of climbing. Honestly I don't
remember it ever mentioning pitons at all but granted I read it last time few
years ago.

~~~
npsimons
It was more an overview, a "well, if you're going to use pitons, here's how to
use them safely" at least in the case of the tie-off loop with a piton that
had bottomed out.

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paulgerhardt
If you enjoyed this post, pick up a copy of Carroll Smith's "Nuts, Bolts,
Fasteners and Plumbing Handbook"[1]

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_.

[1]
[https://www.amazon.com/gp/product/0879384069/](https://www.amazon.com/gp/product/0879384069/)

~~~
devbug
Sounds great! Just ordered a copy.

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.

[1]
[https://www.amazon.com/dp/0486683567/](https://www.amazon.com/dp/0486683567/)

~~~
lutorm
There's Hoerner's "Fluid Dynamic Drag" which is interesting if you care about
drag. It's pretty old, but is focused on practical applications:
[https://docs.google.com/file/d/0Bx0MqOfev7dnTnB0eFRIN2JQb0k/...](https://docs.google.com/file/d/0Bx0MqOfev7dnTnB0eFRIN2JQb0k/edit?pli=1)

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Dangeranger
Black Diamond funded research into optimal ice screw placement a number of
years ago.

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."
    

The chief researcher was Chris H. Harmston, you can find the full study write
up here: [http://www.needlesports.com/content/ice-screw-
placement.aspx](http://www.needlesports.com/content/ice-screw-placement.aspx)

~~~
maxerickson
You can use * on each side of the text for italic quotes.

 _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._

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knodi123
I've always wondered - are things like ice screws and pitons always single-
use? Does climbing like this basically require you to discard hundreds of
dollars of equipment with each face you climb?

~~~
npsimons
> are things like ice screws and pitons always single-use?

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.

~~~
amaks
Pitons are used a _lot_ in mixed winter climbing when often there are no other
ways to protect.

~~~
npsimons
That's what I've heard, that you want pitons for those ice filled cracks which
would normally take cams or chocks but are currently otherwise occupied. I've
not had a chance to do ice climbing yet, but am looking forward to taking a
class in the early months of next year.

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peterbraden
Interesting analysis, but ice anchors depend far more on the quality of the
ice and the conditions than the actual strength of the screw. One reason I've
heard for downward positioning is that the screw can channel heat into the ice
and melt faster around it, so a downward positioning acts as a lever to keep
the screw engaged.

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KayEss
That seems a horrific mix of SI and imperial units. How is it possible to
reason about anything with such a mishmash?

