Shackle ratings - part 2

[Jimbo]

The gremlin just munched me thread, right in front of my very eyes !, never fear - this hopefully, will be a 'copy & paste' of what was in it.

Did another recovery today - had to extract my mate, his Navara (on road tyres) and 16' Ifor car trailer from his waterlogged field - and whilst we were hooking up the Yellowstraps (pukka bits of gear I must say), it dawned on me that my shackles might not be up to the job.

The shackles are stamped "WLL 3/4" - does that mean 3/4 tonne, or am I being dim  

If they are 3/4 tonne rated, is that enough - or do I need meatier ones ?

Jim
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Tyke



Joined: 29 Nov 2005
Location: Skelmanthorpe, West Yorkshire, 53:35:29N 1:38:55W
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 Posted: Wed Jan 18, 2006 4:57 pm    Post subject:    

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Theoretical design capacity is normaly 5 times the Working Load Limit (WLL) for quality lifting shackles.

Your 3/4's would therefore be limited to 3.75Tonne but I still wouldn't like to trust them at that.
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Jake



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 Posted: Wed Jan 18, 2006 4:59 pm    Post subject:    

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I've got some 4 1/2tonne rated shackles.
So buy the above post, that means they are rated to 23 3/4 tonne?
Is that right?

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'Challenger' 1996 Land Rover Discovery 2.5 Tdi Es

[colintandy]

:(scared): now thats scary cos the yellow strap is probably rated at somethink like 55 tonne and the shackle you attached to vehicle has a 3.5 rate add a few more tonnage on the vehicle thats being recoverd and some when :(scared):  the shakkle breaks its like a flying bullet that will come through the rear window and front window and if you lucky it might stop when it hits a tree :(scared): i would suggest using a 5tonne rated shackle and higher ,normally when recovering a truck from the mud.ect you can quite easily be pulling a 10 tonne load depending on the severity of the ground and angle because of the resistance that gets in front of the wheels ect..

[Jimbo]

I guessed the shackles would be a bit on the weak side  :oops:

There's a Lifting-hire shop near here, they advertise/sell/hire cherry pickers and general site equipment - assuming that they sell shackles, is there any difference in a shackle sold for lifting, as opposed to towing ?

Jim

[thumbs]

they will be rated differently for lifting rather than towing, same shackle but will be lower rating for lifting, straps are done like this aswell, then it depends on if you double them up etc, bit complicated how it all works, should say on shackle what it will take.

shackles are normoally painted different colours for what they are rated at, the hire shop should be able to help you no probs.

made me think though, i bet mine are under rated for what i do with them.

[clips]

Another way for heavy work is to make a bridle and split the load between the shackles

[Jimbo]

OK, looked on the Sppedy Hire website - their shackles are 'SWL' rated, how does this differ from 'WLL' ratings ?

And final question in this series - what sort of rating should we be using ?

Jim

[colintandy]

:D its science all science  :D i would definetly start with 5 tonne rating and certanly look for other ways to lighten the load by either doubling up or bridling the chassis so as to pull from 2 good recovery points and to keep any snatching down to a minimum as this is when alot of breakages happen  :shock:

[Tyke]

i would definetly start with 5 tonne rating

I would agree on that Colin. They might be a bit bigger and heavier but better be safe than sorry. Picking up on what you said earlier about the strength of straps, then it makes sense to rate the shackles higher than the strap to avoid the possibility of the shackle breaking first. Seen flying shackles in my daily work as a mechanical engineer and trust me, they are pretty scary.

Would suggest being very carfull about where they are mounted as well. Seen more than just a bumper pulled off vehicles stuck in the gloop. Multi point mounting will spread the load and help in tricky situations to allow a better angle for the pull.

Finally be aware that some mountings will introduce a bending moment into the pin which can effectively multiply the forces applied to the shackle and pin by very large amounts. Always try to mount the shackle so it can 'turn and swivel' and allow the recovery load to be applied directly to the mounting points. It goes without saying that these should be sound and suitable for the loads expected. Swivelling blocks, as on your vehicle, and most others who have seriously considered recovery,  are the correct way but not always to be found on all vehicles, my own included at the moment, (But that will be changing shortly).

If in any doubt always err on the safe side and dont forget a blanket over the strap, rope or whatever to absorb the energy should the strap fail.

I know I'm 'preaching to the converted' on many things here but newcomers to the scene don't always recognise the dangers involved in recovery situations.

BE SAFE RATHER THAN SORRY

Cheers for listening guys - hope I havn't bored those who already know  

[Jimbo]

Thanks for all the useful info - much appreciated.

Time to go shopping for some 5T shackles !

Jim

[Lostboy]

Thinking of things breaking during recovery, has anyone got a copy of the video of the towing eye coming off the car when it was being recovered by a Rangie? Might be a useful thing to point people to when talking about making sure you have good kit...

[EvilEd]

I use 4.75t SWL shackles everywhere..... And a Bridle across the front of the Jeep..... then a 12t rated rope with a 8T rated Bridle.

Theory is..... Bridle breaks first, hopefully at an end so that it has to "Unspool" itself from the rope (Stopping the rope from springing back)
I do not use a shackle from the rope to the bridle.
Second weakest point is the rope, may spring back, but again, no shackles flying with it.
The shackles should be the strongest point. (Jst over 23t and split between two)

And if they don't have two recovery points available, I only tow them out at my discression  :twisted:

Wish I could find the site I read a year or so ago....
It read similar to....
on a 10% incline, you add 20% to the weight
On a non smooth surface (Gravel) add a further 10%
If stuck in mud add 200%
If stuck in mud down beyond axles add 400%
My jeep is 1.4t
So if my jeep is in a hole up to it's belly in mud, we're talking about a 7.7T smooth pull. Now look at the figures for a 110  :shock:
(I think these were the figures, will try to find the link again later)

Is your kit up to it ???

[EvilEd]

Not the place, but some heavy reading if you want to.....

http://www.pajero.dn.ru/book/rec.pdf

[Tyke]

Not the place, but some heavy reading if you want to.....

Heavy Reading? . . . . more like Essential Reading.

The maths and theory is just plain and simple mechanics . . . most gcse level schoolkids would understand it.

Nice find though, downloaded it to reference at my lesiure. Cheers for posting the link fella  

[Ja1983]

...which reminds me, i need to sort out some recovery points on the truck. i take it best option is something securley bolted to the chassis railes?

i have a proper toyoa tow bar thats gunna get butchered (the drop removed as it looses a foot of ground clearance) it hasa build in bumper (big tube section) is it worth welding some suitably rated..."thingys" on before i go for the powder coating? :?