Recovery Tech- "WLL versus Safety factors" - JeepForum.com
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post #1 of 67 Old 11-06-2016, 07:31 PM Thread Starter
mrblaine
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Recovery Tech- "WLL versus Safety factors"

The number one question I see asked about any device used for recovery is what is it rated at for strength.

A good discussion needs to take place to put all of the various industries and their rules into the proper perspective so that the mixing and matching of safety factors and Working Load Limits is understood so you can make a PROPER informed decision.

The easiest way to start is to give an idea of what one industry "rigging for overhead lifting and crane work" requires typically.

Most devices that will be used with a hoist for overhead lifting of anything have a WLL that is 1/5 of breaking strength as the typical minimum safety factor and they tend to go higher.

Put another way, if a crane wants to lift a 1000 lb. load, the cable on the hoist will be rated at a minimum breaking strength of 5000 lbs and any shackle, sling, or bridle that sees the lifting load will be rated in a similar fashion.

Most all of the devices used in the rigging industry for overhead lifting are specified in that manner. If you want a shackle or d-ring that you can use for a 1000 lb. load, it is marked permanently with a WLL (working load limit) of 1/2 Ton or 1000 lbs. You can calculate the breaking strength at a minimum by multiplying that number by 5 to find out what it breaks at.

I'll get some pictures up tomorrow to compare a few things to show just how ridiculous the recovery industry is but we have to start some where.

So, if we try to apply an unrelated industry's standards to what we use and do during a recovery, what is the WLL of your 9500 lb winch that has a 5/16" steel cable on it rated at 9800 lbs breaking strength?

We learned a few things in the snatch block thread, apply that and start thinking about how much less sense it makes to mix and match industry standards.


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post #2 of 67 Old 11-06-2016, 08:44 PM
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wll of 1900 lbs on winch and 1960 on cable?

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post #3 of 67 Old 11-06-2016, 09:13 PM Thread Starter
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Originally Posted by RDPrimeaux View Post
wll of 1900 lbs on winch and 1960 on cable?
Close enough. How many folks do you know that would accept the fact that the near 1000 dollar winch they just bought can only be used to pull a max load of sub 2000 lbs?

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post #4 of 67 Old 11-06-2016, 09:24 PM
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I can accept that, that's why I carry a snatch block...
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post #5 of 67 Old 11-07-2016, 01:00 AM
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Glad I got my smittybilt XRC 8 for free then Now if only it didn't have a line out speed equal to that of a drunk turtle...

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post #6 of 67 Old 11-07-2016, 06:09 AM Thread Starter
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Glad I got my smittybilt XRC 8 for free then Now if only it didn't have a line out speed equal to that of a drunk turtle...
The point really isn't what you paid for your winch or even what it is worth. It is the fact that it isn't a hoist. A hoist is used for overhead lifting, you don't have a hoist so why do you want to apply the standards from one industry to another?

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post #7 of 67 Old 11-07-2016, 06:38 AM
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I'm going to guess that the industry standard for rigging cranes and overhead loads is applied with different things in mind such as the 100s of thousands of dollars of damage a break will cause, as well as countless lives potentially lost, especially in an urban setting. I dunno, maybe I'm way off. Maybe the lines are longer and there's more stretching and contracting going on too.

But since you specifically brought up the winch I have a question that I've been dying to ask someone for years, who could provide a good answer. Why is a 10,000# winch only secured with 4 small grade 5 (or metric equivalent) 5/16" (or metric equivalent) bolts? It doesn't seem right, although I have personally seen nor heard of winch mounting bolts breaking.

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post #8 of 67 Old 11-07-2016, 07:32 AM Thread Starter
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I'm going to guess that the industry standard for rigging cranes and overhead loads is applied with different things in mind such as the 100s of thousands of dollars of damage a break will cause, as well as countless lives potentially lost, especially in an urban setting. I dunno, maybe I'm way off. Maybe the lines are longer and there's more stretching and contracting going on too.

But since you specifically brought up the winch I have a question that I've been dying to ask someone for years, who could provide a good answer. Why is a 10,000# winch only secured with 4 small grade 5 (or metric equivalent) 5/16" (or metric equivalent) bolts? It doesn't seem right, although I have personally seen nor heard of winch mounting bolts breaking.
The winch is held to the winch plate with that size bolt because that is what it takes to perform the task at hand. The reason you question it is due to normal lack of understanding (that we are all capable/guilty) of what it takes to perform the task.

I'm investigating building a test stand/bench for testing parts used in recovery to figure out some more things. While digging around looking for the column buckling strengths so I know what size square or rectangular tubing to use, I came across a post on a forum from a guy wanting to know what size tube to use for legs on his stand for a 250 gallon aquarium with a weight of around 2000 lbs or 1 ton.

Several suggestions indicated he should step up to 2" x 2" 1/4" wall square tube. In reality, he needed 1x2 20g rectangular steel tube and it was overkill with a total load capacity for the 4 legs of around 15,000 lbs or 1 leg could carry nearly twice the weight of the aquarium. The recommended size or close to it in 1.5 x 2.5 x 12g or about 1/8" thick walls could carry a total of around 80,000 lbs.

So, when you bolt your winch down with 4 of those little bitty bolts, they have employed a safety factor of twice what it needs to stay put. Put another way, the 4 bolts generate about 20,000 lbs of clamping force to stop the winch from moving around.

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post #9 of 67 Old 11-07-2016, 07:52 AM
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Originally Posted by mrblaine View Post
Most devices that will be used with a hoist for overhead lifting of anything have a WLL that is 1/5 of breaking strength as the typical minimum safety factor and they tend to go higher.
So, if I want an 8000# winch, and I also want to follow this rule... How big is a 40,000# winch?
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post #10 of 67 Old 11-07-2016, 07:56 AM
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Quote:
Originally Posted by mrblaine View Post
I came across a post on a forum from a guy wanting to know what size tube to use for legs on his stand for a 250 gallon aquarium with a weight of around 2000 lbs or 1 ton.

Several suggestions indicated he should step up to 2" x 2" 1/4" wall square tube. In reality, he needed 1x2 20g rectangular steel tube and it was overkill with a total load capacity for the 4 legs of around 15,000 lbs or 1 leg could carry nearly twice the weight of the aquarium. The recommended size or close to it in 1.5 x 2.5 x 12g or about 1/8" thick walls could carry a total of around 80,000 lbs.
I actually had to to figure out almost that exact thing once upon a time (270 gallon tank). I wish I remembered exactly what we ended up using but the nice looking cabinet you see does have a pretty sturdy steel subframe under it. I really miss that tank, although it was a lot of work. Saltwater with live coral tank maybe a hobby that you can waste more money on than jeeps.
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post #11 of 67 Old 11-07-2016, 08:16 AM Thread Starter
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So, if I want an 8000# winch, and I also want to follow this rule... How big is a 40,000# winch?
I've seen a 20,000 lb winch on the front of a widened Suburban and it was big enough that it would probably drop the front of a 4" lifted TJ by at least 2" if you hung it off the front bumper and loaded it with steel cable.

What we need to do instead is go the other way and recognize and understand that our winches are not being used under the same rules. They are not hoists, they are winches. The applicable safety factors from the overhead rigging industry can be used as guidelines to help pick out recovery gear, but they are no way straight across applicable unless you plan to hold all items in the recovery chain to the same standards. If you hold your winch to the same standard, you paid a lot of money for something that has the power of a good come-along.

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post #12 of 67 Old 11-07-2016, 08:26 AM Thread Starter
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Originally Posted by Knuckelhead View Post
I can accept that, that's why I carry a snatch block...
I'll bet you good money you have a snatch block that is over rated by those standards by at least double and your anchor shackles by at least 4 times??

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post #13 of 67 Old 11-07-2016, 10:27 AM
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So what standards should we be using when reviewing our winch and recovery gear?
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post #14 of 67 Old 11-07-2016, 11:19 AM
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I would like to see some real world load testing on an average rock crawling outing. Hooking digital recording scale to the end of the winch line during the average recovery to show what the actual pulls are. I would imagine that there would be a few spikes that come close to the stall/breaking point of the line, but I would say that most of the pull is within a 2:1 or greater break/pull amount.

I will agree that marketing/sales has thrown off the perception of what a winch is capable of as compared to a hoist, if people would read the hoist specs, they will find the comparable gear ratio/HP/line size ratings have the 5:1 safety factor already built in.

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post #15 of 67 Old 11-07-2016, 11:23 AM Thread Starter
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So what standards should we be using when reviewing our winch and recovery gear?
How much can your winch pull?

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