Hunting Washington Forum
Equipment & Gear => Power Equipment & RV => Topic started by: Rob on December 12, 2022, 02:23:19 PM
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I have a few winch rigging questions regarding anchor load and mechanical advantage.
Below is an image I took from somewhere as it comes close to demonstrating the questions I have.
First some assumptions:
Truck weight – 4 tons
Winch power – 6 tons
For the purposes of my questions, ignore any loss of effectiveness or increased load that you may encounter due to wraps of line on the winch, angles, grade, suction, rigging tackle, etc. I am just looking for some principles (and I can apply those resistances later based on conditions).
For Situation A (Single Line):
-Load on the winch and Anchor would both be 4 tons.
-Using a 3x1 safety factor based on Winch pulling strength of 6 tons, I would want the tree strap and shackle to be 18 Tons. First Question: when looking at the strength of components like shackles, tree saver straps, and snatch Blocks, are you looking at Working Load Limit, or breaking limit?
For situation B (Double Line).
-This is a 2x1 mechanical advantage system (Right?)
-Load on each line would be 2 Tons due to the addition of the snatch block. 2 tons on the winch, and 2 tons on the attachment point on the truck.
-Load on the Anchor would be 4 Tons
-POTENTIAL load that could be applied to the anchor could be up to 12 tons (2x the winch strength or 6 tons on each line)
Questions: am I correct on my last bullet about load being potentially 12 tons? If so, would you be looking at anchor components capable of 36 tons for a worse case situation (deeply mired extraction in mud, steep hill, etc)
For Situation C (Triple Line)
-This would be a 3x1 mechanical advantage system (I think)
-The load on each line would be 1/3 of the truck weight, or 1.33 tons (Right?)
-What are the anchor loads for a 4 ton extraction?
Anchor 1: 2.66 Tons?
Anchor 2: 1.33 Tons?
Anchor 3: 2.66 Tons?
I have more questions, but this is probably too many for a first post anyway!
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I would double up on a single line anchor.
What I mean is if your pulling 6 ton anchor strap needs to be for 12 ton,or 10,000lb test minimum.
I still see the load the same even when pulley is added.
Even though your winch is not working as hard.
Let me give example .
Your truck slides out off the mountain ,rolls,whatever and for some reason or another it jerks the line.
Your anchor point could still break even if at 12 ton on anchor line.
Big jolts to the line ,
Like when you pull trees with a cable,you can tighten the line then start pulling right at the end of the line. Or you can back up and really feed her the fire and jolt the line.
You risk breaking the cable just from force,even though the tree is not 10,000lb.
But I might be wrong.
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Shock loads is what your describing :tup:
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Depending on the type and quality blocks, you loose a lot the more you add.
When I replace the wire rope I'm going all soft shackles and rollers, so easy.
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In my logging career as a chokerman, riggin slinger or a hook or skidding with a drum CAT,
I’ve witnessed more chokers, shackles, mainlines, skidding lines, taglines,haulbacks, straps, stumps pulled, and haywire parted due to hard sustained pulls rather than hard sudden shock. You’d be on a hard pull, and either because of terrain or weight, it would part. I’ve witnessed some pretty wild riggin with some very big logs on hi lead shows and the shock is just incredible. But pull that line, stretch the strands out of their lay, and bam, you’ve parted er
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I watched a skyline break on the bottom on a canyon we were hooking, using extensions we were so far down. The carriage, logs and whole works come down on our heads. I couldn't see how much haul line was left and smacked the carriage with the turn :(
That broke the skyline off its anchor on the dozer blade
Carriage hit a stump and buried half way through it, then engine inside was just bits of metal inside the carriage
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Keep it simple -
Winch rated for 12000 lb.
Just total pieces of rope to it.
Snatch block anchor needs 24000# as it sees two lines.
Never put 2 rope ends on single anchor on vehicle - they aren’t made for 24000# - as shown in your figure 3. Yes rig will likely pull free before you over load attachment point but don’t risk it.
Use more than 25k Rope Shackles to attach snatch block for 12k winch. I use 45k rope shackles.
U want breaking strength at least 10% more than this for emegency us. Day to day commercial use of course double or triple safety factor.
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The load value would be the same for each part of line you add, whether splitting the load over 2, 3, 4, or even 6 parts of line. Kinetic recovery ropes are high rated ropes designed to stretch with the intention of increasing the pull until the stretch relaxes, like mine is a 30K rope that can stretch 8ft so once its snugged up the rope will load up and stretch to compensate for necessary strain required for a given load. Soft shackles, recovery rings, and overrated ropes, synthetic winch lines and any other gear you use should be easily able to handle max load, working with minimums gets people hurt, the scenarios in hunter399 anecdotal scenario is hillbilly stupid stuff that gets people hurt, you dont jerk cable, intentional shock loading is stupid.
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For anchor points 1 and 3, the load on the rope depends on the angle of the rope. I learned this back when I was a rock climber, or rather pretending to be one. If the angle is small, the load is smaller. If the angle is big, the load on the rope can actually be the full weight of the truck.
(https://climbtallpeaks.com/wp-content/uploads/2019/07/045-angle-between-anchors-1024x579.jpg)
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For anchor points 1 and 3, the load on the rope depends on the angle of the rope. I learned this back when I was a rock climber, or rather pretending to be one. If the angle is small, the load is smaller. If the angle is big, the load on the rope can actually be the full weight of the truck.
(https://climbtallpeaks.com/wp-content/uploads/2019/07/045-angle-between-anchors-1024x579.jpg)
Yes , that is why all the drawings show ropes parallel to each other. If a rope were too much of a angle ,say to re direct the line to a different location , that line would offer no mechanical advantage as I understand it.
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The load value would be the same for each part of line you add, whether splitting the load over 2, 3, 4, or even 6 parts of line. Kinetic recovery ropes are high rated ropes designed to stretch with the intention of increasing the pull until the stretch relaxes, like mine is a 30K rope that can stretch 8ft so once its snugged up the rope will load up and stretch to compensate for necessary strain required for a given load. Soft shackles, recovery rings, and overrated ropes, synthetic winch lines and any other gear you use should be easily able to handle max load, working with minimums gets people hurt, the scenarios in hunter399 anecdotal scenario is hillbilly stupid stuff that gets people hurt, you dont jerk cable, intentional shock loading is stupid.
Well the example I gave was a truck rolling off a mountain.
Or pulling a tree out for firewood.
Shock loading is real bud.
You can go from a total safe situation to a total unsafe in a hurry.
Intentionally or not.
I can tell ya one thing ,I've broke my share of 10,000lb winch cables pulling firewood trees out.
I've also fixed said cables on the spot.
And continued pulling trees out.
I'll post a pic of a snatch block that's unbreakable at least with a pick up truck.
Nothing is intentional until you have to do it.
Trucks roll,sucked into mud,getting stuck is never intentional.
You can turn around at the end of the dirt road and drive off the edge just turning around.
When your in a jam,sometimes that hillbilly,fudd,stuff might save ya some walking.
All I was trying to say with my first post was.
Due to shock loading ,intentional or not.
I would want my anchor line rated for twice the amount my winch could pull.
Due to safety reasons of shock loading. Intentional or not.
I suppose you carry a tool that measures the amount of weight on the line at all times,then give up if your at max load. Ya that's not me.
Max load and minimum load can change real quick.
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https://www.bing.com/videos/search?q=mechanical+advantage+of+pulleys+explained+winching&&view=detail&mid=BC0FD99D779AB4811CDBBC0FD99D779AB4811CDB&&FORM=VRDGAR&ru=%2Fvideos%2Fsearch%3Fq%3Dmechanical%2Badvantage%2Bof%2Bpulleys%2Bexplained%2Bwinching%26FORM%3DVDRESM
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For anchor points 1 and 3, the load on the rope depends on the angle of the rope. I learned this back when I was a rock climber, or rather pretending to be one. If the angle is small, the load is smaller. If the angle is big, the load on the rope can actually be the full weight of the truck.
Yes , that is why all the drawings show ropes parallel to each other. If a rope were too much of a angle ,say to re direct the line to a different location , that line would offer no mechanical advantage as I understand it.
Yeah, my problem is that the trees are never in the right spot like the diagrams. :chuckle: Or there are no trees except the one that is 8" too far away.
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For anchor points 1 and 3, the load on the rope depends on the angle of the rope. I learned this back when I was a rock climber, or rather pretending to be one. If the angle is small, the load is smaller. If the angle is big, the load on the rope can actually be the full weight of the truck.
Yes , that is why all the drawings show ropes parallel to each other. If a rope were too much of a angle ,say to re direct the line to a different location , that line would offer no mechanical advantage as I understand it.
Yeah, my problem is that the trees are never in the right spot like the diagrams. :chuckle: Or there are no trees except the one that is 8" too far away.
EXCEPT on the wet side... on the dry side COILS of line are necessary!
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Good feedback and anecdotes.
So when looking for anchor material, do you buy for working load or max breaking load?
As in, a snatch block may have a 10 ton working load limit and a 15 ton max breaking load. If you need, say 12 tons for an extraction, would this block work? I am assuming not.
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The 12 tons would include whatever safety margine you build in....
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Good feedback and anecdotes.
So when looking for anchor material, do you buy for working load or max breaking load?
As in, a snatch block may have a 10 ton working load limit and a 15 ton max breaking load. If you need, say 12 tons for an extraction, would this block work? I am assuming not.
It’s possible I think. But I would add another block. A block working load should equal the load.Add a second block and you are covered as I see it. :dunno: That’s what I would do.
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Good feedback and anecdotes.
So when looking for anchor material, do you buy for working load or max breaking load?
As in, a snatch block may have a 10 ton working load limit and a 15 ton max breaking load. If you need, say 12 tons for an extraction, would this block work? I am assuming not.
It’s possible I think. But I would add another block. A block working load should equal the load.Add a second block and you are covered as I see it. :dunno: That’s what I would do.
Don't ask what I would do. :chuckle: :chuckle: :chuckle: :chuckle:
If that block is from hobo frieght ,I wouldn't push it too far past the limit. :chuckle: :chuckle: :chuckle: :chuckle:
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It's not really rocket science, use tree anchors and blocks you couldn't possibly break, and bag the winch line or at least stand well clear.
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It's not really rocket science, use tree anchors and blocks you couldn't possibly break, and bag the winch line or at least stand well clear.
Ding ding ding.
No one stands outside the truck.
Getting firewood your in
the truck when I'm pulling stuff.
Plus sometimes I will pull stuff down the road if there is a shady spot close by. :chuckle: :chuckle: :chuckle: :chuckle:
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I guess I am just looking for the principles so I can make good decisions.
I hear folks say they want a margine of 3x for anchors and i see two ratings on materials. How are those folks calculating 3x? WLL or MBL?
I also understand from my rock climbing days that there is an anchor that is perfect, and one that is good enough. In other words you can add more gear and improve the security of an anchor but that comes at the expense of gear and time. Or you can build something that will sustain a fall factor of 2 with some margine and call it good.
I see people making a judgement call based on experience and since i dont have the depth of many on here, i don't yet trust my judgement so I need to know the principles.
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You can winch yourself out with two logs and a rope :chuckle:
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You can winch yourself out with two logs and a rope :chuckle:
Some that trusty paracordage. :chuckle: :chuckle: :chuckle:
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I guess I am just looking for the principles so I can make good decisions.
I hear folks say they want a margine of 3x for anchors and i see two ratings on materials. How are those folks calculating 3x? WLL or MBL?
I also understand from my rock climbing days that there is an anchor that is perfect, and one that is good enough. In other words you can add more gear and improve the security of an anchor but that comes at the expense of gear and time. Or you can build something that will sustain a fall factor of 2 with some margine and call it good.
I see people making a judgement call based on experience and since i dont have the depth of many on here, i don't yet trust my judgement so I need to know the principles.
I would trust your judgement
Only you know what your truck wieght,winch,all that.
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Ok. Thanks anyways!
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If i can find a good resource on the physics of these systems I will post it.
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I guess I am just looking for the principles so I can make good decisions.
I hear folks say they want a margine of 3x for anchors and i see two ratings on materials. How are those folks calculating 3x? WLL or MBL?
I also understand from my rock climbing days that there is an anchor that is perfect, and one that is good enough. In other words you can add more gear and improve the security of an anchor but that comes at the expense of gear and time. Or you can build something that will sustain a fall factor of 2 with some margine and call it good.
I see people making a judgement call based on experience and since i dont have the depth of many on here, i don't yet trust my judgement so I need to know the principles.
Go try it. Get a buddy set up couple winching scenes and try it before you need it. Than carry what works for you.
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The science stuff ....
All I know is every time you loop through a block you reduce what your winch pulls by almost half.
You see a crane with a block and the cable loop though a few pully on a single block.
Same principle winch on crane is only gonna lift so much.
So you increase lift,pull,whatever that way.
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I guess I am just looking for the principles so I can make good decisions.
I hear folks say they want a margine of 3x for anchors and i see two ratings on materials. How are those folks calculating 3x? WLL or MBL?
I also understand from my rock climbing days that there is an anchor that is perfect, and one that is good enough. In other words you can add more gear and improve the security of an anchor but that comes at the expense of gear and time. Or you can build something that will sustain a fall factor of 2 with some margine and call it good.
I see people making a judgement call based on experience and since i dont have the depth of many on here, i don't yet trust my judgement so I need to know the principles.
Go try it. Get a buddy set up couple winching scenes and try it before you need it. Than carry what works for you.
:yeah:
Try it first is a great idea.
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Definitely plan on trying all this out once I understand the basics (and get the winch mounted!)
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The science stuff ....
All I know is every time you loop through a block you reduce what your winch pulls by almost half.
You see a crane with a block and the cable loop though a few pully on a single block.
Same principle winch on crane is only gonna lift so much.
So you increase lift,pull,whatever that way.
Cryder Science ? :chuckle:
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Working my way thru this article. pretty good so far.
https://www.steelsoldiers.com/upload/misc/FM20-22.pdf
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The science stuff ....
All I know is every time you loop through a block you reduce what your winch pulls by almost half.
You see a crane with a block and the cable loop though a few pully on a single block.
Same principle winch on crane is only gonna lift so much.
So you increase lift,pull,whatever that way.
Cryder Science ? :chuckle:
Only other science I know .....
Is Cryder Science... :chuckle: :chuckle: :chuckle:
Load your truck with firewood and that cable will break a lot faster. :chuckle: :chuckle: :chuckle: :chuckle:
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Don't let em give ya guff hunter399, you prolly got more experience dragging things with cable than they'll ever have :chuckle:
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Don't let em give ya guff hunter399, you prolly got more experience dragging things with cable than they'll ever have :chuckle:
No worries.
I'll be honest haven't broke a cable in awhile,but I have done it. It takes a lot of force to break a 10,000lb test winch cable.
My truck will barely do it empty,a lot of jerking ,and a lot of shock loading to do it.
I can't tow any trailers,the ball on my hitch is bent down ,for some reason. :chuckle: :chuckle: :chuckle:
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Don't let em give ya guff hunter399, you prolly got more experience dragging things with cable than they'll ever have :chuckle:
No worries.
I'll be honest haven't broke a cable in awhile,but I have done it. It takes a lot of force to break a 10,000lb test winch cable.
My truck will barely do it empty,a lot of jerking ,and a lot of shock loading to do it.
I can't tow any trailers,the ball on my hitch is bent down ,for some reason. :chuckle: :chuckle: :chuckle:
My back license plate is caved in for some reason....
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Don't let em give ya guff hunter399, you prolly got more experience dragging things with cable than they'll ever have :chuckle:
No worries.
I'll be honest haven't broke a cable in awhile,but I have done it. It takes a lot of force to break a 10,000lb test winch cable.
My truck will barely do it empty,a lot of jerking ,and a lot of shock loading to do it.
I can't tow any trailers,the ball on my hitch is bent down ,for some reason. :chuckle: :chuckle: :chuckle:
My back license plate is caved in for some reason....
:chuckle: :chuckle: :chuckle:
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Not to thread jack here.
It seems to me that when a cable breaks it whiplashes some. But when you break a chain ,that sucker always and I mean always comes back and hits the truck.
Anybody have similar experience.....
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Not to thread jack here.
It seems to me that when a cable breaks it whiplashes some. But when you break a chain ,that sucker always and I mean always comes back and hits the truck.
Anybody have similar experience.....
Hunting buddy has a pretty impressive divot in the tailgate of his truck from a shackle.
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Don’t forget to think outside of the box! One time up in the Quilcene mountains, I’d gotten a little squirrely in my YJ and went off the road on the downhill side, with both driver’s side tires well off the road. Before I had a winch. Before I had lockers. Well, I’m a long ways from help.
I takes inventory of what I always have in my rig. I had regular shackles, a skookum haywire block, my spare 661 saw and a half section of haywire that I’d spliced eyes to. I formulated a plan.
I fastened the hindu end of the strawline to the passenger side front shackle, crossed the road and climbed a good sized hemlock, up high enough to help me out, around the tree, and back to the Jeep, creating two lines. Next I cut a good stout green limb and cut a twister stick, put it between the lines and twisted until I got some tension on the lines and put the long end of the stick against the road bed to hold my stick and tension.
I fire up my saw, grab a wedge and put an uphill quartering face cut in that hemlock. I remember watching the kerf wanting to start sit back on my saw and if that happens, I really stuck then! But I pop a wedge in, give er a few taps and down goes the tree, and up onto the road goes my Jeep.
Use your head!
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I don’t know if it applies to recovery, but out in the woods, you always rig a shackle with the pin to the yarder, or the pin towards people and stuff, and the shackle itself on the other side. So if anything happens, only the pin flies, not the shackle itself
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OK, I think I have the principle I was looking for in scenario three above from that link I sent:
Situation 3:
Load: 8,000 lbs
# of snatch blocks: 2
Total load 8,000+1600 = 9600
Load per line: 9,600/3=3,200
Load on Winch: 3,200 lbs
Load on Anchor 1: 6,400 lbs
Load on Anchor 3: 6,400 lbs
Load on Anchor 1: 3,200 lbs
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I don’t know if it applies to recovery, but out in the woods, you always rig a shackle with the pin to the yarder, or the pin towards people and stuff, and the shackle itself on the other side. So if anything happens, only the pin flies, not the shackle itself
Brilliant. and I like using the tree felling to extract your vehicle.
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Don't forget to paint them with a color that stands out. Nothing worse than chasing a pin in the snow or a dirt road.
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OK, I think I have the principle I was looking for in scenario three above from that link I sent:
Situation 3:
Load: 8,000 lbs
# of snatch blocks: 2
Total load 8,000+1600 = 9600
Load per line: 9,600/3=3,200
Load on Winch: 3,200 lbs
Load on Anchor 1: 6,400 lbs
Load on Anchor 3: 6,400 lbs
Load on Anchor 1: 3,200 lbs
What's the additional 1600# from?
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OK, I think I have the principle I was looking for in scenario three above from that link I sent:
Situation 3:
Load: 8,000 lbs
# of snatch blocks: 2
Total load 8,000+1600 = 9600
Load per line: 9,600/3=3,200
Load on Winch: 3,200 lbs
Load on Anchor 1: 6,400 lbs
Load on Anchor 3: 6,400 lbs
Load on Anchor 1: 3,200 lbs
What's the additional 1600# from?
Tackle resistance.
From that link:
18. Tackle Resistance
Due to friction created by a sheave rotating on its
pin, flexing of the rope around the sheave, and
the rope scuffing in the groove of the sheave, there
is a loss in energy as the rope passes around the
sheave. This loss is considered as resistance because it must be overcome before the resistance
of the load can be overcome. Each sheave in the
rigging will create resistance. The rule to determine tackle resistance is: 10 percent of the load
resistance times the number of sheaves (not
blocks) in the rigging. As an example, a load resistance of 30,000 pounds and a tackle with 3
sheaves is being used, 10 percent of 30,000 pounds
equals 3,000 pounds, times 3 (3 sheaves) equals
9,000 pounds tackle resistance
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Short answer is, count the # of snatch blocks, and add 10 of load for each one.
Two snatch blocks on an 8K lb load = +20%, or 1,600 lbs.
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OK, I think I have the principle I was looking for in scenario three above from that link I sent:
Situation 3:
Load: 8,000 lbs
# of snatch blocks: 2
Total load 8,000+1600 = 9600
Load per line: 9,600/3=3,200
Load on Winch: 3,200 lbs
Load on Anchor 1: 6,400 lbs
Load on Anchor 3: 6,400 lbs
Load on Anchor 1: 3,200 lbs
What's the additional 1600# from?
Tackle resistance.
From that link:
18. Tackle Resistance
Due to friction created by a sheave rotating on its
pin, flexing of the rope around the sheave, and
the rope scuffing in the groove of the sheave, there
is a loss in energy as the rope passes around the
sheave. This loss is considered as resistance because it must be overcome before the resistance
of the load can be overcome. Each sheave in the
rigging will create resistance. The rule to determine tackle resistance is: 10 percent of the load
resistance times the number of sheaves (not
blocks) in the rigging. As an example, a load resistance of 30,000 pounds and a tackle with 3
sheaves is being used, 10 percent of 30,000 pounds
equals 3,000 pounds, times 3 (3 sheaves) equals
9,000 pounds tackle resistance
This sounds about right to me.👍
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So circling back to my original set of questions:
Variables:
Load 4 Tons (8,000 lbs)
Tackle resistance (10% of load per snatch block sheave)
Max Winch pull (6 tons, 12,000 lbs)
Pull per line = total load with resistance / # of lines
Load per anchor = load per line * # of lines to anchor
Situation 1: Single Line:
Mechanical Advantage = 1:1
Load on Winch: 8,000 lbs
Load on Anchor: 8,000 lbs
Situation 2:
Mechanical Advantage = 2:1
load: 8,000 lbs
# of snatch blocks: 1
Total load: 8,800 lbs
Load per line: 4,400 lbs
Load on the Anchor: 8,800 lbs
Load on the winch: 4,400
Load on the truck anchor shackle: 4,400
Total load on the truck itself across all anchor points: 8,800
Situation 3:
Load: 8,000 lbs
# of snatch blocks: 2
Total load 8,000+1600 = 9600
Load per line: 9,600/3=3,200
Load on Winch: 3,200 lbs
Load on Anchor 1: 6,400 lbs
Load on Anchor 2: 3,200 lbs
Load on Anchor 3: 6,400 lbs
Total load on vehicle (3,200+6,400)=9,600
Consequently, if you move anchors 1 and 2 to the same tree, the tree will see 9,600 lbs of pull with 3,200 of the pull being felt by Anchor 2 and 6,400 being felt by anchor 1.
So if you have a weak link in anchor material, put it on anchor 2….
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And if you are looking for a 3x margin for anchor materials, then in the situations above, approx. 30K would give you that. (Still not clear if you want 30K in WLL or MBL)
however, if you are dealing with a slope or mire situation, then the load penalties add up fast...
Grade resistance: max resistance is the weight of the load
Overturning resistance: should be estimated as = to 1/2 of the vehicle weight
Mire resistance:
• Wheel depth = 1x load
• Fender depth 2x load
• Cab depth 3X load
Taking into consideration that pulling an 8K lb vehicle across flat, smooth ground will only require about 800 lbs of pull. So honestly, if a truck weighs in at 8K, and is mired in mud to the wheels, then the numbers of my 3 scenarios above would work out. otherwise, I would be way over winched (which is good news).
If mired to the fenders, then 8K becomes 16K plus tackle resistance, so I would have to use a 2:1 or 3:1 system and consider the loads being put on anchors and anchor gear very carefully.
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Situation 3 with max winch pull of 12,000 lbs (load would need to be 10K lbs with tackle resistance of 20% (10,000*1.2 = 12,000)
Each line would be pulling 12K (6 Tons)
This would put:
• 24K on anchor 1
• 12K on anchor 2
• 24K on anchor 3
• Total pull on the truck would be 36K! That could very easily pull a bumper off, or destroy a winch mount.
A suppose a way to throttle the power of the winch is to leave layers of line on the spool.
Layer 1: 12,000 (100%)
Layer 2: 9,517 (79%) (approx. full weight of truck is 8,500)
Layer 3: 7,885 (66%)
Layer 4: 6,732 (56%)
Leaving 3 full layers on the spool and starting your winching on the 4th layer would reduce the 36,000 pull down to around 20,200 lbs. If that is spread with the winch mount taking 6732 lbs and a frame mounted tow hook taking 13,464 lbs that would help reduce risk if you are worried a deeply mired extraction might exceed working capacities of your rigging.
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Careful out there
https://www.bing.com/videos/search?&q=removing+stumps+with+block+and+tackle&view=detail&mid=16D367DA5FA1404476DD16D367DA5FA1404476DD&form=VDMCNR&ajaxhist=0&rvsmid=614AA48F75A260B37A12614AA48F75A260B37A12
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https://www.bing.com/videos/search?&q=pulling+stumps+with+snatch+blocks&docid=608050245879618448&mid=C4729FA4A65E46B2432BC4729FA4A65E46B2432B&view=detail&form=VDMCNR&rvsmid=529A6A72DA0D50D429C5529A6A72DA0D50D429C5&ajaxhist=0
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So circling back to my original set of questions:
Variables:
Load 4 Tons (8,000 lbs)
Tackle resistance (10% of load per snatch block sheave)
Max Winch pull (6 tons, 12,000 lbs)
Pull per line = total load with resistance / # of lines
Load per anchor = load per line * # of lines to anchor
Situation 1: Single Line:
Mechanical Advantage = 1:1
Load on Winch: 8,000 lbs
Load on Anchor: 8,000 lbs
Situation 2:
Mechanical Advantage = 2:1
load: 8,000 lbs
# of snatch blocks: 1
Total load: 8,800 lbs
Load per line: 4,400 lbs
Load on the Anchor: 8,800 lbs
Load on the winch: 4,400
Load on the truck anchor shackle: 4,400
Total load on the truck itself across all anchor points: 8,800
Situation 3:
Load: 8,000 lbs
# of snatch blocks: 2
Total load 8,000+1600 = 9600
Load per line: 9,600/3=3,200
Load on Winch: 3,200 lbs
Load on Anchor 1: 6,400 lbs
Load on Anchor 2: 3,200 lbs
Load on Anchor 3: 6,400 lbs
Total load on vehicle (3,200+6,400)=9,600
Consequently, if you move anchors 1 and 2 to the same tree, the tree will see 9,600 lbs of pull with 3,200 of the pull being felt by Anchor 2 and 6,400 being felt by anchor 1.
So if you have a weak link in anchor material, put it on anchor 2….
There's only 1 line though, and its still 8000lbs, -10% after each block.
Don't go by what you think the load is, but total rated capacity. The load will be highly variable. I wouldn't even include the load in your equations, it'll either pull, or it won't.
When winching you only add blocks if the last method failed.
Direct pull = fail
Add block, did it pull?
Dig :chuckle:
I don't really see a whole lot of situations going more than one block, you'll run out of line and gear quickly.
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So circling back to my original set of questions:
Variables:
Load 4 Tons (8,000 lbs)
Tackle resistance (10% of load per snatch block sheave)
Max Winch pull (6 tons, 12,000 lbs)
Pull per line = total load with resistance / # of lines
Load per anchor = load per line * # of lines to anchor
Situation 1: Single Line:
Mechanical Advantage = 1:1
Load on Winch: 8,000 lbs
Load on Anchor: 8,000 lbs
Situation 2:
Mechanical Advantage = 2:1
load: 8,000 lbs
# of snatch blocks: 1
Total load: 8,800 lbs
Load per line: 4,400 lbs
Load on the Anchor: 8,800 lbs
Load on the winch: 4,400
Load on the truck anchor shackle: 4,400
Total load on the truck itself across all anchor points: 8,800
Situation 3:
Load: 8,000 lbs
# of snatch blocks: 2
Total load 8,000+1600 = 9600
Load per line: 9,600/3=3,200
Load on Winch: 3,200 lbs
Load on Anchor 1: 6,400 lbs
Load on Anchor 2: 3,200 lbs
Load on Anchor 3: 6,400 lbs
Total load on vehicle (3,200+6,400)=9,600
Consequently, if you move anchors 1 and 2 to the same tree, the tree will see 9,600 lbs of pull with 3,200 of the pull being felt by Anchor 2 and 6,400 being felt by anchor 1.
So if you have a weak link in anchor material, put it on anchor 2….
There's only 1 line though, and its still 8000lbs, -10% after each block.
Don't go by what you think the load is, but total rated capacity. The load will be highly variable. I wouldn't even include the load in your equations, it'll either pull, or it won't.
When winching you only add blocks if the last method failed.
Direct pull = fail
Add block, did it pull?
Dig :chuckle:
I don't really see a whole lot of situations going more than one block, you'll run out of line and gear quickly.
There is 4 pages of "white board cyphering". If I saw you in the ditch, it's a simple let's see what we can do. I would try and get you out. instead of burning daylite.
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Thanks for the links Ghost, good stuff.
My main interest is trying to understand the principles behind all this, gear selection, and I have been wondering how to determine impact of pull on anchors.
Real life would be more along the lines of try direct pull and see if that works, then add a block, etc as mentioned. If I need to winch, I won't be breaking out the pen, paper and calculator. But being aware of potential danger points associated with excessive load on inadequate anchors seems like a wise bit of education to have.
Ihave built a lot of climbing anchors and trusted them with my life - but I was sure to understand the principles first!
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Thanks for the links Ghost, good stuff.
My main interest is trying to understand the principles behind all this, gear selection, and I have been wondering how to determine impact of pull on anchors.
Real life would be more along the lines of try direct pull and see if that works, then add a block, etc as mentioned. If I need to winch, I won't be breaking out the pen, paper and calculator. But being aware of potential danger points associated with excessive load on inadequate anchors seems like a wise bit of education to have.
Ihave built a lot of climbing anchors and trusted them with my life - but I was sure to understand the principles first!
I am in the process of real life trail right now. I decided to take on a large Mt. Ash stump in my front yard. I could have it ground down but figured since I am retired I would see what a 71 year old guy could do with it.
I dug two feet deep around it today.
The stump is 3 ft across and the root ball is 10 ft across.
I hooked my truck to it straight pull and just tugged on it some while a buddy watched . No joy.
He said it rocked a little but not much. We figure it has about 800 lbs of dirt on it. So tomorrow I am going to try to get the dirt off the back side and lighten it up.
Than I am going to position my drop gate trailer next to it and try to winch up into the trailer with one block. Add blocks as needed.
I will be using my portable winch rated 2K straight pull.
I will post how it goes. Might take me a few days.
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Sounds like you need some giant powder. Or a hoe
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You are going to need a lot more blocks and rope ! I've done some big stumps and pulled out with a truck and snatch strap after a lot of digging - figure 30,000 lbs.
Problem is wood has a tensile strength of about 4000 psi - that means a 2" root can resist 12000 lbs before breaking.
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You are going to need a lot more blocks and rope ! I've done some big stumps and pulled out with a truck and snatch strap after a lot of digging - figure 30,000 lbs.
Problem is wood has a tensile strength of about 4000 psi - that means a 2" root can resist 12000 lbs before breaking.
Yeah I knew it would be a chore. But I am stubborn. My plan is to dig as much dirt as I can from under it tomorrow than give it a try. If that doesn’t work I will Witt let it down with my chain saw. Stand by.
MT. Ash does not appear to have a tap root. I am fairly confident that I got all the roots cut today. The tree was dying and we had it cut down two years ago. It did sprout some shoots.But the large roots 6 inch or more were all rotted.
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Rob you are on the right track with things, here are a few principles that may help you out:
1) an easy way to determine mechanical advantage is to count the lines attached to the moving load(you are correct in your number of parts in your example)
2) safe working load, or working load limit is the only number that matters in rigging and choose your components accordingly. Pay attention as slings and such have a different rating in choked/basket/straight configurations.
3)10% friction per block is a good rule of thumb, however it builds as your rigging moves through the blocks..ie a three parted 8000# Load will have 2666 + 2932 on block/anchor 1; 2932 + 3225 on block /anchor 2.
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You guys are all over thinking this stuff. Get the best mount and heaviest winch needed for your rig and probable scenario(s), have good quality straps and shackles, a good block and use your head. Are you going to do math or get unstuck? You going home or staying the night? Chances are, you are gonna get good and stuck where you may not be able to pull this up. Maybe you won’t be able to rig up like the examples because of trees or rocks or whatnot. Unless you are getting wicked out there wheeling, or over driving your ability, most recoveries are pretty straight forward. Don’t get yourself jammed up to begin with.
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So to move an 8000# load in this scenario assuming 10% each block friction:
Winch pulls 2666 lbs
Anchor 1 has 5598 lbs
Anchor 2 has 6157 lbs
Anchor 3 has 3225 lbs
Truck bumper sees 8823 lbs
Obviously your not going to do the math in the field, however having a real understanding of how things work will keep you out of trouble :tup:
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F=W divided by MA
F= force
W = weight
MA = Mechanical Advantage
:chuckle:
Failure= Experience
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You guys are all over thinking this stuff. Get the best mount and heaviest winch needed for your rig and probable scenario(s), have good quality straps and shackles, a good block and use your head. Are you going to do math or get unstuck? You going home or staying the night? Chances are, you are gonna get good and stuck where you may not be able to pull this up. Maybe you won’t be able to rig up like the examples because of trees or rocks or whatnot. Unless you are getting wicked out there wheeling, or over driving your ability, most recoveries are pretty straight forward. Don’t get yourself jammed up to begin with.
I think you are not getting the reason behind this thread. Its not about breaking out a slide rule in a snow storm on the side of a mountain and spening 30 min calculating the most efficient rigging to extract a rig while it slowly sinks in quicksand. I was wanting to understand the physics behind the basic rigging setups so that i can better understand how to avoid doing something stupid in the field.
Overloading an anchor can destroy equipment and even be fatal so I thought it would be good to spend some time understanding how it all works and sharing what I learned
So for the record I am definitely overthinking it right now!
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So to move an 8000# load in this scenario assuming 10% each block friction:
Winch pulls 2666 lbs
Anchor 1 has 5598 lbs
Anchor 2 has 6157 lbs
Anchor 3 has 3225 lbs
Truck bumper sees 8823 lbs
Obviously your not going to do the math in the field, however having a real understanding of how things work will keep you out of trouble :tup:
I don't think in those terms
Winch can pull 8000
Therefore the blocks and rigging need to be 50,000 lbs :chuckle:
Done!
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Thanks highclimber, appreciate the info.
Regarding Working load limits, here is what I settled on: pick gear with a WLL equal to or greater than the force you expect to see. The Max breaking load is your margin for safety.
In other words, if you expect to see 9 tons on a snatch block, get one with a 10 Ton WLL. If the Max Breaking limit is 15Tons, then your safety margin is 6 tons.
Would you agree?
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WLL is set by the industry and regulators. A snatch block with a WLL of 10,000 pounds has a new ultimate strength of 30,000 or 50,000 pounds (3x or 5x)
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I pulled the wll and mbl numbers off the first 10 ton snatch Block I found on Amazon. Probably picked a bad example as I though MBL was on the order of 3-5x as you noted.
SALMAN 10 Ton Aluminum Wheel Snatch Block Offroad Recovery Winch Accessory https://a.co/d/6dtrhDX
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Harbor Freight 24k snatch block
https://www.harborfreight.com/forged-snatch-block-58175.html?utm_source=google&utm_medium=cpc&utm_campaign=17890472041&campaignid=17890472041&utm_content=140972254553&adsetid=140972254553&product=58175&store=3293&gclid=EAIaIQobChMIlNn2zPP6-wIVnBetBh0zsQRWEAQYAiABEgKgSPD_BwE
Amazon 38k rope shackle
https://www.amazon.com/Shackle-Synthetic-Breaking-Strength-Ramsey/dp/B07GR3ZNXB/ref=asc_df_B07GR3ZNXB/?tag=hyprod-20&linkCode=df0&hvadid=312123707036&hvpos=&hvnetw=g&hvrand=9389632968651862774&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=1024413&hvtargid=pla-592063441177&psc=1&tag=&ref=&adgrpid=58868508141&hvpone=&hvptwo=&hvadid=312123707036&hvpos=&hvnetw=g&hvrand=9389632968651862774&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=1024413&hvtargid=pla-592063441177
Winch to snatchblock at tree anchor and back to truck anchor. Good for 99% of your winching.
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I'll just confuse ya ,spin this way around. :chuckle: :chuckle:
If you split some firewood ,and block up all four tires,does your anchor need to be as strong...... :chuckle: :chuckle:
Chew on this one.. :chuckle: :chuckle:
Do I even need an anchor....lol,😆 :chuckle: :chuckle:
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If you are putting wheel blocks under a vehicle you are trying to pull out, you have bigger issues than the strength of the anchor it is attached to!!!
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I pulled the wll and mbl numbers off the first 10 ton snatch Block I found on Amazon. Probably picked a bad example as I though MBL was on the order of 3-5x as you noted.
SALMAN 10 Ton Aluminum Wheel Snatch Block Offroad Recovery Winch Accessory https://a.co/d/6dtrhDX
A manufacturer can use any safety factor they want, but OSHA is very strict in their definitions and regulations.
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gotcha. makes sense.
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Oh man, I don't think I'd use china stuff :o
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Thanks highclimber, appreciate the info.
Regarding Working load limits, here is what I settled on: pick gear with a WLL equal to or greater than the force you expect to see. The Max breaking load is your margin for safety.
In other words, if you expect to see 9 tons on a snatch block, get one with a 10 Ton WLL. If the Max Breaking limit is 15Tons, then your safety margin is 6 tons.
Would you agree?
Yes that is a good line of thinking.
Also WLL or SWL is different for different components of rigging, they have different safety factors (shackles, slings, blocks, wire rope vs fiber rope etc)
Also, I guarantee that the winch line on your 12k winch isn’t rated for 12k lbs… probably closer to 2,500 or 3,000 FYI. Most times when your stuck it won’t be an issue because the actual pull required might be less than that if it’s just a traction issue. but if you are buried pretty good, consider starting with at least a 2 parted recovery to save your winch line.
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Also, I guarantee that the winch line on your 12k winch isn’t rated for 12k lbs… probably closer to 2,500 or 3,000 FYI.
All the 12k winch synthetic ropes have breaking strength over 12k. A typical quality 3/8” rope has a minimum breaking strength of 17,800 lbs. You could actually squeeze by with a quality 5/16 but I would stick to 3/8”.
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Also, I guarantee that the winch line on your 12k winch isn’t rated for 12k lbs… probably closer to 2,500 or 3,000 FYI.
All the 12k winch synthetic ropes have breaking strength over 12k. A typical quality 3/8” rope has a minimum breaking strength of 17,800 lbs. You could actually squeeze by with a quality 5/16 but I would stick to 3/8”.
Agreed, but we are talking safe working loads not breaking strength :tup:
14,200 is also very common breaking strength for 3/8 EIPS wire rope, 5:1 safety factor puts it at 2840 SWL
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Thanks highclimber, appreciate the info.
Regarding Working load limits, here is what I settled on: pick gear with a WLL equal to or greater than the force you expect to see. The Max breaking load is your margin for safety.
In other words, if you expect to see 9 tons on a snatch block, get one with a 10 Ton WLL. If the Max Breaking limit is 15Tons, then your safety margin is 6 tons.
Would you agree?
Yes that is a good line of thinking.
Also WLL or SWL is different for different components of rigging, they have different safety factors (shackles, slings, blocks, wire rope vs fiber rope etc)
Also, I guarantee that the winch line on your 12k winch isn’t rated for 12k lbs… probably closer to 2,500 or 3,000 FYI. Most times when your stuck it won’t be an issue because the actual pull required might be less than that if it’s just a traction issue. but if you are buried pretty good, consider starting with at least a 2 parted recovery to save your winch line.
Yes this and NO China stuff. Im a retired crane operator and Ive seen many rigging failures. Not to hijack, but FOR VEHICLE RECOVERY, as this seems to be mainly about, Im a fan of synthetic ropes, recovery rings, and soft shackles. I have half a dozen soft shackles and over 100ft of ropes plus heavy nylon straps and recovery rings. I have done winch less recoveries with comealongs. I have used winches, but dont have one myself (except on quad) because Ive learned to avoid most bad things. Good equipment is expensive but worth every cent if you need it. A winch isnt always useable and a large number of stuck vehicles usually only need the assistance of another truck to give them a tug. I always carry what I need to be extracted by another vehicle, and Ill say if you are exceedingly adventurous, Its always best to go with another rig. That being said, weve all been stuck on solos.
Because of my many years of work experience, I dont advocate used worn out cables, especially if theyve been repaired or spliced. You dont know how bad theyve yielded and you could easily end up injured. Besides, anything not certified and in new condition wasnt allowed on the jobs, by law.
If you look around on youtube theres tons of stuff on synthetic rigging, even making your own eyes and soft shackles, plus and accident with a steel shackle that was launched by a break in the rigging and went through the windshield and killed the driver. Another thing I didnt see mentioned is choking with cables. That significantly reduces their capacity.
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If you are putting wheel blocks under a vehicle you are trying to pull out, you have bigger issues than the strength of the anchor it is attached to!!!
Why would I put an anchor or wheel blocks on the vehicle your pulling out ,that's crazy.
And yes I would block the wheels on the vehicle with the winch ,doing the pull.
Let this blow your minds.
If I cut a block of wood 32in long ,basically twice the length of a piece of firewood. Split into quarter,snug them under the tires ,like a glove.
Do you think your winch is gonna have a harder time dragging that truck.
When you do that ,you making the surface area of your tires wider,and the firewood is gonna bite into the ground better than your tires ever will.
You should hook your winch to a tree,parking brake,emergency brake apply. Drag your truck a few feet.
Then do it block up as I described.
Tell me how much harder your winch had to work to pull it. :chuckle:
Like said in other comments.
There never is a tree where you need it to be.
You might have to compromise.
Your truck is an anchor,just have to figure out how to keep it from moving .
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No hunter uses overhead crane or man carrying 5:1 working load limit standards for vehicle recovery winches. An 18000 lb rope on a 12k winch is all you need. You don’t need or want a very short 60,000 lb rope on a 12,000 lb winch. Have winched out a 12,000 lb deuce and a half many times with a 5/16 cable.
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Puzzle for today.
I have a 2k portable winch.
Got to get this stump 2 ft out of the hole and up the ramp into my trailer.
Going to park the trailer hooked to the truck at the hole.
Anchor straps to the trailer frame and truck.
Run a snatch to the stump and back to trailer.
The winch will be 50 ft behind the stump hooked to a tree.
How many snatches will I need?
We will see.
Later.
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Puzzle for today.
I have a 2k portable winch.
Got to get this stump 2 ft out of the hole
How many snatches will I need?
Zero
You need a bonfire :fire.:
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Puzzle for today.
I have a 2k portable winch.
Got to get this stump 2 ft out of the hole and up the ramp into my trailer.
Going to park the trailer hooked to the truck at the hole.
Anchor straps to the trailer frame and truck.
Run a snatch to the stump and back to trailer.
The winch will be 50 ft behind the stump hooked to a tree.
How many snatches will I need?
We will see.
Later.
If no fire..
Don't do a direct pull. Wrap the chain around the stump down low as you can and put the tail of the chain opposite of the trailer, so the chain is up over the stump rolling it out instead of pulling it out
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Well the verdict is in.
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If you are putting wheel blocks under a vehicle you are trying to pull out, you have bigger issues than the strength of the anchor it is attached to!!!
Why would I put an anchor or wheel blocks on the vehicle your pulling out ,that's crazy.
And yes I would block the wheels on the vehicle with the winch ,doing the pull.
Let this blow your minds.
If I cut a block of wood 32in long ,basically twice the length of a piece of firewood. Split into quarter,snug them under the tires ,like a glove.
Do you think your winch is gonna have a harder time dragging that truck.
When you do that ,you making the surface area of your tires wider,and the firewood is gonna bite into the ground better than your tires ever will.
You should hook your winch to a tree,parking brake,emergency brake apply. Drag your truck a few feet.
Then do it block up as I described.
Tell me how much harder your winch had to work to pull it. :chuckle:
Like said in other comments.
There never is a tree where you need it to be.
You might have to compromise.
Your truck is an anchor,just have to figure out how to keep it from moving .
I was introducing humor to the thread since it was not clear what was being chocked... I don't know you but I am pretty sure you would not chock the wheels of the vehicle being extracted!
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Well the verdict is in.
You did that portable proud !
:tup:
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Well done!
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Well I had to change my original plan but all worked.
I dug around it. And dug around it more. Tried to straight pull with one block. The winch moved it in the hole but couldn’t drag it up the two ft lip.
Added another block at trailer near winch and ran back to stump and put a third block than back to winch.
That got it started and up to ramp.
I than took a blue 5000k strap and wrapped it Lower around the stump and connected it to the chain which I had in place already.
Pulled it right in the trailer with power to spare.
Although not sur how I will get out of trailer at the dump site. :dunno:
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One more
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If you are putting wheel blocks under a vehicle you are trying to pull out, you have bigger issues than the strength of the anchor it is attached to!!!
Why would I put an anchor or wheel blocks on the vehicle your pulling out ,that's crazy.
And yes I would block the wheels on the vehicle with the winch ,doing the pull.
Let this blow your minds.
If I cut a block of wood 32in long ,basically twice the length of a piece of firewood. Split into quarter,snug them under the tires ,like a glove.
Do you think your winch is gonna have a harder time dragging that truck.
When you do that ,you making the surface area of your tires wider,and the firewood is gonna bite into the ground better than your tires ever will.
You should hook your winch to a tree,parking brake,emergency brake apply. Drag your truck a few feet.
Then do it block up as I described.
Tell me how much harder your winch had to work to pull it. :chuckle:
Like said in other comments.
There never is a tree where you need it to be.
You might have to compromise.
Your truck is an anchor,just have to figure out how to keep it from moving .
I was introducing humor to the thread since it was not clear what was being chocked... I don't know you but I am pretty sure you would not chock the wheels of the vehicle being extracted!
I think he means if you're using your vehicle to pull another stuck vehicle out, using your truck as the anchor
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Yep
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I've slid my old Dodge lot's of times, holding the brakes, sliding all 4 tires winching.
I run my bumper up against a tree to anchor, or tie off to a tree. I prefer to run my bumper against something but its a buckstop type of deal, not factory, not squishy.
17,500lb winch
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That field manual link I posted had some interesting ways to improve holding power of the winching vehicle (deadmans, pickets, etc). More involved that what I would want to build unless i was in dire straights with no alternatives.
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Thanks highclimber, appreciate the info.
Regarding Working load limits, here is what I settled on: pick gear with a WLL equal to or greater than the force you expect to see. The Max breaking load is your margin for safety.
In other words, if you expect to see 9 tons on a snatch block, get one with a 10 Ton WLL. If the Max Breaking limit is 15Tons, then your safety margin is 6 tons.
Would you agree?
Yes that is a good line of thinking.
Also WLL or SWL is different for different components of rigging, they have different safety factors (shackles, slings, blocks, wire rope vs fiber rope etc)
Also, I guarantee that the winch line on your 12k winch isn’t rated for 12k lbs… probably closer to 2,500 or 3,000 FYI. Most times when your stuck it won’t be an issue because the actual pull required might be less than that if it’s just a traction issue. but if you are buried pretty good, consider starting with at least a 2 parted recovery to save your winch line.
Yes this and NO China stuff. Im a retired crane operator and Ive seen many rigging failures. Not to hijack, but FOR VEHICLE RECOVERY, as this seems to be mainly about, Im a fan of synthetic ropes, recovery rings, and soft shackles. I have half a dozen soft shackles and over 100ft of ropes plus heavy nylon straps and recovery rings. I have done winch less recoveries with comealongs. I have used winches, but dont have one myself (except on quad) because Ive learned to avoid most bad things. Good equipment is expensive but worth every cent if you need it. A winch isnt always useable and a large number of stuck vehicles usually only need the assistance of another truck to give them a tug. I always carry what I need to be extracted by another vehicle, and Ill say if you are exceedingly adventurous, Its always best to go with another rig. That being said, weve all been stuck on solos.
Because of my many years of work experience, I dont advocate used worn out cables, especially if theyve been repaired or spliced. You dont know how bad theyve yielded and you could easily end up injured. Besides, anything not certified and in new condition wasnt allowed on the jobs, by law.
If you look around on youtube theres tons of stuff on synthetic rigging, even making your own eyes and soft shackles, plus and accident with a steel shackle that was launched by a break in the rigging and went through the windshield and killed the driver. Another thing I didnt see mentioned is choking with cables. That significantly reduces their capacity.
I also run cranes and do rigging. If any components are not labeled or have China on them they get tossed.
I would use a lot of them for home stuff under some circumstances.
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Almost all logging cable is made in Korea and China. A little from Mexico. Strawline, haul back, straps, choker bells, hindus, you name it.