This topic has been archived, and won't accept reply postings.
So I was wondering and I know I'm going to get lots of unhelpful answers here but figured someone would be able to give something sensible . . .
I remember years ago reading that an average lead fall was normally in the region of 5-7kn of force on the top piece of gear (very arbitrary I know).
I was looking at my little brass nuts with a strength of between 4 and 7kn I then also thought about being about 14 stone (87kg), a fair bit more fully dresssed with a rack and helmet etc on.
Now assuming that there is a good amount of rope in the system and that there is no real rope drag from zig zagging ropes or from ropes running over rough rock etc. If my top bit of gear is an IMP how much more danger am I in than someone who weighs for example 10 stone.
To dumb it down lots, if a 50kg climber would exert 5kn would I at 90kg exert 9kn or does it multiply up or down. Assuming same ropes and gear etc and that the gear holds and doesn't rip through the rock etc
I know there are many variables that make this impossible to answer but in a lab test situation what would the outcome be? Death for the fatties?
Cheers for any useful thoughts.
I remember years ago reading that an average lead fall was normally in the region of 5-7kn of force on the top piece of gear (very arbitrary I know).
I was looking at my little brass nuts with a strength of between 4 and 7kn I then also thought about being about 14 stone (87kg), a fair bit more fully dresssed with a rack and helmet etc on.
Now assuming that there is a good amount of rope in the system and that there is no real rope drag from zig zagging ropes or from ropes running over rough rock etc. If my top bit of gear is an IMP how much more danger am I in than someone who weighs for example 10 stone.
To dumb it down lots, if a 50kg climber would exert 5kn would I at 90kg exert 9kn or does it multiply up or down. Assuming same ropes and gear etc and that the gear holds and doesn't rip through the rock etc
I know there are many variables that make this impossible to answer but in a lab test situation what would the outcome be? Death for the fatties?
Cheers for any useful thoughts.
4
In reply to kermit_uk:
My impression has always been that 5-7kN would be a fairly serious fall rather than any kind of average.
A heavier person will undoubtedly exert somewhat more force on the gear, all other things being equal, but as you say there are a vast number of factors. I doubt whether you'll be able to get any very useful answers. Even JimTitt probably wouldn't be able to tell you all that much.
My impression has always been that 5-7kN would be a fairly serious fall rather than any kind of average.
A heavier person will undoubtedly exert somewhat more force on the gear, all other things being equal, but as you say there are a vast number of factors. I doubt whether you'll be able to get any very useful answers. Even JimTitt probably wouldn't be able to tell you all that much.
2
In reply to kermit_uk:
You'd have to test rigorously and and I'm sure there'd be a lot of noise in the measurements from fall to fall, rig to rig but if I were a betting man my bet is that peak runner load scales as a linear ish function of climber weight on a like fall for like fall basis, perhaps with some input of belayer's weight for slicker running rope set-ups.
How much extra risk you're at as a fatty (me too!)... Anecdotally the answer would appear to be relatively little since we hear of precious few accidents caused by gear (rather than placement) failure in the wild whether the climber be fat or thin.
jk
You'd have to test rigorously and and I'm sure there'd be a lot of noise in the measurements from fall to fall, rig to rig but if I were a betting man my bet is that peak runner load scales as a linear ish function of climber weight on a like fall for like fall basis, perhaps with some input of belayer's weight for slicker running rope set-ups.
How much extra risk you're at as a fatty (me too!)... Anecdotally the answer would appear to be relatively little since we hear of precious few accidents caused by gear (rather than placement) failure in the wild whether the climber be fat or thin.
jk
Post edited at 21:54
4
In reply to jkarran:
While I agree, I think that placement failure must also be partly related to loading so us larger climbers are more likely to pull out gear.
From a purely engineering perspective it's got too may variables to easily model, but will be roughly proportional to masses involved.
While I agree, I think that placement failure must also be partly related to loading so us larger climbers are more likely to pull out gear.
From a purely engineering perspective it's got too may variables to easily model, but will be roughly proportional to masses involved.
1
1
In reply to fraserbarrett:
Perhaps us larger climbers are also older climbers of long standing, so our placements are better
- i.e. informed by experience, possibly ???
Perhaps us larger climbers are also older climbers of long standing, so our placements are better
- i.e. informed by experience, possibly ???
4
4
In reply to kermit_uk:
Ok. In the same spirit, a similarly dumbed-down answer to try to get a vague theoretical answer at least...
I think less. More force than the lighter climber, but not *that* much more, here's why:
If the 90kg climber falls the same distance that the 50kg climber falls before the rope comes tight, and then also decelerates to a stop over the same distance afterwards, then yes - 5kN for the one will mean 9kN for the other. But this doesn't happen, because the rope stretches further.
Just for a moment, lets take away the rope and drop both climbers onto a perfectly elastic bungee. I've just convinced myself that the peak impact force, and also the distance travelled between the rope/bungee pulling tight and the climber coming to a stop (before beginning to bounce back up) will increase with the square root of the climber's weight. (So a monster 200kg climber will exert twice the force of the 50kg climber, whilst also travelling twice as far - the thing that defines a perfectly elastic spring/bungee/whatever is that they're kind of the same thing, the force is proportional to the extension.)
In this case 5kN for the 50kg climber will mean 6.7kN for the 90kg climber.
(Because the square root of 9/5 = 1.34 meaning 34% more impact force, and also 34% further distance travelled whilst decelerating to a stop.)
Ok, now lets put them both on a via ferrata instead, with one of those screamer type via ferrata lanyards. The 50kg climber falls, stitching rips at 5kN, and after he stops the climber see's he's ripped 5cm of stitching out. When the 90kg climber falls his stitching will also rip at 5kN, but after he's stopped he'll notice that 9cm of stitching ripped.
> To dumb it down lots, if a 50kg climber would exert 5kn would I at 90kg exert 9kn or does it multiply up or down. Assuming same ropes and gear etc and that the gear holds and doesn't rip through the rock etc
Ok. In the same spirit, a similarly dumbed-down answer to try to get a vague theoretical answer at least...
I think less. More force than the lighter climber, but not *that* much more, here's why:
If the 90kg climber falls the same distance that the 50kg climber falls before the rope comes tight, and then also decelerates to a stop over the same distance afterwards, then yes - 5kN for the one will mean 9kN for the other. But this doesn't happen, because the rope stretches further.
Just for a moment, lets take away the rope and drop both climbers onto a perfectly elastic bungee. I've just convinced myself that the peak impact force, and also the distance travelled between the rope/bungee pulling tight and the climber coming to a stop (before beginning to bounce back up) will increase with the square root of the climber's weight. (So a monster 200kg climber will exert twice the force of the 50kg climber, whilst also travelling twice as far - the thing that defines a perfectly elastic spring/bungee/whatever is that they're kind of the same thing, the force is proportional to the extension.)
In this case 5kN for the 50kg climber will mean 6.7kN for the 90kg climber.
(Because the square root of 9/5 = 1.34 meaning 34% more impact force, and also 34% further distance travelled whilst decelerating to a stop.)
Ok, now lets put them both on a via ferrata instead, with one of those screamer type via ferrata lanyards. The 50kg climber falls, stitching rips at 5kN, and after he stops the climber see's he's ripped 5cm of stitching out. When the 90kg climber falls his stitching will also rip at 5kN, but after he's stopped he'll notice that 9cm of stitching ripped.
Post edited at 22:43
8
In reply to kermit_uk:
It is a fair point especially with marginal gear IMPs and micro cams etc my guess would be more fail due to rock crumbling around the placement rather than gear failing and this again is more likely to happen if you are heavier I guess.
A good point on distance travelled and rope stretch. so a 50kg climber with a 50kg belayer is going to be better off than a 90kg climber with a 90kg belayer however not 5kn - 9kn better off because the 90kg climber will get more stretch.
So a lighter belayer and more dynamic catch will help to offset the heavier climber. However this doesn't help if the ground is a little bit close.
I think I am now adding a full E point to all climbs i do with even slightly marginal gear. I think anyone over 100kg could add 2 E points.
30% increase is pretty substantial if the placement is already iffy although I am now starting to think more in terms of gear ripping than snapping.
I also guess a decent low impact rope will help a fair bit too.
It is a fair point especially with marginal gear IMPs and micro cams etc my guess would be more fail due to rock crumbling around the placement rather than gear failing and this again is more likely to happen if you are heavier I guess.
A good point on distance travelled and rope stretch. so a 50kg climber with a 50kg belayer is going to be better off than a 90kg climber with a 90kg belayer however not 5kn - 9kn better off because the 90kg climber will get more stretch.
So a lighter belayer and more dynamic catch will help to offset the heavier climber. However this doesn't help if the ground is a little bit close.
I think I am now adding a full E point to all climbs i do with even slightly marginal gear. I think anyone over 100kg could add 2 E points.
30% increase is pretty substantial if the placement is already iffy although I am now starting to think more in terms of gear ripping than snapping.
I also guess a decent low impact rope will help a fair bit too.
2
In reply to kermit_uk:
but heavier people have a low impact arse for the shorter decks so knock some grades off again.
but heavier people have a low impact arse for the shorter decks so knock some grades off again.
5
1
In reply to kermit_uk:
Simplifying completely:
Kinetic energy of a falling climber is 0.5mv^2
so increasing your mass by 10% (you compared to a 79ish kg climber) will increase your energy by 10%.
Increasing your fall by 10% (11foot fall compared to 10foot), however, will increase the energy by 21%.
I'd be more concerned over the latter on marginal gear
Simplifying completely:
Kinetic energy of a falling climber is 0.5mv^2
so increasing your mass by 10% (you compared to a 79ish kg climber) will increase your energy by 10%.
Increasing your fall by 10% (11foot fall compared to 10foot), however, will increase the energy by 21%.
I'd be more concerned over the latter on marginal gear
2
In reply to aceagles:
But if the increase in fall distance is down to the rope stretch not more rope or higher above the gear does that increased fall and therefore rope stretch not decrease the load. Still be higher than a lighter climber but not as much?
But if the increase in fall distance is down to the rope stretch not more rope or higher above the gear does that increased fall and therefore rope stretch not decrease the load. Still be higher than a lighter climber but not as much?
In reply to kermit_uk:
You might be correct but the only solution is to do actual testing.
It may be that the impact load is not increased by heavier climbers ( in proportion to weight ) but the maximum load is spread over a longer time span as the system stretches, who knows?
You might be correct but the only solution is to do actual testing.
It may be that the impact load is not increased by heavier climbers ( in proportion to weight ) but the maximum load is spread over a longer time span as the system stretches, who knows?
In reply to Rick Graham:
This has naturally enough been tested a fair few times over the years, the simplest version is probably this one: www.safeclimbing.org/education/Heavy_Climbers_Beware.pdf
This has naturally enough been tested a fair few times over the years, the simplest version is probably this one: www.safeclimbing.org/education/Heavy_Climbers_Beware.pdf
4
In reply to jimtitt:
Thanks for that.
Interesting so at 90kg to get the same impact force as 80kg I need to reduce the fall factor from 1.7 to 1.4
That's a pretty big difference which realistically you will never be able to do.
It is quite linear weight to force more so that I thought however I would hazard a guess that in real world situation it would not be so clear cut.
Cheers for the info. Basically fatties gonna die on RPs.
A self induced case of food poisoning before any sketchy trad maybe.
Problem is I'm not actually fat just not a scrawny person. Once got down to 13 1/4 stone, lightest I've ever been.
Thanks for that.
Interesting so at 90kg to get the same impact force as 80kg I need to reduce the fall factor from 1.7 to 1.4
That's a pretty big difference which realistically you will never be able to do.
It is quite linear weight to force more so that I thought however I would hazard a guess that in real world situation it would not be so clear cut.
Cheers for the info. Basically fatties gonna die on RPs.
A self induced case of food poisoning before any sketchy trad maybe.
Problem is I'm not actually fat just not a scrawny person. Once got down to 13 1/4 stone, lightest I've ever been.
2
In reply to kermit_uk:
Many heavier climbers have fallen on RPs and not seriously damaged them let alone snap them. It depends on many other factors especially the softness of the 'catch'.
Many heavier climbers have fallen on RPs and not seriously damaged them let alone snap them. It depends on many other factors especially the softness of the 'catch'.
2
1
In reply to kermit_uk:
Slow dissipation of energy by the harness compressing your beer belly and fat arse will more than make up the difference to a skinny climber who will be stopped hard as their "system" has less give and will therefore shock load the anchors.
At least that´s what I hope will save me!
CB
Slow dissipation of energy by the harness compressing your beer belly and fat arse will more than make up the difference to a skinny climber who will be stopped hard as their "system" has less give and will therefore shock load the anchors.
At least that´s what I hope will save me!
CB
4
In reply to kermit_uk:
Yes, Thanks to Jim for knowing where to look for an answer.
Not quite linear if you use a calculator, the good news is that the increase in impact load is not quite as much as the proportional increase in weight.
Clear cut ? either a piece holds or not Get plenty in if you can.
> Thanks for that.
Yes, Thanks to Jim for knowing where to look for an answer.
> It is quite linear weight to force more so that I thought however I would hazard a guess that in real world situation it would not be so clear cut.
Not quite linear if you use a calculator, the good news is that the increase in impact load is not quite as much as the proportional increase in weight.
Clear cut ? either a piece holds or not Get plenty in if you can.
1
In reply to cb294:
And if the worst comes to the worst, us fatties will have the impact with the ground spread over a wider area.
And if the worst comes to the worst, us fatties will have the impact with the ground spread over a wider area.
1
In reply to kermit_uk:
I plotted it in Excel and fitted a 2nd order polynomial trendline to back extrapolate down to RP ratings.
I assumed two 91kg climbers exerting 1.785kN on the gear at rest. I also used the rule of thumb from Jim's linked document gear that experiences 2/3rds more force .
The curve predicts that 4kN will be exceeded a little over a fall factor of 0.2! e.g. a 60cm fall from above gear with 6m of rope out.
I mostly did it because I weigh just under 91kg currently
I plotted it in Excel and fitted a 2nd order polynomial trendline to back extrapolate down to RP ratings.
I assumed two 91kg climbers exerting 1.785kN on the gear at rest. I also used the rule of thumb from Jim's linked document gear that experiences 2/3rds more force .
The curve predicts that 4kN will be exceeded a little over a fall factor of 0.2! e.g. a 60cm fall from above gear with 6m of rope out.
I mostly did it because I weigh just under 91kg currently
Post edited at 15:13
In reply to maxticate:
Fall factors don't work that accurately for smaller falls because of the various other 'gives' in the system (knots, harnesses, non-rigid climber, friction on runners belayer lift, slip on the belay plate etc). I also can't see many falls being taken on RP's with only 6m of rope involved.
Fall factors don't work that accurately for smaller falls because of the various other 'gives' in the system (knots, harnesses, non-rigid climber, friction on runners belayer lift, slip on the belay plate etc). I also can't see many falls being taken on RP's with only 6m of rope involved.
1
1
In reply to Offwidth:
Yes its probably nearly impossible to arrive at a verifiable exact figure for any given situation.
So I'm going to opt for no falls onto single RPs where can help it
Yes its probably nearly impossible to arrive at a verifiable exact figure for any given situation.
So I'm going to opt for no falls onto single RPs where can help it
1
In reply to kermit_uk:
I don't know the maths but I have taken a fall from about 6ft above a very small brass hb nut (2nd smallest I think) and it didn't break and I weigh 92 to 94kg so you should be ok.
Unpleasant experience though.
I don't know the maths but I have taken a fall from about 6ft above a very small brass hb nut (2nd smallest I think) and it didn't break and I weigh 92 to 94kg so you should be ok.
Unpleasant experience though.
1
In reply to kermit_uk:
I am definitely not a faller. Even on sport I don't like to fall if I can help it.
I know it will never be clear cut and I will still try and avoid falling but I have recently been on some tenuous moves above a 6kn micro wire and thought I really don't want to fall off at the minute. It got me wondering how much more I should hold on the dear life compared to those of a slighter build.
A fair bit seems to be the findings though maybe it's not as bad as I thought.
I am definitely not a faller. Even on sport I don't like to fall if I can help it.
I know it will never be clear cut and I will still try and avoid falling but I have recently been on some tenuous moves above a 6kn micro wire and thought I really don't want to fall off at the minute. It got me wondering how much more I should hold on the dear life compared to those of a slighter build.
A fair bit seems to be the findings though maybe it's not as bad as I thought.
In reply to kermit_uk:
A few years back I fell quite a distance when a hold broke on Soho Sally (Millstone). I had an HB1 some feet below, and an HB3 over and further down right. I came to no harm. I weigh 65K max, so I guess that helped!
A few years back I fell quite a distance when a hold broke on Soho Sally (Millstone). I had an HB1 some feet below, and an HB3 over and further down right. I came to no harm. I weigh 65K max, so I guess that helped!
In reply to Ade in Sheffield:
Larger climbers are older climbers, therefore they only use hexes, well placed.
Larger climbers are older climbers, therefore they only use hexes, well placed.
In reply to kermit_uk:
For the situation you present, i.e. one where there is no significant friction along the rope, the force on your top runner will be determined largely by the force your belayer exerts on the rope. This depends on the rope/belay device/hand grip combination but 2kN is usually considered to be a good approximation; if the rope tries to pull with a greater force than this 'grip limit' it will slip through the belay device - and the belayer's hands. As soon as the force exerted by the falling leader reaches about 3kN on the top runner's krab friction here will reduce this to the 2kN 'grip limit' in the rope down to the belayer. The total force on the top runner will therefore be 3kN+2kN = 5 kN.
If the fall is a small, low fall factor one then it's energy may just stretch the rope and the forces may not reach the 3kN/2kN limits.
Therefore for the idealised situation you have proposed, where there is no significant friction along the rope, the weight of the falling climber makes no difference to the force on the top runner but a heavier climber will fall further than a light one before they are stopped as they have more energy.
However once there is considerable friction along the rope the situation becomes more complex and the climber's weight will affect the force on the top runner.
I hope this helps.
For the situation you present, i.e. one where there is no significant friction along the rope, the force on your top runner will be determined largely by the force your belayer exerts on the rope. This depends on the rope/belay device/hand grip combination but 2kN is usually considered to be a good approximation; if the rope tries to pull with a greater force than this 'grip limit' it will slip through the belay device - and the belayer's hands. As soon as the force exerted by the falling leader reaches about 3kN on the top runner's krab friction here will reduce this to the 2kN 'grip limit' in the rope down to the belayer. The total force on the top runner will therefore be 3kN+2kN = 5 kN.
If the fall is a small, low fall factor one then it's energy may just stretch the rope and the forces may not reach the 3kN/2kN limits.
Therefore for the idealised situation you have proposed, where there is no significant friction along the rope, the weight of the falling climber makes no difference to the force on the top runner but a heavier climber will fall further than a light one before they are stopped as they have more energy.
However once there is considerable friction along the rope the situation becomes more complex and the climber's weight will affect the force on the top runner.
I hope this helps.
This topic has been archived, and won't accept reply postings.
Loading Notifications...