Understanding Climbing Fall Forces on Small Gear
|
As a single pitch sport climber I never paid much attention to equipment and fall ratings. Now that I have been trad climbing for a short period, I am trying to understand the fall forces on small gear. One climb I have been enjoying is a finger crack for the first 20 feet and will only accept my Metolius 0, 00 and a DMM #6 brass. I am able to get gear in every 5 feet, but if I, a 165 lb climber, falls 2 feet above my first piece, a solidly placed Metolius 0 that is rated at 5kn, would it blow? The force calculators say that a 2' fall with only 8' of rope out is almost 10 kn's on a dynamic rope. How do you process all this information on a climb? Please be kind. |
|
What force calculator are you using? 10kN seems a bit high for your example. |
|
D.Buffum wrote: (1) The rating of the piece of protection is the force at which the piece will break, not necessarily the force at which it will pull from its placement. The placement can be quite variable. (2) The rating on your rope is the maximum force your rope will impart onto the top piece of gear in a two-meter, factor 2 fall with a 180 lb deadweight on the end. This fall force calculator puts you at just over 5.25 kN using the data you supplied. Not sure where you got 10 kN.I could be mistaken, but I thought the UIAA data was measured at the leader (not pro) and was for a slightly smaller (FF ~1.8) fall. I briefly tried to look this up before my post, but came up short. Agreed that the strength of the rock around the placement could be an issue, though. |
|
|
|
I appreciate the technical side of my question, but how do you apply this in practical application? Are there any general rules you follow when climbing above smaller gear? |
|
Keithb00ne wrote:I appreciate the technical side of my question, but how do you apply this in practical application? Are there any general rules you follow when climbing above smaller gear?I'd say use one of the simpler fall force calculators putting in various fall distances then plug pieces that are safe assuming that's an option. |
|
Your math suggests that your 1st piece was 6' off the belay. I probably wouldn't bother with a marginal piece so low. |
|
Some incorrect information above regarding rope impact force rating. This is merely a test result in a severe fall simulation with a 1.77 fall factor, 80 kg weight and a static belay on a brand new section of rope. This is very hard to duplicate in the field. Keep in mind all ropes lose elasticity with use and time. So this number would be higher if you retested this rope after lots of use. |
|
|
|
Kirtis wrote:http://junkfunnel.com/fallforce/ One of the best fall calculators out thereBetter than the last one but still makes simplifying assumptions about the rope modulus if you look at the source code. |
|
Kirtis wrote:http://junkfunnel.com/fallforce/ One of the best fall calculators out thereRubbish, it uses the wrong rope factor. |
|
I think John Marsella's post above is the best answer to your question. Rather than doing mental calculations, you are better off doing whatever it takes to not fall. If that requires being on some other, easier route, that is your best option by far. |
|
this is entirely anecdotal... but, I have fallen 15+feet without rope stretch on a 00 purple C3 rated 6KN on a 9.4mm rope in Zion sandstone. no blow out. I have taken 20ft falls on 0 and 00 C3's and 1 TCU's no blow out. if that helps at all with your confidence on small gear. a nice bouncy rope and a soft catch do wonders on thin pro. |
|
Calculating fall forces makes for an interesting discussion, but the reality is there are too many variables in the real world for that to give you a good idea of what's going to happen. Sometimes you take a 30ft whipper onto a microcam and it holds, sometimes you take a 10ft fall and it rips. |
|
Kirtis wrote:http://junkfunnel.com/fallforce/ One of the best fall calculators out thereAccording to what standard? That the picture is nice? As Jim says, its rubbish, and you don't need to inspect the source code (god knows what else might be wrong there) to figure out the calculator is worthless. The key is that the rope modulus is estimated by the elongation at 80kg, and this gives a seriously inaccurate result. Assuming they get the math right, such calculators only stand a chance if they begin with the UIAA impact rating of the rope or the effective rope modulus, if you happen to know it, which seems highly unlikely. The accuracy of such simple calculators, based on modeling the rope as an undamped spring, is not great; you can think of them as probably overestimating the worst-case scenario for most situations. As far as I know, there is only one calculator out there that gets the theory right and so is the only one that deserves any attention at all, the one by Jay Tanzman at jt512.dyndns.org/impactcalc…. As for climbing over small gear, the crude theory based on spring models has little to offer. Do your best to place a lot (this often means stopping in places that are not comfortable) and try to climb down rather than fall going for it. Double ropes (properly handled by the belayer, something that cannot always be counted on) offer a significant advantage if you are managing to get overhead protection that is marginal. |
|
Place small pro well and equalize when in doubt. It's tough to break or pull gear when using it properly. Place it well and in good stone, and it will do its job - even the small stuff. |
|
what's to analyze? plug some small gear and back up with solid gear and whip on them and see what happens for yourself! how can you trust the opinion of a public forum where every other person's opinion is...i don't know; the maths is pretty complicated; i'd rather just not fall... |
|
Since we all know that equalization can't be perfectly achieved in a static anchor, how does one equalize small gear when on lead (ie bad stance) ? And does it achieve anything? |
|
Matt N wrote:Since we all know that equalization can't be perfectly achieved in a static anchor, how does one equalize small gear when on lead (ie bad stance) ? And does it achieve anything?Sliding x between both pieces. If you can hang on enough to slot two pieces of pro, it doesn't take much longer to equalize them with a sling and biner. It takes a bit more endurance and practice to do it one handed, but it's easy enough if the stance isn't too desperate. I'll usually equalize small pieces if I can when before runouts, especially on climbs where I'm pushing my grade. Does it achieve anything? I'm sure someone here can pull out anecdotes or data claiming otherwise, but most experienced leaders will vouch for equalizing marginal or thin placements when possible. |
|
Wow, lots of confidence here about falling on tiny gear. |
|
Greg D wrote:Some incorrect information above regarding rope impact force rating. This is merely a test result of the amount of force on the top piece of gear, (not the climber) in a severe fall simulation with a 1.77 fall factor, 80 kg weight and a static belay on a brand new section of rope...I hate to beat a dead horse, but this is pretty important. I looked around and I'm fairly certain that the UIAA measures force on the *leader*. Here are a couple non-official links: alpineexposures.com/pages/f… rei.com/learn/expert-advice… If someone has info that they are really testing the force on the *top piece*, I would love to see it, as that would significantly lower the forces for a given fall factor and rope. |