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majid_sabet
Aug 6, 2007, 5:22 AM
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Alright n00bs, you had two weeks since I posted my 3:1 MA, and now quiz time.
To review 3:1 click link
http://www.rockclimbing.com/...;;page=unread#unread
Three questions;
What type of MA we got here
A- simple MA
B- Complex MA
What is the MA on both system combined ?
A- 4:1
B- 8:1
C- complex 3:1
D- 7:1
E- 5:1
Assuming all ropes are in straight line. if tire weights 300 lbs, how much weight Joe is pulling +_.
[URL=http://imageshack.us]
(This post was edited by majid_sabet on Aug 6, 2007, 4:55 PM)
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curt
Aug 6, 2007, 5:28 AM
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Who the hell is Joe? Also, I'll guess (C) - what do I win?
Curt
(This post was edited by curt on Aug 6, 2007, 5:30 AM)
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majid_sabet
Aug 6, 2007, 5:30 AM
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Sorry curt, It was Jay
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j_ung
Aug 6, 2007, 1:39 PM
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I'll guess 5:1, 60lbs, but I've never seen this set up before.
I'll guess complex, because it doesn't look very "simple." Also, though I don't have anywhere near the rescue experience you do, I think there are better ways to achieve 5:1, such as redirecting a Z-drag and getting a little help from old man gravity (or even piggybacking a C onto a Z (since you have an extra piece of rope) for 6:1). This looks similar to that, but unless Joe/Jay wants to continually untie and adjust the length of the blue rope, I don't think he'll be able to get the tire to the top with this particular system.
(This post was edited by j_ung on Aug 6, 2007, 1:45 PM)
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j_ung
Aug 6, 2007, 1:44 PM
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Does this system reduce friction over a more simple set up that might achieve the same theoretical advantage?
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trenchdigger
Aug 6, 2007, 3:13 PM
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j_ung wrote: Does this system reduce friction over a more simple set up that might achieve the same theoretical advantage?
Nice job, Jung... 5:1 is correct, as is "complex".
The cool thing about this system is that it's a simple mod to turn a 3:1 system into this 5:1. Sure, you could just stack a Z-rig on a 3:1 system with the same extra equipment to get 6:1, but with this 5:1 system, you still only have one prusik to reset with each haul. With the 6:1, you would have two prusiks to reset.
The 5:1 shown will surely get the tire to the top - and without retying anything. Simply haul until the pulley on the blue rope gets to one end of the rope, reset the prusik on the main line, and haul again.
There isn't much difference friction-wise if you assume all pulleys have the same loss, though the 6:1 is ever so slightly less efficient.
One thing to keep in mind with this system is that one of the pulleys endures twice the load of the other two pulleys (80% of the weight of the tire). If you have pulleys of different strengths, choose their locations wisely.
(This post was edited by trenchdigger on Aug 6, 2007, 3:28 PM)
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stymingersfink
Aug 6, 2007, 9:35 PM
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trenchdigger wrote: The 5:1 shown will surely get the tire to the top - and without retying anything. Simply haul until the pulley on the blue rope gets to one end of the rope, reset the prusik on the main line, and haul again.
You see, majid has forgotten his progress capture device on the red pulley of the green rope, so he'll merely be lifting the weight up and lowering it back down with the system he has designed here. Perhaps such was his intention, however, IDK.
With inefficiencies inherent with pulley hauling systems, I'll guess about 65-70ish pounds of upward force will be exerted by the sorry sucker at the top of the line. The fact that the hauler is not wearing a helmet means that an asteroid will certainly fall fall from the sky striking his noggin and knocking him unconscious, causing the load to fall abruptly to the ground from whatever height it had been raised to, thereby crushing and killing someone in the middle of an attempt to attach a truck to the tire.
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trenchdigger
Aug 6, 2007, 10:28 PM
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stymingersfink wrote: trenchdigger wrote: [IMG]http://img329.imageshack.us/img329/5350/untitled1lj4.jpg[/IMG] The 5:1 shown will surely get the tire to the top - and without retying anything. Simply haul until the pulley on the blue rope gets to one end of the rope, reset the prusik on the main line, and haul again. Sorry, ain't gonna happen. You see, majid has forgotten his progress capture device on the red pulley of the green rope, so he'll merely be lifting the weight up and lowering it back down with the system he has designed here. Perhaps such was his intention, however, IDK. With inefficiencies inherent with pulley hauling systems, I'll guess about 65-70ish pounds of upward force will be exerted by the sorry sucker at the top of the line. The fact that the hauler is not wearing a helmet means that an asteroid will certainly fall fall from the sky striking his noggin and knocking him unconscious, causing the load to fall abruptly to the ground from whatever height it had been raised to, thereby crushing and killing someone in the middle of an attempt to attach a truck to the tire.
hah... I stand corrected.
Is it ironic that I'm sitting in a tire shop getting new tires put on my truck?
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el_layclimber
Aug 6, 2007, 10:37 PM
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I would not identify myself as a noob, but I have no idea what is going on there.
That's why I: a. do not do anything that involves hauling (or pooping in a bag and saving it).
b. do not get in accidents/fall in crevasses/ have a partner do same, and have to self-rescue.
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majid_sabet
Aug 6, 2007, 10:50 PM
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el_layclimber wrote: I would not identify myself as a noob, but I have no idea what is going on there. That's why I: a. do not do anything that involves hauling (or pooping in a bag and saving it). b. do not get in accidents/fall in crevasses/ have a partner do same, and have to self-rescue.
You do not need to hide it, just say you only do bouldering
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curt
Aug 7, 2007, 2:31 AM
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majid_sabet wrote: el_layclimber wrote: I would not identify myself as a noob, but I have no idea what is going on there. That's why I: a. do not do anything that involves hauling (or pooping in a bag and saving it). b. do not get in accidents/fall in crevasses/ have a partner do same, and have to self-rescue. You do not need to hide it, just say you only do bouldering
Well, at least boulderers are smart enough to avoid hauling 300 lb. tires up the rock.
Curt
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stymingersfink
Aug 7, 2007, 2:39 AM
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trenchdigger wrote: stymingersfink wrote: trenchdigger wrote: [IMG]http://img329.imageshack.us/img329/5350/untitled1lj4.jpg[/IMG] The 5:1 shown will surely get the tire to the top - and without retying anything. Simply haul until the pulley on the blue rope gets to one end of the rope, reset the prusik on the main line, and haul again. Sorry, ain't gonna happen. You see, majid has forgotten his progress capture device on the red pulley of the green rope, so he'll merely be lifting the weight up and lowering it back down with the system he has designed here. Perhaps such was his intention, however, IDK. With inefficiencies inherent with pulley hauling systems, I'll guess about 65-70ish pounds of upward force will be exerted by the sorry sucker at the top of the line. The fact that the hauler is not wearing a helmet means that an asteroid will certainly fall fall from the sky striking his noggin and knocking him unconscious, causing the load to fall abruptly to the ground from whatever height it had been raised to, thereby crushing and killing someone in the middle of an attempt to attach a truck to the tire. hah... I stand corrected. Is it ironic that I'm sitting in a tire shop getting new tires put on my truck?
you ARE wearing a helmet... right?
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rasoy
Aug 7, 2007, 3:11 AM
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Trenchdigger
Nice analysis and stymingersfink nice sharp eye.
Majid, you really need to stop calling these people here n00bs.
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stymingersfink
Aug 7, 2007, 3:49 AM
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trenchdigger wrote: One thing to keep in mind with this system is that one of the pulleys endures twice the load of the other two pulleys (80% of the weight of the tire). If you have pulleys of different strengths, choose their locations wisely.
Um, I'm thinking along a different set...
The first red pulley above the tire would experience 200% of the weight of the tire, no? 100% of the initial weight, plus the 100% necessary on the other side to perform the lift.
Am I totally off with that line of thinking? If pulley strength were a consideration, I'd definitely put the strongest one in the position mentioned above. Hopefully it has the largest sheave, too.
edit to add:
Durr... the system with the blue rope will provide a portion of the lift, thereby relieving the pulley mentioned above of x-percentage of the entire load. The top pulley will hold 100% of the load while resetting the haul (if it were a pro-traxion lets say, with ratchet engaged!), but the pulley would experience less load when actually hauling due to the secondary pulley system taking some of the load off??!?
I guess I haven't spent enough time working with complex pulley systems...
(This post was edited by stymingersfink on Aug 7, 2007, 4:07 AM)
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trenchdigger
Aug 7, 2007, 4:13 AM
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stymingersfink wrote: trenchdigger wrote: One thing to keep in mind with this system is that one of the pulleys endures twice the load of the other two pulleys (80% of the weight of the tire). If you have pulleys of different strengths, choose their locations wisely. Um, I'm thinking along a different set... The first red pulley above the tire would experience 200% of the weight of the tire, no? 100% of the initial weight, plus the 100% necessary on the other side to perform the lift. Am I totally off with that line of thinking? If pulley strength were a consideration, I'd definitely put the strongest one in the position mentioned above. Hopefully it has the largest sheave, too.
See the attached photo. Here's my logic...
Assume you're pulling with tension T at point (A).
Assume the pulleys are frictionless.
Assume the system is loaded, but static (not accelerating or moving).
The red circles are pulleys.
The blue and green lines are ropes.
The blue line at pulley 2 is attached to the anchor, not the pulley.
If the tension at point (A) is T, then the tension at points (B) and (C) must also be T.
For equillibrium at pulley 1, the tension in the blue rope at point (F) must be 2T. Therefore the tension at point (E) must also be 2T.
For equillibrium at pulley 3, the tension at point (G) must be 4T.
The tension, then, at the load (H) must be the sum of (G) and (C) which is 5T - hence the 5:1 mechanical advantage.
If we look at the tensions in the lines, pulleys 1 and 2 endure 2T, or 2/5ths of the load. Pulley 3 must endure 4T, or 4/5ths of the load.
(This post was edited by trenchdigger on Aug 7, 2007, 4:18 AM)
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stymingersfink
Aug 7, 2007, 5:04 AM
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trenchdigger wrote: stymingersfink wrote: trenchdigger wrote: One thing to keep in mind with this system is that one of the pulleys endures twice the load of the other two pulleys (80% of the weight of the tire). If you have pulleys of different strengths, choose their locations wisely. Um, I'm thinking along a different set... The first red pulley above the tire would experience 200% of the weight of the tire, no? 100% of the initial weight, plus the 100% necessary on the other side to perform the lift. Am I totally off with that line of thinking? If pulley strength were a consideration, I'd definitely put the strongest one in the position mentioned above. Hopefully it has the largest sheave, too. See the attached photo. Here's my logic... Assume you're pulling with tension T at point (A). Assume the pulleys are frictionless. Assume the system is loaded, but static (not accelerating or moving). The red circles are pulleys. The blue and green lines are ropes. The blue line at pulley 2 is attached to the anchor, not the pulley. If the tension at point (A) is T, then the tension at points (B) and (C) must also be T. For equillibrium at pulley 1, the tension in the blue rope at point (F) must be 2T. Therefore the tension at point (E) must also be 2T. For equillibrium at pulley 3, the tension at point (G) must be 4T. The tension, then, at the load (H) must be the sum of (G) and (C) which is 5T - hence the 5:1 mechanical advantage. If we look at the tensions in the lines, pulleys 1 and 2 endure 2T, or 2/5ths of the load. Pulley 3 must endure 4T, or 4/5ths of the load.
I knew my logic was failing me somewhere, else how would there be a mechanical advantage, eh?
I suppose with pen an paper i MAY have figured it out eventually, but probably not as quickly as I might have had I tried googling it.
Obviously then, pulley 3 would be the point to place the stronger pulley if there were wide disparities in pulley strengths. All other things being equal, of course.
I noted in your explanation that the blue rope labeled (E) was attached to the anchor itself, not the pulley (2). A key point in your equation when considering pulley strengths (i believe?).
However, in your summary the sum of the tension forces felt by the pulleys totals 6/5ths the load. Can you explain this a little more for me?
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majid_sabet
Aug 7, 2007, 5:15 AM
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rasoy wrote: Trenchdigger Nice analysis and stymingersfink nice sharp eye. Majid, you really need to stop calling these people here n00bs.
I call every one n00b in a good way and people should not take it too personal as I even call myself noob too.
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trenchdigger
Aug 7, 2007, 5:41 AM
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stymingersfink wrote: I noted in your explanation that the blue rope labeled (E) was attached to the anchor itself, not the pulley (2). A key point in your equation when considering pulley strengths (i believe?).
Yah, basically. Otherwise that pulley's attach point to the anchor would take 4T of load. Also, your average pulley doesn't have an attach point on both ends (though some do).
stymingersfink wrote: However, in your summary the sum of the tension forces felt by the pulleys totals 6/5ths the load. Can you explain this a little more for me? 
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majid_sabet
Aug 7, 2007, 5:45 AM
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trenchdigger wrote: stymingersfink wrote: I noted in your explanation that the blue rope labeled (E) was attached to the anchor itself, not the pulley (2). A key point in your equation when considering pulley strengths (i believe?). Yah, basically. Otherwise that pulley's attach point to the anchor would take 4T of load. Also, your average pulley doesn't have an attach point on both ends (though some do). stymingersfink wrote: However, in your summary the sum of the tension forces felt by the pulleys totals 6/5ths the load. Can you explain this a little more for me? I don't think it really matters (it would actually be 8T rather than 6T, making the pulley totals 8/5ths of the load). I don't know without thinking about this more, but it may tell you something else useful about the system. Or it may not
Tranch
Draw me a 5:1 closed system
I hope you know how to do it without google.
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reno
Aug 7, 2007, 6:02 AM
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15.683:1.782 hauling ratio.
Freaking n00b OP.
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el_layclimber
Aug 7, 2007, 6:13 AM
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majid_sabet wrote: el_layclimber wrote: I would not identify myself as a noob, but I have no idea what is going on there. That's why I: a. do not do anything that involves hauling (or pooping in a bag and saving it). b. do not get in accidents/fall in crevasses/ have a partner do same, and have to self-rescue. You do not need to hide it, just say you only do bouldering
When I was a boy, I was taught how to climb. We didn't have none of this sport climbin' or trad climbin', or bouldering with them pads. We climbed stuff. We just called it climbing. If it was tall we used a rope. If we wanted safety and fun, we used a top-rope.
We saw some guys rap-bolting and some guys aid climbing. They did little climbing. It looked slow and boring. We called that whack and dangle tom-foolery.
As for hauling and self-rescue, I would like to know more, but given the available hours I have I would rather spend them climbing. Yes, I will probably be in one of your accident posts one day, and someone will call you an asshole for making a direct quotation of the clueless reporter who wrote my traumatic brain injury up in the paper as "Safety thinamajigs that failed when he put them in a crevasse in the cliff face he was scaling."
Oh, I also totally jerked off all through high-school physics.
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stymingersfink
Aug 7, 2007, 6:22 AM
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trenchdigger wrote: stymingersfink wrote: However, in your summary the sum of the tension forces felt by the pulleys totals 6/5ths the load. Can you explain this a little more for me? I don't think it really matters (it would actually be 8T rather than 6T, making the pulley totals 8/5ths of the load). I don't know without thinking about this more, but it may tell you something else useful about the system. Or it may not
Is the extra 3/5ths lost as inefficiency within the system? There's something wrong here... the pulley system, as a total, should only experience 5/5ths the mass of the load, plus perhaps a small percentage of efficiency lost as friction within the system. I'm finding it hard to believe that 3/5ths the load, or 180lbs of tension, is added due to inefficiency within the system.
Can I get a ruling from the judges please?
Rasoy? I know you've got someone who can provide an experiential/scientific answer for me in layman's terms. Care to enlighten me/us?
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trenchdigger
Aug 7, 2007, 2:25 PM
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stymingersfink wrote: There's gotta be something I'm missing here... at least, that's what my understanding of the law of conservation of energy is telling me. WTF?
stymingersfink wrote: Is the extra 3/5ths lost as inefficiency within the system?
Let's say you throw in a few change of direction pulleys. We're assuming they're frictionless, so they should have no impact on the end result of the system, but they'll jack up this ratio you're coming up with.
stymingersfink wrote: There's something wrong here... the pulley system, as a total, should only experience 5/5ths the mass of the load, plus perhaps a small percentage of efficiency lost as friction within the system. I'm finding it hard to believe that 3/5ths the load, or 180lbs of tension, is added due to inefficiency within the system.
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trenchdigger
Aug 7, 2007, 4:13 PM
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majid_sabet wrote: Tranch Draw me a 5:1 closed system I hope you know how to do it without google.
Major Sorbet
If we assume the pulleys are 100% efficient (or if we included a bunch of complicated friction and thermodynamic calculations), then this is a closed system.
Do you know the definition of a "closed system" without Googling it?
Did you possibly mean a simple 5:1 system?
(This post was edited by trenchdigger on Aug 7, 2007, 4:14 PM)
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sgauss
Aug 7, 2007, 4:49 PM
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Excellent diagram, excellent explanation! Thanks!
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