SummitPost.org

Hopefully some might find this interesting. Curious as to people's thoughts. I am in the process of tracking down the original numbers that go with the pictures.

http://coldthistle.blogspot.com/2013/11 ... ology.html

I am not really familiar with reverse thread screws... what exactly is the difference?

The test is interesting... however it seems to me that to test it better you would want the force perpendicular to the screw right? Seldom in real life would the force be applied in the direction tested. Also perhaps could measure the force required, if you had the means, rather than just look at the remains.

Chad,

Look closely at the threads of your screws or zoom in here: http://blackdiamondequipment.com/en/ice ... 0ALL1.html

See how the threads aren't symmetric in cross-section? They have one side (toward the handle) that's nearly 90 degrees to the main axis, and the other (toward the tip) that's around 45 degrees.

"Reverse thread" screws reverse that.

As others have said, it's a good theory (ice should withstand compression better than shear) but I don't know how much difference it actually makes when the angle of pull is not straight out of the ice.

Ah I see. Got it.

Such a small difference. But I can see how it would have an impact, and that maybe it wouldn't.

But it seems like the cost to manufacture it either way would be similar, so if it really made a difference when the force is applied correctly then why wouldn't everyone do it the same way?

Better yet, why have an asymmetric thread profile at all? Whether cast, rolled or cut, I bet a near-90-degree angle is harder to manufacture (or at least increases wear on the tooling). Somebody must have had a theory that an asymmetric, vertical-handleward thread was actually a good idea. Which is interesting, because most wood screws and ordinary bolts have symmetric threads.

Hooray for Google and Wikipedia: An asymmetric thread is called a "buttress thread", and it's used in "power screws" a.k.a. "leadscrews" that drive machinery. (Think of the screw along the axis of a vise or the screw in a folding car jack: that's a power screw.) Wikipedia says the square face minimizes friction - I'll have to think about that, but if it generalizes to ice screws then that could be the answer: easier to drive into the ice if true.

(If you're exerting high power in both directions, you'd use a "square thread" (near-vertical on both faces); buttress threads are for when you only need low friction in one direction.)

With all the new advances in technology, isn't it still the quality of ice that has an overwhelming influence on whether or not a screw will hold? I can read the studies and see the differences in concrete when force is perfectly outward, but how does this translate to the real world? It seems like the most consequential advances in ice screws will continue to be been in speed and easement of placement, rather than strength.

BTW, I'm not an ice climber, so correct me if I'm mistaken.

What I would assume these tests are challenging the metal properties the screw is made from, especially threads. And it is easy to believe if the screw survives the concrete it would definitely be “safe” with ice.

As Chad noticed these tests do not consider other angles; we may just assume the core of the screw would survive them as well; although, I have heard about ice screws braking during a fall (good ice).

Once we designed unbreakable ice screws, however, I would put focus on various ice conditions and screw shapes to withstand a fall securely and those tests don’t really show that too much. Till then I would still prefer “NO Fall” policy. Or perhaps I’m wrong (I don’t use ice screws too often).

I think that is what the test is supposed to be about, clmbr... not testing the screw's ability to not break, but it's ability to stay within the ice.

But the test is the wrong angle, and doesn't actually measure the force required for failure.

The OP hasn't been back since the thread was started. If they hadn't signed up three years ago I would have already assumed it what just to lead traffic to the blog post.

mrchad9 wrote:I think that is what the test is supposed to be about, clmbr... not testing the screw's ability to not break, but it's ability to stay within the ice.

But the test is the wrong angle, and doesn't actually measure the force required for failure.

The OP hasn't been back since the thread was started. If they hadn't signed up three years ago I would have already assumed it what just to lead traffic to the blog post.

In either way I would definitely use the real testing material (ice blocks) than the cement. Ice and concrete have different properties. Ice gets softer and melts under the pressure of a metal object, for instance.

It melts under the pressure of any object! (not just metal)

mrchad9 wrote:It melts under the pressure of any object! (not just metal)

Yeah, but I’ve not seen ice screws from other materials yet. But I’ve not seen many other things yet too.

mrchad9 wrote:I think that is what the test is supposed to be about... not testing the screw's ability to not break, but it's ability to stay within the ice.

The OP hasn't been back since the thread was started. If they hadn't signed up three years ago I would have already assumed it what just to lead traffic to the blog post.

Nice guess. Testing the holding power of various ice screw designs from several angles actually, all according to UIAA standards. Which is why they use a specific cement media that the UIAA specifies for such tests. I haven't been back. The link was an opinion (all mine, not "they") offered as such. I could care less about my blog's traffic.

The Grivel testing is rather dated now but not well published or seen bitd from what I remember. Thought it worth passing around since I was bitching about or bragging on specific gear I like anyway. It is all trivia if you do climb ice. And nonsense if you don't have a clue.

For anyone that actually does climb ice there is a difference on how screws place in ice..any ice, good or bad. Obviously my preference is ease of placement. But the differences in pull strength and how the various thread designs effect the ice (or concrete) when stressed is interesting (at least to me) as well. FWIW the cost of screw manufacture has little to nothing to do with how the threads are cut, They are all done on cnc screw machines anyway. It is the hanger and final finish that is the biggest additional cost past the initial materials costs. Easy enough to see for yourself by picking a few of them up for a side by side comparions. Trivia matters there.

Still... why would you form an opinion based on a pull straight outwards? In a real situation the angle would be closer to 90 degrees.

I don't. Why would you? Read the comments and test data again.

"Testing the holding power of various ice screw designs from several angles actually, all according to UIAA standards."

Some of what you are missing it that any ice screw, like any nail, has to bend first to be pulled. The exception is have the support material fail first. Like bad ice. No history of ice screws braking in use that I know of in a fall. They always bend, even bending they may not fail (pull out), if the ice is solid enough. You can see in the concrete failure in the pictures around the screw where they did test different angles. No bent screws.

If the material is going to fail around the screw as the concrete eventually did in their testing wouldn't you want the force spread over a larger area than just the tube's hole? Or would you want the screw to have enough grip on the ice to rip off a fair size piece as well when it fails? If you have any clue on what a V thread will hold (we belay off them) then the answer would seem obvious to me. If you don't climb ice I suspect it is not such an obvious answer.

I can't read the test data. No speaka de Italiano.