Recovery 101 including acronyms and definitions

[weeds]

we will see how this rolls as recovery topics can get a bit heated......

this thread will kinda be like wikipedia where i will update post one once there is a concensus i.e. the number of thanks on each post

we need to keep it in laymans terms so that it is easy to read, understand and apply

we might start with acronyms

SWL - Safe Working Load
is the load that a piece of lifting equipment, lifting device or accessory can safely lift, suspend, or lower without fear of breaking. This should be mark on the equipment by the manufacturer. The SWL is calculated using a safety factor For example, 5:1 (5 to 1, or 1/5). An example of this would be a chain that has a MBL of 2000 lbs would have a SWL or WLL of 400 lbs if a safety factor of 5 (5 to 1) is used

WLL - Working Load Limit
which is the maximum working load designed by the manufacturer. The load represents a mass or force that is much less than that required to make the lifting equipment fail or yield, also known as the MBL The SWL is calculated using a safety factor For example, 5:1 (5 to 1, or 1/5). An example of this would be a chain that has a MBL of 2000 lbs would have a SWL or WLL of 400 lbs if a safety factor of 5 (5 to 1) is used

MBL Minimum Breaking Load
is the minimum load required to make the piece of equipoment fail

GBS Guaranteed Braking Strain
Is this the same as MBL?

[Hymie]

RecL Recovery Load. SWL refers to the working limit of equipment used to lift things off the ground.
The Recovery load, where a load is being pulled at an Angle less the 45 Degrees above the horizontal is usually the SWL Doubled, as the load is not leaving the ground it is not classed as lifting tackle.
Therefore, a shackle that is rated at 3.2 Tonnes for SWL can be safely used in Recovery situations up to 6.4 Tonnes, provided the load is not taken above 45 Degrees above the horizontal.

[Tank]

Hymie wrong, a SWL/WLL limit that is stamped/embossed on to a piece of lifting/recovery gear. is just that, regardless whether it is in the air or not. The SWL is the same no matter what it is used for, for instance a Guy Wire on a Mast or antennae has a SF of 2, if your scenario was correct it would have a SF of 1 because it is not lifting off the ground. Regards Frank.

[mools]

SF - Safety Factor

I dare not attempt a definition.

[Tank]

SF - Safety Factor

I dare not attempt a definition.
When a piece of rigging/recovery equipment is manufactured to comply with Australian Standards (AS....) it has to be "Rated" by a government approved Lab.
First the (say for instance a wire rope or sling) sling is stetched on a machine till it breaks, they do this a few times to establish the Guaranteed Breaking Strain, known as the GBS, lets say this GBS of this sling or any other rigging/recovery gear (whatever) is a known 10 tonnes.
Because wire rope can be used in many different applications a Safety Factor was introduced, for instance, General Purpose can be lifting slings or winch cables, where they are subjected to rough wear and tear, the SF is 5, so a 10 tonne GBS winch cable or sling has a SWL of 2 tonne. As stated in another post earlier in this thread the GBS lessens with every use/abuse, so the powers that be decided that a SF of 5 would keep us safe.
Other examples are Guy Wire/Standing rigging has a SF of only 2, because it is not dragged on the ground, overloaded or abused. Where as a Lift/Elevator that conveys People off the ground has a SF of 10, so if the SWL of the Lift is 5 tonnes than the cable must have a GBS of 50 tonnes.
The point is if you work within the SWL limits and maintain and regularly inspect your recovery equipment it should last a long time, abuse/misuse it and it could kill you, Regards Frank.

[Tank]

we will see how this rolls as recovery topics can get a bit heated......

this thread will kinda be like wikipedia where i will update post one once there is a concensus i.e. the number of thanks on each post

we need to keep it in laymans terms so that it is easy to read, understand and apply

we might start with acronyms

SWL - Safe Working Load
is the load that a piece of lifting equipment, lifting device or accessory can safely lift, suspend, or lower without fear of breaking. This should be mark on the equipment by the manufacturer. The SWL is calculated using a safety factor For example, 5:1 (5 to 1, or 1/5). An example of this would be a chain that has a MBL of 2000 lbs would have a SWL or WLL of 400 lbs if a safety factor of 5 (5 to 1) is used

WLL - Working Load Limit
which is the maximum working load designed by the manufacturer. The load represents a mass or force that is much less than that required to make the lifting equipment fail or yield, also known as the MBL The SWL is calculated using a safety factor For example, 5:1 (5 to 1, or 1/5). An example of this would be a chain that has a MBL of 2000 lbs would have a SWL or WLL of 400 lbs if a safety factor of 5 (5 to 1) is used

MBL Minimum Breaking Load
is the minimum load required to make the piece of equipoment fail

GBS Guaranteed Braking Strain
Is this the same as MBL?
SF for chains are different to wire/rope, usually a SF of 2.5 is used, all rated chains have the Grade/tensile rating marked on them, it can be on each link or spaced out evenly along the chain, never buy chain that has no stamped links, buy from rigging suppliers, they are usually made up or you can order to suit your needs, Regards Frank.

[Tank]

Quote: "MBL Minimum Breaking Load
is the minimum load required to make the piece of equipoment fail

GBS Guaranteed Braking Strain
Is this the same as MBL?"

I have no idea what MBL stands for, is it Max or Min and what do either mean, I think GBS is the easist to understand, Regards Frank.

[Hymie]

Hymie wrong, a SWL/WLL limit that is stamped/embossed on to a piece of lifting/recovery gear. is just that, regardless whether it is in the air or not. The SWL is the same no matter what it is used for, for instance a Guy Wire on a Mast or antennae has a SF of 2, if your scenario was correct it would have a SF of 1 because it is not lifting off the ground. Regards Frank.

Sorry Tank, I beg to disagree.
SWL only applies to loads lifted off the ground.
Source:
Australian Army Recovery Training Course handbook, craploads of course notes and tests and 16 years of doing it for a job.

( I think I know what I'm talking about)

[Tank]

Sorry Tank, I beg to disagree.
SWL only applies to loads lifted off the ground.
Source:
Australian Army Recovery Training Course handbook, craploads of course notes and tests and 16 years of doing it for a job.

( I think I know what I'm talking about)
So why don't they put 2 weights on recovery/rigging gear, SWL is the weight at which the item is subjected to Safely. Your statement makes out that something being dragged along the ground is half as heavy or that you can't be injured by an object on the ground.
Look go here
http://www.workcover.nsw.gov.au/formspublications/publications/Documents/rigging_guide_2005_005.pdf
and show me the item that backs up your statement, a shackle or a sling with SWL stamped on it doesn't know whether it's lifting something off the ground or not, it's all related to HOW much load is applied, Regards Frank.

[justinc]

Worth adding to Franks detailed post about Safety Factors, the ''crane code'' (Is it still called that?) IIRC lists seperate SF's for equipment used where personnel are involved like lifts, vehicle hoists and other items where people are working under or riding in an object suspended or lifted. The lift was the example that prompted this reply as you can see the SF is doubled effectively where passengers are involved. Our vehicle hoists have to comply similarly as we work under them, and they are considered a high use / wear item with a reasonably high duty cycle and varying loads.

Please correct anything above Frank, if you see anything you disagree with or can add as this is from memory and not up to date.

JC

[FeatherWeightDriver]

SF - Safety Factor

I dare not attempt a definition.

SF is a magic number that is used to divide the MBS to get SWL. ;)

There may or may not be a "standard" SF for certain types of gear in certain situations, but there is generally no standard SF for all of the pieces involved in a load chain, for example in a winch recovery the SF for the tree sling, shackle, pulley, cable, winch, winch bar, bolts used to attach the winch bar will almost certainly all be different.

Some manufacturers do not tell you what the SF on a specific piece of gear is, whilst others do (either by exposing the SF or MBS).

Per previous post the SF for applications with people in, on or under the load are generally double what you might see for applications where people are not in direct contact / near the load chain.

Knowing the SWL but not the SF / MBS is interesting, but not helpful if you want to really know how safe the whole load chain is.

Any time gear is used for life support / older / degraded / not used in the manner intended the SF should be increased accordingly (reducing the effective SWL), as failing to do this risks breaking the gear well under the SWL printed on the tin.

Flame suit on! :twisted:

[FeatherWeightDriver]

Quote: "MBL Minimum Breaking Load
is the minimum load required to make the piece of equipoment fail

GBS Guaranteed Braking Strain
Is this the same as MBL?".

The difference is CYA ;)

I suspect they are calculated the same, but the manufacturers who use MBL are removing any doubt or claim that they are guaranteeing the quoted number is right, as "guarantee" is a very specifically defined legal term... :angel:

[Blknight.aus]

we will see how this rolls as recovery topics can get a bit heated......

this thread will kinda be like wikipedia where i will update post one once there is a concensus i.e. the number of thanks on each post

we need to keep it in laymans terms so that it is easy to read, understand and apply

we might start with acronyms

SWL - Safe Working Load
is the load that a piece of lifting equipment, lifting device or accessory can safely lift, suspend, or lower without fear of breaking. This should be mark on the equipment by the manufacturer. The SWL is calculated using a safety factor For example, 5:1 (5 to 1, or 1/5). An example of this would be a chain that has a MBL of 2000 lbs would have a SWL or WLL of 400 lbs if a safety factor of 5 (5 to 1) is used

WLL - Working Load Limit
which is the maximum working load designed by the manufacturer. The load represents a mass or force that is much less than that required to make the lifting equipment fail or yield, also known as the MBL The SWL is calculated using a safety factor For example, 5:1 (5 to 1, or 1/5). An example of this would be a chain that has a MBL of 2000 lbs would have a SWL or WLL of 400 lbs if a safety factor of 5 (5 to 1) is used

MBL Minimum Breaking Load
is the minimum load required to make the piece of equipoment fail

GBS Guaranteed Braking Strain
Is this the same as MBL?

from the texts Im using

MBL can also be the Manufactured Breaking Load and its worked out off of a batch of items that are tested to destruction and the MBL is whatever the lowest failure point was. This is the number that you should be using to calculate out your SWL/WLL.

GBS is the highest of the same batch.

dont forget, on paper, when calculating WLL/SWL as soon as you have people in or on the gear being lifted/moved you are supposed to double the safety factor

Is there a difference between SWL and WLL? Yes.

The WLL is the maximum load that can be put onto and Item BEFORE the SWL is caculated and includes the Safety Factor.

Now to make it confusing......

Some companies have their gear marked with an SWL which is then fed through rigger maths to give you the WLL. Other companies will give you a WLL which is fed through rigger maths to give you an SWL. You can also use the provided SWL/WLL and come up with the Caclulated SWL/WLL

Better is some (most now) companies will give you a tag on the bit of kit that shows you all the permissible ways of using the bit of kit AND what the end result of the rigger maths is.

The current trend however is to have the WLL as the number that you use in rigger math to get to the Calculated WLL or SWL.

Hypothetical.

I have a Single leg sling that is 20 feet long and has a MBS (I prefer to use the MBS rather than the GBS) of 20000Kg. The standard safety factor for THIS particular type of sling is 5:1 this gives me a WLL of 4000KG. Basically this means that EYE to EYE on the sling I can safely put 4000KG of load

Now if I take that same sling and double it over then use it to lift up a round object I get a SWL of 8000KG

If I loop the sling back over itself to form a hitch I have to apply about a 25% reduction to the WLL to get the SWL so Im down to 3000kg

end hypothetical...

Heres a generic sling chart from a manufacturer that calculates out what you can do with various version of their slings
https://www.aulro.com/afvb/images/imported/2013/05/866.jpg

The WLL would be the vertical application and the SWL would be all the ones to the right of it. For a straight pull WLL=SWL

heres a sample of the kind of tag that would be on the sling itself
http://www.unirope.com/syntheticslings/images/sling_tag_c.jpg

This is usually what you find on a single leg chain or extension
https://www.aulro.com/afvb/images/imported/2013/05/867.jpg

in this case the WLL of the sling this is attached to needs to be used to calculate the SWL.

And this is whats usually on a premade chain sling.
https://www.aulro.com/afvb/images/imported/2013/05/868.jpg
all the gonkulating is done for you.

and heres a link to a page with piccy's that does a pretty good job of explaining it.

Rigging With Slings: Basic hitches, Working Load Limits, Sling angle, Reach (http://www.fdlake.com/rig-slng.html)

If the item you're using is something like a winch or a crane in effect the WLL and SWL are interchangable because they are the same value and what you name that value comes down to local legislation/manufactures preference and the whimsy of the local OH+S nut.

http://www.dotengineering.com.au/p7lsm_img_1/fullsize/5T_Mobile_Gantry_fs.jpghttps://www.aulro.com/afvb/images/imported/2013/05/869.jpg

other things you might see are
Maximum load (ML)
Capacity (CAP)
Rated To
Limit
Test load
Proof load


good luck.

[Hymie]

So why don't they put 2 weights on recovery/rigging gear, SWL is the weight at which the item is subjected to Safely. Your statement makes out that something being dragged along the ground is half as heavy or that you can't be injured by an object on the ground.
Look go here
http://www.workcover.nsw.gov.au/formspublications/publications/Documents/rigging_guide_2005_005.pdf
and show me the item that backs up your statement, a shackle or a sling with SWL stamped on it doesn't know whether it's lifting something off the ground or not, it's all related to HOW much load is applied, Regards Frank.

I'm just going by years of experience handed down since the Military started pulling stuff of Battlefields.
REME came up with the formulas for the use of Terminal Tackle, RAEME adopted it, I just worked with it and taught people how to use it in the recovery role and the lifting role.
Have a look here, page 52, right at the bottom. And have a look at the table, you will see that for recovery the SWL is X 2.

REME Recovery Manual (http://www.scribd.com/doc/33845487/REME-Recovery-ManualI'm) not trying to be a smart ass, but that's how it is.

[FeatherWeightDriver]

Interesting read, particularly the bit about recovery gear having a WLL but not a SWL. Thanks for the link.

The 2 x factor removal makes sense if the WLL was calculated with people in / on / under the load, and you are in a static load recovery situation where the only downside of breaking gear is broken gear.

Personally if people or property damage will result directly from recovery gear failure (and by that I mean cars rolling of cliffs and other such nastiness) I add another 2x or more to the stated factors.

Dynamic loading / recoveries is a whole other ball game...

[Hymie]

That's why the rule of thumb is 45 Degrees being the cutoff point when the TPR, (Total Pull Required), is calculated out.

[ecn226]

Seems Hymie and I learnt in the same place but we still used the recl on all recovery jobs regardless of the gradient. I do remember though that the gradient reistance formula changed to full cas. weight above 45 degrees.

[clubagreenie]

I agree that gear has, but not necessarily should have, a different SF for different applications. The same risks apply weather gear is carrying people or just materials. Should it fall the variables are how far [and so quantity of damage], direction of fall and associated spread of materials, subsequent potential of damage to other objects and structures and potential for injury/death. SF should assume worst case scenario, that would result in potential for death or injury. The flip side is that it would result [pending everyone following the rules] in requiring recovery gear that would be massively oversized.

Which is why for an un-suspended load I think there is room for an alteration of the safety factor. But there should be no such thing as a safety factor of 1. This would just result in people self assessing a non need for safety and using devices at the limit of their strength. Similar to what I've seen when the safety factor is displayed and what it is known. If the device is rated to 2000kg and 5:1, the device is simply treated as a 10,000kg object.

Devices should be marked at their factored rated stength. Documentation should note detail such as MBS, SF etc but this info should not be marked on the gear, those that would use stuff to it's absolute limit are probably most likely not to read the book either.


Acronym.
AFD: Absolute ****in Dickhead; Someone who uses in a way that I don't like [I]and cannot justfy reasonably why.

I.E. If Tank or Hymee were to do something I didn't like they'd [and fairly and reasonably] explain why and I would probably defer to them [especially if made sense] but I'd hope that there would be two way communication and I could give & ask opinion and feedback on my thoughts of doing it differently.

Try doing this with (and generalising here) Toyota, Nissan etc but especially Rodeo/Hilux drivers. Jeeps seem to be ok.

[Tank]

My point is that as the GBS/MBS/???, changes downward (diminshes) from the first use, so it is impossible to know what the GBS etc. is after say 3 months hard use, is it now 1/2 of what it was or has it only lost 5% of it's capacity, only way to tell is break it in a Lab test.
That's why SF's are used for different work situations and onlySWL/WLL's should be used as the max. weight lifted or pulled, no other method is safe, Regards Frank.

[FeatherWeightDriver]

Acronym.
AFD: Absolute ****in Dickhead; Someone who uses in a way that I don't like [I]and cannot justfy reasonably why.

lol nice catch.

One of my pet hates is people standing way too close to recoveries / winching, or being in the "line of fire" if something lets go.

Particularly when you watch spectators at comps on a certain 4wd tv show :angel:

[Hymie]

lol nice catch.

One of my pet hates is people standing way too close to recoveries / winching, or being in the "line of fire" if something lets go.

Particularly when you watch spectators at comps on a certain 4wd tv show :angel:

Oh I just love watching those 4WD how to videos when they start winching and have some poor bugger standing next to a live winch rope while it is winching and they are moving the Recovery Damper along the rope so it doesn't foul in Snatch blocks or winch Fairleads.
Just get the hell out of the danger arc FFS.

[GlennWA]

Just researching this myself and came across the thread that is reasonably current

I do note that no mention of Australian Standards has occurred. For your info:

Shackles AS2741-2002. The design factor for shackles is 6. Therefore a grade S 16mm shackle with a WLL of 3.2T must have minimum breaking strength of 19.2T. Shackles must also be ductile and deform before failing. The proof test for this particular shackle is 6.4T and it must be proven to pass without deformity and with continued serviceability.

Lifting Chain AS2321-2006. Using 8mm Grade T (80) (800MPa) chain with a WLL of 2 tonne as an example. The WLL is based on a factor of 4. Again there is an elongation minimum requirement before failure. This chain has a breaking load test of 8.2T and a proof test of 4.1T.

To throw a spanner in the works you can compare a similar strength chain that is used under a different standard

Transport Chain AS4344-2001. Using 8mm Grade 70 (700MPa) chain with a lashing capacity (LC) of 3.8T. Note no reference to WWL. The LC and the WLL can not be compared directly as there are different design factors. In this case the minimum breaking strength is 7.5T. The proof test is to a minimum of 50% of this (3.75T). All chain is tested to this proof test and must be free from imperfection etc. Note that the breaking strength is inline with the reduction in tensile strength of the material from 800MPa to 700MPa but there are different testing requirements and load ratings.

The physics are the same. It is just the application of quality control processes and design factors that change in accordance with the use of the equipment.

If you have read this far it's time for the pearler. there is NO recovery standard. There are NO recovery rated points. If there is please tell me the standard that the manufacturer has rated these against. The best guide for recovery has been mentioned and has been developed over numerous years - that is the recovery mechanic's handbook or its fore-bearers.

The handbook mentions that chains and shackles have a safety of factor of 2 in the recovery role. i.e. 8mm grade 70 chain is 3.8T and a 16mm grade S shackle is 9.6T but it is common to just multiply the WLL of shackles x 2. The reasons for the reduced safety factor are the gradual take up of tension and the conservative estimates of the total pull required (TPR) calculations used in the handbook.

TPR is a series of calculations that take into account the ground, slope and vehicle condition. A worst case scenario for my 110.

Bogged in mud over the axles with a 110 at GVM gives a rolling resistance of 1500kg.

A 30 degree gradient gives an additional 1500kg. (mud uphill??)

A busted wheel gives an additional 250kg.

The safety factor is an additional quarter of the running total - 812kg

The Total Pull required is the overall sum which is just under 4100kg.

A 16mm grade S shackle and 8mm grade 80 chain would suffice according to my calculations.

The handbook does not mention kinetic recovery (snatch straps). Speaking to a 20+ year very senior recovery mechanic the forces are simply unknown and there is no design factor or safety factor that can be reasonably applied.

I did pick up a snatch strap however due to their convenience and ability to smooth out shock loads when used with common sense. If I ever need to use a snatch strap in anger (driving away at full blast with plenty of slack) I will revert to a winch and shovel - its safer.

I also opted for some 8mm Grade 70 drag chain given the unlikelihood of the above scenario and the price difference for grade 80 for only 14% increase in outright strength. Interestingly enough a lot of the recovery kits on the market come to a similar conclusion.

Hope that may be of use to someone

Cheers

Glenn

[clubagreenie]

I love going into stores and asking what standard their "rated" gear is tested to.

I like the TPR rating system, it seems to be a reasonable estimation of additional loading by type of additional load.

I've been looking st some Rudd rotating points to replace the fixed eye bolts I have, for size (to fit the holes I currently have) and they out rate what I currently have but are $135- each and are pink.

Conversely the specialist I buy through are of the opinion that given the size of the eye bolt and shackle which allows angular movement without loading of the shackle pin was fine. As pictured, this is the maximum deflection of the shackle when used with the equaliser strap.

https://www.aulro.com/afvb/images/imported/2014/08/464.jpg

Interested in Tanks opinion as to wether or they are too deflected (the pin end of the shackle does not actually make contact with the flange end of the eyebolt). The included angle of the strap is below the maximum allowed to maintain the straps rating.
http://imageshack.us/photo/my-images/39/l1ff.jpg/

[FeatherWeightDriver]

Assuming the yellow webbing in that last pic is sitting at the load bearing angle then I agree that setup is not doing the recovery point and shackle any favours. Assuming the inside of the recovery point is rounded and not a tube, the shackle pin is too big.

I would not be comfortable using that setup for a recovery as pictured. Even if the numbers printed on each piece of gear are very large, that setup is not loading the hardware in the way it was designed to be used, and certainly not the way in which it was tested.

Why not rotate the recovery point 90 degrees (until the recovery point looks like an O looking from above) so the shackle rotates freely to align to the equaliser strap load?

Then again, even if you rotate the recovery point you will still have the same loading problem if you ever need to set up your recovery pull more than about 10 degrees above or below the line of the car chassis.

[Tank]

Assuming the yellow webbing in that last pic is sitting at the load bearing angle then I agree that setup is not doing the recovery point and shackle any favours. Assuming the inside of the recovery point is rounded and not a tube, the shackle pin is too big.

I would not be comfortable using that setup for a recovery as pictured. Even if the numbers printed on each piece of gear are very large, that setup is not loading the hardware in the way it was designed to be used, and certainly not the way in which it was tested.

Why not rotate the recovery point 90 degrees (until the recovery point looks like an O looking from above) so the shackle rotates freely to align to the equaliser strap load?

Then again, even if you rotate the recovery point you will still have the same loading problem if you ever need to set up your recovery pull more than about 10 degrees above or below the line of the car chassis.
A swivel eyebolt is the ideal and a vertical pin axis is the way to go, in most cases of recovery using strap/cable/rope and shackle with the shackle pin vertical the tower/towee is usually on the same plane as the towed, i.e. the same hill/gradient. a misaligned shackle being used contrary to it's design parameters can easily become the weakest link in the recovery set-up and you don't want to be standing near a flying shackle part, FWD you will find that a shackle in a vertical pin situation (depending on the size of the collared eye bolt hole) will rotate much more than 10 degrees before binding, as stated a swivel eye-bolt is the go, Regards Frank.

[clubagreenie]

The strap isn't indicative of the actual angle when under load. I was trying to hold the strap & shackle at the correct angle (it's pictured at slightly more than when in use) while being rained on. When at the correct angle the shackle isn't making contact with the collar of the eye bolt nor is the outer side of the shackle sitting loaded against the eye.

Frank, in a vertical pin setup why is i that you can achieve more than 10deg rotation before binding but not in a horizontal setup? Or am I reading it wrong?

[Tank]

As I said it depends on the size of the hole, bigger the better, and when you think about it unless you were at the bottom of a vertical climb, why would you need to angle the shackle up, there is always the option of turning the eye to face horizontal if that was the case, but in normal winching up a hill don't see the problem, Regards Frank.

[FeatherWeightDriver]

Frank, in a vertical pin setup why is i that you can achieve more than 10deg rotation before binding but not in a horizontal setup? Or am I reading it wrong?

Try this next time it is not raining... ;)

Set up your shackle and sling as you did for the picture.

1) Pull the sling tight directly behind the recovery point. Now walk the sling left and right and see how far it goes before it binds. IT will get to the point in your picture and bind.

2) Pull the sling tight directly behind the recovery point. Now lift the end of the sling higher and drop it lower and see how far it goes before it binds. You will be able to get the sling directly above / below the recovery point and the shackle will still not bind.

[FeatherWeightDriver]

As a picture is worth 1000 words, for the avoidance of doubt...

https://www.aulro.com/afvb/images/imported/2013/06/221.jpg

So even if the shackle does not bind in the previous picture, loading that way is "not recommended"

[FeatherWeightDriver]

Bolt shear strength table:

Newcastle High Tensile Bolt Company :Home Page (http://www.hi-tensilebolt.com.au/Shear%20Met.html)

Bolt breaking load table:

Newcastle High Tensile Bolt Company :Home Page (http://www.hi-tensilebolt.com.au/Breaking%20-%20Metric.html)

[FeatherWeightDriver]

Interesting discussion of a number of recovery related topics, including how much force is actually required / generated in real life recover situations (hint - LOTS!)

Pirate4x4.Com - Extreme Four Wheel Drive (http://www.pirate4x4.com/tech/billavista/Recovery/)

[Islandnomad]

Wouldn't this issue go away if you reversed the shackle ie had the bow end in the eye bolt and the shackle pin in the equaliser loop? I suppose you would still have to rotate the eye bolt 90 degrees so it wouldn't bend, but it would be a better setup. I think?

[cuppabillytea]

Sorry Tank, I beg to disagree.
SWL only applies to loads lifted off the ground.
Source:
Australian Army Recovery Training Course handbook, craploads of course notes and tests and 16 years of doing it for a job.

( I think I know what I'm talking about)
Tank is right. You wouldn't want to be anywhere near a peace of gear when it fails under heavy load. Every action has an equal and opposite reaction. I know a few people who can give first hand accounts of what that feels like,(The ones who lived that is). It doesn't matter what direction the force is in. The result is the same.

[NesserJo]

Very useful info on this thread