UKC

Ice Screw Failure

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Euan 15 Apr 2002
Hi

I am during research into failure of ice screws and have seen all the litature on the subject on the web from BD etc
I am just wondering from people experience with them after taking a fall, how they failed or what happened to them. ie did the screw bend, did the hanger rip off, did the ice fail etc
Details of how the screw was placeed would be useful as would be the condition of the ice at the time of placing

All help would be appreciated
Thanks
Euan
stonemaster 15 Apr 2002
In reply to Euan: Sorry, been lucky enough not to have suffered failure even though the screws I have fallen on were of no name eastern European origin off a mat on the sidewalk of Cham. Good luck on your project.
fingers of butter 15 Apr 2002
In reply to Euan: A lot has been debated about this topic, so I would recomend using the 'search forums' tool at the begining of the message board. good luck, and post your conclusions please.
OP Blitz 15 Apr 2002
In reply to Euan:

I'd have a glance at Mark Twights book Extreme Alpinism, he makes ref. to some interesting tests carried out by the French guides association in regarding to falls and loading, one good point relating to tying off screws when in a shallow placement was a good read, apparently under a large fall tying off causes a higher chance of tube fracture than tying at the hanger. Good reading.
 london_huddy 15 Apr 2002
In reply to Blitz: at the risk of being accused of the dreaded crime of thread hijack...
after reading twight's stuff i nolonger tie screws off, if it's less than 1/3 of the way in it's shit anyway but i'll tie it off and pretend to myself that it's good, but if it does ground out, then i'll just clip it. opinions please!
 sutty 15 Apr 2002
In reply to hindu:
Why not tie the screws off, the screws will only shear if you load them beyond their design parameters. how did the frenchies test them, drop an elephant on them? If they fail tied off, they would also fail not tied off, or tear out. Use a bit of common sense when reading articles.
BTW not seen twights book, just know a bit about loadbearing devices.
Probably better to tie off and use a waist belay if it is dubious so you reduce the shock loading.
 TobyA 16 Apr 2002
In reply to sutty: Sorry Sutty but thats completely wrong, the problem is the screw failing at all it is in it bending and then the tie off slipping down and being cut by the hanger. A screw can bend and not come out, so if the hanger is clipped no problem, but if a tie off is used, that could be cut and down you go. So it is wrong to say "If they fail tied off, they would also fail not tied off, or tear out." Failure due to ice breaking and failure due to how the screw is clipped is totally different.

Hindu - have you been trying to place screws at less than 90 degrees to the ice on solid ice to resist the leverage problem as the BD research suggests?
 Toby_W 16 Apr 2002
In reply to TobyA: We were doing that in France (<90) after reading the research but then 2 of us were sad engineers and it seemed to make sense.
Cheers
Toby
hendrik 16 Apr 2002
In reply to Euan:
You should look at the book: "Ice climbing" from Craig Luebben. It's a book from the how to climb series. It has a chapter about the failure of ice screws with all failures and pictures. You can buy it on amazon.com
best regardings
 london_huddy 16 Apr 2002
In reply to TobyA:
yeah, the couple of time i've had to place too long a screw in good but thin ice (~7cm thick) i've placed a 10cm screw angled in the direction of load (ie downwards) by a few degrees and then clipped the hanger.

This goes with all the tests i've found but as yet i've not had to see if they're right and intuition (placing them at 10deg against direction of loading) is wrong!
 sutty 16 Apr 2002
In reply to TobyA:
Sorry Toby, got the wrong end of the stick there, didn't realise that it was the sling that was failing.
Ok, tie off as usual and then if and when the sling fails have a back up sling on the hanger, result, the first sling has taken the shock load and there is only a small fall on to the second. Treat it as a disposable screamer.
Would that be ok?
 TobyA 17 Apr 2002
In reply to sutty: I see the logic, might work but sounds a bit fussy - easier just to carry the right length of screws for the job! The other big difference in ice climbing over the last few years is that we are all now being encourage to place our screws angled slightly upwards into the ice, therefore tying off is hopeless because it just slides down the screw anyway.
 sutty 17 Apr 2002
In reply to TobyA:
Yes, nice to carry the right tools, however for when you dont have them I am suggesting a death preventing suggestion.
Not being an ice climber could you tell me why you are placing ice screws slightly upwards into the ice. It seems to me that this may help to make them less secure than slightly downwards, where is the engineering logic in this?
If you dont believe me stick your axe into a slope upside down with the pick pointing up, you will have a much better grip on the handle. or do you do that sometimes already?
Graham B 17 Apr 2002
In reply to sutty:
I believe the logic in placing screws pointing slightly downwards only works in GOOD ice where a nice tight placement is possible. In theory the load is spread all the way up through the threads (which are very strong) and does not produce such a high stress concentration under the screw at the point it emerges from the ice. This high stress can shatter the ice and thus weaken the placement.

At least thats my take on it..

 TobyA 17 Apr 2002
In reply to sutty: Sutty you have to think of ice as a laminate not as a solid, which is why ice dinner plates.

If you put the screw in downwards, when the weight goes onto it the outer layers of ice will most likely fracture, which means the screw is now 'sticking out a bit', this of course means the lever affect starts causing successive failures of ice deeper and deep until the screw pulls.

Puting the screw in angled slightly upwards, means the force from a fall is more like trying to pull the screw out of the ice straight rather than levering it through the ice. The threads on modern screws are so good that it is basically impossible to pull them out straight. The force doesn't fracture the ice in the same way. See www.bdel.com for the full results of their tests.
George Mac 01 May 2002
In reply to Euan:
I took a twenty five/thrity foot fall years ago on devils delight on Hells Lum. I went onto a DMM snarg, which had gone in up to 3/4 way, which I had then hasilty clipped with a DMM screamer, pumped stupid I kept going nearly got to the top, in fact pulling over the bulge when wheee. The snarg held, the screamer screamed and I lived to tell you this tale. I still have the snarg. I also have a mate out in the States who took a huge whipper of Frigid Inseminator, broke a screw and hit the deck, followed by the route collapsing on him - he survived and is back climbing.

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