Thread: Snatch Strap Question

Originally Posted by disco_2008

Dan,
I always wonder the same thing. I would love it know.. Why get a 8ton Strap is the shackles are only rated to 4 ton...

Straps are rated for their minimum breaking strain (when new), so 8,000 kg strap should break at a load just above 8,000 kg

Rated shackels have a safety factor of 5X their rated load so 3,700 kg shackel should fail at 18,500 kg.

What your tow hook fails at, or more importantly the other vehicles tow hook is another story!

Originally Posted by Xavie

What a surpise. ARB won in a 4wd action mag.

The testing is independant. Actually, I tend to think that the ARB strap winning is really the result of a previous comparo where the ARB strap did poorly. I think that ARB pride themselves on the products that they make and sell and were surprised when the strap came apart at the stiching. Aparently they revised what they were doing to produce the current crop of straps.

I've heard comments from them regarding other products that they sell that have been along the same lines, notably trying to work out why the Warn winches with the same power and same gearing pull less than some of the other cheaper winches..... and it came down to drag in the winch brakes. Again likewise with the revision to the ARB compressors which are apparently under rated by them in their performance

Originally Posted by jimbo110

Straps are rated for their minimum breaking strain (when new), so 8,000 kg strap should break at a load just above 8,000 kg

Rated shackels have a safety factor of 5X their rated load so 3,700 kg shackel should fail at 18,500 kg.

What your tow hook fails at, or more importantly the other vehicles tow hook is another story!

Absolutely. These are also dry breaking strains.

I think that there are a few recovery points out there that will fail before the strap does.

So if you dont have a 11 ton recovery point on your car ther is no point for a 11 ton snatch strap? ..

Originally Posted by disco_2008

So if you dont have a 11 ton recovery point on your car ther is no point for a 11 ton snatch strap? ..

Thats correct in terms of outright force, but the 11 ton strap will last longer than the 8 ton strap, so you will have increased life.

Its not quite as simple as ratings. As Jimbo said their are 5x fold ratings for shackles, same applies for most rigging and lifting gear as safety margins are put in place. Rope rescue is the same with an 8:1 safety margin observed, so infact these items are way under rated. Of course that does not mean you should exceed the SWL.
The difference is most 4x4 recovery gear such as snatch straps are rated to their maximum breaking strain and have no real safety margin. It is worth enqiring about safety margins when you buy a product and I doubt most 4x4 retailers would be able to tell you. Also important why you buy rated shackles not just generic hardware store ones.
There are also some subtle differences eg the force transfered to the recovery point may be no where near the force actually generated into the strap. Generally the force generated in the strap will concentrate in the centre, but the eyelets are the weak point and if they snap it is usually the stitching in the eyelets that goes.
Recovery points are rather subjective in their capacity, but should always be chassis mounted with high tensile bolts.
Some testing on this would be interesting. I think more emphasis on recovery point ratings is needed.
The hook type recovery points should actually bend before the bolts break, hence a safety factor. The strap will come off if they do and can cause damage or injury but not to the same degree as a shackle. Using D type shackles is another matter as they will deform but usually this will not be seen until they break by the untrained or not so observant and then become lethal. However it is unlikely a 4.8 tonne shackle will fail before a 11,000kg strap. A point to remember is if you go to 11, 15 or 19,000kg straps you should also go up in the shackle SWL to match. While as said a 4 tonne shackle has a safety of 20 tonnes built in if used with a 19,000kg snatch strap is right on its safety limits if loaded up and way outside the safety margin.
The major factor here is to inspect all your equipment prior to and after use for any damage and if possible observe any deformaties when being used (without putting yourself in danger). Any distortion in shackles or recovery points should be assessed and retired immediately (put a grinder through them so that they can not be used again). The recovery straps and winch ropes are a bit different and they are allowed to accommodate a certain amount of damage and still be serviceable within certain tolerances. If you are unsure or untrained get a rigger or someone with inspection qualifications to inspect for you. Consider whatever damage is visible to your eye, there is probablly many more times that damage within the item being checked.

Originally Posted by disco_2008

Dan,
I always wonder the same thing. I would love it know.. Why get a 8ton Strap is the shackles are only rated to 4 ton...

Most 4x4 shops can supply you with 7.2 tonne SWL D shackles, they are the most common along with 4.8 tonne but there are other variants out there depending on manufacturer. Higher rated shackles are also available but may be special order for most 4x4 retail shops.
If you are concerned go to a specialised rigging supplier and their reps are usually qualified riggers and inspectors of such equipment and can allay an fears eg Bullivants.
As I have said in another post in here the 4 tonne rating on a shackle has a safety of at least 5:1 so is in effect a 20 tonne breaking strain, a snatch strap is rated at its breaking strain and generally has no safety margin. Confusing and stupid to have 2 sets of rules.
I have had custom made 15tonne and 19 tonne snatch straps made and there are suppliers that will get these for you, but they become significantly dearer. We get them to recover trucks. Also you will need to uprate your shackles to match.

Originally Posted by disco_2008

Dan,
I always wonder the same thing. I would love it know.. Why get a 8ton Strap is the shackles are only rated to 4 ton...

The shackle has a WLL with a huge safety factor for lifting applications etc. I don't recall the test figures, but they fail at something like 23000kg and undergo significant plastic deformation (permanent bend) before they fail. It's more likely that you'll tear the point or the chassis out than break a 4T shackle.