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Help - What are the likely effects of dropping a cam 50m - should i worry/replace or is it fine
In reply to John Kelly:
What type of cam is it?
Did it land on a rock?
If so I would think about retiring it, at least maybe check it for damage, but some hairline cracks could be unseen , this might make me paranoid when placing it and render its security factor less.
What type of cam is it?
Did it land on a rock?
If so I would think about retiring it, at least maybe check it for damage, but some hairline cracks could be unseen , this might make me paranoid when placing it and render its security factor less.
In reply to John Kelly:
Did it land on bedrock or grass?
Most people would retire it, stating the precautionary principle and some folklore about microfractures. To retire it is the only sensible advice anyone would ever give you.
(personally, I may keep using it if it didn't land on rock, and on the principle that I never rely on one bit of protection).
Did it land on bedrock or grass?
Most people would retire it, stating the precautionary principle and some folklore about microfractures. To retire it is the only sensible advice anyone would ever give you.
(personally, I may keep using it if it didn't land on rock, and on the principle that I never rely on one bit of protection).
In reply to John Kelly:
I dropped 2/3rds of my rack from 6 pitches up La Demande onto the talus below (rocks and scree). The cams have held many falls since.
I dropped 2/3rds of my rack from 6 pitches up La Demande onto the talus below (rocks and scree). The cams have held many falls since.
In reply to gd303uk:
Camelot yellow
Top F route gimmer to ash tree ledge - bounced down a few rocky ledges and came to rest on grass lump - oddly there was a massive wallnut (which i had previously not spotted) on same ledge
john
Camelot yellow
Top F route gimmer to ash tree ledge - bounced down a few rocky ledges and came to rest on grass lump - oddly there was a massive wallnut (which i had previously not spotted) on same ledge
john
In reply to John Kelly:
To be honest if you're asking the question then you should probably replace it just for peace of mind
To be honest if you're asking the question then you should probably replace it just for peace of mind
In reply to John Kelly:
If it still works, ill have it, just to stop you worrying about Micro Fractures.
If it still works, ill have it, just to stop you worrying about Micro Fractures.
In reply to John Kelly:
Well, a fall from 50m would be about 110kmh (approx 70mph) when it hits the ground (assuming the cam was in constant free fall, i.e. wasn't slowed down by anything on the way down AND making the assumption that the cam has negligible mass - they aren't particularly large are they)
The surface it landed on would greatly affect the impact force. If the cam landed on a large, sturdy slab or rock which did not break or fracture on impact, the resulting force on the cam would be a hypothetical force of around 24/25kN. If it landed in a deep puddle, mud or soft grass, a large proportion of the force could be dissipated by the surface on which it landed, potentially reducing the force to only 2 or 3 kN.
The area it is exerted over is probably about only 1cm^2 which would, worse case scenario, give a pressure on the cam of 250Mpa (250000 KN/m^2).
Not knowing what cam you have, I have made the rash assumption that it is made from an aluminium alloy, perhaps 6061 or 6063. These alloys have a hardness between 300 and 1000 MPa, depending on the temper.
Conclusion and DISCLAIMER:
Looking at those numbers it would suggest that your cam is PROBABLY fine. However, they are indeed, just numbers. If the cam landed on a particularly pointy piece of rock the pressure would increase significantly. Or if the cam is made of a different material, this would change the calculation. Also, if I had any expertise in physics or maths beyond GCSE, this would probably be more accurate. I know NOTHING about engineering but I know how to read a data sheet. Any choice you make is YOURS! I can't be held responsible for you getting injured or dying.
What I would do: I'd keep using the thing, but that's just me.
Well, a fall from 50m would be about 110kmh (approx 70mph) when it hits the ground (assuming the cam was in constant free fall, i.e. wasn't slowed down by anything on the way down AND making the assumption that the cam has negligible mass - they aren't particularly large are they)
The surface it landed on would greatly affect the impact force. If the cam landed on a large, sturdy slab or rock which did not break or fracture on impact, the resulting force on the cam would be a hypothetical force of around 24/25kN. If it landed in a deep puddle, mud or soft grass, a large proportion of the force could be dissipated by the surface on which it landed, potentially reducing the force to only 2 or 3 kN.
The area it is exerted over is probably about only 1cm^2 which would, worse case scenario, give a pressure on the cam of 250Mpa (250000 KN/m^2).
Not knowing what cam you have, I have made the rash assumption that it is made from an aluminium alloy, perhaps 6061 or 6063. These alloys have a hardness between 300 and 1000 MPa, depending on the temper.
Conclusion and DISCLAIMER:
Looking at those numbers it would suggest that your cam is PROBABLY fine. However, they are indeed, just numbers. If the cam landed on a particularly pointy piece of rock the pressure would increase significantly. Or if the cam is made of a different material, this would change the calculation. Also, if I had any expertise in physics or maths beyond GCSE, this would probably be more accurate. I know NOTHING about engineering but I know how to read a data sheet. Any choice you make is YOURS! I can't be held responsible for you getting injured or dying.
What I would do: I'd keep using the thing, but that's just me.
Post edited at 22:47
In reply to John Kelly:
Just seen
Just seen this. I would keep using that cam (see previous disclaimer).
Just seen
> Camelot yellow
> Top F route gimmer to ash tree ledge - bounced down a few rocky ledges and came to rest on grass lump - oddly there was a massive wallnut (which i had previously not spotted) on same ledge
Just seen this. I would keep using that cam (see previous disclaimer).
Post edited at 22:47
In reply to gdnknf:
are you saying that alu alloy is unaffected by 250MPa as its rated to 300-1000MPa - great
its a yellow camalot - it bounced and slip violently down crag so probably didn't reach the max force suggested
there is a 1/2mm deep gouge so a lot energy used doing that
i had already pretty much decided to keep it
are you saying that alu alloy is unaffected by 250MPa as its rated to 300-1000MPa - great
its a yellow camalot - it bounced and slip violently down crag so probably didn't reach the max force suggested
there is a 1/2mm deep gouge so a lot energy used doing that
i had already pretty much decided to keep it
In reply to John Kelly:
That's exactly what I'm saying.
Bearing in mind that ALL my knowledge of physics came from my GCSEs and that there are a LOT of assumptions in that bit of ugly maths. I'm sure an engineer will be along sooner or later to explain where I have gone wrong though, I would be happy to continue using that cam if it were mine. Of course, only you can make that decision!
> are you saying that alu alloy is unaffected by 250MPa as its rated to 300-1000MPa - great
That's exactly what I'm saying.
Bearing in mind that ALL my knowledge of physics came from my GCSEs and that there are a LOT of assumptions in that bit of ugly maths. I'm sure an engineer will be along sooner or later to explain where I have gone wrong though, I would be happy to continue using that cam if it were mine. Of course, only you can make that decision!
In reply to John Kelly:
MIT report showing no evidence of crack/fissure formation before carabiner failure (with x-ray testing methods): http://stuff.mit.edu/afs/athena/course/21/21w794/olddave794stuff/model/Okal...
Microfractures are a myth.
I say give the cam the food test, if it looks and smells ok it probably is.
MIT report showing no evidence of crack/fissure formation before carabiner failure (with x-ray testing methods): http://stuff.mit.edu/afs/athena/course/21/21w794/olddave794stuff/model/Okal...
Microfractures are a myth.
I say give the cam the food test, if it looks and smells ok it probably is.
In reply to John Kelly:
As already said, if you've the slightest doubt in your mind about any of your gear, bin it.
The thought just niggles away in your mind everytime you use it.
As already said, if you've the slightest doubt in your mind about any of your gear, bin it.
The thought just niggles away in your mind everytime you use it.
In reply to John Kelly:
http://www.geir.com/mythbuster.html
I'll point you in the direction of this good article and I'll let you make your mind up.
http://www.geir.com/mythbuster.html
I'll point you in the direction of this good article and I'll let you make your mind up.
In reply to John Kelly:
Visual inspection would be the key. A friend 1.5 dropped about 70m with minimal bounce deformed the cams on impact. However a friend 3.5 seemed fairly happy after 200m bouncing down a Dolomite face.
Visual inspection would be the key. A friend 1.5 dropped about 70m with minimal bounce deformed the cams on impact. However a friend 3.5 seemed fairly happy after 200m bouncing down a Dolomite face.
In reply to birdie num num:
Yeah that's fine if you can find it, although I would recommend you attach it to your own rucksack to avoid it happening again
The new green lid looks pretty .
> What about a helmet? would 200 metres be ok?
Yeah that's fine if you can find it, although I would recommend you attach it to your own rucksack to avoid it happening again
The new green lid looks pretty .
In reply to gdnknf:
I believe you have made a huge number of assumptions, rash and otherwise, in your calculation. (I speak as someone who studied engineering to degree level and, while I am no metallurgist, I know enough to know the limits of my own knowledge, and the knowledge I had at O level.)
If it's the Vickers hardness that you've been using for those alloys then AAUI that's about plastic deformation ie whether the thing will get dented or bent. Who cares if a cam has a dent? What the user needs to know is whether it will be significantly weakened either structurally or mechanically. I think you'd have to go a lot further in your analysis to be able to determine that. Whether that would actually be worthwhile, given the mass of assumptions that you've had to make to get as far as you did, I'd seriously doubt.
You also seem to have assumed (a) that the cam has landed on a single cam lobe, and (b) that it's the integrity of the cam lobe that matters. I'd suggest that the cam lobes are probably amongst the toughest components in the cam. The stem, axles, return springs etc are equally if not more likely to be vulnerable in an impact to the sort of damage which could render the device unsafe to use.
Botom line: IMO your calculations are about as reliable a decision-making guide as elsewhere's dodgy statistical analyses in the bowline thread, and have little if anything to say about whether the cam might be safe to use in future.
I'd go with BenTiffin's advice: the cam's owner should carry out a visual inspection, and check that the mechanical operation of the cam is unimpaired. (As ex0 sas, micro-fractures are a myth and can be ignored as a failure mechanism.) Then it's up to the owner to decide whether, in extremis, they'd be happy to trust their life to it.
> Not knowing what cam you have, I have made the rash assumption...
I believe you have made a huge number of assumptions, rash and otherwise, in your calculation. (I speak as someone who studied engineering to degree level and, while I am no metallurgist, I know enough to know the limits of my own knowledge, and the knowledge I had at O level.)
If it's the Vickers hardness that you've been using for those alloys then AAUI that's about plastic deformation ie whether the thing will get dented or bent. Who cares if a cam has a dent? What the user needs to know is whether it will be significantly weakened either structurally or mechanically. I think you'd have to go a lot further in your analysis to be able to determine that. Whether that would actually be worthwhile, given the mass of assumptions that you've had to make to get as far as you did, I'd seriously doubt.
You also seem to have assumed (a) that the cam has landed on a single cam lobe, and (b) that it's the integrity of the cam lobe that matters. I'd suggest that the cam lobes are probably amongst the toughest components in the cam. The stem, axles, return springs etc are equally if not more likely to be vulnerable in an impact to the sort of damage which could render the device unsafe to use.
Botom line: IMO your calculations are about as reliable a decision-making guide as elsewhere's dodgy statistical analyses in the bowline thread, and have little if anything to say about whether the cam might be safe to use in future.
I'd go with BenTiffin's advice: the cam's owner should carry out a visual inspection, and check that the mechanical operation of the cam is unimpaired. (As ex0 sas, micro-fractures are a myth and can be ignored as a failure mechanism.) Then it's up to the owner to decide whether, in extremis, they'd be happy to trust their life to it.
In reply to Martin W:
I did say there were A LOT of assumptions in that calculation! I did it more for my own amusement than anything, see how much physics I could remember. I did put a disclaimer on that I could be wrong.
I agree, visual inspection:
http://www.coolclimbing.com/images/rock/gear/SandRockJuly2301PICT0242_small...
> Botom line: IMO your calculations are about as reliable a decision-making guide as elsewhere's dodgy statistical analyses in the bowline thread, and have little if anything to say about whether the cam might be safe to use in future.
I did say there were A LOT of assumptions in that calculation! I did it more for my own amusement than anything, see how much physics I could remember. I did put a disclaimer on that I could be wrong.
I agree, visual inspection:
http://www.coolclimbing.com/images/rock/gear/SandRockJuly2301PICT0242_small...
In reply to John Kelly:
If it's fine it's fine, if it's knackered it's knackered.
I dropped one 50 odd meters into a very shallow rockpool it was fine. Landing differently or onto rock it could have been damaged. I've since lost it which is a shame but my loss is someone else's gain, I hope they're still using it.
jk
> Help - What are the likely effects of dropping a cam 50m - should i worry/replace or is it fine
If it's fine it's fine, if it's knackered it's knackered.
I dropped one 50 odd meters into a very shallow rockpool it was fine. Landing differently or onto rock it could have been damaged. I've since lost it which is a shame but my loss is someone else's gain, I hope they're still using it.
jk
Post edited at 15:50
In reply to John Kelly:
If it's damaged it'll be bent axles or deformed/ovalised pivots in the ali lobes. The various numbers up-thread are I'm afraid largely meaningless and shouldn't form the basis of any decision.
jk
> are you saying that alu alloy is unaffected by 250MPa as its rated to 300-1000MPa - great
> its a yellow camalot - it bounced and slip violently down crag so probably didn't reach the max force suggested
> its a yellow camalot - it bounced and slip violently down crag so probably didn't reach the max force suggested
If it's damaged it'll be bent axles or deformed/ovalised pivots in the ali lobes. The various numbers up-thread are I'm afraid largely meaningless and shouldn't form the basis of any decision.
jk
In reply to John Kelly:
How about 400 metres?
On the Salbitschin Villieger? Pfeiller I dropped a cam 3 as did some German lads. Their cam glanced a 2.5 inch crack after said 400m and set itself in a perfect placement ready to clip ! My cam went the full distance to the scree.
We used each other's cam for a couple of days then swapped back.
So just use it if it still looks OK.
> Help - What are the likely effects of dropping a cam
How about 400 metres?
On the Salbitschin Villieger? Pfeiller I dropped a cam 3 as did some German lads. Their cam glanced a 2.5 inch crack after said 400m and set itself in a perfect placement ready to clip ! My cam went the full distance to the scree.
We used each other's cam for a couple of days then swapped back.
So just use it if it still looks OK.
In reply to armus:
Oh, give it up you old Misery you... give us a hug and Let your hate go... snoogans :-D
> Calmed down have you then?
Oh, give it up you old Misery you... give us a hug and Let your hate go... snoogans :-D
In reply to John Kelly:
Hey, dont Look at me, im Cool... armus, you Cool?
We Cool!
> In reply to Choss and armus
> get a room
Hey, dont Look at me, im Cool... armus, you Cool?
We Cool!
In reply to John Kelly:
My second dropped a Cam from exactly the same place. What is it about topping out on the F route?
Still using it incidentally.
My second dropped a Cam from exactly the same place. What is it about topping out on the F route?
Still using it incidentally.
In reply to gdnknf:
Impressive try!
After having spent 5 years studying engineering... I dare not even try to answer such questions.
If it were my cam....If it looked fine I'd keep it. If I was nervous I'd try testing it, a lead fall or few with it well backed up ought to be the ultimate confidence builder.
After all, that's all you care about, the chance that it'll hold a fall.
Impressive try!
After having spent 5 years studying engineering... I dare not even try to answer such questions.
If it were my cam....If it looked fine I'd keep it. If I was nervous I'd try testing it, a lead fall or few with it well backed up ought to be the ultimate confidence builder.
After all, that's all you care about, the chance that it'll hold a fall.
Post edited at 07:21
In reply to needvert:
i don't think there is much chance of modelling the circumstances but as you say good try by gdnknf
looks good, is good - works for me
i don't think there is much chance of modelling the circumstances but as you say good try by gdnknf
looks good, is good - works for me
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