Creepy
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Post by Creepy on Mar 4, 2015 23:31:47 GMT -4
An 8000lb winch comes with 5/16" cable. I don't think 5/16" cable is up to 16,000 lbs. maybe I'm wrong. ###Edit#### I'm wrong. It's 8000 on each line for a total of 16,000. No risk. I've been totally nervous all these years using smaller line. For totally no reason. Never too old to learn something new. Thanks 6 for an explanation dumbed down far enough for even me to understand. As you were!! Well here is one for you, and anyone else that would like to jump in on the fun. Did you know that taking your winch line to a snatch block and back to your jeep DOES NOT double it's pulling strength. You gain pull because you have used more line off of the spool therefore getting the full pull from the winch. In order to double the pull you must use 2 snatch blocks. One snatch does double the pull. the tree strap holding the snatch will see twice the pull the winch does. 8K winch, doubled back to rig with a snatch, will produce 16K on the tree strap. = 16K pulling you forward, from an 8K winch. A winch only delivers the maximum-rated pulling power when the cable is on the innermost layer. Pulling from subsequent layers reduces that power by about 20 percent per layer.
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coolwind1
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Post by coolwind1 on Mar 5, 2015 6:49:29 GMT -4
Think of it this way. If you attach a single pully on a ceiling. Now you put a rope threw that pulley. Put a loop on one end of the pulley rope and put 200lbs on it. Now if you pull the other end of the rope you will be lifting 200lbs. The pully itself and rope will experience 200lbs of force. Now think of the 200lbs of weight is your jeep, the other end of the rope you are pulling is the winch. There is no mech. advantage. The full 8,000lbs pull will only decrease after the first row on the winch barral and will slowly decrease as you get more wraps on that barrel. :-)
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Post by derekmac on Mar 5, 2015 7:43:11 GMT -4
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dan
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Post by dan on Mar 5, 2015 9:25:40 GMT -4
By using a snatch block, you are pulling with a 2:1 ratio. For every foot of line winding onto the drum, the rig is only being pulled 6". That effectively doubles the amount of pull force.
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Post by SocialWheeler on Mar 5, 2015 10:52:36 GMT -4
Well here is one for you, and anyone else that would like to jump in on the fun. Did you know that taking your winch line to a snatch block and back to your jeep DOES NOT double it's pulling strength. You gain pull because you have used more line off of the spool therefore getting the full pull from the winch. In order to double the pull you must use 2 snatch blocks. One snatch does double the pull. the tree strap holding the snatch will see twice the pull the winch does. 8K winch, doubled back to rig with a snatch, will produce 16K on the tree strap. = 16K pulling you forward, from an 8K winch. A winch only delivers the maximum-rated pulling power when the cable is on the innermost layer. Pulling from subsequent layers reduces that power by about 20 percent per layer. That's what I thought.
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GOAT
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Post by GOAT on Mar 5, 2015 14:17:44 GMT -4
I love 4x4 and Jeep math..... Should be taught in school.
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Creepy
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Post by Creepy on Mar 5, 2015 15:41:44 GMT -4
Think of it this way. If you attach a single pully on a ceiling. Now you put a rope threw that pulley. Put a loop on one end of the pulley rope and put 200lbs on it. Now if you pull the other end of the rope you will be lifting 200lbs. The pully itself and rope will experience 200lbs of force. Now think of the 200lbs of weight is your jeep, the other end of the rope you are pulling is the winch. There is no mech. advantage. The full 8,000lbs pull will only decrease after the first row on the winch barral and will slowly decrease as you get more wraps on that barrel. :-) Nope. Your simple example is wrong. the hook into the ceiling will see 400lbs. Yes, the rope will see 200lbs per side. The pully is lifting the 200lb weight, and also seeing the 200lb force you are exerting to lift. add them together to see force acting on ceiling hook, or tree strap as it were. (There is also a 10% frictional loss for the wire going thru the snatch block, not shown in calcs) Here, look: I drew a picture The amount of line on the drum is accounting for 20% capacity loss per layer. Derek's link is stating 10% per layer. 8000K winch on bottom layer = 8000K capacity 8000K winch on 2nd layer = 8000 X .20 (20% reduced capacity) = 1600. Winch will pull 8000 - 1600 = 6400. 8000K winch on 3rd layer = 8000 X .40 = 3200. Winch will pull 8000 - 3200 = 4800. (Getting close to half capacity.) 8000K winch on 4th layer = 8000 X .60 = 4800. Winch will pull 8000 - 4800 = 3200lbs. (less than half capacity by only spooling out a few feet.) Everyone got it?
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Creepy
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Post by Creepy on Mar 5, 2015 15:51:48 GMT -4
By using a snatch block, you are pulling with a 2:1 ratio. For every foot of line winding onto the drum, the rig is only being pulled 6". That effectively doubles the amount of pull force. The bolded text is questionable. the first two statements are correct on their own merits, but do not prove the conclusion. the pulley is the doubler, as it transfers two line loads on the winch cable, to one line load to the anchor. see diagram above.
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jmurphy
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Post by jmurphy on Mar 5, 2015 16:06:34 GMT -4
The key in Jan's sketch being the winch line hooked back to the vehicle so it experiences the full 16000 lb force. If you attach your winch line to a third body the force on the vehicle won't increase. (Right?) Force and distance all work into it is what Dan was getting at. Double the force and half the distance the vehicle moves so the winch does the same work per drum rotation. Or something like that...
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Enos
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Post by Enos on Mar 5, 2015 16:17:02 GMT -4
If you attach your winch line to a third body the force on the vehicle won't increase. (Right?) Correct, you are just changing the angle of the pull, no mechanical advantage to this setup.
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Creepy
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Post by Creepy on Mar 5, 2015 16:18:48 GMT -4
The key in Jan's sketch being the winch line hooked back to the vehicle so it experiences the full 16000 lb force. Force and distance all work into it is what Dan was getting at. Double the force and half the distance the vehicle moves so the winch does the same work per drum rotation. Or something like that... If 'it' is the tree strap, yes. But you appear to be referring to the winch line. The winch lines are seeing two equal loads, whan added together by the pulley, the TREE STRAP sees double. Have another look, the winch line DOES NOT see double load, ever! The winch would stall, the whole purpose of the effort is to keep a small load on winch, while exerting double load on TREE STRAP. second statement makes no sense. lol
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Post by TomWood on Mar 5, 2015 16:20:24 GMT -4
I love that this has gotten this discussion going, I am learning quite a bit. One question comparing Jan's notes to Dereks link about the reduction of pull per layer.
In your example Jan you take the 20% off 16000lbs for each layer, in the link it takes the percentage off the lbs that layer is at. So for yours every layer its losing 1600lbs of pull, in the link it changes according to the layer, 1600lbs for the first layer then it would be 20% of the 6400lbs remaining for the second layer, which would remove 1280lbs.
I would tend to lead to the percentage of remaining force rather than initial force, but I am new at this as well. Thoughts?
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Creepy
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Post by Creepy on Mar 5, 2015 16:35:39 GMT -4
Take another look at my calcs. - I took 20% off each layer starting from bottom layer, with an 8K winch. - There is no 16000 in my calcs. - every layer loses a percentage of capacity....not 1600. My calcs do change with each layer. - I don't understand the last question.
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Post by TomWood on Mar 5, 2015 16:36:48 GMT -4
8000K winch on bottom layer = 8000K capacity 8000K winch on 2nd layer = 8000 X .20 = 1600. Winch will pull 8000 - 1600 = 6400. 8000K winch on 3rd layer = 8000 X .40 = 3200. Winch will pull 8000 - 3200 = 4800. (Getting close to half capacity.) 8000K winch on 4th layer = 8000 X .60 = 4800. Winch will pull 8000 - 4800 = 3200lbs. (less than half capacity by only spooling out a few feet.)
^^That information removes 1600lbs of pull for every layer, this is what I was referring to.
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Post by TomWood on Mar 5, 2015 16:38:43 GMT -4
The percentage increased which is the same as removing 20% from 8000 for each layer.
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