My Reverso tumbled down 300 ft of granite, is it still good???

brenta wrote: Suppose our Reverso is traveling at 30 m/s when it hits the ground. A very small fraction of a second later, its velocity is 0. The acceleration is very large, and so is the force, even though the mass of the Reverso 3 is less than 0.1 kg. Let's work backward from your 0.6 kN. Assuming the mass is 0.1 kg for simplicity, this means that the acceleration peaks at 6000 m/s^2. That's a lot, but it means that, assuming acceleration is constant, the Reverso is stopped in 5 ms and in that time it covers 75 mm. So, unless the falling Reverso deforms substantially and manages to dig a hole where it hits the ground, the 0.6 kN bound sounds very, very optimistic.

beyond this - when belaying, the force is distributed over a large surface area of a reverso (as it was engineered to function), while in this reverso's fall impact, we don't know where the force was applied or how large of a surface area was involved. perhaps it was one of the corners of the device. or maybe the reverso hit a sharp point of rock.

so while the device may very well be safe to use, we probably can't determine that from the rating of the gear and the amount of energy needed to stop it once it's fallen 300 feet.

Yeah with the tumbling and striking various points of the rock on the way down there is no way to calc out the impact all along the piece, your choice to use it. I'll keep an eye on the "accidents in north american mountaineering-chincy and using dropped gear section" to see if it works for you or should I say your partner.

Geir Hundal wrote: beyond this - when belaying, the force is distributed over a large surface area of a reverso (as it was engineered to function), while in this reverso's fall impact, we don't know where the force was applied or how large of a surface area was involved. perhaps it was one of the corners of the device. or maybe the reverso hit a sharp point of rock. so while the device may very well be safe to use, we probably can't determine that from the rating of the gear and the amount of energy needed to stop it once it's fallen 300 feet.

Do you throw a cam away when you fall on it. I guarantee the force on the cam lobes is greater than dropping a belay device 300 feet. Black diamond tested carabiners dropped 1000 feet off the Salathe and they all broke above rated strength.

JohnWesely wrote:I guarantee the force on the cam lobes is greater than dropping a belay device 300 feet.

You may very well default on that guarantee.

This guy shot a reverso with a .357 mag. Do you think that is more or less force?

geir.com/mythbuster.html

Justin Tomlinson wrote:After the climb, we went down and found it dinged up in several places. Overall the thing is very well intact, aside from a couple sharp edges from the impacts (which I intend to file down). Gear manufacturer's say to discard any dropped gear. Would you continue to use it?

Buy a new one! If you can't afford one right now, use a münter hitch until you can.

Geir Hundal wrote:mark- i pulled a couple of heavily used carabiners this week; they both held 5,000 pounds without failure. both of them were over 10 years old, one of them was worn almost exactly 1/3 of the way through the stock (rope wear). this is obviously a tiny sample size, but it appears from these two samples that metal fatigue doesn't greatly reduce static pull strength in all cases. i'll pull more stuff over time and PM you if i run across anything. regards, geir

As I already offered, you need to repeat cycles of loading. I also think you need to develop a better testing standard. You're drawing a conclusion that isn't accurate based on two manual tests which are suspect in method.

I already know fatigue reduces strength as metals we use in rigging systems are not resilient as say an aircraft wing (which are also subject to fatigue, though they are made to be incredibly more flexible to handle moving/turbulent air -- surprisingly aircraft usually have a low safety factor in engineering design because they gain more safety in resilience).

If you can cycle loads at preset starts, stops, & duration, that might help provide a better result. Maybe hit the same biner repeatedly with 5000 ft lbs and see how many cycles you get without/until failure. I think you could also incorporate a penetrating dye so you can get a visual on potential stress areas that may be developing into failure. Then maybe go into cycles where you know the failure, reduce the max loading and start seeing failure at lower loads; you can probably get a fairly decent failure point curve. Start taking each manufacturers biner and then tell us who's making the better biner.

brenta wrote: You may very well default on that guarantee.

When the OPs belay device breaks, then I will deal with that.

Nick Przybysz wrote: If a piece undergoes plastic deformation, and does so without failure, it is going to undergo some degree of strain hardening. I realize that there is going to be a stress concentration on any point where it is knicked, as metal is removed which reduces the cross sectional area, resulting in a higher stress during a load. It is unlikely that a small stress concentration is going to cause catastrophic failure, especially from cyclic fatigue. That is true that it becomes more brittle, but only a small amount. The gear is also likely not talking any large impacts. If you where to drop it over and over and over, you might have a problem. As for the paper clip example, bending it once is plastic deformation, resulting in strain hardening. Bending it multiple times over is going to result in a tension-compression fatigue cycle, which causes the failure, not brittleness

You don't know what you are talking about. You are not going to improve upon the properties of 7075-T6 (the most common Aluminum alloy used in climbing) by trying to strain harden it in a post heat treated state. Do you know the strengthening or failure mechanisms in this alloy? It is nothing like a paper clip.

JohnWesely wrote: Do you throw a cam away when you fall on it. I guarantee the force on the cam lobes is greater than dropping a belay device 300 feet. Black diamond tested carabiners dropped 1000 feet off the Salathe and they all broke above rated strength.

Hey John,

Honestly, I think you're right in that the device is probably fine. However, I hesitate to say "go ahead and use it" because the consequences of being wrong are so high. I'd be willing to bet $20 that the device would pull test to near full strength, but not someone's well-being.

Just my view, no insult intended. :)

to answer your question, i don't throw away my cams when i fall on them. that would be really expensive for me as i fall on my gear constantly.

JohnWesely wrote: When the OPs belay device breaks, then I will deal with that.

That's a good idea. You don't have to justify your unfounded claims, while the others don't need to waste more time on them.

brenta wrote: That's a good idea. You don't have to justify your unfounded claims, while the others don't need to waste more time on them.

And you don't have to justify your unfounded claims either. Isn't it nice how that works.

Geir Hundal wrote: Just my view, no insult intended. :) .

How dare you have an opposing point of view. ;)

JohnWesely wrote: And you don't have to justify your unfounded claims either. Isn't it nice how that works.

I gave a justification that you apparently are not equipped to understand. That's very different. If you can find fault with my argument about why 0.6 kN is unrealistic, go ahead. In addition, if you can point to where in this thread you have put forth any argument in support of your claims, go ahead. "As far as I can see" and "I guarantee" simply don't cut it.

I have broken several carabiners while doing bolt replacement projects. These are the carabiners that attach my funkness device to the bolt hanger being removed. Some of them failed on their first day out, others after several dozen bolts being replaced. I always assumed the failure was due to gate flutter and I do tend to get a rythm going when funking the crap out of those old leepers. This discussion has opened my mind to the possibility that the failure may be in fact from repeated stress, although this would not explain the big difference service live of those biners broken.

If anyone is interested I could provide a few for testing.

Mark Nelson wrote: As I already offered, you need to repeat cycles of loading. I also think you need to develop a better testing standard. You're drawing a conclusion that isn't accurate based on two manual tests which are suspect in method. I already know fatigue reduces strength as metals we use in rigging systems are not resilient as say an aircraft wing (which are also subject to fatigue, though they are made to be incredibly more flexible to handle moving/turbulent air -- surprisingly aircraft usually have a low safety factor in engineering design because they gain more safety in resilience). If you can cycle loads at preset starts, stops, & duration, that might help provide a better result. Maybe hit the same biner repeatedly with 5000 ft lbs and see how many cycles you get without/until failure. I think you could also incorporate a penetrating dye so you can get a visual on potential stress areas that may be developing into failure. Then maybe go into cycles where you know the failure, reduce the max loading and start seeing failure at lower loads; you can probably get a fairly decent failure point curve. Start taking each manufacturers biner and then tell us who's making the better biner.

Hey Mark,

If I understand your previous posts correctly, you believe that carabiners, belay devices, etc should be periodically replaced due to potential metal fatigue:

Mark Nelson wrote:the whippers typical in climbing should have gear be replaced at some point in time though they may not be subjected to a high load at any one time as you may not be able to pick up the actual physical fatigue damage equipment goes through.

Did I paraphrase you accurately?

I have no doubt that the studies demonstrating metal fatigue are valid. However, I think that in actual use of climbing gear, weakening due to metal fatigue is small compared to its ultimate strength (particularly with belay devices, the topic of the OP). Part of my reasoning for this is that I'm not convinced that cyclical loading done experimentally in a lab accurately models real day-to-day use in climbing. Add to this the fact that there are few (if any) reports of belay devices failing under normal use.

The two quick pulls were I mentioned were intended as an example of gear that did not seem to be weakened with normal use, not to conclude that I am correct. I'd need (at minimum) a well controlled study with large sample sizes and an appropriate statistical test to back up that claim.

As I don't resources immediately at hand for such a study, I will just have to keep pulling heavily used gear to gain some more perspective. Perhaps I'll find some concrete examples of metal fatigue in common day-to-day use of climbing gear. But honestly I remain somewhat skeptical at this point.

Again, no offense intended, just my thoughts on this.

Regards,
Geir

brenta wrote: I gave a justification that you apparently are not equipped to understand. That's very different. If you can find fault with my argument about why 0.6 kN is unrealistic, go ahead. In addition, if you can point to where in this thread you have put forth any argument in support of your claims, go ahead. "As far as I can see" and "I guarantee" simply don't cut it.

What do you think is a more realistic calculation?

Edit: I am sorry for being so arrogant. I don't know jack about physics and I misunderstood the calculator I was using. The forces were much higher. You were right.

JohnWesely wrote: What do you think is a more realistic calculation?

I think you missed the earlier talk about not knowing the details of the collision means you can't calculate the forces. Did it land and stick? bounce straight up? Hit two edges and bounce away spinning?
All of these would give different answers, some by orders of magnitude. Plus since the reverso is not a ball, you have to factor in the geometry and orientation it was in when it hit. I can't do these calculations. So i buy a new belay device when i drop one. Geir and many other are probably right that it is fine and no one has ever died from a belay device failing. I just know my partners or I won't be the first.

The best way to find out non-destructively would be to have it tested with dye penetrant. If no cracks (I'm not talking about micro-fractures so don't start) were found I'd use it again, but this will cost you more than your $30 unless you know some one.

Geir Hundal wrote: I have no doubt that the studies demonstrating metal fatigue are valid. However, I think that in actual use of climbing gear, weakening due to metal fatigue is small compared to its ultimate strength (particularly with belay devices, the topic of the OP).

Actually some good input over the eve. Yes, I think you have a couple of the points to be taken from the SMC presentation.

What we're talking about is exactly the mindset. Fatigue is the tiny mouse nibbling that nobody notices (to borrow that phrase).

The onset of the impact is probably important as well, but the end result occurs. Slowly building energy until finally reaches its failure point over the course of a hundred times; or do you use high impact onset and reach failure in 3 times? In either case the point being, failure occurs at some point.

Gear doesn't recover its rating. Is micro-fracture? No, but weaknesses do develop from fatigue. Are 200 whippers good enough to bust the biner? It depends. As Kevin offered, you can fail something in short order by being completely static, it matters somewhat that the original rating of something was 22kN, safety factor of 100:1, or whatever; the better indicator of failure is fatigue, lack of resiliency, or both.

Maybe another question to ask is why do I then pounce on the shock-load as crap if short static hits can fail stuff? Climbers unknowingly incorporate more resiliency in a system than can be offered by testing, though we are moving closer toward changing some of the perceptions that have been introduced. One good example is climber mass composition being distinctly different than using steel plates to do drop tests. I doubt though that some things will change; people need to feel the importance of being in charge of stuff, be enamoured by physical talent, or be the big hero no matter what science stares them in the face. nothing like a saturday morning tangent over coffee

Mark Nelson wrote: Actually some good input over the eve. Yes, I think you have a couple of the points to be taken from the SMC presentation. What we're talking about is exactly the mindset. Fatigue is the tiny mouse nibbling that nobody notices (to borrow that phrase). The onset of the impact is probably important as well, but the end result occurs. Slowly building energy until finally reaches its failure point over the course of a hundreds times; or do you use high impact onset and reach failure in 3 times? In either case the point being, failure occurs at some point. Gear doesn't recover its rating. Is micro-fracture? No, but weaknesses do develop from fatigue. Are 200 whippers good enough to bust the biner? It depends. As Kevin offered, you can fail something in short order by being completely static, it matters somewhat that the original rating of something was 22kN, safety factor of 100:1, or whatever; the better indicator of failure is fatigue, lack of resiliency, or both. Maybe another question to ask is why do I then pounce on the shock-load as crap if short static hits can fail stuff? Climbers unknowingly incorporate more resiliency in a system than can be offered by testing, though we are moving closer toward changing some of the perceptions that have been introduced. One good example is climber mass composition is distinctly different than using steel plates to do drop tests. I doubt though that some things will change; people need to feel the importance of being in charge of stuff, be enamoured by physical talent, or be the big hero no matter what science stares them in the face. nothing like a saturday morning tangent over coffee

I think this discussion has helped give me a little direction for where to look for fatigued gear. I know of several hard sport climbs here that have fixed biners subjected to hundreds of falls. I'll talk with some of the locals to see if I can switch them out and take a look at them.

Regards,
Geir