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12th May 2018, 04:56 PM
#21
I am he, fear me
Originally Posted by
Mike02Ti
Just because your point is rated to 5000kg doesnt mean you can swing 5000kg off it.
Many other factors can come into play. Chassis strength and the actual condition (eg rust inside) of it being one.
Another is the other rigging gear your using like shackles , extension straps, the bolts holding the recovery point or anything else used in the recovery
Say for instance your 8000kg snatch strap is used off one 5000kg recovery point.
You connect to the bloke helping you out with a hitch reciever with a 4700kg shackle
Now on your recovery point you attach a 3200kg shackle. The whole system of rigging gear thst you have just attached is effectively rated at 3200kg as that is the weakest link. Hope this makes sense.
I have even seen recovery points put on with bog standard galvanised bolts. Bloke didnt know any different. They fit and screwed in and he used them not knowing they weren't rated for bugger all. All he said was they wont rust. So something else to check as your hooking up.
If you bridle it depending on the angle of the pull, one side of the chassis will load up more than the other if its anything other than a dead straight line pull.
Side loading may also play a factor depnding on the gear used.
Once extra angles come into play and side loading etc all these factors will reduce the SWL of the recovery. But yes a bridle should be used wherever possible on both cars , not just the one being recovered.
Its something to be very mindful of when doing these recoverys as the forces can be tremendous.
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Uuuummmm ... not quite.
You are mixing ratings.
Some of those components are rated at breaking strain (BS)... (EG the snatchie)
Some are rated at Working Load (WLL)... (EG the 3.2 Shackle)
The load limit of that rig in the example isn't necessarily 3200.
As when the BS of the 3.2 WLL shackle is taken so you compare apples to apples it is at least 4 times or as much as 7 times the WLL. IE the BS of the 3.2T rated shackle is a minimum of 13 ton.
The shackle will therefore be the strongest component not the weakest
The max rating of the rig in the example is 2.5 ton to 3.5 ton depending.
Reason is the lowest rated item is the tow bar the hitch receiver is attached too so depends on that
Dolphins are so smart that within a few weeks of captivity, they can train people to stand on the very edge of the pool and throw them fish.
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12th May 2018 04:56 PM
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12th May 2018, 05:54 PM
#22
Expert
Originally Posted by
the evil twin
Uuuummmm ... not quite.
You are mixing ratings.
Some of those components are rated at breaking strain (BS)... (EG the snatchie)
Some are rated at Working Load (WLL)... (EG the 3.2 Shackle)
The load limit of that rig in the example isn't necessarily 3200.
As when the BS of the 3.2 WLL shackle is taken so you compare apples to apples it is at least 4 times or as much as 7 times the WLL. IE the BS of the 3.2T rated shackle is a minimum of 13 ton.
The shackle will therefore be the strongest component not the weakest
The max rating of the rig in the example is 2.5 ton to 3.5 ton depending.
Reason is the lowest rated item is the tow bar the hitch receiver is attached too so depends on that
Not picking fights here , whilst you are correct in the breaking strain vs swl / wll you should never exceed the SWL of anything used. The safety factor is there for a reason.
Yes there is a safety factor that exceeds the SWL of a shackle. It does not mean you can use it up to breaking strain.
Snatch straps are totally different as they stretch. They should technically be thrown out after 8 to 25 uses due to the nature of them. Please note that figure depends on how well the strap is maintained as well as what the manufacturer recommends. They are also made to take a shock load for a very small period of time and not a constant load.
They can not be rated in the same way as a shackle or a normal soft sling or chain. This is why they have to be rated at breaking strain and not a SWL
Shackles can be used over and over again provided they are worn too much or warped / bent.
Try telling worksafe or a government body " oh i used the 3.2 t shackle over the SWL it is rated for then it let go and smacked that bloke in the head over there" and see what happens.
Any rigging job that is done (and this is exactly what you are doing in a recovery is rigging) should use the lowest rated component as the maximum weight. No matter what that component is or whether that component is rated at Breaking Strain or SWL/ WLL.
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12th May 2018, 06:47 PM
#23
I am he, fear me
Thats cool, gotta agree to disagree... IMHO recovery isn't rigging
Rigging is static and mostly a 'one off' operation, recovery is kinetic and often multiple steps.
As for the worksafe scenario (not that worksafe have any authority in recce applications but certainly get involved in workplace)... if a lift fails how do you explain to worksafe that 99% of riggers run a shackle up then back off a tad but the manuf states rated Shackles don't achieve WLL unless the pin is torqued down tight.
The reason a rated shackle is insisted upon in vehicle applications is to ensure component quality and not the rating per se.
Which is why shackles that are actually rated lighter than the load are specified in the towing safety chain regs.
EG the shackle stipulated under the Regs for up to 1600 Kg Load is 0.5T WLL and up to 3.5 ton load is 1.0T WLL and the various state Departments specify against Proof Load not WLL.
(QLD linky thingy but all states are the same now AFAIK) https://www.tmr.qld.gov.au/~/media/S...wing_guide.pdf
4WD Recovery wise, another example I show to students is an 8,000 Kg rated snatchie and an 8,500 rated shackle... it almost takes two people to lift the shackle.
But, the bottom line IMHO is always use what you know is safe and if in doubt don't... or at least video it for Utube
Dolphins are so smart that within a few weeks of captivity, they can train people to stand on the very edge of the pool and throw them fish.
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12th May 2018, 07:21 PM
#24
Legendary
If I may stick my nose in here ,whatever you use for the rating or SWL etc as you both have pointed out and done a great job of explaining but to the layman am I right or wrong in assuming there is no way of knowing what weight your playing with if the vehicle is bogged to the floor ?
Seems to me that in my example it would be almost impossible to determine the weight and therefore the Breaking strain required , which maybe why so many recoverys end in tragedy or near miss .
For me if I can't winch I dig and I'm an expert plus at getting bogged .
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12th May 2018, 07:31 PM
#25
Patrol God
All Ill say is because there is no actual off road recovery equipement . We as Aussies have adopted lifting equipment to do the job
This has been thrashed to death over the years, now the consensus is to winch if thats slower tuff titties , far safer than other ways that are
available. Think it trough and you might get home in one piece without a hole in your 4x4 or worse you its not rocket surgery be safe,, better than limping for the rest of your life ,,,,eg only
04 ST 3lt auto, not enough Mods to keep me happy, but getting there
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13th May 2018, 12:37 PM
#26
Expert
As far as rigging onsite yes many riggers usually seat the pin then back off 1/4 turn. If used like this the rigger and/ or the site the pin would be moused so that it does not come loose. Now i do know riggers who do this as thats how they were taught etc and i agree it is wrong.
Depending on who you ask the usual reason they give for backing off is to stop the pin from binding. The shackle should be derated when used like this though and again should be moused.
As far as a safety chain on a trailer that again is different to a recovery. I do remember a time where they didnt really have much of a regulation regarding this other than it needed to be there and connected to the vehicle. I also agree that using rated shackles was to control a quality issue of what was being used in the past. Same with T grade chain now being used. Yes they asses it this way to breaking strain instead of SWL
Im hoping you mean a much larger shackle that 8.5t though cos they only weigh about 2.5kg though.
The biggest issue there is, is that there is no set guidelines or rulings other than manufacturer recommendations.
Even Nobles guide on recovery is very basic. For those who dont know Nobles is a provider of rigging gear and NATA certified tester. So basically anything to do with loads they are the people to talk to.
Link to their guide.
https://www.nobles.com.au/Admin/Publ...are+in+Use.pdf
@GQtdauto yes there is no set calculations for you being bogged deep in mud, sand or any other way you can get stuck. Hence why these recoveries are so dangerous. Who knows if your vehicle is going to pop out nice and easy with a gentle pull or get hung up on that hidden tree trunk in the mud no one has noticed. Is your mate pulling you out slightly sideways from you and not dead straight on. This is exactly why i say recoveries are rigging as you should be derating gear due to the variables faced as well as having some understanding of angle factors, safe use of gear and the understanding of what may go wrong and how.shackle_side_load_chartandillustration.jpeg
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13th May 2018, 01:21 PM
#27
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Awesome information, Cheers All Blokes!!
I’m assuming “side loading” is why we should only ever use rated ‘bow’ shackles for recovery. Is it still ok to use rated ‘D’ shackles for trailer safety chains? Some trailer configurations we’ve got can’t seem to fit bows only longer shanked D’s I guess their called?
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13th May 2018, 01:28 PM
#28
Legendary
Originally Posted by
MB
Awesome information, Cheers All Blokes!!
I’m assuming “side loading” is why we should only ever use rated ‘bow’ shackles for recovery. Is it still ok to use rated ‘D’ shackles for trailer safety chains? Some trailer configurations we’ve got can’t seem to fit bows only longer shanked D’s I guess their called?
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I'm old enough to remember the pig tails that were welded to the tow bar , you just put the chain over that .
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13th May 2018, 01:39 PM
#29
Expert
Originally Posted by
MB
Awesome information, Cheers All Blokes!!
I’m assuming “side loading” is why we should only ever use rated ‘bow’ shackles for recovery. Is it still ok to use rated ‘D’ shackles for trailer safety chains? Some trailer configurations we’ve got can’t seem to fit bows only longer shanked D’s I guess their called?
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Bow shackles by design are made not only to fit wider straps / gear on them but to allow them to take a side load.
A D shackle should only be used straight on and are not designed for a side load.
Rated D shackles on a trailer are fine as as per what ET posted the link to above as long as its rated.
They say this:
"A Bow shackle will provide flexibility for greater angular movement compared to a “D” shackle."
So merely a recommendation that bow shackles should be used where possible.
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13th May 2018, 04:49 PM
#30
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Cheers Mike, ET’s kind link seems to error off my phone.
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