Has anyone ever had a 4,000kg winch strap fail?

Submitted: Tuesday, Jun 06, 2006 at 11:06

ThreadID: 34669 Views:3925 Replies:7 FollowUps:25

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Scubaroo

Looking for some real world experiences here - has anyone ever had a 4,000kg winch extension strap fail? Under what circumstances? Hand winch or vehicle mounted? Had the strap done much work prior to failing?

I've got a hand winch, and am thinking a 20m or 30m 4,000kg will be sufficient - I know I could potentially exceed that load by using a snatch block on a winch, but my thoughts are that I wouldn't be using the two in conjunction. It's more of a "just in case" item rather than something I ever plan on using (no point having a hand winch if the nearest tree is more than 20m away and you've only got a 20m cable), and I'm trying to justify to myself spending almost double the money for the same length 6,000kg straps - an item that will likely never be used. Spend enough money on stuff I *do* use.

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Reply By: Rosco - Qld - Tuesday, Jun 06, 2006 at 11:25

Reply By: Sand Man (SA) - Tuesday, Jun 06, 2006 at 12:12

Tuesday, Jun 06, 2006 at 12:12

In the words of Professor Julius Somner Miller, "WHY IS IT SO?"

Why is a "Snatch Block" called such?
You don't "snatch" with it at all. It merely reduces the pulling effort of a cable going through it.

So, it should be called a "Winch Block" because it is used with one, either manually, electrically, or Hydraulically driven.

Bill

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AnswerID: 177006

Follow Up By: Scubaroo - Tuesday, Jun 06, 2006 at 12:15

Tuesday, Jun 06, 2006 at 12:15

Good question! I've always called them a snatch block, but winch block is probably used more commonly.

Anyway, where's the "block" bit come from? There's nothing square about them - it's a pulley!

FollowupID: 433019

Follow Up By: Rosco - Qld - Tuesday, Jun 06, 2006 at 12:27

Tuesday, Jun 06, 2006 at 12:27

I think you'll find they're called this due to the fact they are openable and can be "snatched" over a cable, rather than have to thread the cable through, as is the case with a normal block.

Absolutely nothing to do with "snatch" recoveries.

Cheers

FollowupID: 433024

Follow Up By: Member - MrBitchi (QLD) - Tuesday, Jun 06, 2006 at 13:21

Tuesday, Jun 06, 2006 at 13:21

Snatch Block Basics

FollowupID: 433029

Follow Up By: hoyks - Tuesday, Jun 06, 2006 at 13:47

Tuesday, Jun 06, 2006 at 13:47

And they are called a 'block' because back in the bad old days on sailing ships, the pulleys for hoisting the sails and the tensioning stays on the masts were made out of blocks of wood with holes and grooves bored through the block that the rope ran through.
No wheels were used in the middle of the pullies as the only material they had was steel and it tended to rust up and fail at sea and most times was inaccessible in order to do maintenance.

FollowupID: 433034

Follow Up By: Pajman Pete (SA) - Tuesday, Jun 06, 2006 at 14:33

Tuesday, Jun 06, 2006 at 14:33

Snatch - because you can 'snatch' a bight of the rope or line.

Block - because originally all 'pulleys' were cut from a solid block of wood:

Cheers

Pete

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FollowupID: 433043

Follow Up By: Pajman Pete (SA) - Tuesday, Jun 06, 2006 at 15:32

Tuesday, Jun 06, 2006 at 15:32

Not quite hoyks, Brass and bronze sheaves were used at least as early as the 1560s. You may be thinking of 'deadeyes' -

Pete

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FollowupID: 433053

Follow Up By: Mike Harding - Saturday, Jun 10, 2006 at 07:34

Saturday, Jun 10, 2006 at 07:34

Site Link

Excellent link Mr Bitchi - thanks for that, I learned some very interesting stuff.

Mike Harding

FollowupID: 433904

Reply By: HJ60-2H - Tuesday, Jun 06, 2006 at 12:31

Tuesday, Jun 06, 2006 at 12:31

Yes, quite a few. Used in recovery at competition events. Got to th epoint that we now only use 8K ones. They dont fail under normal use, but are still the weakest link in a recovery set up so can be set up to be safe when they do fail.

AnswerID: 177009

Follow Up By: ro-dah-o (WA) - Tuesday, Jun 06, 2006 at 22:11

Tuesday, Jun 06, 2006 at 22:11

I wouldnt think that it is always the weekest link in a recovery set up.

If I had a 1.6tn shackle and a 4tn extension strap, the weakest link in my set up is certainly the shackle.

I would agree that they are the most prone to breakage, but not the weakest link per say.

FollowupID: 433128

Follow Up By: HJ60-2H - Tuesday, Jun 06, 2006 at 22:40

Tuesday, Jun 06, 2006 at 22:40

True. If I were to use a boot lace it would be the weakest link. Or perhaps an unated shackle. The thought of using anything less than a 3.2T rated shackle scares me. If I saw a 1.6T shackle in a recovery set up I'd be walking away from it all. Each to their own though.

A 3.2 T rated shackle will break around the 4 x its rated capacity. A strap will break before 2 x its rated capacity.

FollowupID: 433135

Follow Up By: Scubaroo - Tuesday, Jun 06, 2006 at 23:57

Tuesday, Jun 06, 2006 at 23:57

Most straps break just below, at or just over their rated capacity judging by the mag tests. The strap rating can pretty much be considered the failure point. A shackle has something like a five times safety factor - basically anything over 3.2t should be good, it's just a matter of picking the size you need.

FollowupID: 433140

Follow Up By: ro-dah-o (WA) - Wednesday, Jun 07, 2006 at 08:41

Wednesday, Jun 07, 2006 at 08:41

1.6tn was only used as an example.

I am the same, never use a shackle with a swl of less than 3.2tn.

scubaroo is right about the safety factor. The swl is calculated on the MBL (mean break load) of the device. If memory serves me right, the mbl is divided by a factor of 5 for hardware (shackles and snatch blocks etc) and 8 for soft ware (extension straps, ropes, etc). This is set out by standards australia.

I know it relates to rope and industrial rescue equipment, but not 100% sure about recovery gear. How well policed is the sale of recovery gear?? Does it have to meet any stringent indusrty satandards? This is a debate question, but a genuine 'I dont know' sort of question.

FollowupID: 433156

Follow Up By: HJ60-2H - Wednesday, Jun 07, 2006 at 11:31

Wednesday, Jun 07, 2006 at 11:31

Generally the gear we typically use in 4wd recovery is the same used in industrial lifting and hoisting, shackles, blocks, cables etc. So the standards that apply to this industry and policed by Workcover and the like apply.

Though a recovery strap labeled as a "4WD strap" is probably excluded from the above.

There arent that many Australian Standards that are enshrined in law so although they exist you dont have to meet them in most cases, though is is usually sensible to do so. Lifting & hoisting and electrical safety ones are (fortunately) one of the few that are required to be complied with under the law.

FollowupID: 433191

Follow Up By: ro-dah-o (WA) - Wednesday, Jun 07, 2006 at 12:02

Wednesday, Jun 07, 2006 at 12:02

"There arent that many Australian Standards that are enshrined in law so although they exist you dont have to meet them in most cases,"

thats what i was afraid of. Its a shame as the potential for injury would be quie high, and the consequences high

FollowupID: 433194

Follow Up By: Mike Harding - Saturday, Jun 10, 2006 at 07:51

Saturday, Jun 10, 2006 at 07:51

My understanding is that Oz standards only apply to "lifting" equipment. 4WD recovery equipment is "pulling" equipment and, as such, any ratings given to it are what the seller thinks is a good idea. Of course this doesn't preclude someone selling lifting shackles (say) for 4WD work but if a strap is _not_ certified for lifting then it's rating is, in reality, anyone's guess.

btw even Oz standards do not provide the guarantee many assume - I bought a number (120) electrical enclosures rated to IP66 (rain proof) which let water in due to one bad design fault and another bad manufacturing fault - caveat emptor.

Mike Harding