The forces on your piece in a leader fall....

[A_Little_Off_Route]

With an appropriately fitting harness, the forces on your piece during a fall shouldn't be..... oh, wait, not that piece.

 

 

I've searched and searched and can't seem to find a clear answer to the question of how much force does one usually expect will be exerted on the top piece of gear during a leader fall.

 

I am aware that there are a bunch of variables and most of the discussions I have read are focused on either the maximum possible forces, forces on the rope or climber, or extreme situations.

 

What force (or more likely range of forces) can one expect from your "average to bad" trad lead fall? Say a factor 0.5 25 footer or so.

 

What about a smaller fall say a 10-15foot fall towards the end of the rope with a very low fall factor?

 

I think it is a relevant question because it can help one judge just how thin of pro can be used in a given situation (micro nuts or TCUs anyone?) and when would it be appropriate to attach a screamer. For example, I have a #0.5 wild country nut that I like but it is rated for 4KN. I have 2 other nuts I use often that are rated for 6kn. Would the forces in my expected falls be >4kn or >6kn, what about if I attached the screamer?

 

Any help in this area, with example calculations, educated guesses or links would be appreciated.

 

Off_Route

Edited June 12, 2012 by A_Little_Off_Route

[shaoleung]

Unless you're a total math junky and want to get into the gnarly physics of it all, here's a calculator. http://www.myoan.net/climbart/climbforcecal.html

 

In the end, all the math and measuring in the world is no sub for experience and steady breathing.

[sdizzle25]

Ive always wondered this, perhaps a side effect of being more of a college student than a climber. Found this one, have seen others: http://junkfunnel.com/fallforce/

A quick plug in says you will be good with your 6 kn piece, and computers know everthing about rock climbing

Obviously the number of variables are huge, especially when most of your gear is going to break above its "rating".

I have also heard that your femurs are only rated to about 8 Kn or something. Even if you factor 2 your entire 60 you will be hard pressed to blow your c4/reasonable stopper in a perfect placement in perfect rock.

And then there is always the major caveat that the rock will probably break before before your piece, which, living in Oregon, is always the main issue for me.

[sdizzle25]

I guess to answer your question instead of spray you down with my life story, most normal falls seem to fall under or well under 5. " real bad" falls can get to 6-7ish. factor 2 falls can get up to just below 10 kn, in which case you are in a world of shit on several different levels

[A_Little_Off_Route]

Unless you're a total math junky and want to get into the gnarly physics of it all, here's a calculator. http://www.myoan.net/climbart/climbforcecal.html

 

In the end, all the math and measuring in the world is no sub for experience and steady breathing.

 

I played around with that calculator and it seemed like no matter what extremes I put in the fall was always 6KN +/- 0.5KN. That didn't seem right to me....

 

Off_Route

[shaoleung]

Did you click the ft/meters buttons?

[JosephH]

I think it is a relevant question because it can help one judge just how thin of pro can be used in a given situation (micro nuts or TCUs anyone?) and when would it be appropriate to attach a screamer.

Well, I suppose there are people out there who are capable of thinking about this sort of thing while placing pro, but I've never met one, and can't imagine it myself. In the end I guess I couldn't really care less what the numbers are and in any case I wouldn't be capable of looking at a placement and somehow relating it to relatively abstract numbers in that way.

 

But I do place and climb over a lot of small / marginal gear, however, and to my mind it's way more about taking the time to get intimately familiar with the capabilities of your gear, the characteristics of the rock, and about developing a more intuitive sense and feel of what any hypothetical or actual placement can bear. Once you have that, then the numbers are basically irrelevant (for me anyway) as placements naturally just boil down to 'yes' / 'maybe' / 'possibly-if-everything-is-and-remains-just-so' / 'no' / 'hell no'! ('possibly' typically gets a screamer).

 

But it does takes time, yardage and, in the end, falls to develop an solid intuitive feel for it all and I can't think of any useful shortcuts to shorten the learning curve besides climbing with better leaders and getting in even more yardage.

[A_Little_Off_Route]

I clicked the feet buttons. For a 185lb climber try these two:

 

35ft of rope out and 15ft above last piece. (add rope stretch and a runner and you're inches from decking) 6.7kn according to the machine and a FF of 1.4.

 

Now try 185lbs, 135ft of rope (getting close to the top of your 50m rope) out and 15ft above last piece. Machine says 5.2KN and a FF of 1.1.

 

How about 185lbs, 135ft of rope and ONE foot above your last piece (ie you're holding it and it's on a short draw) 4.7kn and a FF 1.0

 

That's not much variation between nearly decking from a 30ft whipper with little rope out and "falling" one foot with your whole rope out to catch/stretch you. Also, shouldn't the 1 footer on a long rope be a FF of less than 1.0? Something doesn't seem right.

 

The other problem is that this calculator (like many others) calculates forces on the CLIMBER during a fall. So in theory the piece above should get between 100-200% of the calculated figures though I can't find a reliable number for the "pulley effect" or "friction coefficient" to use for calculating that top piece force from the climber force numbers. From memory of many years ago it was something like 1.6x.

 

By the calculations produced from this website it appears that my 4KN wire wouldn't hold a 1ft fall with my whole rope out. Better not use it at all....

 

Also my regular nuts, even in the largest size are rated to 10kn which would regularly be snapping in half from more severe falls.

 

Off_Route

[A_Little_Off_Route]

In the end I guess I couldn't really care less what the numbers are and in any case I wouldn't be capable of looking at a placement and somehow relating it to relatively abstract numbers in that way.

 

This is exactly what I am hoping to be able to do. To be able to look at my 4KN Wild Country nut that I always seem to be able to find a spot for and think, "The rock's solid, the placement is good, and there is a lot/little rope out so it is decent/marginal/needs a screamer."

 

In order to be correct in my abstract/intuitive assumptions I wanted to ground myself in some numbers rather than ground myself with a few falls.

 

The leaders I climbed with would never talk numbers but would rather say "that little wire might hold ya' but I wouldn't count on it." I'd still like to know some more of the numbers behind placing marginal pro so that I can add it to my "intuitive equation" on the rock.

 

Off_Route

[rob]

I'd just add that i wouldn't ever count on a screamer turning a marginal placement into good pro

[JosephH]

I'd just add that i wouldn't ever count on a screamer turning a marginal placement into good pro

I've blown a couple of dozen screamers in falls over the years without any of those pieces blowing so I'm somewhat forced to believe the screamers played a contributing role to that outcome given all of those placements were small and / or marginalized in some way or another. All the screamers blew either partially or for their full length - typically blowing about half their length over all and we reused the partially blown ones after sport taping them back together, so a bunch of those screamers saw multiple falls until they were fully deployed. Lots over those falls were on micronuts, crack 'n ups, and 2-3# loweballs.

 

And I've taken an equal or greater number of falls on similar placements without screamers; some held, some blew so I over time I've developed a reasonable feel for what's likely and unlikely to hold in the way of small / marginal pro. I typically only carry the screamers on occasion, usually on FAs where I suspect the rock quality and / or placements are likely to be somewhat marginal in some way or another.

[rob]

Well, I'm talking about a marginal placement, not the size of the pro. For example, a poorly placed #3 is not suddenly good pro (or even better) just cause you slap a screamer on it. Otherwise, why bother learning to set pro at all? Just put screamers on everything.

[JosephH]

As am I. All the placements I'm talking about were small and if I were just talking about good small pro I wouldn't be talking screamers. I've taken six 25' whippers in a row on a good #3 Loweball without a screamer, ditto for falls onto unscreamered small nuts and crack 'n ups that were as bomb as they can be. That's not what I'm talking about - when I clip a screamer on a piece it's because I consider the piece marginalized in some fashion. And I don't use screamers for comfort either, if I don't think they'll make a difference I won't bother with a truly marginal placement at all.

 

But your point should be well-taken - don't count on a screamer to turn utter shite into a good piece. If you don't know what you're looking at to begin with they aren't going to substantially improve your odds or track record.

[rob]

As am I. All the placements I'm talking about were small and if I were just talking about good small pro I wouldn't be talking screamers. I've taken six 25' whippers in a row on a good #3 Loweball without a screamer, ditto for falls onto unscreamered small nuts and crack 'n ups that were as bomb as they can be. That's not what I'm talking about - when I clip a screamer on a piece it's because I consider the piece marginalized in some fashion. And I don't use screamers for comfort either, if I don't think they'll make a difference I won't bother with a truly marginal placement at all.

 

yeah, this makes sense, and of course it might make a difference, especially with a "good placement" in poor rock, etc.

 

My point, and I think we agree, is that if you place a piece and think, "this is marginal" (for whatever reason) and then you place a screamer on it, it's still possibly marginal, even if the screamer ends up helping. You wouldn't (or at least, I wouldn't) act as though it were suddenly a good piece -- in my mind, it would still be marginal and I'd want to get a good piece in when I could.

[A_Little_Off_Route]

I'd just add that i wouldn't ever count on a screamer turning a marginal placement into good pro

 

What??!! I thought that the way it works is you pays your money for a screamer, clip it on, and if you fall then John Yates Himself will reach down from the heavens and catch you on a downy soft pillow.

 

Seriously though, while I do think they are a really great innovation and a well made piece of kit, your point is well taken.

 

Off_Route

[mattp]

I agree with Joseph here.

 

There are too many factors that go into this equation than can be summarized in any simple answer and, really, it takes a lot of experience for one to be able to readily and accurately assess placements and the force that may be applied to them. And, while screamers may help marginal placements, I think overall judgment about what makes a placement solid is more important than the use of a screamer.

 

Aid climbing experience is probably a plus. Significant leading and falling experience is also a plus. But both can be dangerous.

[Buckaroo]

the junkfunnel link calcs force on the pro

 

but all these calculators seem like they are going on the high side of the forces

 

last summer on DHLA I fell on a 3/4 DMM Wallnut while rope soloing with a Rock Exotica Soloist. This 3/4 nut is rated at 3 to 4 Kn. All these calculators put the fall at 5.5 to 6.5 Kn. So according to the calcs the piece should have broken.

 

The Soloist is a positive locking type device so no real give there. Apparently the IRL scenario is more dynamic than these calculators. The human body itself is not a dead weight, it's going to give a dynamic load. Knots tighten up, friction through all the beaners.

 

I don't see why you couldn't go to one of the practice rocks and do some intentional falling. I used to do that on City Park just to get rid of falling fear. Why couldn't you do that to test what will hold and what won't? Just use a fat rope and bomber back up gear with lockers right behind your test piece.

[edwardsm]

This little document is an interesting read and pretty relevant I think.

 

http://www.safeclimbing.org/education/Heavy_Climbers_Beware.pdf

 

The part I find most interesting is that even at 200lbs loaded down with gear, a climber would only generate between 8 and 9 kN up to a fall factor of 1.7, which is high!