It is very possible. For instance, lets say you are aid climbing on some C3 pitch, and you take a daisy fall onto the tiny cam below you. Thiscould easily happen if you are not super carefull, and even if you are super carefull.

I think most of those very small pieces with low ratings are intended to be used primarily for bodyweight aid climbing placements. And many come with warnings that say something to that effect.

When you say placement, do you mean the quality of the crack you are placing the protection in? ie angle, tapering etc?

(and I dont trad)

As for gear failures in soft rock involving tracking, I don't think that the longer time involved in bigger falls with the same fall factor is an issue, because my understanding of the tracking phenomena is different, and I do know that, as mentioned, there is no peak force acting longer.

Here's what I think happens with tracking. There is a tracking threshold for the placement, i.e. the force at which tracking begins. I am going to assume for simplicity that this force remains approximately constant once tracking has begun. So what happens in a tracking failure is that the rope elongates until the tension creates a force on the piece equal to the tracking threshold. Once tracking begins, there is no further rope elongation; the rope tension remains at the level needed to initiate tracking. Energy absorbtion changes from rope elongation to the work needed to track the cam through the rock, a straight (force) X (distance) calculation if the tracking threshold is really constant. What you have, in effect, is a screamer, with tracking resistance replacing stitch ripping. Whether or not the piece fails depends on whether or not the work done in dragging it to the lip of the crack, when added to the energy absorbed by rope stretching up to the tracking threshold elongation, equals the potential energy of the fall.

Although I don't find validity in the time argument, I do agree, from the perspective of the analysis just given, that a big fall with a given fall factor is more likely to cause a tracking failure than a small fall with the same fall factor. This is because rope elongation up to the tracking threshold plus work done in tracking represents a fixed quantity of energy absorbed, whereas the bigger fall (with same fall factor) does have more potential energy to be absorbed. (The fact that there is more rope to absorb this additional energy does not intervene here because energy absorbtion has been switched to the tracking mechanism before the rope could do its job.) Thus the fall does not end with the tracking inside the crack and the piece blows. Note that the longer elongation time for the rope occurs before tracking begins and so has nothing to do with the ultimate failure of the piece.

Also, how would you say a longer fall applies to the sequencial ripping of pieces in a 3 (or more) piece semi-equalized (cordalette) anchor. (Or does it?)

Could you please apply your analysis to the case where the belayer is "peter pan'ed" higher off the belay due to a longer fall of same FF.

to adress tedc question

Could you please apply your analysis to the case where the belayer is "peter pan'ed" higher off the belay due to a longer fall of same FF.

Also, how would you say a longer fall applies to the sequencial ripping of pieces in a 3 (or more) piece semi-equalized (cordalette) anchor. (Or does it?)

there must be a measureable (and i'd think significant) amount of energy used up in snapping a cable rated to 10kn

Missed several points:
1. a fall with ff 2.0 will not generate 12 kn , rather 10 kn with a modern rope in (very) good condition. the 12 kn is the maximum limit stated by the UIAA standard.
2. if you do not have any carabiner acting as a pulley in your system, the anchor onto which you have affixed the belay system will see the total force of the fall 10kn.
3. if you have setup a draw on the anchor, by virtue of the friction on the biner, the force seen by the belayer side is ~= 60%, the force seen by the anchor is ( 100% +60% ) the force felt by the climber = 16 kn

Missed several points:
1. a fall with ff 2.0 will not generate 12 kn , rather 10 kn with a modern rope in (very) good condition. the 12 kn is the maximum limit stated by the UIAA standard.
2. if you do not have any carabiner acting as a pulley in your system, the anchor onto which you have affixed the belay system will see the total force of the fall 10kn.
3. if you have setup a draw on the anchor, by virtue of the friction on the biner, the force seen by the belayer side is ~= 60%, the force seen by the anchor is ( 100% +60% ) the force felt by the climber = 16 kn

1. This assumes that there is no difference between a 1.78 and a 2. Also the 12kn limit applies to a 1.78 fall. this means it could go higher in a ff2 and still pass the test

2. only if the rope is tied directly to the anchor

3.edit

I believe it is possible to extrapolate the maximum force inflicted to the dummy for a ff 2.0 either from the modulus of the rope given by the static elongation or from the modulus given by the test at ff1.78.
The issue: we get 2 different values,

Nonetheless, using the second formula, a rope that inflict 10 kn in a ff 1.78 can be predicted to inflict 10.5 kn in ff 2.0

If you say you are going to address my question then address it. Your text does not refer to the differing effects of a long and short fall and that is the (hijacked) subject of this thread.

The primary source of work is the work done in stretching the rope, but there is also the work done against frictional forces (which can be highly significant in the case of a dynamic belay), perhaps work done in elongating a screamer, and in the case of soft rock, the work done in dragging a piece through a yielding medium.

Here are two question that have been indirectly reference in a few of the posts.

1)
What are the relative mechanisms and pro and cons of using a jumping(or getting lifted) dynamic belay versus purposely letting rope slide through the belay device?

2)
How does the theoretical fall factor force compare to the real world fall factor force for any given fall?


edit to add

How significant of a difference is there between a ff 1.78 and a ff2?

I'll take a shot at it. In principle, the load on the top piece depends on the famous H/L ratio; H=total length of fall (before rope stretch) and L= amount of rope from leader to belayer. However extensive research and mathematical modelling by the Italian Alpine Club suggest what a lot of people suspected---the total length of rope involved is, in practice, less than the amount from leader to belayer because friction against carabiners and against the rock prevents the full length of available rope from responding to the forces at the top biner. This means that with the real-life L smaller, the ratio H/L is bigger and the tension developed in the rope at the top biner is higher than one would expect from the classical H/L calculation.

regarding lifting, the CMT said
"It can be noted that the belayer's lift at the maximum safety load instant (roughly 0.2 sec) is very little: this is somewhere in contrast with the current believing of the climbing world.
In fact it is a common belief that the belayer's lifting reduces the safety chain loads.
Actually it is the low braking force generated by the belayer the true origin of the low load of the harness belaying technique also according to the tests: the low inertial force is due to the small mass involved in the braking action typical of this type of braking."

Due to the risks of belayers jumping into the face in order to "soften" the fall", I prefer to stay firmly planted and attempt to let a few cm of rope slip

dear alpnclbr1

thanks to your very good idea of collecting rgold contribution in http://www.rockclimbing.com/...iewtopic.php?t=62477, I found that before I could write up anything remotely clear, rgold did it

I think you are misinterpreting this. In the experiment, as far as I can tell, the belayers did not intentionally jump, but were passively lifted. An intentional, well-timed jump increases the time over which the energy of the fall is absorbed and therefore decreases the impact force on the climber and the anchor.


Nobody jumps into the face. You are speaking from ignorance.

-Jay

So in a sense, you get credit for that.

Your point "An intentional, well-timed jump increases the time over which the energy of the fall is absorbed and therefore decreases the impact force on the climber and the anchor. "
doesn't make physics sense to me.

I would on the other hand agree on
An intentional, well-timed jump decreases the inertia of the complete braking system, decreases momentarily the friction on the top biner, thus allowing the lifting of the counterweight to occur, increases the amount of rope sliding against friction in all intermediate biners. The additional mechanical work and additional transformation into heat bleeds the fall energy. This combined with the additionnal lenght of rope involved in absorbing the fall thus decreases the impact force on the climber and the anchor. The interplay of several mechanisms instead of just the rope streching means that the fall last longer, but it is not the increased duration that decreases the impact force.

Ps: No one I know volontarily jump into the rockface, but I have seen quite a few time a tiny gf fly up to the first bolt when belaying a (heavy) friend of mine.

Dynamic "jump" belay seems much more practical for good stances on the ground. In a multiple pitch hanging belay or in snow/ice, I do not see myself attempting to soften a fall by jumping; letting ropes slip seems more practical.

The data at "Forces on the Falling Climber Depending on Different Belaying Techniques were computed for low ff =0.375 and with limited runs.
http://www.leeds.ac.uk/sports_science/abstracts/climb99/wnachbauer1.htm they always seem strange as the force with dynamic belay and HMS are reported higher than dynamic belay with grigri....Could it be that the jump cause the belayer to forego letting the rope slip and thus cancel the benefit of the HMS ?