Shackle strength physics

[ahmadtaha1988]

Hi all,

If a soft shackle is rated for 12,000 pounds what exactly does that mean....?

Does it mean if you dangle 12,000 lbs from it it wont break...?

How does that translate to force when we talk about vehicle recovery?

Say said shackle is being used to recover a 5000 pound vehicle that is burried down deep. The rope is attached to a 10,000 pound vehicle that accelerates to 20 miles per hour and this is not sufficient to pull the car out, thus the shackle ends up being subject to this force.

Surely this force is proportional to the speed and mass of the pulling car (even to the square of speed). We can calculate the force applied by the pulling car using its speed and mass, but how does that translate to something that can be compared to the rating of the rope which is in lbs... would be comparing newtons to lbs...

The background is that I had a soft shakle break leading to a an accident that took put my mirror, beat me up a bit, and beat up the exterior of the car.

Thanks

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[wibornz]

A 12,000 pound soft shackle is rated pretty low. All of mine are rated over 32,000 pounds.

 

[cOtter]

I agree with Ted. Appears that you may have been using a shackle not intended for the load possibly necessary to recover a vehicle.

 

[Ratbert]

Are you talking minimum breaking strength (MBS) or work load limit (WLL)? If both aren't listed then find another manufacturer.

 

[DonH63]

Hitting a shackle, any shackle, with a 10,000 pound vehicle accelerating at 20 mph is likely to break it. F = m*a is in general a dynamic force while shackles are rated for static force (breaking strength or load limit).

1 lbf (pound-force) is about 4.5 N

 

[Zandcwhite]

I want to see the 10,000lb recovery vehicle that accelerates to 20mph in the ~5-15 feet of slack you should have in a recovery rope? If you where using a tow strap and not a kinetic strap you shouldn't be shock loading it period. If you were using an actual kinetic recovery rope or strap, the stretch helps to lessen the loading of the shackles and recovery points. If you were shock loading your soft shackle to the point of failure I'd say you're lucky it broke and only cost you a mirror as you'd be hard pressed to find a recovery point rated for more than 10k pounds on most vehicles. A winch blanket or heavy jacket over the rope can help with the whip in a failure, but I'd argue you were yanking too hard and sometimes a shovel is necessary vs more skinny pedal in a recovery situation.

 

[Old Jeeper]

Hi all,

If a soft shackle is rated for 12,000 pounds what exactly does that mean....?

Does it mean if you dangle 12,000 lbs from it it wont break...?

How does that translate to force when we talk about vehicle recovery?

Say said shackle is being used to recover a 5000 pound vehicle that is burried down deep. The rope is attached to a 10,000 pound vehicle that accelerates to 20 miles per hour and this is not sufficient to pull the car out, thus the shackle ends up being subject to this force.

Surely this force is proportional to the speed and mass of the pulling car (even to the square of speed). We can calculate the force applied by the pulling car using its speed and mass, but how does that translate to something that can be compared to the rating of the rope which is in lbs... would be comparing newtons to lbs...

The background is that I had a soft shakle break leading to a an accident that took put my mirror, beat me up a bit, and beat up the exterior of the car.

Thanks

Generally speaking there are 2 numbers on each rope, pulley or what ever.

1) Working Load Limit: Max safe working load

2) Breaking Strength: Point of expected failure

Rule of thumb is max safe working load is 1 / 3 of you Point of expected failure.

All this is based upon new equipment, time and use can degrade these numbers significantly.

If your 12,000 lb number = Breaking Strength, then you max Working load would be rated at 4000 lbs or 1 / 3rd of its Breaking strength.


Soft shackles: Friends don't let Friends do Soft Shackles, the first word in Soft Shackles is SOFT!

If you have ever worked around very heavy equipment, like 60+ tons and seen what can happen trying to extract that you would never buy a soft shackle which by the way, degeriates starting on day 1 from UV, use , rocks, metal shackles you name it.


Ohh but my Jeep only weight 4500 lbs and it will never exceed the working rate of 12,000 lbs...RIGHT?

WRONG. Mr SOFT Richard man. Lets say you have a 2 door and the back of your jeep behind the foot wells if 4' x 4' and you just got stuck up to your fenders in goopy mud. How much weight is now sitting in the back of your Jeep?

Multiple Choice:

1) None, I have nothing in the back of my Jeep

2) Got my tools and ice chest and stuff for a week of wheeling, about 1000 lbs

3) 338,688 lbs

If you guessed 338,688 lbs you guessed RIGHT!

So my BiL we are out with his group of Mud Wheelers and he gets his Chevy Blazer stuck to the fenders from taking a different path thru a swamp. None of them could get him out.

BiL Calls a HD wrecker. FAIL. Wrecker guy knows another HD Wrecker guy and and calls he arrives and the 2 of them FAIL. NOTE its a straight pull as they cannot get close enough to lift and pull.

I suddenly ask my BiL if he has battery power drill in that tool box? He say yes, then do you have a ½ in or bigger drill bit? YES!

I wade over thru the muck and start drilling holes in the bed. IIRC I drilled about 24 spreading across the 4 x 6 ft area.

Wrecker pulled him out. Weight of AIR at Sea Level is 14.7 lb per square inch. Drill the holes allow air to come in as it was being pulled and that is how you extract and BREAK the vacuum in a muck deep truck.

 

[fspalt]

Yes please be careful out there! This thread always comes to mind when people start asking these questions. Everyone always wants to lend a hand but best to avoid getting involved if you don't know what you are doing / the risks involved.

https://www.jlwranglerforums.com/fo...connection-to-matts-off-road-recovery.111084/

 

[Old Jeeper]

Yes please be careful out there! This thread always comes to mind when people start asking these questions. Everyone always wants to lend a hand but best to avoid getting involved if you don't know what you are doing / the risks involved.

https://www.jlwranglerforums.com/fo...connection-to-matts-off-road-recovery.111084/

VERY good comment!


I have seen a lot of accidents over the years, most start out small and minor, no one is hurt, just some help and a winch or a strap and it will all be fine.

THEN, Jerry Jeeps Be Me comes running along with his running buddy, Woody Winch. Those 2 come in screams we are here to save you. Their winch line is broken strand wire, don't get near it. The rest of the gear when scrape off the rust is stamped CHINA. They will attach to any part of your Jeep that can get a shackle on. Fenders, bumpers, grill guards , tie rods, you name it and its not off limits.

As soon as they show I walk away and don't come back..

Saw Jerry and Woody hook on to a trailer ball and it snapped and flew thru the windshield killing a passenger.

Seen them tie 2 pieces of cable together to make a longer one, tie failed and Jerry got wrapped up in his own cable, could have been worse, could have put out his eye.

I used to recommend to people buy a winch, changed my mind, for many, it will only lead to something between a minor issue and catastrophic results!

Now when the Jerry-Woody show starts I give some one the number for Angel Flight and I drive off....

 

[Ratbert]

Rule of thumb is max safe working load is 1 / 3 of you Point of expected failure.

Maybe I'm paranoid, but I wouldn't buy from a vendor that uses a divisor of 3 to calculate work load limit. 4 seems to be a much more appropriate divisor to give you a reasonable set of expectations.

 

[thance]

Hi all,

If a soft shackle is rated for 12,000 pounds what exactly does that mean....?

Does it mean if you dangle 12,000 lbs from it it wont break...?

How does that translate to force when we talk about vehicle recovery?

Say said shackle is being used to recover a 5000 pound vehicle that is burried down deep. The rope is attached to a 10,000 pound vehicle that accelerates to 20 miles per hour and this is not sufficient to pull the car out, thus the shackle ends up being subject to this force.

Surely this force is proportional to the speed and mass of the pulling car (even to the square of speed). We can calculate the force applied by the pulling car using its speed and mass, but how does that translate to something that can be compared to the rating of the rope which is in lbs... would be comparing newtons to lbs...

The background is that I had a soft shakle break leading to a an accident that took put my mirror, beat me up a bit, and beat up the exterior of the car.

Thanks

Based on your info above you are looking at about 133000 foot pounds.

https://www.omnicalculator.com/physics/kinetic-energy?c=USD&v=mass:10000!lb,velocity:20!mph

 

[J0E]

Are you talking minimum breaking strength (MBS) or work load limit (WLL)? If both aren't listed then find another manufacturer.

The best vendors list MBS and WLL but they also charge double. I use these $25/pair SS, 1/2", rated at 57K BS (and that is BS, that's probably average BS at best). I've done several hard yanks with my 1.25" Bubba kinetic rope. My 1.25" Bubba is twice the size and twice the BS as what most folks buy (7/8").

With any recovery, plan for the worst. Even if these SS break, nobody gets injured and there's no damage.

 

[Ratbert]

The best vendors list MBS and WLL but they also charge double. I use these $25/pair SS, 1/2", rated at 57K BS (and that is BS, that's probably average BS at best). I've done several hard yanks with my 1.25" Bubba kinetic rope. My 1.25" Bubba is twice the size and twice the BS as what most folks buy (7/8").

With any recovery, plan for the worst. Even if these SS break, nobody gets injured and there's no damage.

I personally wouldn't buy something as critical as this from a seemingly randomized-name Amazon-only company that apparently doesn't even have a web site. They don't even have sufficient budget to hire a decent Chinese to English translator for their "Strong than Metal" product. Thanks, but no thanks.

And I'm pretty sure the better vendors charge a hell of a lot more than double those prices.

 

[J0E]

I personally wouldn't buy something as critical as this from a seemingly randomized-name Amazon-only company that apparently doesn't even have a web site. They don't even have sufficient budget to hire a decent Chinese to English translator for their "Strong than Metal" product. Thanks, but no thanks.

And I'm pretty sure the better vendors charge a hell of a lot more than double those prices.

Can't blame you for that, but it's 1/2" rope, heavier than the name brand. And rope is a commodity that a Chinese company can buy the same rope as Bubba. And I use them expecting them to fail so no one can be hurt. But I've yanked hard enough to break a 7/8" yankum kinetic rope and the SS held.

I've got a pair in each of my 3 Rubicons and another pair in my recovery bag.

 

[wibornz]

Soft shackles can take hard hit and heavy pulls, if you buy a quality ones. Your typical hard shackle D-Ring that you see on Jeeps are usually rated at 18,000 pounds. The ones I use are rated at 32,000 pounds.

I do carry a hard shackle with me because there are times that there is nowhere to hook a soft shackle to because of sharp edges.

If you watch Matts Off Road Recovery Youtube channel, you will see him hook soft shackles to Class A motorhome and at times semi trucks and pull them out of mud and sand. He also does hard runs to the end of his kinetic rope while doing these recoveries.


The secret is to buy quality products. Recovery gear is not a place you want to pinch pennies.


Jump to the fifteen minute mark to see the rescue.

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