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If you buy any professional grade rigging components like shackles, pear links, etc. they are industry rated with a SWL safe working load which is four times the breaking strength. I believe that most if not all vehicle winches and related rigging are rated at their breaking strength. This being said, if you have a 10k winch and a 10k swl shackle, the winch will fail at 10k, but the shackle will fail at 40k. I think the large safety margin is mainly due to compensating for shock-loads when rigging with a crane which are not so much of an issue for off-road winching.

CentAr712 wrote:This being said, if you have a 10k winch and a 10k swl shackle, the winch will fail at 10k, but the shackle will fail at 40k.

Newbie side-question here (I have not been around enough winch operations... and when things failed it was always the rope): Will the winch fail (i.e. a component will break) at 10k, or will it just stop pulling? :?:

the specs are about 4500 lbs but I wondering about the safety factor ie. winch should be X times Curb weight etc.

I don't know if you'd label it a "safety factor" or not, but I was under the impression that the largest extra demand would likely be encountered in wet conditions, like mud or snow. Then the concern would be the extra suction caused by the wetness, and I'd think that could be substantial. I've read manufacturers literature which suggested between 1.5 and 2 times the weight of the vehicle.

Tirfor winches just stop pulling so you can't easily exceed a safe limit. They keep hold of the wire rope at that point though. As for what happens if a load beyond that limit is somehow applied, perhaps when the car you are winching is unexpectedly hit by a train, I don't know. I imagine it would get you on Youtube though.

Those ratchet winch things eventually twist (perhaps not the cast one in the initial posting, but certainly the cheaper ones) and the ratchet teeth fail to engage, releasing all the tension at once- which can be startling. Been there.

Tony

I am fairly certain that the rated load for a truck mounted winch is it's max pulling power and even then it's only with a single layer on the drum; each additional layer of rope reduces max pull. I am not sure at what point the brake on the winch will give out, but I would guess that it has to at least exceed the max pull rating. I'm sure the detailed specs are in the info that is supplied with your specific winch.

When referring to "safety factor" in regards to rigging, we are typically referring to when a piece of rigging will break or mechanically fail. I think "safety factor" in the context that it was mentioned earlier refers to how you calculate how big of a winch you need to pull how big of a truck. Generally a common rule of thumb is 1.5 times the loaded weight of the truck while others use a more more complicated formula which breaks it down in detail.

If I'm not mistaken, the more complicated formula states that basically, in a worse case scenario of being buried in mud to the frame with a 100% uphill grade pull you will actually need closer to a 4:1 pulling power to truck weight ratio, but realistically at that point I think 20,000# of pull on a pinz will literally pull it apart if you weren't really careful.

you want the more complicated version, then read through this. It does contain some valuable information.
http://armypubs.army.mil/doctrine/DR_pu ... _30x31.pdf

Recovery, not a 12 step program.. this article provides many good insights.

BillaVista's Recovery Bible.

http://www.pirate4x4.com/tech/billavista/Recovery/

edzz wrote:Recovery, not a 12 step program.. this article provides many good insights.

BillaVista's Recovery Bible.

http://www.pirate4x4.com/tech/billavista/Recovery/

Ah yes - I forgot about that document (and have actually read it at least once a long time ago - getting old no doubt!)
Here are some key points on this topic (rest of article is very good as are many of Bill's write-ups).

"Most, if not all, winch manufacturers will tell you to select a winch based on 1.5 times the gross vehicle weight. This often leads to less than satisfactory results for 2 reasons:

1) Most people are terrible at actually estimating the gross weight of their rig as it sits on the trail, full of gas, tools, equipment, food, camping gear, people, the dog...everything. Heck, in some cases the real figure can actually exceed the GVWR of the vehicle. Simple advice here - either err WAY on the heavy side, or get your rig weighed in trail trim.

2) More importantly, the "effective weight" of a "stuck" 4x4 is very often FAR more than 1.5 times the GVW. The following data on how to more accurately estimate the "effective weight", is taken from the world of professional heavy recovery - the guys that recover Tractor-trailers that have flipped on their side for instance, as well as U.S., Canadian, and UK Military recovery manuals.

Once you have accurately estimated or measured the trucks loaded weight (LW) you can calculate the resistance to be overcome in any recovery situation (this is commonly known as the ROLLING resistance). There are 4 types of resistance that must be accounted for to accurately assess the resistance that must be overcome. These are surface resistance, damage resistance, mire (stuck) resistance and grade (slope) resistance. Calculate them all as follows:

Surface resistance
A pull of 1/10 LW will cause a free wheeling truck to move on a hard, level surface.

A pull of 1/3 LW will cause a free wheeling truck to move on a softer surface, such as grass or gravel,

Damage resistance:
A pull of 2/3 LW will be required to move if the wheels cannot rotate (as if the brakes were fully applied), the pull required to overcome the resistance (drag) the truck id 2/3 or 67% of the LW. Damage resistance includes surface resistance (i.e. you only use one or the other)

Stuck (mire) resistance:
A pull of 100% of LW will be required if the truck is stuck to a depth of the sidewall on the tires.

A pull of 200% of LW will be required if the truck is stuck to the hubs.

A pull of 300% of LW will be required if the truck is stuck to the frame..

Mire resistance includes damage resistance (i.e. you only use one or the other)

Grade (slope) resistance:
Upgrade (vehicle has to be recovered up a slope or grade)

15 degrees - add 25% of LW

30 degrees - add 50% of LW

45 degrees - add 75% of LW

Vehicle recovery on level ground - no correction

Downgrade (vehicle has to be recovered down a slope or grade)

15 degrees - subtract 25% of LW

30 degrees - subtract 50% of LW

45 degrees - subtract 75% of LW

Final figure:
Add surface or damage or mire resistance and grade resistance, and this is your final figure or rolling resistance. This is the amount of pull the winch must apply in order to recover the stuck vehicle.

Example:
My trail rig fully kitted out weighs in at 5000 lbs. I get stuck down a rock ravine that's about 45 degrees steep, and there are big rocks up to the frame hanging it up.
Rolling resistance is 5000lbs x 3 + (5000 x 0.75) = 18,750 lbs.
As you can see, this is significantly more than the 5000lbs x 1.5 - 7500lbs the manufacturers would have you believe.
You may be wondering how one could ever possibly recover the vehicle in this example, given that the largest commercially available 4x4 recovery winch is 15000 lbs and that most are in the 8-9000lb range. The answer is by using multi-line rigging"

super interesting- i've been thinking these exact same thoughts ever since getting the front wheels stuck in mud up to the axle. please keep it coming.

The answer is by using multi-line rigging"

Yeah, that and making certain to have tow points on the vehicle capable of withstanding such a force.

Nice write-up about the issue. Thanks for posting.

You make some very good points about loading up a recovery load in different circumstances. Here is Aust we have had a few fatalities with equipment failures (more so snatch (kinetic) recoveries rather than winch) and metal recovery components being projected through windscreens into cabins and killing people inside. These are often the result of not using "rated" recovery points on vehicles or using tow balls as the recovery point.

Garry

Garrycol wrote:You make some very good points about loading up a recovery load in different circumstances. Here is Aust we have had a few fatalities with equipment failures (more so snatch (kinetic) recoveries rather than winch) and metal recovery components being projected through windscreens into cabins and killing people inside. These are often the result of not using "rated" recovery points on vehicles or using tow balls as the recovery point.

Garry

This brings up a point about come-a-longs and other hand wenches; there is no way to operate these devices without being in the path of harm if the cable or a coupling fails. With an electric winch you can control the pull from a safer position.

With a snatch / pull type recovery, I don't really think having rated recovery points or rigging is the answer since no rigging used in industry is typically rated for dynamic shock-loads. It's very hard to measure or anticipate the force that will be exerted in those circumstances. Typically you want to avoid shock-loads on your gear at all times and the real answer is to not consider pulling and jerking a viable recovery method. A seemingly small shock-load can easily exceed the working limits of even greatly over sized rigging, albeit only for a fraction of a second, it's still enough to break things. The only safe way to do that sort of recovery would be to just use ridiculously over-sized hardware and have a truck built like a tank. I personally only consider that recovery method a last resort.

A seemingly small shock-load can easily exceed the working limits of even greatly over sized rigging, albeit only for a fraction of a second, it's still enough to break things.

This is some very serious discussion, and hopefully folks take heed. One of Wisconsin's biggest military vehicle collectors was killed a couple years ago by just such an accident, when the tow point they were using broke.

http://redrockonair.com/news/2012/02/09 ... rry-marsh/

CentAr712 wrote:With a snatch / pull type recovery, I don't really think having rated recovery points or rigging is the answer since no rigging used in industry is typically rated for dynamic shock-loads. It's very hard to measure or anticipate the force that will be exerted in those circumstances. Typically you want to avoid shock-loads on your gear at all times and the real answer is to not consider pulling and jerking a viable recovery method. A seemingly small shock-load can easily exceed the working limits of even greatly over sized rigging, albeit only for a fraction of a second, it's still enough to break things. The only safe way to do that sort of recovery would be to just use ridiculously over-sized hardware and have a truck built like a tank. I personally only consider that recovery method a last resort.

Chris, thanks for your input and answering my question about (electric) winch failure.
Am I correct at stating that kinetic ropes are controversial because their use sometimes borders on "pulling and jerking", and their abuse is just that?