Weakest point in winch and rigging?

[kerry]

It was also more likely that it was the truck bed that failed, not the frame, but it could be both.

If you slow down the video, you can see the frame cracked in two, just behind the cab.

 

[xcmountain80]

Can I point out this is not a REAL tow truck, just because it has the rigging that billy bod ordered from the local auto parts store doesn't make it a tow truck. I have liked to have seen an actual tow truck pull him out. That rig was designed for pulling cars from accident scenes or disabled vehicles. This was clearly a stuck and disabled vehicle, I wonder if the tow guy was like well you owe me a new truck?


Aaron

 

[Redline]

Yep, a single-rear-wheel, single boom truck, maybe intended for Repos or (easy) off-highway recoveries. But I agree that the real problem was the loose-nut-behind-the-wheel.

I know little about recovery but certainly a bit more than that bozo.

Can I point out this is not a REAL tow truck, just because it has the rigging that billy bod ordered from the local auto parts store doesn't make it a tow truck. I have liked to have seen an actual tow truck pull him out. That rig was designed for pulling cars from accident scenes or disabled vehicles. This was clearly a stuck and disabled vehicle, I wonder if the tow guy was like well you owe me a new truck?


Aaron

 

[xcmountain80]

Why is it that jobs requiring some skill always attract the not so skilled?


Aaron

 

[madizell]

Why is it that jobs requiring some skill always attract the not so skilled?


Aaron

Usually because they don't regularly pay very much.

 

[madizell]

If you slow down the video, you can see the frame cracked in two, just behind the cab.

All I can see is a gap between the cab and bed. Even stopped, I can't see the frame at all. I suppose it could be cracked, but since the frame channel on the Ford is a C-channel, not boxed tube, I would expect that it simply collapsed without breaking. They are not that hard to bend. I wonder if any of the folks in the video actually owned any of the vehicles they were driving, with the possible exception of the old Toy pickup. These looked like kids driving Mom and Dad's vehicles, and the tow truck guy is anyone's guess.

 

[Crookthumb]

Failing to pull a mere Disco out of the mud from the front, would it not have been prudent to do it from the back, the direction in which the vehicle entered the obstacle, and the direction in which resistance to recover would be least? The guy drove out eventually by passing just behind the Disco so obviously he could have accessed the Disco from the rear.

He did try to pull from the rear. I originally saw the clip on Facebook. I didn't know if it would post here or not. If so it is a little clearer.

http://www.facebook.com/home.php#/video/video.php?v=86450905441&oid=2204603930

 

[Crookthumb]

I agree that there were so many things that should not have been attempted. Unfortunately many don't think about would could happen if something were to go wrong. Look at all the crap flopping around in the bed of the Toy. Get rid of it or secure it. Simple little things can have a big effect.

 

[toledotimber]

I know it's a bit late, but I figure since most of the posts were pretty off topic, no one will care. The weakest point in any winch rigging setup (so long as we're assuming that decent mounting points have been used and that no original parts have been replaced with non-original ones on the winch) is the pin that holds the winch hook to the cable, possibly in a tie with the mechanical crimp that forms the loop in the cable. The answers about the winch operator being the weakest link are cute, and often all too true, but I doubt what the O.P. had in mind.

 

[michaelgroves]

The weakest point in any winch rigging setup (so long as we're assuming that decent mounting points have been used and that no original parts have been replaced with non-original ones on the winch) is the pin that holds the winch hook to the cable, possibly in a tie with the mechanical crimp that forms the loop in the cable.

I'd agree those are possible points of failure, but not ones that strike me as the most common ones! Are you suggesting they are designed to be the weakest link? Or that it just turns out that way?

 

[AndrewP]

I think the pin idea is probably true, and in fact is why I upgraded from the 3/8 hook that the winch came with to a larger forged hook with a 1/2 pin. That way I know the hook is much stronger than the cable, and as an added bonus, is easier to get two tow strap eyes on when doubling up for a pull.

 

[ntsqd]

The pin and the area of the hook adjacent to it's hole do need serious attention during the design phase. The pin is loaded in double shear and it's calc's are fairly straight forward once the WLL and minimum Factor of Safety are set. The area around the pin's holes are similarly straight forward calcs though there are more of them. Where this whole aspect of the system will fail is substitution of inferior materials and seemingly small variances in final forged dimensions or in the location of the pin hole. In the region around the holes a small loss in cross section can have large effects. The bend in the hook is no small design challenge itself.
Given that those making hooks of quality have BT, DT I will trust that they have worked out a shape that takes all of this into account.

Personally, I'd rather set up for a shackle of a size appropriate to the winch than use a hook at all.

I would be more concerned with a non-thimbled rope causing too small of a bend radius around the pin. Such is exactly the same problem as a kink in a wire rope. I would venture that the synthetics are more forgiving of this, but I've no info on that.

 

[soenke]

......And this brings me to one of the biggest benefits of synthetic rope (and this goes to the OP's question): that if anything breaks, let it be the rope. If you've rigged to take care of the possibility of a runaway load, then it's almost unheard of for an HMWP winch rope to cause injury through breaking. The real danger is when, say, a shackle on the end of a snatchblock breaks. Then the whole snatchblock can come flying back at high speed. Same problem when any rigging hardware breaks (towing eyes, harnesses, tree-strops etc.). Unlike Andrew P, I have seen a couple of shackles and winch hooks break, and several steel winch cables, luckily all without injury. And don't let's get started on dangerous breakages when using kinetic ropes!

So for safely rigged winching, failure of (synthetic) winch line is about the safest breakage scenario there is. I will probably never retire my synthetic rope unless it's visibly damaged - but I do now carry a spare rope, new and complete, which will take me five minutes to install in the event that I break my first rope. (I could, of course, use this spare as my extension rope and as my tailing rope as well, but in my case, I've carried another rope for that purpose ever since my primary rope was new).

We use Dyneema rope as well on our MM for self recovery.
A spare rope ist perfekt but breakages can even be spliced or just knotted.
The main advantage is safty and weight!

We use Dyneema rope for that reason for the shackles too, I haven´t seen them mentioned so far. (and they are easy to store, no rattling when driving pists)

http://www.svb.de/index.php?sid=251...nid=116261&tpl=&pgNr=1&lang=1&listtype=search


(very expensiv) blocks are available with aproved operating loads up to 5000kg, though breaking load would be much higher

http://www.kohlhoff-online.de/documents/Loop Products UVP.pdf

Sönke

 

[michaelgroves]

Some pretty nifty "shackles" and "blocks"! I like the idea of a lightweight, harmless shackle.

But I imagine that in practice, you'd have to go for a much heftier guage of rope shackle to match the strength of the winch-line. Synthetics don't like compressive forces, which is why they snap much more easily if they are knotted or belayed around something with a small diamete (hence the use of steel thimbles to make a hard eye at the end of the winch-line).

Rgds,

Michael...

 

[soenke]

our shackles are aproved for an operating load 10.000kg, never had a problem ...even using kinetik ropes. Befor I had smaller ones with 5.000kg, I just used two...