Winches: Broken wire recoil....

Hi John,
I don't believe the blanket does any good, well, not the size as used by most 4wder's anyway.

I do know that winch ropes fly with the greatest of ease and do kill and maim people ! Education should also include using rated recover hooks on vehicles and not flimsy tie downs !

Can you tell us about what the unfortunate person was actually doing when the accident happened ?

John,
I think the issue here is that airbrakes are useless in preventing recoil.

Thats why heavier objects are being used now - bag full of sand or dirt, heavy chain etc

About 9 months ago I had to pull a mates bogged Malloo ute out of a salt lake. He was a long way out and I didn't have enough, cable, strap to reach him. Anyway some blokes from a local station came out with about 40m of old cable coiled onto an old split rim. I didn't like the look of it but had no option. Thinking it was going to break I tied the now empty cruiser split rim to the wire rope using some 8mm poly rope. When the cable did snap it broke that 8mm rope like it was a cotton thread and the rim moved about an inch (the distance the cabel recoiled was amazing). From that point on I've realsied that a little bag weighing maybe 3kg that people hang over the rope aint going to do much to prevent the wire flicking around.

Mind you Myth busters did do a test to try and cut a pig carcuss in half doing a set up of this thing. They used huge cable and bigger forces than you could ever do with a 4x4winch but it never did more than leave a nasty ring around the pig. But when you watch the rope whipping around the pig in slow-mo the energy in it would certainly kill you.

The use of an air blanket, bag what ever is to reduce the recoil so the force is applied downward (the ground offers greater resistance to air) reducing injury to the upper body if the thing breaks. That is to say if u are in the way, which you shouldn't be to start with. It won't stop it but it will slow it down.

Note the injury specified in the post. Upper body, lucky he didn't lose an eye.

Hi John, If you are implying that a towel works, well if you saw it then ok. But, I have seen a fold out recovery kit holder secured with velcro tapes on a steel winch rope and it may as well not have been there ! It was no use at all, the rope was just a blur and slapped up the front of the vehicle leaveing whip marks on the front of the bonnet.

oops, Just re read it u said "horizontal", the principal still stands apply a small vertical force and the bullet will head down. Given it's velocity it will get there pretty quick and into the ground where it's speed will be reduced greater than that of wind resistance. Depending on variables height, force ect it is difficult to say which one hits the ground first.

Wouldn't like to be the one applying the force to the bullet. lol.

But, back on topic I still say throw something over the cable.

A liitle story to add some colour to this thread. Some while ago I worked offshore on the oil & gas fields. The barge we were on was lifting a 1600 ton module with two steel tugger lines between the ends of the module and winches on the barge to stop rotation of the module.

Unfortunately a swell came up whilst the load was in mid air, and the module started to swing. Things of this size tend to move extremely slowly but once they are moving it is not good news.

Anyway one of the tugger lines snapped under the loads, close to the attachment point on the module - about 50 metres of 1" cable suddenly became airborne, twisting in every direction (a bit like a garden hose when the tap is full on). The overall direction was back towards the barge! Most people ducked behind the wave surge barriers (nice and meaty, for obvious reasons) but one poor crew member caught the force of the flying cable across the top of his head removing his most of his scalp.

A rapid evacuation by helicopter and the guy made a good recovery with most of his hair growing back.

Now I know this was on a bigger scale than our caravan situations but it serves to reinforce the potential dangers that lurk, and the need for care and attention by all concerned. That broken cable can go in any direction regardless of gravity!

R Send

Beware! A little knowledge can be dangerous.

Most of the "physics" above is a mixture of invalid assumptions and unwarranted over-simplifications. All the above refer to simplified models where the mass of the objects being discussed can be considered as being concentrated at a single point.

The dynamics of compound bodies - such as a flying steel rope - are vastly more complex, and cannot be analysed by simple mathematical models. In fact, the behaviour of a flying steel rope would be virtually chaotic, and unable to be predicted with any degree of accuracy. Chaotic motion is unpredictable because small differences in initial conditions magnify up into big variations in subsequent behaviour. So length, thickness, tensile strength etc of the rope, tension in the rope, the pattern of breaking of the strands, angle to the horizontal, and a host of other variables will affect the resulting motion in a way no one can predict.

The best law to take account of is Murphy's one, and always assume the worst possible outcome.

That being said, If one could predict where a break could happen, one could attach weights each side of the possible breakpoint such that the resulting rope ends were attached VERY strongly to the weights, and the weights were such that the momentum of the recoiling rope would be dissipated by the inertia of the weights, then there probably would be no big drama if the rope snapped. The difficulty would be to know where the break would be, how heavy the weights would need to be, and how they could be attached to the rope so they could not come adrift. (The momentum of the rope isn't just "mass x velocity" because the rope is a compound object with all its "parts" moving in slightly different directions at different velocities)

Hi All

I am a great believer in throwing a towel or something loose over the cable, not the rigid ARB or recovery bag types. I have seen two cables snap one was an old tree puller and the other a 4WD winch, the tree puller had nothing on it and I was lucky as it went by me it sliced my jeans open just below my knees but never touched me, the second I was watching and the guys doing it just threw a towel over it and at the time I thought what a joke, but when it snapped the towel got caught up in the cable and the cable started to wrap around the towel but it only did it because it was soft. I think a rigid one would not catch it only slide along it.

So that is my two cents worth.

Have fun

Craig