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majid_sabet
Aug 8, 2007, 6:40 AM
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EFingers wrote: trenchdigger wrote: Try again... I'll give you a clue: It's a trick question. Trick question? What 2:1 or is it that since the diagram doesn't accurately show the top pulley in a fixed position, does the whole thing fall apart?
top pulley is fixed to anchor
all other pulleys are moving
so what is the MA ?
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binrat
Aug 8, 2007, 1:21 PM
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I'll try it, compound 6:1
Am I right???
Binrat
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trenchdigger
Aug 8, 2007, 3:15 PM
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majid_sabet wrote: top pulley is fixed to anchor all other pulleys are moving so what is the MA ?
Still stalling eh?
trenchdigger wrote: 1) Define "closed system" as it pertains to hauling systems. 2) Define simple, complex, and compound as they pertain to hauling systems. 3) Which of the 5:1 systems in this thread is more efficient? The simple system shown here, or your illustrated complex 5:1 system? BONUS) Show me a COMPLEX 7:1 MA hauling system. |
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rasoy
Aug 8, 2007, 5:07 PM
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OK I'll give him (Majid) help for 2)
Simple Pulley Systems
Basically one continuous rope flowing between the pulleys.
Tension in the rope remains the same throughout in the simple pulley system.
Compound
1 simple pulley system pulling another simple pulley system. The advantage being greater MA for the same number of pulleys in simple system thus reducing overall loss due to friction.
Complex
Are basically neither simple nor compound. Thats why they're complex 
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majid_sabet
Aug 8, 2007, 5:47 PM
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binrat wrote: I'll try it, compound 6:1 Am I right??? Binrat
Binrat
just quietly delete your post before any one else see it.
it does not look good
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thomasribiere
Aug 8, 2007, 5:54 PM
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majid_sabet wrote: binrat wrote: I'll try it, compound 6:1 Am I right??? Binrat Binrat just quietly delete your post before any one else see it. it does not look good
aren't we allowed to make mistakes? Stop being haughty, please.
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trenchdigger
Aug 8, 2007, 6:00 PM
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rasoy wrote: OK I'll give him (Majid) help for 2) Simple Pulley Systems Basically one continuous rope flowing between the pulleys. Tension in the rope remains the same throughout in the simple pulley system. Compound 1 simple pulley system pulling another simple pulley system. The advantage being greater MA for the same number of pulleys in simple system thus reducing overall loss due to friction. Complex Are basically neither simple nor compound. Thats why they're complex
Good answer...
I'd add that a "Complex" system will often involve multiple sections of rope rather than one continuous section. #3 is probably the most useful of the questions. Maybe your friend Majid can answer that one?
(This post was edited by trenchdigger on Aug 8, 2007, 6:04 PM)
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majid_sabet
Aug 8, 2007, 6:13 PM
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thomasribiere wrote: majid_sabet wrote: binrat wrote: I'll try it, compound 6:1 Am I right??? Binrat Binrat just quietly delete your post before any one else see it. it does not look good aren't we allowed to make mistakes? Stop being haughty, please.
Tom
you are allowed to make mistakes but not BINRAT. He falls in to a different catogory where he can not effort of making any mistakes.
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majid_sabet
Aug 8, 2007, 6:22 PM
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trench
You see , no matter who answers you , you still need to re correct it and modify it so it could please you. This is why I try not to answer or create additional conflicts.
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trenchdigger
Aug 8, 2007, 6:22 PM
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majid_sabet wrote: Tom you are allowed to make mistakes but not BINRAT. He falls in to a different catogory where he can not effort of making any mistakes.
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trenchdigger
Aug 8, 2007, 6:29 PM
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majid_sabet wrote: trench You see , no matter who answers you , you still need to re correct it and modify it so it could please you. This is why I try not to answer or create additional conflicts.
Emphasis my own...
Quoted for posterity.
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binrat
Aug 8, 2007, 7:00 PM
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majid_sabet wrote: thomasribiere wrote: majid_sabet wrote: binrat wrote: I'll try it, compound 6:1 Am I right??? Binrat Binrat just quietly delete your post before any one else see it. it does not look good aren't we allowed to make mistakes? Stop being haughty, please. Tom you are allowed to make mistakes but not BINRAT. He falls in to a different catogory where he can not effort of making any mistakes.
M.S.
But I can have fun and try to get things going here.
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cracklover
Aug 8, 2007, 7:18 PM
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trenchdigger wrote: majid_sabet wrote: trench You see , no matter who answers you , you still need to re correct it and modify it so it could please you. This is why I try not to answer or create additional conflicts.Emphasis my own... Quoted for posterity.
No surprise. The biggest troll on rcdotcom will not bite the bait on anyone else's line!
I certainly won't let Majid off the line by answering any of the questions for him, but while I'm posting, here's my answer to one of his. This is fun!
In this system, we do seem to have a problem:
The problem is that this is a single continuous line, so all the parts of it should have the same tension. But the part I've marked ?X is being expected to hold twice the force that the tension in it can hold. I don't know what would happen, but I imagine that the first pulley would not be held down by that line, and would just fly up to the top pulley. Am I right?
GO
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trenchdigger
Aug 8, 2007, 7:38 PM
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cracklover wrote: trenchdigger wrote: majid_sabet wrote: trench You see , no matter who answers you , you still need to re correct it and modify it so it could please you. This is why I try not to answer or create additional conflicts.Emphasis my own... Quoted for posterity. No surprise. The biggest troll on rcdotcom will not bite the bait on anyone else's line! I certainly won't let Majid off the line by answering any of the questions for him, but while I'm posting, here's my answer to one of his. This is fun! In this system, we do seem to have a problem: [IMG]http://i10.tinypic.com/4ztflt0.jpg[/IMG] The problem is that this is a single continuous line, so all the parts of it should have the same tension. But the part I've marked ?X is being expected to hold twice the force that the tension in it can hold. I don't know what would happen, but I imagine that the first pulley would not be held down by that line, and would just fly up to the top pulley. Am I right? GO
Yah, you've got it. Pull up, and the pulley on the left moves up, the rope runs through the pulleys, and the load remains stationary.
Contrary to popular belief, this system does actually have a use in technical rescue in one specific situation - when Majid is on the end of the line.
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cracklover
Aug 8, 2007, 8:49 PM
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And this one looks like 9:1 to me.
Complex or compound?
GO
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rasoy
Aug 8, 2007, 9:14 PM
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That is a simple 3:1 pulling on a simple 3:1
Thus it is a compound 9:1
You guys still at this? Instead of grilling people with questions why not explain different systems and their advantages and disadvantages.
Trying to be the smartest guy here does not help others nor makes for a good learning experience.
It will just turn people off and they'll go else where?
(This post was edited by rasoy on Aug 8, 2007, 9:15 PM)
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stymingersfink
Aug 9, 2007, 12:05 AM
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rasoy wrote: Trying to be the smartest guy here does not help others nor makes for a good learning experience. It will just turn people off and they'll go else where?
george_carlin wrote: My God's dick is bigger than your God's dick! |
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rasoy
Aug 9, 2007, 1:34 AM
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So number 3 isn't being answered by Majid? Why?
"3) Which of the 5:1 systems in this thread is more efficient? The simple system shown here, or your illustrated complex 5:1 system?"
The (Majid) illustrated complex 5:1 should be more efficient than the simple due to less friction (1 less pulley). Friction and drag are your enemies in raising systems.
One common mistake rescuers tend to make is not making the main pull anchor high. They tend to tie around a tree down low at the base. Get it high as you practically can and then back tie to another anchor from that. (backup). You'll minimize friction.
I wouldn't set it up Majid illustration like that with the ropes crossing over each other.
Majid and trench don't bail out of this thread ..... explain your points and make it a good worthy thread.
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EFingers
Aug 9, 2007, 2:45 AM
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cracklover wrote: In this system, we do seem to have a problem: [IMG]http://i10.tinypic.com/4ztflt0.jpg[/IMG] The problem is that this is a single continuous line, so all the parts of it should have the same tension. But the part I've marked ?X is being expected to hold twice the force that the tension in it can hold. I don't know what would happen, but I imagine that the first pulley would not be held down by that line, and would just fly up to the top pulley. Am I right? GO
Ok, I just set this up just using carabiners because I don't have pulleys. When I pulled up on the rope there was too much friction on the top pulley giving only the use of the lower 2 for a MA of 4:1. If i pulled horizontally away from the system making less friction the rope would pass through all of the pulley, so this could actually work.. When I picture this I see it as the top pulley lowers the MA because it increases the rate that the load will rise. So if I'm seeing this right my third and final guesstamation is 3:1.
So another answer from the noob MA is 3:1??
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majid_sabet
Aug 9, 2007, 3:20 AM
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EFingers wrote: cracklover wrote: In this system, we do seem to have a problem: [IMG]http://i10.tinypic.com/4ztflt0.jpg[/IMG] The problem is that this is a single continuous line, so all the parts of it should have the same tension. But the part I've marked ?X is being expected to hold twice the force that the tension in it can hold. I don't know what would happen, but I imagine that the first pulley would not be held down by that line, and would just fly up to the top pulley. Am I right? GO Ok, I just set this up just using carabiners because I don't have pulleys. When I pulled up on the rope there was too much friction on the top pulley giving only the use of the lower 2 for a MA of 4:1. If i pulled horizontally away from the system making less friction the rope would pass through all of the pulley, so this could actually work.. When I picture this I see it as the top pulley lowers the MA because it increases the rate that the load will rise. So if I'm seeing this right my third and final guesstamation is 3:1. So another answer from the noob MA is 3:1??
I got two images for you so you could understand the system
image A (left) is a chage of direction. you are not having any MA cause you are only using the pulley to redirect the load so load weights the same at the end of the line.
Image B is MA cause you are now dividing the load in to two and each side is sharing the total weight so your load of 100 Lbs is actually feels like 50 Lbs per side or 2:1 MA .
Now you need to go back and look at my image and figure out where the change of direction is applied and where you have the MA (if any) and then combine them.
[URL=http://www.imagehosting.com] 
(This post was edited by majid_sabet on Aug 9, 2007, 3:22 AM)
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rasoy
Aug 10, 2007, 1:37 AM
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LOL
Yeah maybe on paper he's pulling 67.87 pounds.
In the real world there's always way more friction that will slow you down and make you put "One more man on the pull team."
When those lines start going over the edge you'll see what I'm talking about.
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majid_sabet
Aug 10, 2007, 4:26 AM
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[URL=http://imageshack.us]
Shot at 2007-08-09
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delrio
Aug 10, 2007, 10:51 PM
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rasoy wrote: LOL Yeah maybe on paper he's pulling 67.87 pounds. In the real world there's always way more friction that will slow you down and make you put "One more man on the pull team." When those lines start going over the edge you'll see what I'm talking about.
The calculation is valid for a free hanging hoist with pulley-efficiency = 0.9 =90 %.
Known tecnical datas for pulley-efficiency :
Petzl-equipment : 0.9 - O.714
T.Moyer : 0.92 - 0.95
For inffluence of edges see :"The Mechanics of Friction in Rope Rescue"
http://www.amrg.org/...Reports_Papers2.html
Trenchdigger has elaborated exactly the theoretical MA with pulley-efficiency = 1 = 100%, also valid for a free hanging hoist :
(H) = 5 * (A)
Load (H) = 300 lbs => (A) = 300 / 5 = 60 lb
=====================================
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[/image] 
Kopie von Calculation Hoist 1-5-corr1-corr.jpg
