Fall Factor Discontinuity

Could be old news to many. At the same time, some might find this amusing.

Data source: JT's Impact Force Calculator with input of a) rope impact force of 8.7 kN, b) 175 lb leader, and c) rope-over-biner friction factor of 1/3 (which does not apply at fall factor 2).

I believe the linked force calculator is recognized by many as the best on-line source available.

That jump discontinuity in anchor load is a real feature of the situation, so there is nothing the matter with the program that produced it. The plot is a poor representation of the situation because it attempts to draw a continuous graph rather than just representing the jump at FF2, but that's the "fault" of the plotting program, not the fall force calculator. The lowered value at FF2 is part of an ongoing debate about whether it is better or worse to clip the anchor as the first piece, as you know very well considering your caption for the graph.

So what exactly is the problem here? Your post makes it sound as if you are criticizing the calculator for some reason.

Your post makes it sound as if you are criticizing the calculator for some reason.

Glad you mentioned that. It's the opposite: glad to have something well thought out to produce the plot.

Edit: And I think if one tries to reproduce the plot using Jay's tool, one will observe that at FF2 the tool actually combines the force on the climber with the force on the belayer. I corrected that in the above plot by plotting just the force on the climber (with the friction factor set to zero). Hopefully you can see, in posting the plot I am making no criticism of the tool.

So what exactly is the problem here?

None. It's old news to many. But perhaps not to some.
Bill L

The plot is a poor representation of the situation because it attempts to draw a continuous graph rather than just representing the jump at FF2, but that's the "fault" of the plotting program, not the fall force calculator.

Although apparently too subtle, the above is exactly why I made the data points explicit. Perhaps not drawing the line would have removed a bit of that subtlety.

If it's any support, JoshSAR did some drops with a fairly static system and got maybe just over 12kN with a rescue mass (which itself was static -- so trying for the worst case). Again, with a rescue mass and system, this would be a less resilient system than what a lead climber would offer.

Larger drops failed mainline components but the trad anchors held. Drops were in direction intended. And they even tossed in a bad placement to try and see how that would affect an anchor, which it didn't, other than the bad placement blew out.

Modeling and predicted work-ups are fine to start with, but you need actuals to compare and discuss.

I don't think it matters either way as far as maintaining the anchor. If the anchor is questionable to begin with, then it's really not an anchor.

Mike McKinnon wrote:ok for us laymen what is the end result of this.

At least one takeaway:

The highest fall factor is not what necessarily produces the highest force on the "top" piece.

And the highest force (in theory) will break most pieces on our racks. Granted, real peak forces will often be lower than those plotted due to belayer movement, possible rope slippage through the belay device, falls that aren't "clean", etc..

Some cool info from Will Gadd:

willgadd.com/anchor-clipping/

...and the update:

willgadd.com/anchor-clippin…

Some cool info from Will Gadd ...

For a gear anchor, I get a little worried applying the following:

"... clipping the top piece of an anchor makes sense if that piece is super solid AND the belayer is solidly anchored down so they don’t fly ..."

Later he defines a solid piece as a bolt. With gear anchors, it is not unusual to have a solid piece that itself is only rated to 10 kN.

A solidly anchored belayer could mean an upward pull piece slung taught to the belay loop with the belay device also attached to the same belay loop. There may not be a lot give in the belay.

Whether it's possible to exceed 10 kN I don't know for sure; rope will likely slip? But I also know not clipping the anchor piece (i.e., risk a fall onto the belay) should keep forces well below 10 kN.

theres 2 issues with not clipping the top piece/bolt ...

1. the braking position will invert ... climbers have lost control or the brake even when just lowering directly off the harness from the top, never mind high factor falls ... its not a position that many climbers practice braking from, never mind catching hard falls ... how confident are you that your partner can catch you in a factor 2 especially if they dont have gloves or experience with the ATC flipping?

2. squishy ball syndrome ... as anyone who regularly lowers off their harness knows, lowering off the belay loop on a top belay off the harness can be uncomfortable to the male genital area ... this is because the weight is one the belay loop which twist the tie in loops, which then transfers to the anchors ... the brits get around it by belaying off the rope tie in ... if its uncomfortable in body weight situations, imagine the possible testicular pain in a high factor fall ... again most climbers dont practice lowering directly off the top harness to know of this issue

remember also that in the real world you have belay devices, squishy masses and harnesses ... most belay devices will start slipping before 10 kn

honestly if you are REALLY worried about the force on the top piece in a high factor fall, IMO you wouldnt be climbing on a hard catching rope like a maxim or some mammuts ... youd be using a beal or something in the 7-8 kn impact force range ... and youd be using a tube/munter or something with a bit of slip

the reality i think is that for most situations we run into ... loss of rope control is a more important consideration

;)

bearbreeder wrote:theres 2 issues with not clipping the top piece/bolt ... 1. the braking position will invert ... climbers have lost control or the brake even when just lowering directly off the harness from the top, never mind high factor falls ... its not a position that many climbers practice braking from, never mind catching hard falls ... how confident are you that your partner can catch you in a factor 2 especially if they dont have gloves or experience with the ATC flipping?

Unless the piece definitely won't fail = excellent placement & rock, this bites both ways:

Leader clips the top piece in the anchor. Leader falls from above it. Piece fails. Will belayer react fast enough to change brake direction? It's happened and the belayer didn't figure out why so much rope went out until many days after the accident.

bearbreeder wrote:theres 2 issues with not clipping the top piece/bolt ... 2. squishy ball syndrome ... as anyone who regularly lowers off their harness knows, lowering off the belay loop on a top belay off the harness can be uncomfortable to the male genital area ... this is because the weight is one the belay loop which twist the tie in loops, which then transfers to the anchors ...

Have lowered often from the harness. It ain't the most comfortable thing but not bad either. But maybe I'm just not as ... well ... endowed ....

Bill Lawry wrote: Unless the piece definitely won't fail = excellent placement & rock, this bites both ways: Leader clips the top piece in the anchor. Leader falls from above it. Piece fails. Will belayer react fast enough to change brake direction? It's happened and the belayer didn't figure out why so much rope went out until many days after the accident.

which is absolutely true ... which is why some people clip the masterpoint as the first piece ... and why having a belayer who is experienced in catching falls/lowering in the inverted position is important regardless ... how many people do you see practicing that at the crag?

if you think there might be a decent chance of a fall off the belay ... lower the belay down and clip the masterpoint ... or use a fixed point belay ...

you can almost always lower yourself down about 10 feet or so ... i use a method which allows for redundancy in case of sharp edges, allows for total control on the descent and you can ascend the rope back to the belay if needed after

Bill Lawry wrote: Have lowered often from the harness. It ain't the most comfortable thing but not bad either. But maybe I'm just not as ... well ... endowed ....

it depends on the body positioning relative to the load and the anchors ... which you may not have a choice with on a fall off the belay

you realized you just told an AZN that you are LESS well endowed than him

;)

Hey Bear.. You realize youre saying you're a pharmaceutical company? Maybe I'm lost in translation with you being from Canada and all. HAHA..

Kirby1013 wrote:Hey Bear.. You realize youre saying you're a pharmaceutical company? Maybe I'm lost in translation with you being from Canada and all. HAHA..

everyone knows that ASIANS are extremely well endowed ...

;)

AZN=Asian... learning all kinds of stuff from you lately!

bearbreeder wrote:theres 2 issues with not clipping the top piece/bolt ... 1. the braking position will invert ... climbers have lost control or the brake even when just lowering directly off the harness from the top, never mind high factor falls ... its not a position that many climbers practice braking from, never mind catching hard falls ... how confident are you that your partner can catch you in a factor 2 especially if they dont have gloves or experience with the ATC flipping? 2. squishy ball syndrome ... as anyone who regularly lowers off their harness knows, lowering off the belay loop on a top belay off the harness can be uncomfortable to the male genital area ... this is because the weight is one the belay loop which twist the tie in loops, which then transfers to the anchors ... the brits get around it by belaying off the rope tie in ... if its uncomfortable in body weight situations, imagine the possible testicular pain in a high factor fall ... again most climbers dont practice lowering directly off the top harness to know of this issue remember also that in the real world you have belay devices, squishy masses and harnesses ... most belay devices will start slipping before 10 kn honestly if you are REALLY worried about the force on the top piece in a high factor fall, IMO you wouldnt be climbing on a hard catching rope like a maxim or some mammuts ... youd be using a beal or something in the 7-8 kn impact force range ... and youd be using a tube/munter or something with a bit of slip the reality i think is that for most situations we run into ... loss of rope control is a more important consideration ;)

Pardon my ignorance but I have little experience in belaying a Trad Lead and Im curious what this statement means. How/what causes the braking direction to invert on an ATC of the device to 'flip' during a fall such as this?

Greg - You may be taking it too literally with the terms "invert" and "flip". Just work it through your imagination that your climber (and the rope)is at first going above you, then suddenly it all shifts to below you.

You can simulate in your living room the effects of the sudden change in direction of pull in relation to your typical brake hand positioning.

My ex-wife got caught off guard this way. 'Course she said it was merely an "accident", but after that, I don't climb with my beneficiaries...

Greg, think of the belay stance. You'd be expecting to make the catch clean with a lock-off countering the lead climber, but instead they travel past you, jack your ass, and now you try and make the catch in the opposite direction.

That's probably more a concern than force to an anchor; I'd agree with that.

Mark Pilate wrote:Greg - You may be taking it too literally with the terms "invert" and "flip". Just work it through your imagination that your climber (and the rope)is at first going above you, then suddenly it all shifts to below you. You can simulate in your living room the effects of the sudden change in direction of pull in relation to your typical brake hand positioning. My ex-wife got caught off guard this way. 'Course she said it was merely an "accident", but after that, I don't climb with my beneficiaries...

Ok so I think I see what you mean then, basically since the climber is falling below you then your break hand would need to go upwards in order to lock the ATC, a change in direction, which, for people who dont practice it is very difficult to do during an actual lead fall.
And if Im picturing this properly wouldnt it also mildly depend on which side of the belay the leader were to all on? Such as if your brake hand is your right, and the leader falls to the left of you wouldnt the pull of the ATC (and your body) be in the opposite direction of where your break hand would have been? Or is that minor direction difference negated just by the sheer forces of the fall?

@Buff, I do understand the jerking issue, had a similar experience as Mark from a family member nearly decking me due to it. I was mainly confused about the braking direction change issue mentioned by bearbreeder

Greg J wrote: Ok so I think I see what you mean then, basically since the climber is falling below you then your break hand would need to go upwards in order to lock the ATC, a change in direction, which, for people who dont practice it is very difficult to do during an actual lead fall. And if Im picturing this properly wouldnt it also mildly depend on which side of the belay the leader were to all on? Such as if your brake hand is your right, and the leader falls to the left of you wouldnt the pull of the ATC (and your body) be in the opposite direction of where your break hand would have been? Or is that minor direction difference negated just by the sheer forces of the fall? @Buff, I do understand the jerking issue, had a similar experience as Mark from a family member nearly decking me due to it. I was mainly confused about the braking direction change issue mentioned by bearbreeder

it can be caught either side but wit a few caveats

the below assumes a right handed brake ... and bundle of draws is the "climber"

as you can see the device flips ... if you pull your right hand brake to your hip and up ... the braking position is good

the problem is where the rope runs ... its running over your tie in ... in a high factor fall with a lot of slippage or loss of control one can imagine the rope burning though the tie in ...



now heres a fall to the right side, same side as the brake ... the falling climber will twist the belayer to the right ... the problem that the maximum braking power is into your right armpit, or with your right hand way behind you, almost around your back ... not natural breaking positions for someone who doesnt practice these kind of catches directly off the harness



so what can one do? ...

one recommendation by petzl is to flake the rope through tied loops on a biner ... in the case of a loss of control you fall as far as the knot ...



the problem is that overhand knots are a biatch to untie on belay ... so i use slip knots, just make sure the slip is facing the proper direction! ... the slip knot comes apart easily on belay, but should catch a loss of control scenario ...

you can also only put a knot as far as the first solid piece, or your best guess thereoff ...



the other way is to lower yourself ... i find this method works best for me ...

1. tie in LONG with a clove at the masterpoint ... basically you want a bit more slack than what you think youll need to lower ... say 10 feet or so ...



2. on the other strand (not the one yr tied in) .... munter it to your harness



3. LOWER yourself on the munter to the belay position you want ... if all else fails you fall at worst to the length of your tie in ... tie off with a munter/mule



4. now flake the rope over your tie in and set up the belay normally ...



youve now
- reduced the potential fall factor quite a bit
- you probably wont get pulled in and SLAMMED into the wall in a high factor fall if you lowered off say 10 feet or so
- have a massive amount of dynamic rope and knots in the system to absorb the load if everything else fails
- are redundantly connected on 2 strands in case one gets cut
- have a fixed strand you can prussik back up if needed

of course it does use up the rope and you do have to manage the rope climbing strand to make sure it doesnt rub against the other ones, i recommend using a LONG runner at the top for the first clip in ...

as always ... i may be a 10 year old intrawebbing on his nonmindo gaming system ... and you will die if you learn off MP ... so take it all with a grain of salt

;)

I think this answers the question of forces from the above:

Quote from outdoorlink.org/research-pa…

Chris began his presentation with a PowerPoint discussion of forces in the belay chain.
Using extensive dynamometer testing in fairly “real-life” scenarios Chris reached some
of the following conclusions. I have greatly summarized these findings below:
• In stopping falls, the greatest forces are “felt” at the top runner, the one that
catches the fall.
• Here, in a factor 0.4 fall, forces are in the range of 4.2 to 7 kN, depending on the
type of belay and the device used, with the great majority of devices and belay
types generating about 5 kN at the runner.
• Factor 2 falls did not generate greater fall forces than those sustained by the top
runner in much less “severe” falls. Even with nearly static “direct off the anchor”
belay methods such as a GriGri attached to a bolt, factor 2 falls generated only
about 5 kN of force.
• Upward forces on the belayer were about 35 to 40% of the maximum reached at
the top runner.
• Of the common belay devices, tubes (without V groves and teeth) provided the
least friction, followed by Figure 8s, Munter hitches and finally static devices
such as the GriGri. However, all were deemed to be adequate.
• Maximum force was achieved about 0.2 seconds after the load began to be
applied, and diminished rapidly after.
• Significant upward movement of the belayer in off-the-body belays occurred after
this peak was reached, about 0.5 to 0.9 seconds after the initial application of the
load.
• Peak forces on the highest piece were essentially the same when catching a leader
fall in the fixed-point belay, as when catching the same fall with a passive body
belay (as in a hanging belay).

With the above information, Chris reached the following conclusions:
• The belay anchor can never be loaded much beyond 5 kN, even in factor 2 falls
directly onto the anchor.
• Upward pull forces on a fixed-point belay can virtually never be much in excess
of about 2.5 kN, even in the most severe falls.
• Upward pull forces are still sufficiently high to violently lift a belayer several
meters when using an off-the-body belay.
• Downward pull forces are sufficiently high as to violently displace a belayer when
holding a factor 2 fall off-the-body.

In addition to the great white north teddy bear, in terms of lowering the belayer to belayer, I saw this idea from a poster from the taco forum or wherever I forgot which I found really useful because it makes the transition from belaying to seconding instant.

1. Put a locker in the master point.
2. Put a munter hitch in that locker.
3. lower yourself to wherever you want.
4. use another locker and clove hitch the munter brake rope to secure yourself.

This way, you can move up and down (belaying yourself with the munter) and you can transition to seconding instantly.