Weakest point in winch and rigging?

[ntsqd]

The "Chinese Finger Trap" portion is part of the Sampson procedure as well. No surprise there. The problem with it, at least as far as the Sampson instructions go, is that it requires shortening 6 of the 12 strands to 1/2 of the total insertion length - which is a many multiples of the rope's diameter. I did not include doing that in my testing for this reason. My premise for the testing was a quick field repair, and earlier eyelet splicing showed the un-braiding and trimming to not always be very fast.

My theory of the knot failures is that the localized stress of the bend in the line turned the stress into heat. The parted ends looked just like I'd used a flame to separate them. What I failed to recall prior to the testing was that no known knot is stronger than the rope in which it is tied. I should have concentrated on splicing methods from the start.

In my testing of the 'S' weave I did not bury either end in the center of the other line. At 5+ passes it did not prove necessary to strength though if the repairer had the time it certainly would aid in going through the fairlead and in spooling onto the winch drum.

 

[madizell]

Cutting strands to differing lengths creates a taper which spreads stress. I find it tedious even to remember how to do it, and have to refer to written instructions every time, but it does work very well. The whole point of the splice process is to spread the stress of repair over a long length of rope. I don't know what the strength ratio is for such splicing, but it is close to the original strength of unspliced rope.

At one point I carried a splicing kit in the Jeep - fid*, electricians tape, instructions, light line for doing cross-stitching of the splice to anchor the joint, and so on. Now I just carry extra prepared ropes and do the splicing at home.

* A fid is a probe device used to aid in weaving splicing strands through the body of the line. I made mine from coat hangar. You can also use a pencil or pen, a screwdriver, or anything shaped similarly. It works something like a big needle.

 

[R_Lefebvre]

I have tweaked the frame on my CJ-7 with only an 8,000 pound winch by pulling more than I should, off angle (diagonal stress). Better not to use the full capacity of such a winch unless you are pulling on a 2-ton utility truck, which is to say you should not see the winch stall under normal self-recovery scenarios.

Hmmm... this concerns me.

Last week I used my new winch and bumper (ARB, and EP9) for the first time... you guessed it pulling stumps.

The first couple stumps weren't too big and had rotted for about 10 years so they were cake. Armed with a false sense of confidence, I tackled a large fresh stump. I cut all the roots I could, but guessed there was more going straight down. I was using my snatch block to double up the line, and hooked it back to my factory recovery point on the driver's side frame. I used a large shackle, I think 7/8", that was attached to the snatch block, and then I had my chain doubled up around the stump. I was trying to keep a mind on the force and doubling up everything since the line was doubled. I have 2 extra large shackles in my kit for this reason.

Well, now you know of course I just dragged my truck. I had the parking brake set and the trans in park. Not sure if this is the best way to go. I was a little worried about overstressing the parking pall? Oh, it was in low-range too, figured that would help. I noticed when the truck was dragging forward, one of the front tires was actually rolling, which I didn't understand. Then I realized the driveshaft was locked, but probably the other tire was rolling the opposite way because of the diff.

So it wasn't doing much to the stump, until eventually my front bumper started pushing on another large tree, resting against the passenger side front. I was being careful going slow, and then I saw my bumper start move a bit relative to the body, and I gave up. I was worried about "tweaking" my ARB. Soon as I saw it move, I stopped. I don't think tweaked it. It's still dead level. I notice the gap from the body on one side is slightly less than the other, but no angle. I think that was just the tollerance from when I installed it.

I realize now, it would have been better to attach the end of the winch cable to another tree. That way the truck would only have 9000lbs pull, and the tree would share the load. Obviously 18,000lbs was more than enough to pull the truck.

Anyway, now I wonder if I may have twisted the frame or anything? I haven't noticed anything odd at all, and never would have thought of it again if I hadn't ready that. I figure, if the ARB crush cans didn't collapse, there's no way I could have bent the frame?

Was any part of this rigging particularly dangerous? I was trying to double everything up, including the chain I wrapped around the stump.

 

[TJVach]

Anyway, now I wonder if I may have twisted the frame or anything? I haven't noticed anything odd at all, and never would have thought of it again if I hadn't ready that. I figure, if the ARB crush cans didn't collapse, there's no way I could have bent the frame?

Was any part of this rigging particularly dangerous? I was trying to double everything up, including the chain I wrapped around the stump.

"The mounting system is the single most important part of a bull bar design. ARB's mounting systems are specifically engineered for each vehicle, and are designed to spread impact and winching loads evenly over the vehicles chassis, ensuring the bull bar functions properly in extreme circumstances"

This is directly from the ARB USA website speaking about their winch bumpers. I'm not sure if this pertains to your situation, but I was always under the impression that that is what the ARB bumpers are designed to do.

I'm not going to say that your rigging was dangerous, because I am not even close to an expert at winching/setups. If it were me I might tie my truck off to another anchor point in the rear. I don't know if that is a good idea but I figured I'd throw it out there.

 

[michaelgroves]

Obviously the best scenario if the winch and rigging get overloaded is for the winch to simply stall. All the other components should ideally be strong and secure enough to not break up to and beyond the capacity of the winch itself. One good thing about a hydraulic winch is that the ultimate stall torque is very well regulated by the bypass valve on the pump. Electric winches produce undefined but potentially huge strains on the rigging at the instant of stall.

In any case, in practice, there are shock loads, invisible flaws in components, and some unknowable factors that mean that sometimes other parts of the rigging will fail. Being prepared for a breakage is a key part of winch safety. So even if you have a cable rated beyond the winch's capacity, you should treat it as if it might break.

For one thing, winches are not lifting devices, (hence the low safety margins on winching equipment between ultimate breaking strain and rated capacities). Any situation where the load can run away uncontrolled is "lifting", so if one's pulling up a gentle slope, there should be a driver in the winched vehicle to put the brake on. If it's too steep to hold with brakes, then a second rope should be tailed in while winching, anchored separately from the winch rope. I seldom see it done, but it's really not that difficult, and the alternative is risking your whole vehicle in the hopes that not a single one of perhaps a dozen different cheaply made, hard-used, seldom inspected, and poorly maintained rigging components will fail, despite having a low safety margin built in!

(Obviously, of course, most winch pulls are not done to move vehicles up or down gradients - by far the majority are extractions from mud holes, or out of ditches, or out of some awkward situation where the truck is grounded. In which case the secondary rigging is not necessary, as no significant falling is possible).

I personally favour good synthetic (HMWP) rope for winching. I certainly can't agree with the idea that they are only good for one season - I've used mine (moderately heavily, but carefully) for around six years now, and it's still up to the job. I don't trust it, of course, but then I don't trust any winch cable!

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).

 

[jcbrandon]

Thanks to all for your advice and perspectives. I think I'm starting to get a handle on all of this.

As an aside, in my professional life I get to work with some pretty interesting materials (carbon and aramid fibers, thermoplastic adhesives, all kinds of cool stuff). I have a meeting this morning with two gentlemen from DSM Dyneema in the Netherlands. These are the folks who make Dyneema, "the world's strongest fiber". That's what Amsteel Blue and other high-performance winch lines are made out of. Not sure if I can work off-road recovery into the conversation, but it should be interesting nonetheless.

 

[michaelgroves]

I don't think anyone mentioned it explicitly, but of course it should always be remembered that all the loads on the "far" side (the side with the shackle) of a snatchblock (including the load on the snatchblock itself) are higher than the loads on the "near" side (the side the winch rope enters and exits). Anything up to double the load. So whatever you anchor a snatchblock to, needs to be strong enough to take twice the winch's pull.

If you use two or more snatchblocks on the same winch line, each of them will generate double loads on whatever they are anchored to, so try not to ever have two snatchblocks attached to the same anchor, unless it is suitable for four times the winch pull.

Your winch cable, of course, doesn't come under additional strain, and nor does its anchor point.

(Each snatch block you run the winchline through can effectively add "x" amount of total pulling force, where x is the rating of your winch, less some percentage loss for friction - usually estimated at around 15-25%. So one snatchblock can give you (nominally) twice the total pull, two snatchblocks, three times the pull, three snatchblocks, four times the pull etc. But as I said above, each snatchblock and its anchor comes under double the strain of the winchline itself, which is easy to remember.)

 

[Antichrist]

Reading through this I saw a couple of statements that x diameter cable has a breaking strength of....
Wire rope comes in many different ratings. For instance, 7/16 19x7 IWRC Rotation Resistant at 16,600lbs to 6x19 Class IWRC Long-Wear at 23,800.

Personally I prefer wire rope for the type of work I put it to. But I've worked both as a rigger for heavy construction, with a lot of overhead lifting and as a skidder operator with a lot of winching in the woods in rough terrain. I've also been working with vehicular winches for going on 35 years. Unfortunately a lot comes with experience, which can be rough for the inexperienced.

Awareness of your equipment is the key. Don't worry about "fuses", though the shear pin on my deuce and half PTO winch came in handy a couple of times.
Make sure your equipment is in good nic and properly sized (absolutely key) and an electric winch will likely stall before anything breaks.

 

[madizell]

No doubt you are right about different classes of wire rope, and certainly it is good information to have. Most of us who use wire rope on a winch, however, use the rope provided by the manufacturer, or a replacement unit from standard suppliers. My guess is that the winch suppliers are using wire rope nominally suited for the job, not the very best that could be used, which would be why the rating quoted for a size rope were mentioned.

Making the change to high grade wire more difficult, it takes specialty equipment to properly connect eye ends to wire rope to be used in high tension situations. I don't know anyone who has this equipment. Do the suppliers of high grade wire also make the appropriate eye ends on request? Does the high grade wire have handling restrictions or flexure limitations that would make it unsuitable for use on a recovery winch? Can it be used, for example, on a 3 1/2 inch drum and can it run through a hawse or roller fairlead with the minimal angular dimensions found on off road vehicles?

 

[Antichrist]

No doubt you are right about different classes of wire rope, and certainly it is good information to have. Most of us who use wire rope on a winch, however, use the rope provided by the manufacturer, or a replacement unit from standard suppliers. My guess is that the winch suppliers are using wire rope nominally suited for the job, not the very best that could be used, which would be why the rating quoted for a size rope were mentioned.

True, as I recall when I contacted Ramsey, their supplied 3/8" wire rope was rated at about 16,000lb.

Making the change to high grade wire more difficult, it takes specialty equipment to properly connect eye ends to wire rope to be used in high tension situations. I don't know anyone who has this equipment.

Most any rigging company has the equipement on hand. Phone book under Rigging or Crane Rental.

Do the suppliers of high grade wire also make the appropriate eye ends on request?

Some yes, some no.

Does the high grade wire have handling restrictions or flexure limitations that would make it unsuitable for use on a recovery winch? Can it be used, for example, on a 3 1/3 inch drum and can it run through a hawse or roller fairlead with the minimal angular dimensions found on off road vehicles?

Actually the higher rated rope I quoted is more flexible than your standard OEM wire rope. Also you can get a field replaceable end for it that is rated to match the rope.

 

[NothingClever]

The Value of Thread Searches Revealed....

Great post. Thanks to all for rendering their wisdom, observations and experience.

I have a coupla questions (somewhat ancillary) related to the OP.

I like the idea of ARB's crush cans in their bumpers to make the bumper compatible with air bag sensors to prevent premature deployment.

Q1: Is this a proven feature or is this merely marketing?

The reason I ask is because I am going to purchase a front bumper soon and I want it set up for a 2" receiver (winch on a winch cradle for front or rear anchoring).

Amongst the options are, of course, a custom bumper from Armorology, RockWare, Irbis, etc, etc. My issue is I don't have the time to drop off the truck for a few days at one of those locations.

Another option would be to pick up an economical ARB and have a knowledgable welder weld the receiver to the ARB. I think even after the welding, I could save around $300 which, to me, is enough fuel to get me to somewhere around Merida, Yucatan (the long way).

Q2: Anybody have any thoughts on welding an ARB?

Thanks in advance.

 

[rambrush]

Yes the ARB does have the crush zones. Yes ARB states in the paperwork any and all warranties are void if the bumper is modified.
Thus there has been a mod that you actually connect he receiver to the front frame horns. I don't have the time currently but if you search around a bit you should be able to locate it. It might even have been over on the TTORA website forum

 

[NothingClever]

Yes the ARB does have the crush zones.

So, are they truly functional or simply marketing?

Thus there has been a mod that you actually connect he receiver to the front frame horns. I don't have the time currently but if you search around a bit you should be able to locate it. It might even have been over on the TTORA website forum

Thanks....I'll check it out.

 

[cruiseroutfit]

So, are they truly functional or simply marketing?...

I doubt anyone with a stitch of ethics or a sense for liabity would market a bumper as 'airbag approved' with crush cans if it were not the case. I'm thankful the market hasn't eroded to such tactics.

Yes they work and even more so they are tested to be compliant and crush and decelerate per specifications. They are a really neat design that allows crush, yet also allows winching loads through the use of "shear tabs" that break or bend in even of an accident. Furthermore for minor accident where the bumper is not compromised but the crush sections are, these parts are sold individually from ARB.

There are pictures of the ARB crush cans here:
http://expeditionportal.com/forum/showthread.php?t=5371&highlight=crush

There were some detailed pics of the units themselves here but it looks like they were lost with the database issues, none the less there are some details here:
http://expeditionportal.com/forum/showthread.php?p=169775&highlight=crush#post169775

ExPo member Nic (Willman) built a neat bolt in 2" receiver for his ARB bumper, something similar could likely be done for most models.

 

[Willman]

ExPo member Nic (Willman) built a neat bolt in 2" receiver for his ARB bumper, something similar could likely be done for most models.

Here is what i did....from my build thread..

I love my portable Warn winch system that i have on my rig. I need to fab up a front reciever hitch for my winch setup. so...I got out the metal and went to work.

I used 1/4" material since the ARB is only 1/8". I made a plate that goes over the opening for the winch and simply just put a reciever there. I wanted something that looked shape and could be removed in the future.
Here I go!

The ARB needed to moded alittle to fit the new reciever.

Drill the holes and placed the place for fitment. Then i finished welding it all up.

All ready for some paint. The pin fits nice and so does the winch.

Hope this helps

Front/rear mounted winch are a sure great!

I have since sold the winch and the reciever due to buying a trailer....