mini ice screws placement test

[IceIceBaby]

In an experiment, at feathered friend’s rep day, with Petzl, and other presented, we conducted ice screws placement test. The result I observed were unanimous. My theory is: long rigid handle creates the most torque on the starter-hole, and therefore tends to fracture and shedder the first five centimeter of the ice (the outer surface). Also the small knob (the coffee grinder handle) creates more torque (up and down movement) on the placemet therefore enlarging it and creating looser placement when compare with larger pivoting knob like the sonic’s "bolt hanger"

The worst of them were the BD (I will assume that the OP will behave the same), because they have small knob ( coffee grinder pivoting point), and low rotation angle (long stright hanger) which caused an indirect driving force on the screw. Second worst were the Petzl sonic, they preformed conciderbly better then the BD because higher angle of rotation (the force is directed more directly to the screw itself), but still due to rigid handle they were still fracturing the ice too much . The best performer, with almost no fracture, were the Grivel 360 they were the most secure placement and with the cleanest hole as well as the fastest to go in .

Anyway just my two cents

[chriss]

Please take a few minutes to read and restate this entire argument. Statements like this make no sense.

 

"small leveler the (coffee grinder handle) creates more torque (up and down movement)"

 

chris

[IceIceBaby]

Please take a few minutes to read and restate this entire argument. Statements like this make no sense.

 

"small leveler the (coffee grinder handle) creates more torque (up and down movement)"

 

chris

 

Yeah it does!! the combination of long rigid handle and the little knob like the BD “coffee grinder” knob transfer more directly the up and down movement of rotation to the screw part it self as oppose to wider and bigger “coffee grinder” like the sonic

Try holding them both on the same level on the screw part while someone turning then from the coffee grinder point to so you can see what I mean

[Bangedup]

After reading your post several times, I still have no idea what you’re talking about. Please explain your theory and how you define tork.

[JayB]

I think he's saying that the longer hanger creates a longer lever between the applied load and the shaft of the screw, which increases the force on the portion of the screw bearing the greatest portion of the load - which is probably 2-4 inches below the surface of the ice.

As the load is applied to the screw, the longer lever arm concentrates force on this segment of the screw, which creates fractures in the ice near the surface, which ultimately shatters, weakens the placement still more. Once the surface ice is gone the lever effect is even greater, more ice shatters, and the screw fails. Probably why - in good ice - screws cranked in with a downward tilt relative to horizontal (hanger lower than the teeth) seemed to hold the best.

 

Whereas, when you have a screw where the carabiner is essentially hooked right on the end of the screw, the lever effect is minimized, and the screw is consequently less prone to failure by the mechanism described above.

 

At least that's my interpretation of what Neri is saying.

 

Also - the threads on the Grivel screws are reversed, which is supposed to project the load into the interior of the ice, rather than towards the surface like conventional ice screws. At least that's the theory.

 

Looking forward to some major techno-wankage on this thread.

 

IMO - this is all neat stuff to talk about, but things like the quality of the ice that the screw is actually placed in are much more important than this stuff.

 

That being said - Grivels have always been my favorite screws, though I suspect I am in the minority on that one.

[Ade]

What test did you conduct exactly? Unless you state your methodology then your results aren't reproduceable and your conclusions impossible to confirm or deny, let alone debate.

[tomtom]

At FF the other night, they had a couple huge ice cubes that they were screwing.

[EV]

I wish I could explain this a little better than I am going to attempt, but will probably cause more confusion.

 

I was at FF. Saw the BD placement, the Petzl and Grivel placements. They had two huge blocks of ice, maybe four feet by three feet by 18 inches deep (this is a rough estimate on my part).

 

The ice was crystal clear. You could see all the way through, front-to-back, side-to-side.

 

The BD screw was being placed. You could see the ice almost expoding the deeper the screw went in. It almost looked like an instant spider web.

 

The Petzl was easiest to place, but there was still distortion of ice upon placement, but not nearly as much as the BD, maybe 80-90 percent less.

 

The Grivel went in. There were no fissures, or "explosions" or spider webs created - just a very nice, clean placement. No distortion of the inner ice at all.

 

Perhaps some the folks at FF could be a little more artful than I in explaining this. I wouldn't have believed it if I didn't see it. Damndest thing I'd ever seen.

 

I hope I am somewhat clear.

[cracked]

At FF the other night, they had a couple huge ice cubes that they were screwing.

[chriss]

Is this right?

 

1.You placed some short screws in a block of ice.

2.You "felt" that some went in easier than others.

3.It "appeared" that some fractured the ice more than others.

 

No loading. No measurements. Just observation.

 

And from this you concluded that Grivel makes the better screw. I don't mean this to be condescending. Give the details of the "test" and let everyone draw their own conclusions.

 

chris

[cracked]

I think he's saying that the longer hanger creates a longer lever between the applied load and the shaft of the screw, which increases the force on the portion of the screw bearing the greatest portion of the load - which is probably 2-4 inches below the surface of the ice.

As the load is applied to the screw, the longer lever arm concentrates force on this segment of the screw, which creates fractures in the ice near the surface, which ultimately shatters, weakens the placement still more. Once the surface ice is gone the lever effect is even greater, more ice shatters, and the screw fails. Probably why - in good ice - screws cranked in with a downward tilt relative to horizontal (hanger lower than the teeth) seemed to hold the best.

 

Whereas, when you have a screw where the carabiner is essentially hooked right on the end of the screw, the lever effect is minimized, and the screw is consequently less prone to failure by the mechanism described above.

 

I have no clue what iib is trying to say, so I'll work with this.

 

The above doesn't make much sense. The BD hanger is somewhat free-floating, so no matter if the screw is placed at +5 or -5 degrees (or more?) to horizontal, the hangar will point straight down. As long as the force is applied straight down, it doesn't matter how long the hangar is, since there is no moment arm.

 

Now, let's imagine that the BD hangar is 3 inches long, and is fixed relative to the screw, at 90 degrees. Now, when you place said screw at 90 degrees to vertical, the load on the hangar is at 90 degrees to the screw, and the hangar can exert no torque. So, in this case, the screw will have the same pull out strength no matter where the biner is clipped (momement is zero). No, if we tilted the screw at +5 degrees (ie, hangar is higher than the teeth), then the hangar will indeed exert a torque on the screw, increasing the loading of the screw near the surface of the ice.

 

Now imagine that we take this hypothetical screw, and place it at -5 degrees (ie, teeth higher than hangar). Now, with the aforementioned rigidly connected hangar, the force will create a moment around the screw that actually pivots around the teeth of the screw, decreasing the load on the ice near the surface, at least below the screw (the screw will try to pivot around the ice above the screw).

 

But this is useless speculation, since the free-floating hangar design of the BD makes the hangar exert no moment whatsoever within the range of normal placements. So, the hangar design differences between Grivel and BD have no effect upon screw strength.

 

So, I conclude that

a) IIB is drunk, crazy, or stupid

or

b) he didn't mean what JayB is talking about. In this case, I humbly beg elucidation of the subject at hand.

 

Geek in training, over and out.

[cracked]

After reading your post several times, I still have no idea what you’re talking about. Please explain your theory and how you define tork.

Torque can only be defined one way: it's the component of the force applied perpendicular to the moment arm, multiplied by the length of hte lever arm. Since torque is a vector, the direction is given by the Right Hand Rule (RHR).

[cj001f]

Occum's Razor suggests the difference stems from eccentric motion on the part of the Ice Screw. It's possible the 360s design would work better if the wire handle were coaxial with the screw.

 

Really this just sounds like a BS rep test like the Oakley laser beam test of a couple years ago

[IceIceBaby]

I am sorry for my English but JayB was almost on the money cracked you had to be there to see it. It is a theory and I think it makes sense

[JayB]

Cross product of the angular acceleration with the length of the lever arm or something like that.

 

It's been a solid 10 years since the "Physics for Scientists and Engineers." series at UW, and more like 12 since I've actually had to put a working knowledge of cross products et all to use, so the physics is a bit rusty, to say the least.

 

I can think of a number of minor variations that might introduce a moment arm into the mechanics of this situation, but given how irrelevant the physical micro-analysis is to real climbing, and how poor my recollection of physics is, I am going to have to abstain from any further speculations.

 

I am amazed, however, that the testing of this phenomenon has been so limited. You'd think the UIAA and/or any gear manufacturer who thinks they've got the best screw would've given a few grand and a load cell to some graduate students in Canada and produced some solid data on this one years and years ago.

[cracked]

I think I agree with cj001f. So one must strive to create a moment vector whose direction is along the longitudinal axis of said Ice Screw. When one fails and the moment vector's direction varies, the Ice Screw 'wobbles', creating a less than optimal cut in the first centimeter or so of the ice.

[cj001f]

You'd think the UIAA and/or any gear manufacturer who thinks they've got the best screw would've given a few grand and a load cell to some graduate students in Canada and produced some solid data on this one years and years ago.

The only Ice Screw testing I can think of was the Leuben/Harmston testing of almost a decade ago:

http://www.needlesports.com/advice/placingscrews.htm

They found screw held better when placed perpendicular because there was less of a lever effect from the screw itself, not the hanger, on the first several cm of ice.

[catbirdseat]

We have two issues here. The first one has to do with the damage the screw does to the ice as it is PLACED. The other issue is torque applied to the screw in a fall after it is placed.

 

To place a screw you need torque and to get torque you need a lever arm of some sort. The hangar or handle of the screw is what provides the lever arm. The ideal situation would be a Tee-shaped hangar that delivered pure torgue to the screw without any side to side component. This non-angular component is one contributor to ice cracking, but not the only one.

 

Now to address torque applied through the hangar/handle in a fall. The ideal situation in good ice is that the threads of the screw take all the load and there is no lateral force on the shaft of the screw. Setting the screw with a downward angle is one way to place more load in tension and less in shear. The hangar on BD screws acts like a lever arm to the extent that it its ability to pivot to the direction of pull is limited. Some of the designs have a hangar that is much like that of a bolt hangar. There is an entirely separate lever for placing the screw. I think this is a good design feature.

 

Maybe I misread the original post but it seems that the tests done at FF address placement but not pull out strength. It would be interesting to use a drill motor with perfect angular torgue to place all the screws to see how much ice fracturing occurs. Then you could address exactly how much fracturing affects pull out strength.

[cj001f]

Then you could address exactly how much fracturing affects pull out strength.

Given the data provided by the BD tests (the worst ) of screws who f'ing cares? In good ice, a screw is damn solid.

 

The questions raised by the above are:

1) Is this test repeatable?

2) Does this extrapolate into a less solid placement? (does it f'ing matter if BD screws will hold 22+kN lbs)

[DPS]

What test did you conduct exactly? Unless you state your methodology then your results aren't reproduceable and your conclusions impossible to confirm or deny, let alone debate.

What are you, some sort of astrophysicist?

[Chad_A]

What test did you conduct exactly? Unless you state your methodology then your results aren't reproduceable and your conclusions impossible to confirm or deny, let alone debate.

What are you, some sort of astrophysicist?

 

Really...you'd think he had his PhD or something...

[Chad_A]

Neri- I guess in a way, I see what you're saying...I don't know much about the loading or physics of it all, but it must've been disconcerting to see one screw disrupt the integrity of the ice upon placement more than the others.

[Ade]

What test did you conduct exactly? Unless you state your methodology then your results aren't reproduceable and your conclusions impossible to confirm or deny, let alone debate.

What are you, some sort of astrophysicist?

Really...you'd think he had his PhD or something...

 

Yeah... If there's one thing worse than a pompous Brit it's a pompous Brit know-it-all.

 

The study mentioned above appears in "How to Climb Ice" by Luebben. Definitely worth a read.

[David_Parker]

Yo, technophobes...does this shit mean that much to you. How many of you are actually falling on your screws?

 

Ice climbers should not be falling period. Your tools and what's in your head are your pro. If you fall on a screw in good ice, it will probably hold. If it's in shitty ice, well it probably won't matter if it's a BD or a Grivel.

 

If you're mixed climbing, use the bolts.

 

If you want to analyze torque and moment in something we actually experience on a regular basis, lets start a thread in the freshies thread about risers for ski bindings.

 

later......

[Stuart]

Did the test ice block show what happened when you placed an ice axe into it? I wonder if the ice would have shown the same fracturing and splintering as the BD screw or not? Would you not trust an ice axe if it did? Just wondering out loud....