I had an engineering friend work out the math for me on what was the maximum amount of force generated by a 150 pound man falling the maximum length in a factor two fall on a 60 meter rope. Basically falling 120 meters.
He said you reach terminal velocity before you pass the anchors and the maximum force generated by the fall on a 60 meter rope with 30% elongation is 6.81 kn=1536.85 lbs. The human body comes apart at 18 kn. Have a nice day!
MAXIMUM FORCE
Yes and no... initially the gear is much stronger than the body, but I would think after several years of use the metal has fatigued a bit and is slightly weaker.Ernie wrote:So what your saying is our biners can hold the force no problem! Good to know. Sounds like they would even hold as our bodies came apart...intresting.
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[quote="Meadows"]I try not to put it in my mouth now, but when I do, I hold it with just my lips.[/quote]
[quote="Meadows"]I try not to put it in my mouth now, but when I do, I hold it with just my lips.[/quote]
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Well, the maximum allowable impact force for a rope to pass the UIAA drop test is 12kN. This is a number picked by the US military after performing experiments to see what the greatest force a soldier could sustain upon parachute opening.
Where did you get the 30% elongation? That seems a little large. The UIAA rates ropes for static elongation, with most ropes falling around 6-8%.
I believe that a shorter factor 2 fall is actually more severe than the long full rope screamer that you have cited. There will be less rope to absorb the impact. Have your friend calculate 80 kg falling 5 meters on 2.8 meters of rope. This is the UIAA test drop and is supposed to represent the worst case scenario.
Biners are generally good for mid to upper twenty kN. Remember that when you fall the force doubles at the carabiner but is slightly reduced by friction. So if you take a fall that generates 9 kN the force on your pro would be about 1.5-1.75 times that or about 14-16 kN. A carabiner should hold that but your cam won't.
If you are a heavier climber (180+) forces on your gear will be higher as well.
From weakest to strongest you have:
1. Belayers grip - weakest. Can't remember numbers but 6kN comes to mind
2. Protection - most will fail around 12kN (remember forces are doubled at pro)
3. Human body - can sustain up to 12kN
4. Carabiners - 24-28 kN on average. (remember again forces are doubled) if you biner is not in good condition, are cross loaded, or the gate is not closed this could be higher up on the list.
5. Rope
Where did you get the 30% elongation? That seems a little large. The UIAA rates ropes for static elongation, with most ropes falling around 6-8%.
I believe that a shorter factor 2 fall is actually more severe than the long full rope screamer that you have cited. There will be less rope to absorb the impact. Have your friend calculate 80 kg falling 5 meters on 2.8 meters of rope. This is the UIAA test drop and is supposed to represent the worst case scenario.
Biners are generally good for mid to upper twenty kN. Remember that when you fall the force doubles at the carabiner but is slightly reduced by friction. So if you take a fall that generates 9 kN the force on your pro would be about 1.5-1.75 times that or about 14-16 kN. A carabiner should hold that but your cam won't.
If you are a heavier climber (180+) forces on your gear will be higher as well.
From weakest to strongest you have:
1. Belayers grip - weakest. Can't remember numbers but 6kN comes to mind
2. Protection - most will fail around 12kN (remember forces are doubled at pro)
3. Human body - can sustain up to 12kN
4. Carabiners - 24-28 kN on average. (remember again forces are doubled) if you biner is not in good condition, are cross loaded, or the gate is not closed this could be higher up on the list.
5. Rope
In an ideal situation with no other factors, like the rope snagging on something, here's the data.
80 kg falling 2.8 m from above the belay to 2.8 m past the belay generates 8.54kN(1919 lbs.) on the climber-faller. this is the initial force, I didn't calculate the force at the end of the elongation since it would be considerably less.
80 kg falling 2.8 m from above the belay to 2.8 m past the belay generates 8.54kN(1919 lbs.) on the climber-faller. this is the initial force, I didn't calculate the force at the end of the elongation since it would be considerably less.
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