How to tell when a rope is shot

Last week, in a pinch, I used a piece of cordelette and some carabiners to tow a car for a friend. It worked fine, but the scientist in me is now wondering what happens to a static rope when it's loaded very close to its breaking point. Does that do any damage to the rope, and is there any way to tell?

In this case, the rope was a PMI 7mm accessory cord, rated for 10.7 kN MBS. The car weighs 1350 kg. We drove about 5 blocks, maximum 5 mph on level ground. Assuming a rolling coefficient of 0.03, that's about 400 N of force on the rope while moving. Starting from a dead stop would be a bit higher, but I don't know how to calculate that.

Accessory cord is cheap. Retire it if you are at all concerned. You don't want that in the back of your mind when you are leading out above an anchor built with that cordelette.

off the cuff I'd say if it passes visual inspection (no burns, fraying or sheath damage) it's probably fine. And of course you're gonna die.

The realist in me says that you can buy 30' for $13. Roughly 30 cents a foot. Further calculations are unnecessary because 30 cents a foot or $13 is far less than time it took to write the post never mind wonder if "your gonna die"!

Crap, Eric was faster!

Elliott Balsley wrote: and is there any way to tell? I

Really? Just buy a new piece if you're worried about it. Not like its expensive.

Its not the continues force on the cord that is of concern, its the impulse force of getting the car rolling. I don't know how to calculate that(i'm an electrical engineer not a mechanical), but I think the method is youngs modulus.

My guess is that the cord is fine, but I would replace it, but i don't think thats what you were really asking.

Ever try pushing a dead car? On flat pavement it is pretty easy to do

If you were able to untie the knots, I'd say the loads were not alarmingly high.

I once used my cordelette (loop of 7 mm nylon cord tied with dbl fishermans) to pull a Civic out of a very shallow ditch. I expected the cord to break but it didn't. Afterwards the knot was about half the diameter it started at and was rock hard. Instant retirement on that guy.

F= MA.
Have very little to do with the weight, all told.
YOur max forces were during acceleration, which includes deceleration. You know that one time the car in tow hits the brakes before the car towing it does and it pulls back on said front car?
Well... how many G forces did that feel like? .2? .3?
(.2*weight of car = force).

I'd retire it.

Any rope..if you even think about it's safety..then it's time to toss it

Probably fine. Almost definitely fine.

I agree with the "if the knots not welded, definitely fine".