Winch Rigging and Anchor loads

[Rob]

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!

[hunter399]

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.

[KFhunter]

Shock loads is what your describing 

[KFhunter]

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.

[MountainWalk]

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

[KFhunter]

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

[Magnum_Willys]

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.

[buckfvr]

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.

[Stein]

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.

[ghosthunter]

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.

[hunter399]

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.

[ghosthunter]

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

[Stein]

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.   Or there are no trees except the one that is 8" too far away.

[Special T]

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.   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!

[Rob]

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.