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What's a good ice screw rack?

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Re: What's a good ice screw rack?

Postby KyleS » Thu Oct 31, 2013 9:01 am

martinleroux wrote:Bear in mind that in none of the studies did an Abalakov fail at less than 5kN, regardless of horizontal or vertical orientation. That's about five times greater than the load in a typical rappel. So in practice I can't see that orientation makes much difference. I'd be more concerned with finding the best quality ice in which to construct a thread and maximizing the cross-sectional area between anchor holes.
The way that's worded is misleading. Increasing the area between the anchor holes only increases strength up to +/-30° (or 60° if you're looking at it as an equilateral triangle); anything past that creates too shallow of a placement. Really, the only way to increase the area between the anchor holes, keeping the angles constant, would be to use a longer screw. Since you'll obviously be using the longest screw you have already, the only feasible way to increase the strength of your placement would be to change the orientation.

You're right to say that the force exerted on a v-thread is low when used for rappel, but what if you use it for an anchor midway and the leader takes a fall before setting any intermediary pro? Furthermore, since you can never truly tell how solid the ice is, there's no reason not to always use your strongest possible placement and I think it's a good habit to be in.

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Re: What's a good ice screw rack?

Postby seth0687 » Sat Nov 02, 2013 7:57 pm

I prefer BD Express screws....normally use 10s 13s and 16s the most but always have some stubbies too. 19s and 22s are nice for sweet thick plastic ice that you find at cragging areas like vail Lincoln falls and the like, but for general use I stick with 10s 13s and 16s. I think I have some 22s if you are looking for some screws. I'm sure I have some BD turbo screws laying around that I'd let go for a good price.

Email me if you are interested and I can see what I can throw together for you.

Cheers,

Seth

PS- 1st rule of ice climbing: falling on ice is not cool! ;) good luck

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Re: What's a good ice screw rack?

Postby Dave B » Mon Nov 04, 2013 8:48 am

Interesting post over at Cold Thistle about reverse thread screws (Grivel). I know you're locked in with BD, but the post is interesting as is the Chicks With Picks interview with Bill Belcourt of BD.

http://coldthistle.blogspot.com/2013/11/ice-screw-technology.html

ETA: here is the CWP interview. Interesting to here Bill not supporting the use of screamers.

And this re: screw length:

Last question – about screws. Is a short screw as strong as a long screw given the same quality of ice?

Bill: Yes. IF the ice is good, we pull-tested a short screw at 7-8,000 pounds and the ice is plenty strong and its just the wall thickness of the screw and the strength of the hanger that determines failure. Its not the length of the screw that determines failure. If the ice is good, then all screws are equal. Just like with bolts – with granite you can put in a 3” bolt, in sandstone you put in a 4-5” bolt. So the better the quality of the stuff you are putting the pro into, the shorter it needs to be to be full strength.

The threads – what role do they play?

Bill: There are some debates between reversing the threads, how high the threads are, the pitch of the threads all determine somewhat the strength, but also the place-ability of the screw – how many rotations it takes to go in. So the faster you pitch it the less rotations it takes to go in but the more force it will take to turn the screw as its cutting into the ice at a faster rate. Conversely, if you make the threads really fine, the crank pressure would be really low but it would take a lot of revolutions to get the screw in. So you are trying to look for an optimum balance between how much force it takes to crank something in with your hands and how many rotations it takes to get it in so you can get it in and clip it the fastest. As far as reversing the screws, vs with the steep side outward, we’ve frozen a block of ice inside a large steel case, put it in a pull-testing machine – clamped onto the head of the screw with angle iron because the hanger wasn’t up to the amount of force we wanted to put on the screw – and drilled a hole through the angle iron, which allowed us to pull straight out on the threads. In good ice, we pulled the screw to 7 or 8,000 pounds before we started bending the angle iron. Then we just stopped the test. So in good ice, an ice screws resistance to a straight out pull is really high – certainly way stronger than the hanger. The hanger is probably good for 3 to 4,000 pounds. The screw was good for far more than that in a straight out pull.
"There is no cheating in climbing, only lying." - Semi-Rad

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