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shackles and kinetic ropes

 
 
Post new topic   Reply to topic    Difflock Forum Index -> 4x4s -> Gear, Equipment and Vehicle Preparation
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parrotveasey81
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Joined: 13 Feb 2009
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Location: bradford on avon (wiltshire)



PostPosted: Thu Mar 11, 2010 7:18 am    Post subject: shackles and kinetic ropes Reply with quote

have a look here and please give your view on this as he's saying different than what ive been told on here,who is right who is wrong
http://www.daihatsu-drivers.co.uk/node/12714

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bertie_bas205
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PostPosted: Thu Mar 11, 2010 12:12 pm    Post subject: Reply with quote

I read the thread, which bit dude?????




Bertie.
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parrotveasey81
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PostPosted: Thu Mar 11, 2010 12:28 pm    Post subject: Reply with quote

There appears to be much confusion and misinformation about the supposed working loads of kinetic ropes. THEY DO NOT HAVE A WORKING LOAD.

They have a minimum breaking load, this is slightly misinforming as it has to be held at this mimimum breaking load for 30 seconds for the purposes of testing. This is with an erosion factor of 10% to allow for damage, the reality is that no kinetic rope will remain fully stretched for more than a fraction of a second before it begins to contract.

Shackles rated at 4.75 tonnes do not have a minimum breaking point of 31 tonnes, they have to have a factor of safety if 1.7:1 as they are only rated for lifting. They have no rating for shock loadings, it is not the weight that is the problen, it is the sudden load curve or shock loading which causes them to break. In reality the working load would be guaranteed to be 4.75 X 1.7 = 8 tonnes, so nowhere near the rating of a kinetic rope without the shock loading taken into consideration.

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Orangev8
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PostPosted: Thu Mar 11, 2010 12:59 pm    Post subject: Reply with quote

Any other than lifting equipment will do what it says on the tin and break at or around the load indicated. Manufacturers produce lifting equipment to an MBL and will not guarantee failure of the equipment after this figure although most good quality makes such as Crosby or RUD will far exceed the MBL and deform considerably before failing.

the working load limit is then derived by dividing the MBL by the safety factor although Germany has a static safety factor of 10:1 and all man riding across the board has the same factor.

This is all done to allow for Dynamic (shock) load inadvertently coming in but any kit should be thoroughly inspected and destroyed or quarantined if deformed. 5% of deformity is allowable, but how you tell 5% beats me.
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bertie_bas205
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PostPosted: Thu Mar 11, 2010 1:08 pm    Post subject: Reply with quote

The Kinetic ropes and straps i have both have a working load and a breaking strain....

I would agree with the bit about the shackles, not really designed for shock loading.

I try not to use shackles, although this is not always possible....

At the front of my 90 i attach them through the jate rings, no shackle. Though the risk there is the jate failing.

At the rear i use BIG shackles, maybe not the perfect answer....

The question would be, without shackles how would we attach the straps/ropes etc???




Bertie.
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parrotveasey81
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PostPosted: Thu Mar 11, 2010 1:19 pm    Post subject: Reply with quote

bertie_bas205 wrote:
The Kinetic ropes and straps i have both have a working load and a breaking strain....

I would agree with the bit about the shackles, not really designed for shock loading.

I try not to use shackles, although this is not always possible....

At the front of my 90 i attach them through the jate rings, no shackle. Though the risk there is the jate failing.

At the rear i use BIG shackles, maybe not the perfect answer....

The question would be, without shackles how would we attach the straps/ropes etc???




Bertie.


what are your shackles rated at i mean the breaking strength? have they got a safety factor of 1.7:1 or 6:1 or even 7:1 as i have seen/been told different factors??

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parrotveasey81
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PostPosted: Thu Mar 11, 2010 1:25 pm    Post subject: Reply with quote

have a read though this http://landyspares.co.za/files/snatch_straps.htm
lots of good info but i cant get the same answer from atleast 2 different people even the ones that sell recover gear they wont say for sure whats what

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bertie_bas205
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PostPosted: Thu Mar 11, 2010 7:05 pm    Post subject: Reply with quote

parrotveasey81 wrote:
bertie_bas205 wrote:
The Kinetic ropes and straps i have both have a working load and a breaking strain....

I would agree with the bit about the shackles, not really designed for shock loading.

I try not to use shackles, although this is not always possible....

At the front of my 90 i attach them through the jate rings, no shackle. Though the risk there is the jate failing.

At the rear i use BIG shackles, maybe not the perfect answer....

The question would be, without shackles how would we attach the straps/ropes etc???




Bertie.


what are your shackles rated at i mean the breaking strength? have they got a safety factor of 1.7:1 or 6:1 or even 7:1 as i have seen/been told different factors??


The ones i have have a factor of 5:1......

Depending what i'm trying to pull out and how stuck they are, I use either 4.74t or 6.5t. If its a rolling tow i'd probably just use the 3.25 ones....

I dont have a restriction on shackle pin size through my rear recovery points so could go bigger. As i said above i don't use shackles on the front.




Bertie.
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parrotveasey81
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PostPosted: Thu Mar 11, 2010 7:07 pm    Post subject: Reply with quote

thanks also this just come though,what do you think about this

I do not need the links as i can rely upon my own considerable engineering qualifications. As i have previously stated there are considerable sources of misinformation, mainly from unqualified people who have no knowledge of what they are talking about. many are often journalists looking for a sensationalist story, others are mainly retailers, manufacturers, and others with a vested interest in selling equipment.

It is this misinformation which creates the problems, people think it is correct by using "common perception". This is where it sounds logical so it must be right, but as with many things, it is wrong.

Considering the considerable misinformation and general rubbish printed, i am currently composing an article with "THE FACTS". People can then read and make up their own minds, if they accept what i say then fine, we have all learned something new. if they dispute it and end up injured, then tough, they were warned and chose to ignore it.

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bertie_bas205
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1985 Land Rover 90nad

PostPosted: Thu Mar 11, 2010 7:09 pm    Post subject: Reply with quote

parrotveasey81 wrote:
have a read though this http://landyspares.co.za/files/snatch_straps.htm
lots of good info but i cant get the same answer from atleast 2 different people even the ones that sell recover gear they wont say for sure whats what


As it says a very effective recovery tool, yet again ye can't rule out or assess for bloody stupidity...

Different manufacturers have different rating or breaking strains, best to ask the supplier ye buy from just to make sure....


Some good info in that link....






bertie.
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parrotveasey81
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PostPosted: Fri Mar 12, 2010 3:33 am    Post subject: Reply with quote

have a read http://www.daihatsu-drivers.co.uk/howitworks/kerr and then add comments NOTE I DID NOT WRITE THIS
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leeds
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PostPosted: Tue Mar 23, 2010 8:39 am    Post subject: Reply with quote

An interesting read.

A couple of comments however

Quote:

Such systems may be good, but are fraught with danger, and can kill people who do not know how to use them, or use them properly.


ALL recovery systems (not just KERR or snatch) are fraught with dangers, more so if good equipment, good techniques and good safety management are not used

Quote:

Many people connect the ropes to the vehicle, or rope to rope to extend them, using rated shackles, these should never be used, even if they are rated higher than the kinetic rope, very few are; they are not designed to cope with the shock loads imposed.


How do you shock load the shackles with what is basically a large rubber band? Shock loads would imply a load being applied very quickly. Now if you tried (not recommended) a snatch recovery using a steel rope then you would apply shock loads to the shackle.

Quote:
Kinetic straps look like ratchet straps but do not have the same stretching capacity as ropes,


???

Errr a ratchet strap has big metal items attached to them!

A recovery/snatch strap could be confused with a towing/lifting strap.

No mention of material used. The three main polymer materials used in webbing are

Polypropylene
Polyester
Nylons

Polypropylene webbing has no place in the 4 x 4 recovery world. Great as suitcase straps and trouser belts etc but too weak for towing/recovery.

Polyester straps are much stronger but have relatively low stretch in comparison to nylon. Polyester webbing is used in seat belts rather then nylon as you need a strong webbing with little stretch as you don't want to hit windscreen under emergency braking! Polyester is used in ropes where low stretch is required, i.e. single rope techniques/rope access use.

Nylon is used in ropes/webbing where stretch/energy absorption is needed. Nylon ropes are used in climbing for their energy absorption properties/elongation. You would not want to take a fall factor 2 fall on a polyester rope as a nylon rope would be better due to its elastic properties.

Brendan

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