Gu recover points

[Mike02Ti]

Heres a screen shot of it relating to the shackles and chain


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[the evil twin]

For those occasions when 8,000 Kg straps just aren't enough...

Snatch equip1.JPG

[BillsGU]

It's complicated. Yes, there are formulas for recovery. They take into account weight being recovered, rolling resistance, terrain type, terrain angle, and a couple of other variables. The result is the pulling force required to get the crock out of where it is stuck. Army recovery mechs have used these formulas for many years. These calculations allow them to plan their recovery wrt equipment required, pull ratio, etc.

As far as equipment rating is concerned, ET is correct IMHO. All rated recovery equipment is rated for lifting and includes large safety margins. It has been determined by the recovery industry (again mainly driven by the Army at the time) that these large safety margins are unworkable and unnecessary. Again ET is correct in stating that using lifting rating for recoveries (here we are talking trucks, tanks and vehicles with serious weights) it would be impossible for even two people to lift the equipment. (Even then, the Army's recovery tank has a "small" winch installed to allow the main winch cable, connected to the "BIG" winch, to be pulled into place).

For this reason it was determined that recovery equipment would be rated by using 50% of the oringinal breaking strain. (An example would be a shackle with a one ton SWL and a safety factor of five would have a BS of 5 Ton. The recovery industry would use this 1 Ton shackle for a 2.5 Ton recovery).

It has been many years since I have done this type of training and things may have changed, however, if you correctly use rated equipment, the chance of it failing would be close to zero. Also, as I have stated in previous posts, you should always use a snatch strap no higher than 8000 kg for normal vehicle recovery. This ensures that the snatch strap is the "fuse" in the system and if all else fails, it will break before bits are torn off a vehicle.

[Bidja]

Have been reading thru and I would imagine that a BS or SWL would be the component that is rated at this certified working load condition. I would assume there would be a design safety factor built in on top of these limits, eg: static general design say 2.5:1 or for dynamic 5-10:1 depending on the operating environments and the potential risk and impact of failure.

[the evil twin]

Have been reading thru and I would imagine that a BS or SWL would be the component that is rated at this certified working load condition. I would assume there would be a design safety factor built in on top of these limits, eg: static general design say 2.5:1 or for dynamic 5-10:1 depending on the operating environments and the potential risk and impact of failure.

Pretty much...

A goodly amount of equipment which we use/borrow/pinch for recovery operations is manufactured to a Standard (A.S. in most cases) EG Rated Shackles.
Ergo Shackles are rated for lifting, tow bars are rated for towing etc.
None of these components are required by their A.S. to be rated/tested/manuf for recovery, there is no point as that is not the manuf intended use.

Soooo, some Standards work brilliantly for recovery use IE Shackle A.S. and some are absolute shit IE the Tow Ball A.S.
The Standard may or may not apply safety factors and again purely as an example in Shackles it will be 4 to 8 times depending on the class and grade.

Some specialist component manufacturers will proof test or rate against material strength alone.
An example of that is Recovery Points.
Some will send a prototype or example to a lab for destruction or proof testing, some will rate against material IE 'x' thick steel of 'y' grade with a min 'z' mm for any perforation from any edge is = to "A" tons.
These manuf are to be applauded and most will apply a safety factor of their choosing of 2 or more EVEN THO no A.S. applies

Finally, equipment like Snatchies have no Manuf Standards at all.
They only have an A.S Packaging Standard which covers what must appear in/on the packaging and/or labelling.
They are usually rated on material only and almost invariably have no safety factor applied so will fail at or about 'rating'.

All of which is why an 8 ton 'rated' snatchie will fling a 3.5 ton 'rated' Tow ball straight thru a human but tear itself to shreds trying to bust a 3.5 ton 'rated' shackle or snap before it rips out a 5 ton 'rated' recovery point.

[Dr Gary]

Hi mate you can only fit one 12mm flat plate to the drivers side to
fit one to the left you'd need to drop the bullbar. Look at my vender
thread and see if my "tee" shaped ones will fit on the outside of your bull bar
Let me know which style would suit would not take long to get some cut and coated.
Thanks @mudski

Hi TD
I have your recovery plates on my 2006 3.0di. This model had capture nut attachment points on BOTH chassis rails, so I just needed to remove the "tow hook" and then bolt the plates INSIDE the chassis to existing capture nuts.

[Bidja]

Pretty much...

A goodly amount of equipment which we use/borrow/pinch for recovery operations is manufactured to a Standard (A.S. in most cases) EG Rated Shackles.
Ergo Shackles are rated for lifting, tow bars are rated for towing etc.
None of these components are required by their A.S. to be rated/tested/manuf for recovery, there is no point as that is not the manuf intended use.

Soooo, some Standards work brilliantly for recovery use IE Shackle A.S. and some are absolute shit IE the Tow Ball A.S.
The Standard may or may not apply safety factors and again purely as an example in Shackles it will be 4 to 8 times depending on the class and grade.

Some specialist component manufacturers will proof test or rate against material strength alone.
An example of that is Recovery Points.
Some will send a prototype or example to a lab for destruction or proof testing, some will rate against material IE 'x' thick steel of 'y' grade with a min 'z' mm for any perforation from any edge is = to "A" tons.
These manuf are to be applauded and most will apply a safety factor of their choosing of 2 or more EVEN THO no A.S. applies

Finally, equipment like Snatchies have no Manuf Standards at all.
They only have an A.S Packaging Standard which covers what must appear in/on the packaging and/or labelling.
They are usually rated on material only and almost invariably have no safety factor applied so will fail at or about 'rating'.

All of which is why an 8 ton 'rated' snatchie will fling a 3.5 ton 'rated' Tow ball straight thru a human but tear itself to shreds trying to bust a 3.5 ton 'rated' shackle or snap before it rips out a 5 ton 'rated' recovery point.

Yeh, recovery is very unpredictable. Component and equipment selection for use is primarily based on experience and lessons learnt or from listening to those we regard to have the appropriate knowledge or skill set. I certainly would not want to be in the near vicinity of a snatch or fastener failing resulting from recovery activity. Go Go slowly.

Those design safety factor I quoted were from non-tertiary level studies I undertook many yrs back (mech design cert) and worked many yrs on the civvies side of the fence involved in design, trials, test/evaluation and manufacture of gear (maybe similarly to yourself).

[MB]

Best technical conversation ever, good caring blokes!
Seen some Wild Bush shit in heydays hindsight:-(



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[PeeBee]

One important issue I believe is to calm down and think about what and how you are doing things. I have been guilty of rigging a recovery line then getting part way into the action to discover that adrenaline has clouded my decision making or the desire to get going and reach camp. Sitting back for a few minutes and calming down before commencing the task will certainly assist is a safer job execution and could very well result in lower strain on all components. Don't rush the task, its important to get it right the first time as opposed to having a more difficult recovery due to a careless approach.

[threedogs]

@Dr Gary your right later models say 03 onwards had captive nuts under the chassis the
earli Diesels had 3 captive nuts on the inside of the chassis rails nut underneath like the later ones.
Early ones needed a special plate for inside the chassis rail to fit the second one , bull bar would need to come off as well .