Forums: Climbing Information: The Lab:
Post deleted by USnavy
RSS FeedRSS Feeds for The Lab

Premier Sponsor:

 
First page Previous page 1 2 3 Next page Last page  View All


USnavy


Nov 9, 2007, 5:11 PM
Post #26 of 57 (3884 views)
Shortcut

Registered: Nov 5, 2007
Posts: 2664

Post deleted by USnavy [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  

 


shockabuku


Nov 9, 2007, 5:18 PM
Post #27 of 57 (3884 views)
Shortcut

Registered: May 20, 2006
Posts: 4867

Re: [rocknice2] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

What's a force curve (force/time)?


(This post was edited by shockabuku on Nov 9, 2007, 5:20 PM)


jt512


Nov 9, 2007, 5:27 PM
Post #28 of 57 (3877 views)
Shortcut

Registered: Apr 11, 2001
Posts: 21893

Re: [rocknice2] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

rocknice2 wrote:
j_ung wrote:
jt512 wrote:
j_ung wrote:
USnavy wrote:
It suggests this by stating a fall of 5m from a height of 10m produces the same force as a fall of 20m from a height of 40m (both fall factor 1 falls).

The two falls actually don't produce the same force. The farther fall generates much more force, but there's more rope to handle that force in direct proportion. When people say, "both falls generate the same force," what they actually mean is that the top piece feels the same force in both falls, because the longer length of rope "absorbs," more of it.

You are confusing force with energy, and consequently your post makes no sense.

Jay

Me ... several thousand miles ... physics. Thanks for the clarification.

j_ung

Imagine a force curve on a gragh .. Force/time .. The area under the curve is total energy expended.

Another victim of American education?

Edit: Apparently, things aren't much better in Canada.

Jay


(This post was edited by jt512 on Nov 9, 2007, 5:29 PM)


greenketch


Nov 9, 2007, 5:29 PM
Post #29 of 57 (3871 views)
Shortcut

Registered: Jan 12, 2005
Posts: 501

Re: [USnavy] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

USnavy wrote:
Was he actually using dynamic climbing ropes in those videos or were they bungee ropes designed for that type of use? The last jump he did looked like it was with a dynamic rope but I am not 100% on that one.

Yes, Dan did most of his stuff with Dynamic climbing ropes.


flint


Nov 10, 2007, 8:48 PM
Post #30 of 57 (3823 views)
Shortcut

Registered: Jun 20, 2007
Posts: 543

Re: [flint] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

flint wrote:
Do they not teach you math, physics or engineering in the Navy... Some days I am so ashamed of my passport.

OK to the topic. You get a factor one fall at 40m when you fall 20m. This is because you have fallen half the length of the rope you have out. So lets simplify it and say you divided 20 by 40 and you got .5

Now, if you were to jump off a bridge with a 60m rope, you would also be falling the full 60m length... Causing a factor 2 fall, or 60 divided by 60 = 1

This is completely different as I hope this simplified example has shown. No the guys at petzl are pretty sharp at what they do...

Please don't bungee on your climbing rope... Amazing how much someone can learn from the names of the items they purchase... It is a CLIMBING rope, not a climbing/bungee rope.

j-

Little bit of a brain fuck up here... Sorry for the harsh and actually wrong post USnavy. I will come and stand in your corner now.

I am still ashamed of my passport, but for an all new set of reasons.

j-


trenchdigger


Nov 12, 2007, 9:57 AM
Post #31 of 57 (3783 views)
Shortcut

Registered: Mar 8, 2003
Posts: 1447

Re: [jt512] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

jt512 wrote:
rocknice2 wrote:
j_ung wrote:
jt512 wrote:
j_ung wrote:
USnavy wrote:
It suggests this by stating a fall of 5m from a height of 10m produces the same force as a fall of 20m from a height of 40m (both fall factor 1 falls).

The two falls actually don't produce the same force. The farther fall generates much more force, but there's more rope to handle that force in direct proportion. When people say, "both falls generate the same force," what they actually mean is that the top piece feels the same force in both falls, because the longer length of rope "absorbs," more of it.

You are confusing force with energy, and consequently your post makes no sense.

Jay

Me ... several thousand miles ... physics. Thanks for the clarification.

j_ung

Imagine a force curve on a gragh .. Force/time .. The area under the curve is total energy expended.

Another victim of American education?

Edit: Apparently, things aren't much better in Canada.

Jay

This thread just keeps getting better and better, doesn't it Jay? Yeesh...


itstoearly


Nov 12, 2007, 10:25 AM
Post #32 of 57 (3771 views)
Shortcut

Registered: Jun 25, 2005
Posts: 166

Re: [trenchdigger] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

From my understanding, falling 1 foot on 6 inches of rope and falling 200 feet on 100 feet of rope produces the same *peak* force on the anchor point. If you were to compare the graph of the 2, they would be identical, except that the latter would be stretched out over more time.

I would make a graph, but I am busy being lazy.


cantbuymefriends


Nov 12, 2007, 10:57 AM
Post #33 of 57 (3745 views)
Shortcut

Registered: Aug 28, 2003
Posts: 670

Re: [USnavy] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

USnavy wrote:
I noticed that the force calculator on Petzel's site is dependent on fall factor.

Well, that's just what fall factors do. Wink

A 10 m fall on 10 m rope, and a 20 m fall on 20 m rope both have the same fall factors (=1), right? And they also give the same peak force. But How?

Rope stretch (which is the braking distance in the system) is proportional to Force and rope length.
So twice as much rope between you and the belayer will absorb twice as much energy because the rope will stretch twice as much for the same force.

And since the fall is twice as long, the energy in the fall to be absorbed by the rope will be twice as high (E=mgh).

Forget everything about times and kinetic energy in these discussions! They are just unnecessary confusing…


skinner


Dec 9, 2007, 8:01 PM
Post #34 of 57 (3622 views)
Shortcut

Registered: Oct 31, 2004
Posts: 1747

Re: [ptlong] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

A person like USnavy comes along and asks an honest question, which if they understood *why* they wouldn't have asked it in the first place. In response he gets ridiculed by Flint, I guess that's the rc.com way huh?


With only a few posts USnavy may be new to climbing, but gawd.. they should know and fully understand all this stuff before they dare to post here!
It's no wonder there are so many who choose to just lurk.

Welcome to rc.com USnavy Crazy


(This post was edited by skinner on Dec 9, 2007, 8:14 PM)


Partner j_ung


Dec 11, 2007, 5:17 AM
Post #35 of 57 (3582 views)
Shortcut

Registered: Nov 21, 2003
Posts: 18689

Re: [jt512] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

jt512 wrote:
rocknice2 wrote:
j_ung wrote:
jt512 wrote:
j_ung wrote:
USnavy wrote:
It suggests this by stating a fall of 5m from a height of 10m produces the same force as a fall of 20m from a height of 40m (both fall factor 1 falls).

The two falls actually don't produce the same force. The farther fall generates much more force, but there's more rope to handle that force in direct proportion. When people say, "both falls generate the same force," what they actually mean is that the top piece feels the same force in both falls, because the longer length of rope "absorbs," more of it.

You are confusing force with energy, and consequently your post makes no sense.

Jay

Me ... several thousand miles ... physics. Thanks for the clarification.

j_ung

Imagine a force curve on a gragh .. Force/time .. The area under the curve is total energy expended.

Another victim of American education?

Edit: Apparently, things aren't much better in Canada.

Jay

I'll take my own lumps, thanks. The American education system doesn't need me dragging it down further.


lobstertronic


Dec 11, 2007, 7:01 AM
Post #36 of 57 (3545 views)
Shortcut

Registered: Aug 13, 2007
Posts: 59

Re: [flint] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

flint wrote:
Do they not teach you math, physics or engineering in the Navy... Some days I am so ashamed of my passport.

OK to the topic. You get a factor one fall at 40m when you fall 20m. This is because you have fallen half the length of the rope you have out. So lets simplify it and say you divided 20 by 40 and you got .5

Now, if you were to jump off a bridge with a 60m rope, you would also be falling the full 60m length... Causing a factor 2 fall, or 60 divided by 60 = 1

This is completely different as I hope this simplified example has shown. No the guys at petzl are pretty sharp at what they do...

Please don't bungee on your climbing rope... Amazing how much someone can learn from the names of the items they purchase... It is a CLIMBING rope, not a climbing/bungee rope.

j-

The bridge is 59 metres above the ground...


scottek67


Dec 6, 2009, 8:44 AM
Post #37 of 57 (2905 views)
Shortcut

Registered: Apr 6, 2008
Posts: 515

Re: [USnavy] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

brokesomeribs wrote:
silascl wrote:
Your a idiot.

Oh, the irony!


dynosore


Dec 6, 2009, 9:36 AM
Post #38 of 57 (2868 views)
Shortcut

Registered: Jul 29, 2004
Posts: 1764

Re: [j_ung] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

j_ung wrote:
USnavy wrote:
It suggests this by stating a fall of 5m from a height of 10m produces the same force as a fall of 20m from a height of 40m (both fall factor 1 falls).

The two falls actually don't produce the same force. The farther fall generates much more force, but there's more rope to handle that force in direct proportion. When people say, "both falls generate the same force," what they actually mean is that the top piece feels the same force in both falls, because the longer length of rope "absorbs," more of it.

No. Hint: ke=1/2mv^2


dynosore


Dec 6, 2009, 9:41 AM
Post #39 of 57 (2862 views)
Shortcut

Registered: Jul 29, 2004
Posts: 1764

Re: [zealotnoob] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

zealotnoob wrote:
OT: Another quirk of the climbing system that can be surprising is the pulley effect. I.e, if you bail from a climb, off a single piece of pro, by having your partner lower you, you're applying twice the amount of force on that piece than if you rapped from it...

Crazy So, the dead deer hanging from a pulley in my pole barn right now is exerting 250 lbs of force on the pulley, even though it only weighs 125 lbs? That's a good trick! The spring scale attached to the pulley even says 125 lbs, it must be off by a factor of 2. So, when I toprope, I "weigh" 320 instead of 160, as far as the anchor is concerned? No wonder I can't pull that slopey overhang......the things you learn on the internet.


sungam


Dec 6, 2009, 9:55 AM
Post #40 of 57 (2852 views)
Shortcut

Registered: Jun 24, 2004
Posts: 26622

Re: [dynosore] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

dynosore wrote:
zealotnoob wrote:
OT: Another quirk of the climbing system that can be surprising is the pulley effect. I.e, if you bail from a climb, off a single piece of pro, by having your partner lower you, you're applying twice the amount of force on that piece than if you rapped from it...

Crazy So, the dead deer hanging from a pulley in my pole barn right now is exerting 250 lbs of force on the pulley, even though it only weighs 125 lbs? That's a good trick! The spring scale attached to the pulley even says 125 lbs, it must be off by a factor of 2. So, when I toprope, I "weigh" 320 instead of 160, as far as the anchor is concerned? No wonder I can't pull that slopey overhang......the things you learn on the internet.
Are you trying to imply that the pulley effect isn't real?
You're not that stupid, dude. Come on.

And, if you're curious, if there is little or no friction between the the pully and the rope then there is a total of 250lbs hanging on that pully. 125 pounds from the deer, and 125 from whatever the other end of the rope is tied to. (we're ignoring the angles, here).

Think about it - if the deer was exerting 125 pounds on one end of the rope and nothing was pulling on the other, the rope would run through the pully and the deer would fall, right? and since both the weight of the deer and the pull from what the rope is tied to are downwards, that means the downwards force on the pully is the sum of those two.
125+125=250 lbs of downwards force.


jt512


Dec 6, 2009, 10:01 AM
Post #41 of 57 (2849 views)
Shortcut

Registered: Apr 11, 2001
Posts: 21893

Re: [sungam] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

sungam wrote:
dynosore wrote:
zealotnoob wrote:
OT: Another quirk of the climbing system that can be surprising is the pulley effect. I.e, if you bail from a climb, off a single piece of pro, by having your partner lower you, you're applying twice the amount of force on that piece than if you rapped from it...

Crazy So, the dead deer hanging from a pulley in my pole barn right now is exerting 250 lbs of force on the pulley, even though it only weighs 125 lbs? That's a good trick! The spring scale attached to the pulley even says 125 lbs, it must be off by a factor of 2. So, when I toprope, I "weigh" 320 instead of 160, as far as the anchor is concerned? No wonder I can't pull that slopey overhang......the things you learn on the internet.
Are you trying to imply that the pulley effect isn't real?
You're not that stupid, dude. Come on.

He's had two years to think about it.

Jay


sungam


Dec 6, 2009, 10:06 AM
Post #42 of 57 (2847 views)
Shortcut

Registered: Jun 24, 2004
Posts: 26622

Re: [jt512] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

jt512 wrote:
sungam wrote:
dynosore wrote:
zealotnoob wrote:
OT: Another quirk of the climbing system that can be surprising is the pulley effect. I.e, if you bail from a climb, off a single piece of pro, by having your partner lower you, you're applying twice the amount of force on that piece than if you rapped from it...

Crazy So, the dead deer hanging from a pulley in my pole barn right now is exerting 250 lbs of force on the pulley, even though it only weighs 125 lbs? That's a good trick! The spring scale attached to the pulley even says 125 lbs, it must be off by a factor of 2. So, when I toprope, I "weigh" 320 instead of 160, as far as the anchor is concerned? No wonder I can't pull that slopey overhang......the things you learn on the internet.
Are you trying to imply that the pulley effect isn't real?
You're not that stupid, dude. Come on.

He's had two years to think about it.

Jay
Damn, I didn't notice how old the thread was. The post I qouted, however, was made today.
Fricken zombie threads.


milesenoell


Dec 6, 2009, 10:15 AM
Post #43 of 57 (2844 views)
Shortcut

Registered: Sep 19, 2006
Posts: 1156

Re: [dynosore] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

dynosore wrote:
zealotnoob wrote:
OT: Another quirk of the climbing system that can be surprising is the pulley effect. I.e, if you bail from a climb, off a single piece of pro, by having your partner lower you, you're applying twice the amount of force on that piece than if you rapped from it...

Crazy So, the dead deer hanging from a pulley in my pole barn right now is exerting 250 lbs of force on the pulley, even though it only weighs 125 lbs? That's a good trick! The spring scale attached to the pulley even says 125 lbs, it must be off by a factor of 2.

This is one of the best examples you could have thrown out for two reasons.
1) As Magnus pointed out, to get a a full doubling of force you need a frictionless system, and carabiners have a good bit of friction, whereas a pulley has very little, by design.
2) All you have to do to see the doubling affect is tie off the rope to an anchor on the ground rather than to itself, since you already have the scale set up.


sungam


Dec 6, 2009, 10:18 AM
Post #44 of 57 (2838 views)
Shortcut

Registered: Jun 24, 2004
Posts: 26622

Re: [milesenoell] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

milesenoell wrote:
dynosore wrote:
zealotnoob wrote:
OT: Another quirk of the climbing system that can be surprising is the pulley effect. I.e, if you bail from a climb, off a single piece of pro, by having your partner lower you, you're applying twice the amount of force on that piece than if you rapped from it...

Crazy So, the dead deer hanging from a pulley in my pole barn right now is exerting 250 lbs of force on the pulley, even though it only weighs 125 lbs? That's a good trick! The spring scale attached to the pulley even says 125 lbs, it must be off by a factor of 2.

This is one of the best examples you could have thrown out for two reasons.
1) As Magnus pointed out, to get a a full doubling of force you need a frictionless system, and carabiners have a good bit of friction, whereas a pulley has very little, by design.
2) All you have to do to see the doubling affect is tie off the rope to an anchor on the ground rather than to itself, since you already have the scale set up.

Wait, I seem to have misread. It looks like the pully is currently hanging from the scales. In which case the dear isn't 125 pounds, it's like around 70-80 pounds.


giza


Dec 6, 2009, 10:29 AM
Post #45 of 57 (2826 views)
Shortcut

Registered: Oct 22, 2003
Posts: 315

Re: [skinner] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

skinner wrote:
A person like USnavy comes along and asks an honest question, which if they understood *why* they wouldn't have asked it in the first place. In response he gets ridiculed by Flint, I guess that's the rc.com way huh?


With only a few posts USnavy may be new to climbing, but gawd.. they should know and fully understand all this stuff before they dare to post here!
It's no wonder there are so many who choose to just lurk.

Welcome to rc.com USnavy Crazy

Agreed. This is not a forum to be inquiring about legitimate climbing-related topics. It's the arena of douchebag spraylords where every post will be scrutinized and torn apart not only for its content but also its spelling, grammar, the poster's # of posts, etc.

There are plenty of other forums where your question would be answered from a place of knowledge and mutual respect.


milesenoell


Dec 6, 2009, 12:40 PM
Post #46 of 57 (2787 views)
Shortcut

Registered: Sep 19, 2006
Posts: 1156

Re: [sungam] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

sungam wrote:
milesenoell wrote:
dynosore wrote:
zealotnoob wrote:
OT: Another quirk of the climbing system that can be surprising is the pulley effect. I.e, if you bail from a climb, off a single piece of pro, by having your partner lower you, you're applying twice the amount of force on that piece than if you rapped from it...

Crazy So, the dead deer hanging from a pulley in my pole barn right now is exerting 250 lbs of force on the pulley, even though it only weighs 125 lbs? That's a good trick! The spring scale attached to the pulley even says 125 lbs, it must be off by a factor of 2.

This is one of the best examples you could have thrown out for two reasons.
1) As Magnus pointed out, to get a a full doubling of force you need a frictionless system, and carabiners have a good bit of friction, whereas a pulley has very little, by design.
2) All you have to do to see the doubling affect is tie off the rope to an anchor on the ground rather than to itself, since you already have the scale set up.

Wait, I seem to have misread. It looks like the pully is currently hanging from the scales. In which case the dear isn't 125 pounds, it's like around 70-80 pounds.

Not if the rope is tied to itself or back to the deer (as I had presumed). I was assuming that he could tell the difference between a 63 lb and a 125 lb deer. (and a 63 pound deer would be so runty he probably wouldn't be posting about it.)


sungam


Dec 6, 2009, 12:47 PM
Post #47 of 57 (2783 views)
Shortcut

Registered: Jun 24, 2004
Posts: 26622

Re: [milesenoell] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

milesenoell wrote:
sungam wrote:
milesenoell wrote:
dynosore wrote:
zealotnoob wrote:
OT: Another quirk of the climbing system that can be surprising is the pulley effect. I.e, if you bail from a climb, off a single piece of pro, by having your partner lower you, you're applying twice the amount of force on that piece than if you rapped from it...

Crazy So, the dead deer hanging from a pulley in my pole barn right now is exerting 250 lbs of force on the pulley, even though it only weighs 125 lbs? That's a good trick! The spring scale attached to the pulley even says 125 lbs, it must be off by a factor of 2.

This is one of the best examples you could have thrown out for two reasons.
1) As Magnus pointed out, to get a a full doubling of force you need a frictionless system, and carabiners have a good bit of friction, whereas a pulley has very little, by design.
2) All you have to do to see the doubling affect is tie off the rope to an anchor on the ground rather than to itself, since you already have the scale set up.

Wait, I seem to have misread. It looks like the pully is currently hanging from the scales. In which case the dear isn't 125 pounds, it's like around 70-80 pounds.

Not if the rope is tied to itself or back to the deer (as I had presumed). I was assuming that he could tell the difference between a 63 lb and a 125 lb deer. (and a 63 pound deer would be so runty he probably wouldn't be posting about it.)
I suppose. I didn't think about it since I've never seen a 70 pound or a 125 pound deer hanging from a pully so...


milesenoell


Dec 6, 2009, 12:50 PM
Post #48 of 57 (2780 views)
Shortcut

Registered: Sep 19, 2006
Posts: 1156

Re: [giza] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

giza wrote:
There are plenty of other forums where your question would be answered from a place of knowledge and mutual respect.

But where's the fun in that?

edited to add: Oh, I didn't realize this thread was in The Lab. Sorry if I've come off as snarky.


(This post was edited by milesenoell on Dec 6, 2009, 12:54 PM)


Adk


Dec 6, 2009, 4:41 PM
Post #49 of 57 (2707 views)
Shortcut

Registered: Dec 2, 2006
Posts: 1084

Re: [sungam] 60 meter fall (fall factor 1); will a 10.5mm rope hold? [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

sungam wrote:
milesenoell wrote:
sungam wrote:
milesenoell wrote:
dynosore wrote:
zealotnoob wrote:
OT: Another quirk of the climbing system that can be surprising is the pulley effect. I.e, if you bail from a climb, off a single piece of pro, by having your partner lower you, you're applying twice the amount of force on that piece than if you rapped from it...

Crazy So, the dead deer hanging from a pulley in my pole barn right now is exerting 250 lbs of force on the pulley, even though it only weighs 125 lbs? That's a good trick! The spring scale attached to the pulley even says 125 lbs, it must be off by a factor of 2.

This is one of the best examples you could have thrown out for two reasons.
1) As Magnus pointed out, to get a a full doubling of force you need a frictionless system, and carabiners have a good bit of friction, whereas a pulley has very little, by design.
2) All you have to do to see the doubling affect is tie off the rope to an anchor on the ground rather than to itself, since you already have the scale set up.

Wait, I seem to have misread. It looks like the pully is currently hanging from the scales. In which case the dear isn't 125 pounds, it's like around 70-80 pounds.

Not if the rope is tied to itself or back to the deer (as I had presumed). I was assuming that he could tell the difference between a 63 lb and a 125 lb deer. (and a 63 pound deer would be so runty he probably wouldn't be posting about it.)
I suppose. I didn't think about it since I've never seen a 70 pound or a 125 pound deer hanging from a pully so...

He might be posting about it. Ya see. There are briefcase deer ---- < 50 lbs
suitcase deer------ >50 < 100 lbs
Backpack deer ----- >100< 140 lbs
one man drag deer-->140<200 lbs
two man draggers > 200 lbs

the force that any of them exhibit on a pully is not that hard to figure out. If math is tough think of it this way. If you have a backpack deer (you can actually wear it like a backpack) and you weigh the same and you try to lift it off the ground you can't.
If you are a bit heavier you still can't because of friction at the pully. If for some reason you can get it in the air and you both neither go up or down you have how many pounds hanging from the pully now?
For now don't think friction at the pully.
See where I'm going? Tie that off and you have how many pounds on the deer side of the pully and how many at the tie off point? How many are at the pully?

Briefcase deer do taste pretty good.Blush


(This post was edited by Adk on Dec 6, 2009, 4:48 PM)


adatesman


Dec 6, 2009, 6:43 PM
Post #50 of 57 (2684 views)
Shortcut

Registered: Jul 13, 2005
Posts: 3479

Post deleted by adatesman [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  

 

First page Previous page 1 2 3 Next page Last page  View All

Forums : Climbing Information : The Lab

 


Search for (options)

Log In:

Username:
Password: Remember me:

Go Register
Go Lost Password?



Follow us on Twiter Become a Fan on Facebook