Winch Rigging and Anchor loads

[ghosthunter]

[High Climber]

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.

[MountainWalk]

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.

[High Climber]

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 

[ghosthunter]

F=W divided by MA


F= force
W = weight
MA = Mechanical Advantage

 


Failure= Experience

[Rob]

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!

[KFhunter]

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 

I don't think in those terms

Winch can pull 8000

Therefore the blocks and rigging need to be 50,000 lbs 

Done!

[Rob]

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? 

[Knocker of rocks]

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)

[Rob]

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

[Magnum_Willys]

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.

[hunter399]

I'll just confuse ya ,spin this way around.

If you split some firewood ,and block up all four tires,does your anchor need to be as strong......

Chew on this one..

Do I even need an anchor....lol,😆

[Rob]

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!!!

[Knocker of rocks]

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.

[Rob]

gotcha.  makes sense.