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a successful learner…… loves learning…… seeks challenges…… values effort…… persists in the face of obstacles

All content copyright Willem Winch or otherwise credited.


…if you wish good advice consult an old man…

…more 4x4 Tech Articles here:

…the latest Holden Colorado advertisement clip

The controversial YouTube clip showed a Holden Colorado recovering another bogged vehicle in cowboy style with a drag chain. The drag chain was fitted to the tow ball and recovery was undertaken via heavy jerking and acceleration. The clip was in the meanwhile removed and then uploaded in an edited version. One discussion went on here, but there were many other forums where this advertisement clip made a big topic.

Beside the “cowboy style” attitude neglecting all the usual safety procedures the actors in the clip showed, the attachment of the drag chain to the tow ball was mostly criticised; viewers pointed out how dangerous it is slinging the chain just around the tow ball, and that people where killed in similar scenarios where a recovery was attempted with a snatch strap attached to the tow ball: the tow ball broke loose and became a deadly projectile.

Every guideline, snatch strap documentation, every 4x4 course, every instructor will somewhere emphasize the importance of fitting the snatch strap only to vehicle manufacturer rated recovery points;  not to a tow ball and not to tie down points or suspension components as these points are all not suitable for a snatch recovery.

Now, while the clip might not be the smartest advertisement, and while the raised safety awareness shown by the discussions is a good sign in the 4WD communities, the points made in the discussions also show distinct lack of understanding for the physics involved in recoveries.

I followed a lot of threads on several forums quite a while and waited that someone might point it out, but no… IMO most people missed the point.

Again, the advertisement might not be the smartest one, but IMO it is technically not correct to compare it with a snatch strap recovery where an unsafe, not rated recovery point is used. Yes, they slung the drag chain around the tow ball, but - and this is the huge difference - they didn’t use a snatch strap, but a drag chain!

The arguments and the way all the discussions on the forums went really shows that a lot of people still don’t understand the physics in a snatch strap recovery, and that is really something to be concerned of. The huge and all decisive difference between the drag chain and the snatch strap is that the drag chain can’t store the kinetic energy of the towing vehicle - if it breaks it just breaks.

The part that comes lose will move on with the same velocity that it has the moment when it breaks - there is no further acceleration! Therefore if the recovery vehicle would reach maximum velocity of e.g. 20 km/h via its jerking action: this is the maximum velocity the part of the chain - or the tow ball - will achieve.

Now, I don’t want to be hit by a tow ball, part of a chain or other metallic object that is flying with 20 km/h towards me, but nevertheless it needs to be recognised that it is a much lower risk compared with being hit by the same object that is propelled to 200 km/h and more due to the energy stored in a snatch strap!

Consider a catapult or a slingshot: how far can you shoot a stone with a non elastic chain?

It is easy to store the energy equivalent to an energy required to accelerate e.g. a 1-tonne load to 10 km/h and more in a snatch strap; the moment something breaks this energy is set free and due to the relative low weight of a broken part that might have come free, this energy is capable to accelerate it fast enough to transform it into a deadly projectile.

BTW, this is also the reason why winch dampers, which do a great job for winch recoveries, especially for winches with synthetic ropes - are totally useless for snatch strap recoveries!

Their weight is just to small to facilitate a significant dampening to decelerate a part that comes lose - you would need dampers with a weight in order of 300 kg to show an impact; obviously it would be quite challenging to carry such dampers around.

Back to the advertisement: the guys in the clip are definitely not really suitable as role models, but I would have wished that more people who criticised the clip would have pointed out the huge difference between a drag chain and a snatch strap in such a recovery scenario.

A JSA conducted according to industrial standards, or a HAZOP would have shown that the risk by slinging the drag chain around the tow ball is only a minor risk as long as bystanders are kept out of line (an object with a starting velocity of e.g. 20 km/h doesn’t fly too far)… and as long as really only a drag chain would have been employed in the recovery.   


more to come about snatching…

I’m working on a comprehensive article about snatching, snatch recoveries and the physics behind when the discussions about this Holden advertisement popped up in several forums; hence I thought I throw this shorter article in as a “teaser”.

It might - hopefully - help a little bit to develop a better understanding for the real risks in recovery scenarios as the ongoing discussions clearly indicate that there is some significant backlog.

Knowledge about risks and the causes for the risks are mandatory requirement when it comes to plan the right steps in every recovery scenario, no matter what kind of equipment or tools are used.  

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p. issued: June, 2012   -   last  update: 23-02-2013


Comments…

…you can leave a comment on the message board for this article; any comment is accepted as long as content and language is appropriate and civilized… more about site rules here...

…some thoughts about controversial discussions in 4WD forums criticising the latest Holden Colorado YouTube clip…


…viewers raised safety concerns, but it seems that most people missed the point…


note: loading of videos may need some time depending on Internet connection speed.


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…this is - the edited - commercial that sparked the discussions … in this version the slinging of the drag chain around the tow ball is not visible anymore…

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