How much force can be generated in a sport fall

I was talking to a friend the other day and we were both wondering how much force can be created in a sport climbing fall. Specifically how much weight is transfered to the bolt.

us enginerd types may need a little more information than that.
length of fall? angle of rock face? weight of both climbers? kind of rope you are using? fall factor? kind of belay device? kind of belay style? etc. is said fall taking place on earth? moon? mars?

EDIT:
or if you are extremely bored check out: petzl fall simulator

alpinedave.com/fall_machine…

Fun stuff...

For those of us that like to do the calculations there are many specifics required as WiledHorse mentions. In a very, very general sense "sport climb falls" typically generate 2-5kn (850-1150 lbf) but double that is not uncommon (edit: possible). The forces tend to be greatest when you are closest to the ground/close to your belayer.

If you want specific numbers you need to provide data. Amount of rope between climber and belayer, distance above last piece, rope characteristics, weight of climber and belayer or among important factors.

PS. The laws of physics are the same for sport and trad climbing. When you say sport fall I am assuming that just means protection roughly every body length or so. Although that can vary widely as well. (edit: this may not be true per Mark Nelson and the laws of cragging.)

Scott McMahon wrote:http://www.alpinedave.com/fall_machine.htm Fun stuff...

The fall distance is quite understated here. It merely doubles the distance above the last piece. This number will be larger due to amount of slack in system and stretch to mention a few.

Folks also keep in mind, although not a force measurement per se , I would much prefer a 40ft. clean fall off an overhang into space to a 18 foot drop onto a ledge. Just a thought.

Stu Ritchie wrote:Folks also keep in mind, although not a force measurement per se , I would much prefer a 40ft. clean fall off an overhang into space to a 18 foot drop onto a ledge. Just a thought.

Lets do the calculation. 18 foot fall onto ledge. Force onto top piece=0 The piece will hold.

Greg D wrote: Lets do the calculation. 18 foot fall onto ledge. Force onto top piece=0 The piece will hold.

The dreaded factor 0 fall.

Greg D wrote: Lets do the calculation. 18 foot fall onto ledge. Force onto top piece=0 The piece will hold.

Note that the fall distance is not the part to worry about here.

It's amazing how much rope stretch makes a difference. 6% vs 9% makes for a world of difference and could potentially save your ass. What are the downsides to rope stretch? Why don't we climb with 15% stretch? All I can think would be scenarios close to the ground where the stretch would put you on the ground (like when on a top-rope with a beginner and you tell them the rope will catch them, then they fall from 6 feet and even though you've got them locked off, they end up decking in slow motion).

Jeff Fassett and I did some direct measurements using a dynamometer:

With 50 feet of rope out, 10 foot falls resulted in a maximum force of 820 pounds on the top bolt with a GriGri, and 435 pounds with an ATC.

With 20 feet of rope out, 10 foot falls resulted in a maximum of 1030 pounds on the top bolt with a GriGri and 900 pounds with an ATC.

These averages were calculated from 10 falls at each height (five using the GriGri and five using the ATC). In both cases the rope 10.2 mm, although I can't remember the manufacturer off the top of my head (I'm at work right now.)

Of course, these figures are a snapshot, your results will vary depending your rope characteristics, fall factor, friction, belay device, etc.

Patrick J wrote: What are the downsides to rope stretch? Why don't we climb with 15% stretch?

Yes. I have some spare time today. So I will comment. Rope stretch is a tradeoff. More stretch means greater chance of hitting something (ledge, belayer, ground, etc). More stretch means less chance of blowing top piece of gear. I opt for more stretch (low impact force) as I weigh 2 bills +, and mostly climb trad. For light weight people and sport climbing impact force is not as significant IMHO.

Mark Nelson wrote:what was your mass & mass amount?

oops! yeah, i should have mentioned that ... i'm 150 pounds. :)

Greg D wrote: PS. The laws of physics are the same for sport and trad climbing.

The first law of the crag is that sport climbing is neither; how then can the laws of physics apply to such a misnomer-ed activity?

I would imagine a lot of farce could be generated in a sport fall.

shawn bradley wrote:I would imagine a lot of farce could be generated in a sport fall.

Nice :)

Mark Nelson wrote: The first law of the crag is that sport climbing is neither; how then can the laws of physics apply to such a misnomer-ed activity?

Damn it Mark. You got me on this one. Wasn't in my physics text. I should have climbed this route first:

mountainproject.com/v/nevad…

Then, I would have known.

Mark Nelson wrote: sport climbing is neither?

i have heard this many times in my climbing career. i dont really understand it. sounds witty and clever. please explain?

it just doesnt seem very accurate of a statement, thats all.

Andy Kowles wrote: It's not at all accurate, you're right. But if you see a crusty old dude sporting this bumper sticker and a rack full of forged friends you know exactly what it means.

is he going to go rock climbing?

EDIT: btw, i like your choice of words ..."sporting" the bumper sticker. that to me is funny.

sorry about the thread drift Jeremy, earlier.

if this is what you were getting to, your bolt is gonna hold if it was placed right. you cant generate enough force to break it. unless it is a 1/4"er...

i would be more concerned with grooved biners, worn old webbing, and sharp edges that could cut your rope.