zzzzzzzz
cold thistle really needs traffic from SP and all its expert ice climbers
nothing beats arguing for the sake of arguing!

hey Dane, any early season climbs in yet? the Black Dike got climbed out here a couple weekends ago. hope to try out my Cassin X-Alls in the next couple weeks too.

mrchad9 wrote:I can't read the test data. No speaka de Italiano.

ya, my devious plan to drive traffic to bling's translation technology

Hey Anita

Seen these?

Alpinist Newswires
New M9 WI6+R Raises Bar on Colorado's Mt. Evans

Alpine Exposures - Chamonix
Beyond Good and Evil

My Italian is so-so, but I can read the paragraph numbered 3, on page 8:

"Holding power in axial pulls depends on the thread type..." (reversed thread is about 25% stronger in axial pull)... "We reiterate that this difference is not apparent under radial load".

(Go to page 6 for photos of the radial pull test.)

So, zero to microscopic real-world benefit. Meanwhile, I'd be interested to hear if anybody has compared the effort it takes to place a "reverse-thread" screw. My prediction is that standard threads are easier to place, but I'm not prepared to estimate by how much.

I guess you don't need to be an expert ice climber to look at a physics problem.

; - )

I'd be interested to hear if anybody has compared the effort it takes to place a "reverse-thread" screw. My prediction is that standard threads are easier to place

Your prediction is wrong.

Dane1 wrote:

I'd be interested to hear if anybody has compared the effort it takes to place a "reverse-thread" screw. My prediction is that standard threads are easier to place

Your prediction is wrong.

nartreb is being productive and at least sharing relevent information. Right or wrong it is a reasonable hyphothesis, and he has a track record at being correct about these things.

not surprising that posts are being deleted here too. god forbid someone gets criticized.
pathetic

If I had an Instron in my basement, I would run a series of tests myself.

BigMitch wrote:If I had an Instron in my basement, hypothetically I would run a series of tests myself.

Beats the hell out of actually climbing. Hypothetically of course

The threads provide most of the holding power, thus the advice to angle the screw down from tip to hanger. The teeth do most of the work during placement. Try placing a screw you've bottomed-out a couple of times on the same climb - the threads haven't changed, but it is sure as hell a lot harder to crank. Hey Petzl, I want my L'mice!

You guys shouldn't care about things like ice screw technology, just don't fall. Worked for me so far

My prediction is that standard threads are easier to place

Upon reflection, this falls into the category of "good theory, little or no practical difference" (just like "reversed threads are stronger"). But there's still a mystery here.

Obviously, thread profile is irrelevant during the "initial bite" phase where you're just trying to get the teeth to pierce the ice. The threads aren't in contact with the ice, you have to supply all the inward push. Since this is the hardest (and scariest) part, we can just about conclude already that thread profile is no big deal, certainly not in comparison to tooth sharpness.
Next is a short transition stage where the threads begin to take hold, but you're still actively pushing on the screw. Thread profile is still mostly irrelevant here.
Finally comes the "spin the handle" phase, where the threads, by definition, are pushing against the ice with a total force that exceeds the resistance from the teeth. If there is such a thing as a dramatically more efficient thread profile, this is where you'd feel the difference. That's assuming otherwise identical screws. Sharpen the teeth or increase the handle length, and it'd be pretty easy to overwhelm any difference the thread profile could make. Plus, as I said before, this is already the easy part, so not of great importance.

Which leaves us with the mystery. Somebody had to have made a conscious choice to use asymmetric threads. Even if the manufacturing costs are of no practical importance, it's an interesting design choice. Who made the choice, when, and why did all the manufacturers follow?

I've started looking at online images of old screws, and though it's pretty hard to see the thread profile, I think the Chouinard from 1985 had an asymmetric thread, while the 1975 Chouinard had a symmetric thread (as did the Salewa Warthog of the same era). That leaves a pretty big gap...

Other good sources of info, read and don't assume you know stuff:

http://www.adventure-science.com/files/Ice-Climbing-Anchor-Strength.pdf

http://www.petzl.com/en/outdoor/news/products-news-0/2009/02/12/ice-screws-and-threads-resistance-tests

http://www.jjgeng.com/html/body_ice_screw.html

http://www.ukclimbing.com/articles/page.php?id=4315

and please remember that sharp Ice screws with a good tooth profile is a major part of keeping yourselves safe. I've felt the differences in tooth profile from BD's own ice screws over the year, I had an old screw, still very sharp but clearly harder to start the screw than the newer models...