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Say you got stuck this last time you went wheeling!

Metrodps

Metrodps

Strange but nice guy
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OK after watching a bumper get ripped off a truck this weekend. I thought I would bring this back into focus. Read it; learn it; live it!


Originally Posted by Metrodps
First you need to be absolutely sure that EVERY single piece of equipment used in the task is strong enough and will not fail and thereby endanger life and limb. Hooks should be pointing up that way if they come off they go down. Realize, that for reasons of practicality and economics, your 4x4 recovery equipment is almost certainly undersized.....you can still do the job, using the correct techniques, but you will be much SAFER if you keep this in mind.



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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.​
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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.
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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: ​


[FONT=Arial, Arial, Helvetica]Surface resistance
[FONT=Arial, Arial, Helvetica]A pull of 1/10 LW will cause a free wheeling truck to move on a hard, level surface.[/FONT][FONT=Arial, Arial, Helvetica]
A pull of 1/3 LW will cause a free wheeling truck to move on a softer surface, such as grass or gravel,
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[FONT=Arial, Arial, Helvetica]Damage resistance:[/FONT]
[FONT=Arial, Arial, Helvetica]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)[/FONT][FONT=Arial, Arial, Helvetica]

[/FONT][FONT=Arial, Arial, Helvetica]Stuck (mire) resistance:[/FONT]
[FONT=Arial, Arial, Helvetica]A pull of 100% of LW will be required if the truck is stuck to a depth of the sidewall on the tires.[/FONT][FONT=Arial, Arial, Helvetica]
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)
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[FONT=Arial, Arial, Helvetica]Grade (slope) resistance:[/FONT]
[FONT=Arial, Arial, Helvetica]Upgrade (vehicle has to be recovered up a slope or grade)[/FONT][FONT=Arial, Arial, Helvetica]
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​
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[FONT=Arial, Arial, Helvetica]Final figure:[/FONT]
[FONT=Arial, Arial, Helvetica]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.[/FONT][FONT=Arial, Arial, Helvetica]


Here is the military approach.​

surfaceresistance1.jpg


gradiantresistance1.jpg


The way to attack the situation. Using this method you can free a Hummer buried up to its axles Thanks to Mike Rowe and Dirty jobs.
stuckexample.jpg


If you want to read on recovery operations search for:
FM 9-43-2, Recovery and Battlefield Damage Assessment and Repair.[/FONT][/FONT][/FONT]
​
 
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I have had my frame suffer damage on more then one occasion from being pulled out of a stuck. I blame FOR MUD since he is always pulling. You would think a hook bolted directly to a frame is strong until you see it bent after being pulled out of the mud.:crazy:
 
awesome info...i saw that on dirty jobs, and was amazed...definately gonna use that in the future, if i have too. good info though man, nice.:D
 
You think I pulling then!!!!!! Wait until next time.:D

I've seen more damage done to trucks trying to get them unstuck then trying to get them stuck. Just look at the front of my frame sometime.
 
wow... had to re-read some of that stuff. but nice info. Will keep it in mind next time im stuck!
 
ah thats funny. the last two times I got my scout stuck, we hooked to the bumper of my friends toyota, and pretzeled his rear bumper! my scout is friggin heavy! it weighs over 5000 when loaded for the trail.
 
I wanted to up date this with a link for the [FONT=Arial, Arial, Helvetica][FONT=Arial, Arial, Helvetica]FM 9-43-2, Recovery and Battlefield Damage Assessment and Repair.
[/FONT][/FONT] http://www.usamma.army.mil/assets/docs/FM 9-43-2.pdf

And to give some more information:

As a general rule, the safe working capacity (SWC) of a rope can be obtained by squaring the diameter of the rope in inches (SWC = d 2). This formula gives SWC in tons, allowing a safety factor of approximately four.

Example: SWC of a 1/2-inch rope is .5 x .5 =.25 tons (1/4 ton)

The strength of a chain is measured using the formula, SWC = 8d 2, where SWC = the safe working capacity in tons; d = the diameter of the chain stock in inches.

Example: SWC of a chain with a diameter of 1/2-inch is 8 x .5 x .5 = 2 tons.
 
That's why I have a 40,000 lb. pto winch with 3/4" cable off of 5 ton wrecker truck under my 4x4 :P :)

To pull everybody else out!!
 
Bringing to the front for new guys!
 
FOR MUD said:
You think I pulling then!!!!!! Wait until next time.:D

I've seen more damage done to trucks trying to get them unstuck then trying to get them stuck. Just look at the front of my frame sometime.
Click to expand...

4xcrazy said:
I hope they've learned how and where to use THEN and THAN by now :doah:

:D
Click to expand...

Wow I thought my dyslexia was acting up some where. :doah:
 
ZukiJohn said:
That's why I have a 40,000 lb. pto winch with 3/4" cable off of 5 ton wrecker truck under my 4x4 :P :)

To pull everybody else out!!
Click to expand...

Yes I'm quoting something old. But someone brought back an old thread :zombie18:

I was telling someone how a 12k winch is the bare minimum. Mire 3 with a 45 degree angle.

(6000lb rig x 3 [mire 3 depth]) + (0.75 [45 degree incline pull] x 6000) = 22,500lbs. The worst you could get stuck.

12k winch + snatch block

Now, does a snatch block double your power? Yesssssorta. But you didn't think that x2 pulling power was free did you?

1.1x for your friction of the winch rope, and I won't even get into angles.

24000 x 1.1 = 26,500 - 24,000= 2400lb reduction or a combined power of 21,600lbs

12k Warn + block = 21,600lbs. You're 900lbs short. Granted your angle is straight, and you're on your final revolution of the drum with only a few (approx 5?) wraps of cable on the drum.

Well if one snatch block is doubles, two must triple! Well yeahhhh.... no, no it actually doesn't. I can't recall the ammount, H8 school was years ago. IIRC is roughly a 1/3rd of the 12k +1 snatch block. So in the above senario you'll finally meet your need and with two snatch blocks you'll be able to recover roughly 28,800lbs x 1.1 = 31,680 - 28,800 = 2880. 28,000 - 2880 = 25,920

Final pulling power 25,920 lbs.

Or to over simplify vehicle weight x 4.32
So a safety margin of 3420 lbs or 13.19%

And for further dismay, with all that enormous amount of pulling power.... what's your winch rope rated at :haha: Since when are you lucky enough to have a tree directly in front of you for your snatch block. Further reducing your pulling power due to friction from angles.

I know I screwed up somewhere. But that's the jist :D
 
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