Climbing ropes for car extraction?

[trumpetsailor]

I'm off visiting the family for Xmas. We accidentally dropped an SUV into a ditch tonight after an enjoyable backward driveway slide. I've got an 8.5 mm double rope and more than enough hardware to rig a 6+:1 haul rig.

 

I'm aware of the tensile strength limits for the rope and that overzealous haul systems can reach them.

 

Any guesses as to how much of a static load will start to degrade a half/double rope from a climbing/dynamic perspective? I like the rope.

 

Edit: Whoa. Comealongs are cheap.

Edited December 27, 2010 by trumpetsailor

[rob]

hmm well, 1 newton is something like .22 pounds (pounds-force, not mass), so if you have an idea of how much the car weighs I guess you could figure out how that would translate into newtons to get an idea of overall load on the rope?

 

Personally, though, I wouldn't lead on it again. It would mess with my head.

[trumpetsailor]

Thanks for the quick reply!

 

Yeah - I figure if I start to push up anywhere near the rated tensile strength, I'm starting to accumulate the equivalent of a big fall or more.

 

There's a reasonable chance we'll get this car out with ~4 kN or less of force. Using just one pulley, attached at the car, would step that down to a 2 kN (~400 lb) load in the rope, which seems like it should be within the normal working loads for a climbing rope.

 

Now that I know that comealongs might be had for <$50 + the cost of some haul webbing/wire rope/chain, I'm exploring that option too...

[rob]

ah, christmas memories

[DPS]

I've towed my truck out of a snow bank more than once. My thoughts:

 

1)Using an (expensive) dynamic rope will not be very efficient since much of the force applied will simply stretch the rope rather than move the vehicle. You would be better off with static rope.

 

2)A dynamic rope will be shot after you are done.

 

3)Aluminum carabiners and glacier resuce pulleys may fail. Get steel industrial equipment rated to hold the expected load.

 

4)Drape a blanket over the rope used to haul out the vehicle. This will keep the rope from snapping back and breaking the windshield or denting the towing car. (Voice of experience talking).

 

5)Use 2" tubular nylon webbing to build the anchor. Wrap the webbing around the anchor (e.g. a tree) three times and tie with a water knot with long tails. The anchor is attached to the first strand that went around the anchor, rather than the strand with the knot.

 

5)Getting a tow truck to pull the car out is probably the easiest option, and may not be that expensive depending on where the car is relative to a population center.

[trumpetsailor]

Thanks, DPS! I've pulled other cars before, just not on a dynamic line that I wanted to save. The blanket trick is an essential.

 

Compulsive ice-chipping and careful packing of bramble under the tires let us drive the car out of the ditch this morning.

 

I'm still curious, though the question is now academic:

 

2)A dynamic rope will be shot after you are done.

 

How do you know? I imagine a dynamic rope can hold 0.5 kN for days without any obvious degradation, but I wouldn't climb on a rope that had been left with a 9 kN static load for even a few minutes.

 

Are there any test results for dynamic lines left under considerable static loads (~3-4kN) for long periods of time (hours/days/weeks)?

Edited December 28, 2010 by trumpetsailor

[rob]

I've towed my truck out of a snow bank more than once. My thoughts:

 

1)Using an (expensive) dynamic rope will not be very efficient since much of the force applied will simply stretch the rope rather than move the vehicle. You would be better off with static rope.

 

2)A dynamic rope will be shot after you are done.

 

3)Aluminum carabiners and glacier resuce pulleys may fail. Get steel industrial equipment rated to hold the expected load.

 

4)Drape a blanket over the rope used to haul out the vehicle. This will keep the rope from snapping back and breaking the windshield or denting the towing car. (Voice of experience talking).

 

5)Use 2" tubular nylon webbing to build the anchor. Wrap the webbing around the anchor (e.g. a tree) three times and tie with a water knot with long tails. The anchor is attached to the first strand that went around the anchor, rather than the strand with the knot.

 

5)Getting a tow truck to pull the car out is probably the easiest option, and may not be that expensive depending on where the car is relative to a population center.

 

this all sounds so familiar, for some reason....

Edited December 28, 2010 by rob

[DPS]

 

2)A dynamic rope will be shot after you are done.

 

How do you know?

 

Personal experience. Years ago I got my truck stuck in a snow bank. A big 4 x 4 happened along and was willng to tow me out. The only rope I had long enough was my climbing rope. The 4 x 4 literally sling shoted me out of the snow bank thanks to the elasticity of the rope but it broke and snapped back putting a dent in the tailgate of the other vehicle.

 

I'm sure the forces generated in a manual hauling system are much lower than those generated from a 2 ton vehicle yanking out another 2 ton vehicle (from a running start no less), but I would not want to climb on the rope afterwards.

 

BTW, glad you got the vehicle out of the ditch.

Edited December 28, 2010 by DPS

[num1mc]

http://cascadeclimbers.com/forum/ubbthreads.php/topics/866494/1

 

Many posters, many ideas. It seems as though with the poor efficiency of climbing pulleys, you really aren't going to put out that much force unless you have a huge group pulling

[nhluhr]

I hastily tied off the back of my Subaru to a bridge railing after it was caught in flood waters to prevent it floating away. The rollback later used that rope (10.3mm Petzl Zephyr) to winch the car slowly out of the deeper water so he could hook up his steel cable to crank it onto the flatbed.

 

I'd never use this rope for leading again but it's still fine for top-ropes.

[goatboy]

Anyone ever see that photo of the climbing rope going THROUGH the guy's leg after it snapped while pulling a car out of the ditch? Unbelievable and awful. I can't find it right now, but will keep looking.