Thread: Snatch Strap Question

Originally Posted by leeds

In my past I have made and tested webbing equipment used in caving and climbing. The risk here of personal injury is much higher then in the 4 x 4 area if things go badly wrong., so standards have to be extremely high. Once had a well used, if not abused caving harness returned about two years old as the guy had replaced it with a new one that I had made. Would I be interested in testing it. Lets say that this harness was so badly abraded that I would not even contemplate using it. Surprising enough the harness passed the UIAA (climbing association ) official tests.
This was due to no significant damage to stitch blocks or nicks/cuts in from edge of webbing

So my two cents worth on webbing strops used in 4 x 4 area, assuming no manufacturing fault in webbing or stitching and what weakens them and when to bin them. Not in any particular order

Stitch blocks.
Are there any signs of stitching unravelling? Are there any broken stitches? The odd broken stitch is not too bad get multiple broken stitches then it could be a sign that the strop has been extremely close to its breaking limit.
It might be prudent then to replace it

A good stitch block should in my experience be stronger then the webbing.

Lateral Damage
Nicks and cuts from the side. As a general rule a cut going into the side of a strop say 10% of its width and you will lose normally just over 10% of its strength. So a 8,000 kg strap is now say a 7,000 kg strap. If two or more 10% cuts on same side to same depth in general terms you will not lose any more strength. If you have 2 10% cuts on both edges of strap and your 8,000 kg strap is now about 6,000 kg in strength

Surface Abrasion
This is more difficult to quantify and describe. If it is light and general 'hariness' spread around the strap then you may lose say 5-10% of strength.

If it is concentrated in one area and is the full width of the strap then it is possible to lose significant amount of strength. The percentage loss in this case could easily reach 25+% depending on how deep the abrasion has gone

Internal Abrasion
Filaments inside the strap can be damaged by grit being forced into the strap and the sharp edges of minute particles of sand /grit etc cutting the small diameter filaments which make up a strap. Difficult to quantify the percentage lost in strength in this case. Ideally you would not use a recovery strap in a muddy/sandy situation and avoid this problem BUT you normally get stucky in muddy/sandy/boggy areas so have to live with it.

Washing excess mud off can limit surface mud being later on forced into the strap. Do NOT use pressure washers to clean straps as that will force grit into strap. If you use the wives washing machine, do not use chemicals and do it when she is not at home for your own safety.

UV Degradation
Normally takes reasonable amount of time say 1-2+ years before becoming significant. Store them clean and dry in a bag or box and no problem. I personally would be more worried about cuts and abrasion

Chemical attack
Nylons are considered alkaline resistant and polyester are acid resistant. Note the word resistant they are not proof against these chemicals. Acids will attack nylons and alkalines will attack polyester. What material is the stitching mad from????

Damage by chemical attack is difficult to quantify and is best avoided. Avoid straps coming into contact with any acid, alkaline, oil, solvent etc. If you suspect any contact with chemicals bin them.

Storage
Keep straps in a clean, dry, light proof environment and they should be fine

In Use
Keep them as clean as possible (yeah, yeah I know ) Avoid straps rubbing against trees, rocks ground especially when under load. Keep the webbing as flat as possible. Twisted straps are not as strong due to uneven loading on filaments

Remember a shackle will lose very little of its strength over a long time period if used/stored correctly. A brand new strap can be severely weaken by being badly used once!

Inspect your straps regularly, bin them if you have any doubts. A new strap is a lot cheaper then a windscreen or a visit to the hospital

Regards

Brendan

PS Where is the soap box store here? Time I put mine away

Brendon,
Bang on. I could have gone on for ages as well, but did not want to over complicate things for this poor chap.
Something that should also be considered is using a dampers so if the strap does snap it does not become lethal. Having said that I would far rather the strap snap or come apart at the eyelet stiching than a shackle or recovery point fail. As long as distance is kept it is unlikely a broken strap will become lethal (but still possible) but a shackle or recovery hook would be lethal and or do extensive damage.
As pointed out people dont take into account degradation wether by chemical, water, mould, dew or wear.
One of the big no. no's people should take into account is straps should not be kept on a concrete floor under any circumastances as this leads to degradation from moisture, the lime in the concrete etc. Keep them bagged, dry and off the ground. If used in harsh environments such as mud, sand or salt wash them with soap flakes and string up off the ground to dry. I put mine in the washining machine (front loader) on a gentle wash, then lay them out and scrub with a laundry pure soap bar (wondersoap I think it is called) hose off and rinse cycle in the washing machine gentle again then hang in a shaded area to dry. Then a thorough inspection.
It annoys me no end people who borrow gear and then dont look after it. We lent a strap to some fitters who should know better. When they returned it it came out of the back of their ute deck, after laying in a puddle of diesel / oil that was in the back, not in the bag it went out on. To their amazment I walked out grabbed it and put a knife through it cutting it in half and then informed them that they would never be loaned Emergency Response equipment again and their department would be sent a bill to replace it.
As you have said it amazes how some really ratty gear can still pass testing. Testimony to the person making or stitching it, however if I was unsure I would not use it, even after a test. Same as rescue ropes I have seen them come back after laying in water or chemicals and have done exactly the same and put a knife through them. Not worth the risk.
Cheers
CraigE

Craig sometimes it is extremely important to go back to basics and explain everything again from basic principles. OK some people might say its that idiot Leeds again on his soap box etc, BUT apart from the orginator of a thread, there might be other novices/less experienced people or even experienced people who might say I never knew that or considered that. Coming from a caving background where your life can literally be hanging on a thread I am extremely careful about how I look after my recovery gear and who attaches what to what etc.

I once cost the physic department a fortune many years ago. Went looking for an electrical extension lead and was not happy with what I found. Following morning dumped 4 on safety officers desk with plugs cut off. Response wa oh we will have to do something about it. By end of week when I had dumped over 30 on his desk with plugs cut off the department bought a 100 new ones which were distributed within a week. First month think they got through over 250 new ones and that was in a Physics dept.

It is important to share experiences and if you cock up.. tell peole so other people can learn by your mistakes as well.

Regards

Brendan

Crikey everyone is writing novels in this thread

Originally Posted by Fusion

Crikey everyone is writing novels in this thread

Novels are fiction you silly man

Some of us are writing facts (OK encylopedias!!!)

Regards


Brendan


What are you trying to say? That we are prattling on too much?


Anyway I am off out for a so that will stop me wittering on for a bit

Originally Posted by leeds

Craig sometimes it is extremely important to go back to basics and explain everything again from basic principles. OK some people might say its that idiot Leeds again on his soap box etc, BUT apart from the orginator of a thread, there might be other novices/less experienced people or even experienced people who might say I never knew that or considered that. Coming from a caving background where your life can literally be hanging on a thread I am extremely careful about how I look after my recovery gear and who attaches what to what etc.

I once cost the physic department a fortune many years ago. Went looking for an electrical extension lead and was not happy with what I found. Following morning dumped 4 on safety officers desk with plugs cut off. Response wa oh we will have to do something about it. By end of week when I had dumped over 30 on his desk with plugs cut off the department bought a 100 new ones which were distributed within a week. First month think they got through over 250 new ones and that was in a Physics dept.

It is important to share experiences and if you cock up.. tell peole so other people can learn by your mistakes as well.

Regards

Brendan

Brendan,
I agree 100%. maybe people who specialise in certain areas could put together basic information sheets on topics like this and post in good oil or tutorials.
As yiou are to caving I am to rescue and need to rely on my rope rescue gear amongst other aspects. You would think that with the consequences of this type of equipment failure that there would have to be a decent product sheet included with these types of items, but no. Its a big trap for unwary players. Too many people just get sold equipment, with no instruction, training or competency assessment and some of them should not be allowed near some of this gear let alone a 4x4.

Craig we will have to be extremely careful or otherwise other forum users will accuse us of forming a mutual admiration society!

It is a long time ago now but have also taken part in cave and fell rescue as well, so we probably have large areas of overlapping experiences.

Whilst this conversation is now beginning to wander away from the original subject it is still related to safety and 4 x 4 gear.

What annoys me is lack of information on synthetic winch lines and the test proceedures used on them. For instance no load extension curves appear to exist. No data on extension to failure. Most people will say so what?

In the UK it is a common belief put around by early advertising claims that a synthetic rope when it fails just falls harmlessly to the ground. WRONG! They can fly as much as a steel line. OK it might not hurt as much as a steel line BUT it will hurt. Basically it means the same safety exclusion zone should be around a synthetic line winch recovery as a steel line one.

No extension to failure figures? I personally believe that synthetic winch lines are not as good as steel when it comes to handling shock loads. In theory you should not be able to shock load a winch line.

Consider this. Winching up a steep hill. Driver decides to drive assist and outpaces the winch motor so slack builds up in the line. Looses traction and slides down the hill and is pulled up by the winch line. This in fact is a shock load so the winch line is more prone to breaking. If it breaks vehicle will contine to go backwards down the steep heel.

What about relationship between temperate and strength. A lot of synthetic winch lines are polyethylene (OK a special PE but still PE like disposable plastic shopping bags) PE has a melting point in region of 120C, at which temperature it has zero strength. I am guessing that around 70C there will be a serious reduction in strength. With air temp in Aus can easily reach 40+C that does not leave a large temperature difference before your winch line is seriously weaken

So you are in the desert and have rigged your recovery system and are down to half the first layer. You get a cup of tea/coffee or grab a cold beer before starting the winching. What temp has that synthetic line on drum got to 40/50/60/70/80C because it is sat on a nice black steel thermal sink (i.e. the winch drum) How strong is that nice strong synthetic line now?

Before anyone asks the same effect will occur on the synthetic recovery straps but to a much smaller amount basically because of material used has a melting temperature well in excess of 200+C


Regards


Brendan

Speak of the devil.

4WDAction has a mega snatchstrap comparo in issue No.128.

What a monster of an issue we have for you this month! Australian 4WD Action has been pushing hard to test all of the products and accessories available to the Australian 4WDer, and the huge snatch strap comparo we have this issue is packed full of facts and figures on which snatch strap is best for you and why.

We took over 18 snatch straps through a tug of war torture test, keeping an eye out for when the stitching failed and at what rating the snatch snapped. You can head to p32 in issue 128 of Australian 4WD Action to find out which strap came out on top, where they failed and why.

This is meant to be on the stands just now.

I love the discussion these threads open up..

And great to see so many people are actually safety aware.


Recently we had a recovery situation on a mangrove area..

2 busted 8000kg snatch straps
1 busted 11000kg snatch strap
1 snapped 15000lb winch extension strap
2 broken shovels

And a brand new Warn requiring a rebuild after a double line pull involving 3 vehicles (1 with winch, 2 attached to rear as anchors) resulted in a very destroyed gearbox in the winch...

We covered a grandeous distance of 50meters in 4 hours....