Break a pick?

[tvashtarkatena]

 

Everyone has used a claw hammer to pull a nail with varying degrees of success. IMO the tighter arc on the BD reverse curve is causing a fulcrum point in the area of tooth 3 to 6 where upward leverage will break the BD pick sooner than the straighter angles and less leverage of the Petzl pick. Add bigger stress risers in that same area and less material and th end result would seem obvious.

 

But just how strong is “strong enough”. I’ve had email exchanges with some of the sponsored BD climbers and quizzed them on their own pick breakage. The newest BD tools with current production stock picks just are not breaking. Yes they are wearing out picks by climbing a lot of mixed. But I have yet to hear of a broken pick.

 

Hard to belive just how complicated our little "battle axes" really are But a closer looks shows there is a lot going on.

 

You've superimposed where the tool head is: that doesn't matter. You've got the two tools rotated at different angles of use.

 

I've superimposed these two points (tip point/grip rest) at the same scale, thus orienting the tools the way they'd be used equally. The strike/pick angle of these two tools is actually very similar.

Edited April 17, 2008 by tvashtarkatena

[Dane]

tvash, I would disagree on most, if not all, of your comments and conclusions on this thread. But then I have a lot more detail on the tools than I have bothered to publish in this thread so it should be no surprise. One thing we can agree on is that Petzl makes a nice line of tools. I own and climb on several versions myself.

 

If your cut and pastes efforts are intended to champion the Petzl as a superior tool you won't get a rise from me.

 

If you can't visually verify the obvious design and finish differences in the two company's picks, how can you hope to add anything useful to the discussion past the "atta boy" for Petzl?

 

My pictures show the true pick angles and are taken to highlight the differences in angles between the two tools. 30 seconds with the actual tools in hand will clearly show those differences. Your over lay is not correct. More importantly actually using both tools as intended will quickly show you there is a difference in performance. Outside the photos, most of my comments are no more than personal observation and my own speculation, YMMV of course.

 

Take a look at an actual over lay and decide for yourself if the differenece at the shaft and pick angles will be important to you. Climbing, like many things is life, is all about the details and knowing when they are important and when they aren't.

For most of us none of this will matter climbing ice. To figure out how to improve the design, BD or Petzl, it is the details that will count.

 

 

When you line up the shaft on each tool this is the position of the picks.

 

 

 

[tvashtarkatena]

No, I'm not a Petzl rep, nor do I regularly climb with Will Gadd, as you do. Despite your indignation at being disagreed with, this thread's not about Tvash and Dane. All the major companies make good tools. I'm just trying to point out that most of your conclusions regarding the root causes of the breakage issue seem faulty and, in some cases, wide of the logical mark. It doesn't help that you write off the field experience of most the posters here. Until now, you've passed these personal and likely flawed conclusions off as statements of fact.

 

This is a technical discussion. If you do disagree, back it up with data and analysis rather than another self affirmation of your oft stated expertise. Or you can drop some more names from Rock and Ice, if you wish.

 

I'd say pick breakage is one of those issues which, ummm, matters, so finding a root cause is of importance to anyone using these tools.

 

I look forward to the Boeing guy's response from his metals expert; it will be welcome input from someone who actually knows what their talking about on this particular subject.

 

Edited April 17, 2008 by tvashtarkatena

[John Frieh]

back off

 

dont make it personal

 

 

[tvashtarkatena]

back off

 

dont make it personal

 

 

I'm not, and haven't, but you just did.

 

I'm just looking for some analytical rigor regarding any conclusions that are made here. Anything wrong with that?

Edited April 17, 2008 by tvashtarkatena

[tvashtarkatena]

I scaled the tools to your photo, and lined up the shafts so that a) the picks strike on the same vertical (ice) line and b) the grip positions are lined up, and got this:

 

 

I don't have a Cobra so try it with your two tools in this configuration and see if you get the same result.

[Dane]

This is real..

 

When you line up the handles this is what the picks look like..

BD has a good deal less drop in the pick and the resulting sharper radius in top reverse curve.

 

 

The BD pick in your over lay shows a good bit of Petzl pick below it. The overlay is not accurate but gives a reasonable view. Reverse your overlay and I suspect you'll see how the angle of the picks differ in use. Sometimes it is a lot easier to just use the real thing.

 

 

I'm just trying to point out that most of your conclusions regarding the root causes of the breakage issue seem faulty and, in some cases, wide of the logical mark.

 

Funny that, currently three engineers, two machinists and one metallurgist fine little fault in what I have posted or my thought process on how to better a pick, any pick. Most of that same info has been common knowledge in the climbing community for the last 20 years, so no big surprise.

 

 

 

 

[tvashtarkatena]

Silence doesn't imply consent, although it may imply politeness. As for common knowledge; if the reasons for breaking picks were so well known we wouldn't be having this discussion, would we?

 

Both pics are scaled; both are real. I actually used your pic to scale mine, so they are same same. Your pic doesn't line up the hand grips, so it doesn't compare apples to apples to indicate strike/pick angle. There are only two positional elements a climber directly controls during tool placement: grip location and pick (strike) location (and orientation). If you want to compare the tool geometry of various tools for climbing a vertical surface, you've got to superimpose the grip position and line up the pick points on a vertical line. Line up your tools accordingly, check it out, and get back to us with data rather than comments.

 

Just sayin....

Edited April 17, 2008 by tvashtarkatena

[Dane]

 

My second picture shows the angle of the picks when the handles are lined up as in your last model. It is an apples to apples comparison.

 

Instead of being such an unpleasant prick how about adding something to the discussion past more erroneous info, personal attacks and rehashing the same info?

 

 

[tvashtarkatena]

Apparently you have an emotional issue with being disagreed with, even on a technical level. In keeping with the exploratory spirit of this discussion, however, you might spare the rest of us your tantrums and take those emotional issues to Spray where they belong. I'm going to stay in this discussion, so you might as well find a way to continue participating without losing your composure.

Edited April 17, 2008 by tvashtarkatena

[G-spotter]

My second picture shows the angle of the picks when the handles are lined up as in your last model. It is an apples to apples comparison.

 

 

He's got a point, which it looks like you are misunderstanding.

 

Simply stated: if you hold the handle in your hand, and put the tooth of the pick on a tiny little edge of rock, or touch it to the ice, the tools line up in the Tvash method rather than the Dane method.

 

Your second pick shows the tip of the pics not aligned. It would be more accurate to show the tips of the pics in the same place, the grips in the same place and derive orientation from that.

 

So it would seem that this (Tvash method) is the most accurate way to compare them.

[tomtom]

Ya.

 

It's the angle of the pick entering the ice from someone swinging the tool which is important. For me with curved tools, that means the pinky guard is about an inch from vertical ice, with a center of rotation a little below the wrist.

[fishstick]

Re: Lining up images of tools etc.

Going beyond the purpose of this thread, an easy way for perspective buyers to gain a guesstimate of how various tools might behave is to draw a line running from roughly an inch or two behind the tip of the pick, to the front of the pommel or spike. Look at the angle between that line and the underside of the pick, tip-side. Steeper angles (noticeably under 90 degrees) tend to hook well, but require a distinctive wrist flick. Shallower angles just under 90 degrees provide a more natural swing, but hook less well. In very thin ice, I suspect those near 90 degrees pry ice off the rock to a lesser degree (but it’s just a theory of mine…). Shaft design is still required to stabilize those good hooks – try a BD Fusion and a Scud on the same day to get the idea.

 

Re: Pick volume vs. Strength.

My gut feeling is that taller (front two inches near the tip) picks are somewhat susceptible to breakage as a result of twisting in very hard ice. In a perfect world we don’t twist picks, but in reality we do sometimes load tools via force vectors that don’t align perfectly with the shaft. Picks may also twist as they as they deflect micro amounts as they penetrate through semi-bonded icicles. Picks absorb some of the tool vibration that doesn’t make it to the user’s hands. Shallow (less tall) picks provide a smaller surface which better allows the pick to twist in the ice, rather than on its own axis.

 

Based on the above and personal experience, pick strength likely comes from pick thickness, not height. Good metallurgy and pick design still trump thickness.

 

Re: Bevelled (sharp) tops.

Keeping the top edge of the pick very sharp aids removal, which should also extend the pick’s life. Be sure to file out any stress-rising nicks in the top edge as they occur.

 

Re: Bevelled lower edges.

These also aid removal, as well as seem to aid penetration. I suspect they lower the angles of stress-risers on teeth, and minimize drag while penetrating ice. Less drag, should equal less stress.

 

Regarding stress, I’ve never broken a pick by twisting it in a big, slow manner. I think of picks as shattering (cold metal slamming into hard ice is sort of like a beer glass flying into brick wall). When my picks have broken, they’ve certainly broken 100%. Breakage has become evident only upon removal, which is kind of scary; 80% of body weight may have been hanging on the thing as I was probing with the other stick.

 

My suspicion is that some failures are the result of imperfect metallurgy due to bulk production. It’s far easier to nail the process over the entire length of the pick on one sample, than to do so in a bulk batch of 100 or more.

 

All of this is of course theory…

 

GB

 

[tvashtarkatena]

 

Your second pick shows the tip of the pics not aligned. It would be more accurate to show the tips of the pics in the same place, the grips in the same place and derive orientation from that.

 

 

I did this type of line up in my first comparison, but that was in error; I scaled the Quark larger than the BD to make the two points line up. Both points (the grip and the pick tip) don't line up exactly when scaled equally because of differences in tool geometry.

 

My second comparison: coincident grips, pick tips aligned vertically (as on an ice surface) is the correct one.

Edited April 17, 2008 by tvashtarkatena

[tvashtarkatena]

Bill Belcourt of BD was gracious enough to invite me to call him via PM, so I took him up on his offer today. Hopefully, I won't mangle the essence of our discussion too much.

 

Re: Pick volume vs. Strength.

My gut feeling is that taller (front two inches near the tip) picks are somewhat susceptible to breakage as a result of twisting in very hard ice. In a perfect world we don’t twist picks, but in reality we do sometimes load tools via force vectors that don’t align perfectly with the shaft. Picks may also twist as they as they deflect micro amounts as they penetrate through semi-bonded icicles. Picks absorb some of the tool vibration that doesn’t make it to the user’s hands. Shallow (less tall) picks provide a smaller surface which better allows the pick to twist in the ice, rather than on its own axis.

 

Based on the above and personal experience, pick strength likely comes from pick thickness, not height. Good metallurgy and pick design still trump thickness.

 

 

Per my discussion with Bill, pick height doesn't reduce pick performance as much as pick thickness. Taller and thicker picks are more durable (I=thickness*height^2/12), but picks experience the most work hardening from being bent sideways (when the pick is twisted, as in during a difficult removal), so in that axis I=height*thickness^2/12), i.e., thickness is the most important dimension both for durability and performance. Thick picks shatter hard ice, but last longer. Climbers tend to favor better performance over durability.

 

The laser is both thinner and slightly not as high at the typical breakage point (tooth 4 to 5) as the Cascade. I'll have to get my hands on one to measure it and calculate the differences in I, however. That's one factor.

 

Bill relayed that in BD's experience, picks are fatigued primarily during the twisting involved in removal, and break during actual removal. He also suspects that a minority of climbers break most of the picks. The old 80/20 rule. I asked him what the profile of a pick abusing climber is. His answer was a strong ice climber who can bury a tool over and over without tiring (and how must twist and fatigue it during removal). Curved shafts increase the reefing required to remove picks. He also relayed that mixed climbers tend to trash and replace picks often enough so as not to break them as much. The most picks he's ever seen a single climber break is 5.

 

BD has attempted to reduce the tendency to overdrive picks by lightening their tool heads.

 

Re: Bevelled (sharp) tops.

Keeping the top edge of the pick very sharp aids removal, which should also extend the pick’s life. Be sure to file out any stress-rising nicks in the top edge as they occur.

Nearly all pick breakages start with cracks at one of the bottom teeth, so nicks in the top bevel probably don't matter as much. Bill wants to do more testing on reduced bevel versions of the Laser to see if BD can increase durability without sacrificing performance. The Cascade pick has much less of a top bevel, but sticks fine, for example.

Re: Bevelled lower edges.

These also aid removal, as well as seem to aid penetration. I suspect they lower the angles of stress-risers on teeth, and minimize drag while penetrating ice. Less drag, should equal less stress.

We talked a lot about bottom teeth. BD designs their teeth for stability and ease of removal primarily. Too shallow teeth result in unstable sticks that pop out without warning. Teeth that are too many, too deep, or too sharp are too difficult to remove. The Cascade pick is bead blasted, which knocks off tooth sharpness a bit.

 

BD has played with changing their teeth a bit to prolong pick life, but it only seems to give the pick 20 or 30 more pitches worth. BD hasn't tested for a minimum tooth radius required to maintain durability because they've focused more on ease of removal/stability. I wonder if a shallower 4th tooth (the most common breakage point) might increase durability a hair without degrading performance noticeably.

 

Other issues regarding durability:

 

Fatigue life/testing:

 

The Cascade pick seems to be softer (which may lead to a longer fatigue life). Anyone who uses them can attest that you need to sharpen those puppies often. Bill did limited fatigue testing on a small sample (3 of each) using the CE standards on the Laser and Cascade picks and came up with a 20% longer life for the Cascade, but more testing would be required to make this statistically conclusive. In any case, B rated picks like the Cascade exhibit 8 to 10,000 cycles under the CE test before breaking. I suppose you can do a rough calculation of how many times you twist the shit out of your pick per pitch and figure out how often you need to change them out if you really wanted to geek out on it. According to Bill, most climbers out there change picks when the first tooth has been filed off or when the pick breaks. He discussed the idea of putting a wear mark on picks, similar to wear bars on tires.

 

Market share/installed base:

 

We also discuss the installed base (how many Cascade versus BD picks are out there). Although BD enjoys roughly a 2x market share advantage over Petzl today, that is a snapshot which underrepresents the cumulative number of picks out versus Petzl there since BD's first interchangeable X15 pick was sold. The numbers, however, are not readily available and would require a fair bit of work to come up with.

 

Manufacturing:

 

BD tried water jetting, laser cutting, and even hot forging their picks, and saw no significant difference in durability (the hot forged picks actually lasted slightly less long). They anneal the parts to reduce the hardness of the HAZ and any stress concentration that would be caused by same, then they heat treat. BD laser cuts its own picks (and crampons and a bunch of other stuff), so they have control over that process. If anything, hot forging (Grivel's process...Petzl cold forges) might add stress concentrations by changing the very straight, regular grain structure of BD's raw plate stock.

 

Tool Geometry:

 

The pick angles of the Cobra and Quark are similar enough that this is probably not a significant factor regarding durability.

 

Regarding stress, I’ve never broken a pick by twisting it in a big, slow manner. I think of picks as shattering (cold metal slamming into hard ice is sort of like a beer glass flying into brick wall). When my picks have broken, they’ve certainly broken 100%. Breakage has become evident only upon removal, which is kind of scary; 80% of body weight may have been hanging on the thing as I was probing with the other stick.

 

 

In general, fatigue failures begin as microcracks at the point of failure (maximum stress), which propogate with each cycle. When the overall geometry is reduced to a certain critical point, the remaining pick fails catastrophically under load. This is generally how a ductile material like steel subjected to repeated stress fails.

 

Recommendations to avoid pick breakage (These should be pretty obvious):

 

1) keep your picks sharp, climb with thin picks in hard ice, and don't overdrive them.

2) Don't dry tool and climb ice on the same picks if you can avoid it. Use thicker picks for mixed if you can afford it.

3) Choke up on your tool to aid removal of a stuck pick rather than reef from below if possible. Easier said than done sometimes.

4) Get new picks periodically based on your frequency of climbing, not just when they're an inch shorter than new.

 

Questions Bill would like to resolve:

 

Can BD get away with a reduced top bevel without sacrificing performance?

 

What is the real difference in cycle life between BD and Petzl?

 

What is the real statistical breakage rate differences between same given differences in the quantity of installed base, geometry, and steel hardness?

Edited April 18, 2008 by tvashtarkatena

[Dane]

So who broke picks during the '08/09 season? If so what kind?

 

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