 | Home > Off Topic > Ouch! That must've hurt! |
 
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17382   
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18th Jan 2013 9:29pm |
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| Laurie Member Since: 22 Feb 2008 Location: Sussex, England Posts: 2897  
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Good example of misuse of a KERR.
I've seen a lot worse than that.  |
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18th Jan 2013 9:34pm |
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| Lou Sparts Member Since: 15 Apr 2012 Location: Kent Posts: 1501 
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KERR,s should be banned from sale. 2005 Td5 90 XS
Steve |
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18th Jan 2013 9:39pm |
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| leeds Member Since: 28 Dec 2009 Location: West Yorkshire Posts: 8581
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WHY? You can not account for complete IDIOTS. First idiot was the one who drove off the beach into the sea/lake. It is difficult to actually KNOW what the beach is doing underwater. It could have changed gradient suddenly meaning that the vehicle could roll if change of beach gradient was sudden and steep. The driver (second idiot) doing the 'recovery' obviously was unaware of how to do a recovery OR the strength of his 'recovery point' He also actually drove over the rope! Idiots number 3 and 4 were standing too close and hence in the 'danger zone' Alternatives? Use a tow strap? Polyester ? Smaller extensions and if used in that scenario the way they use the rope then HIGHER forces will be generated! Hence even more DANGEROUS! Nylon recovery straps? Winch? IF you look at the video the extension of the rope does not appear to be a good 20% which I would expect from a proper Kinetic Energy Recovery Rope. Also if you look at the rope at the end of the video it appears to be a 3 strand rope. KERR tends to be plaited nylon rope. A KERR
What ever recovery technique used on 4x4 you can find examples of dangerous practices on Utube etc. OFFICIAL instructions on use of KERR can be found HERE Yes they say should only be used by TRAINED personnel and not on SOFT SKIN vehicles. Do NOT blame the equipment when it is used in the hands of idiots! Learn the differences between different equipment used in recoveries. Learn how to do it safely. Finally keep all unnecessary people out of the danger zone. Brendan |
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18th Jan 2013 10:41pm |
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| diesel_jim Member Since: 13 Oct 2008 Location: hiding Posts: 6092 
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+1 ^^^
Definately not the KERR's fault... it didn't break, the bumper came off! |
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19th Jan 2013 8:49am |
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| bpman Member Since: 21 May 2008 Location: Oslo Posts: 8069 
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reminds me of the Aussie woman who was killed by a towbar the flew thru her windscreen whilst trying to recover someone
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19th Jan 2013 8:55am |
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| landy andy Member Since: 15 Feb 2009 Location: Ware, Herts Posts: 5700 
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Does not look like a KERR to me, as there's not much give on the first couple of snatches.
Andy |
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19th Jan 2013 10:04am |
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| fekete Member Since: 24 Dec 2008 Location: Here on the other end of the computer Posts: 3626 
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Let that be a lesson to them all
 NEVER TAKE LIFE SERIOUSLY. NOBODY GETS OUT ALIVE ANYWAY |
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19th Jan 2013 1:53pm |
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| Supacat Member Since: 16 Oct 2012 Location: West Yorkshire Posts: 11018 
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Because most of us don't have armoured vehicles? If you extend the off-road maxim "as slow as possible as fast as necessary" (or words to that effect) to recovery then you would use a "dead" rope, taking up the slack first and if that did not work move on to linking a couple of vehicles or winching. Would be interesting to know the peak loads imparted by the average KERR or snatch technique. |
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19th Jan 2013 2:28pm |
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| leeds Member Since: 28 Dec 2009 Location: West Yorkshire Posts: 8581
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Nor are the majority of people trained in winching or recovery techniques.
Peak Force or Energy? Peak force can be calculated from Force = Mass x Acceleration. OK in this case technically deaccceleration Mass in this case is the mass of the vehicle doing the recovery. Lets look at some 'hand waving' examples. The vehicle mass is constant. Lets say free length of the rope/strap/chain etc is the same at say 10 metres. Lets say have 2 metres of slack in the rope and the vehicle always has the same speed of v metres/sec when it has taken up the slack. Once the slack is taken up then the (de)acceleration is worked out from the time taken from going from v m/sec down to 0m/sec This time is dependent on the stretch in the rope/strap etc. A KERR might stretch 20% whereas a polyester strap 5% and a chain might stretch say 2%. The (de) acceleration of the KERR is one quarter that of the polyester strap so the peak force would be one quarter of that of the polyester strap and 1/10th of the chain. In a given snatch recovery situation then the extensibility of the rope/strap is a controlling influence over peak forces generated. What force was required to extract that vehicle? OK say stuck vehicle weighs 1500 kg, soft wet sand would have a factor of 4 so force required there would be 375 kg Assume gradient is zero so no factor there. Assume that front wheels are bogged to tyre wall height Then you would need a force of 100% of 1500 kg to overcome mire resistance or 1,500 kg. To recover that stuck vehicle would require a force of 1,875 kg, That bumper that flew could not take that force, so flew off. i.e. it was not very strong. To quote billyvista
To recover that vehicle using a 'dead' rope technique then the controlling factor would be traction being achieved by the towing vehicle. This then depends on the strength of the ground under the tyres. Being wet sand it is not particularly strong, so it is highly probable that the towing vehicle would just dig it so in. So multiple vehicles linked together? Or extra long straps? Would they know how to join straps together safely? Brendan |
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19th Jan 2013 5:47pm |
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