Thread: Synthetic rope question

Well they say in the eBay ad that the " Working Load : 9,500 kg. Or over 20,000 lbs",
which I find amazing that 10mm rope can used to lift almost 10 tonnes, so If they believe that then what else is "true" about their product, if a supplier of recovery gear can't give give you the Safe Working Load/Working Load Limit (SWL/WLL) then buy from someone that can, BTW the thimble in the eye of the rope should be made of steel, Regards Frank.

9500kg sounds about right for the breaking strain of raw 10mm dyneema line (i.e. not spliced), but that's definitely not the SWL.

I struggled to find anyone that would quote a SWL on dyneema rope, probably because of something like this:

Because of the wide range of rope use, rope condition and the degree of risk of life or property, it is not possible to make a blanket recommendation for safe working load. It is ultimately dependent on the rope user to determine what percentage of break strength is their own safe working load

On a related not I stumbled on this thimble end for nylon ropes that I had not seen before. Then again, maybe I'm just slow...

That thimble looks the goods, but if it is aluminium I wouldn't use it, and if a company that makes/sells this type of rope can't give you a SWL when they already know the Guaranteed Breaking Strain (GBS) then they are bull****ting, because 9500kg. sounds better than 1900kg SWL, Regards Frank.

What's peoples thoughts on using synthetic rope through a pulley block.
If you need a Hawse Fairlead on the winch then a pulley block would possibly be frowned upon.

I've been searching for the same answer for months. If there's requirements for syn to use a hawse is there a spec for use of pulleys etc (steel/alloy/plastic of some sort).

Originally Posted by Tank

That thimble looks the goods, but if it is aluminium I wouldn't use it, and if a company that makes/sells this type of rope can't give you a SWL when they already know the Guaranteed Breaking Strain (GBS) then they are bull****ting, because 9500kg. sounds better than 1900kg SWL, Regards Frank.

Of the two figures I'd rather know the GBS rather than the SWL. That way I can be the judge based on the situation if I can get away with a 2x, 5x or 10x safety factor.

As for the thimble, it is aluminium (Viking Offroad Safety Thimble 2 Black) which I guess will means it comes off second best if you are plugging it in to steel shackles

Originally Posted by FeatherWeightDriver

Of the two figures I'd rather know the GBS rather than the SWL. That way I can be the judge based on the situation if I can get away with a 2x, 5x or 10x safety factor.

As for the thimble, it is aluminium (Viking Offroad Safety Thimble 2 Black) which I guess will means it comes off second best if you are plugging it in to steel shackles

The SWL is a Safety Factor, it is used because from the first use of the rope/cable it deteriorates and will eventually deteriorate to the point where it is unusable, so after use over a year or so your GBS is no longer that advertised, that's why if you use a rope to it's GBS the chances of it breaking are certain. How would you be the judge of say a rope that has been used a dozen times and has had the occasional abrasion and been submerged in mud, leaving sharp particles of dirt in the fibres, what is the Breaking Strain of this rope after this.

Commonsense says that if you use a rope to it's SWL/WLL then you will get some life out of it and less chance of failure.
As far as pulleys go wire rope is more adversely affected by snatch blocks than fibre rope, wire rope needs as big a diameter pulley as possible and the groove needs to be the right size for the Dia. of the cable, too narrow and the cable will be pinched, too wide and the cable will be flattened. Common to both rope and wire cable is when they pass over the pulley wheel the outside of the cable/rope is stretched and the inside (closest to groove surface) gets crushed. In a wire cable this causes kinking and broken wires, rope is not as badly affected but it will cause some damage and if the rope has grit in the fibres it will eventually destroy the rope (lower the GBS), another reason to work within the SWL/WLL, Regards Frank.

^^^ I hear you tank, and completely agree the GBS isn't a load to work to, it's the number to calculate from.

Knowing the SWL and the safety factor tells you the GBS, but if the manufacturer does not tell you the safety factor you really don't know much about how strong that gear is at all.

Take rock climbing gear as an example (near and dear to my heart)

All rock climbing gear comes GBS loadings, not SWL. So if I take a piece of rated equipment out of the packaging, and decide to load it up to 90% of GBS for a certain application where failure is not terminal, then that's my call and I should expect the gear to perform.

If on the other hand I am pulling an injured mate up a cliff with non-new gear I will make damned sure my safety factor for every single piece of gear in the link is 1/20th the GBS (20x safety factor) to cover degradation over time, redundancy in the system etc.

In your example if a piece of gear gear goes round a tighter bend, is wet, is older, needs a mid line knot etc. etc. that also needs to be factored, meaning a higher factor for that link.

But the safety factor to apply for each piece of gear, in each situation, is my call and no-one else's.

Another way to look at it is like this: You have a rope with a SWL of 1 tonne. When is it no longer fit for purpose? If you don't understand how the gear works (not saying you don't...) and don't know the GBS (or SWL and safety factor) and you don't know how the gear is being used (static load, dynamic load, wet, dry, old, new, corners, knots) then you simply don't know if it is fit for purpose any more...

Maybe this mob explain it better than I do: The ABCs of Recovery Safety: WLL, SWL, & MBS – Central Overland

Heck actually they do, maybe just ignore me and read the linked web page