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Synthetic Winch Line Failure

(the care and feeding of synthetic rope)

 

About a month after I installed my Viking Offroad synthetic winch line, it was time to go to Moab, Utah for the 7th Annual JeepsUnlimited Moab Run.  This is a non-event trip that I look forward to attending every year as it gives me a chance to see my friends and always make new ones.  With any luck, the 40ish Jeeps that participate usually do just fine, but every now and then, one will end up with a problem.  This year, a nicely built Rubicon was winching up the last obstacle in Pritchett Canyon and rolled.  Somewhere in the middle of this happening, a brand new, never used, 3/8" Masterpull synthetic line failed under load. 

Upon returning home, I checked into the local Jeep forum only to find that another local Jeeper suffered a synthetic winch rope failure over the weekend.  This rope had been on his TJ for approximately two weeks and it was the second time it had been used. 

OK.....there are lots of folks running synthetic winch line but to have two failures in a week by folks that are from my local area is somewhat alarming.  What the heck was going on?  I can see old abused rope failing but not brand new 3/8" synthetic line.

I solicited the help of Jon Jonsson from Winchline.com as I wanted to know what caused these failures.  After all, if I was going to trust my TJ on the end of a synthetic winch line while climbing a water fall, I wanted to make certain that I wasn't going to see the same kind of results as my fellow Jeepers just had.  I sent Jon links to both of the forum threads that were discussing the rope failures.  The threads were populated with good quality photos (thank you people for NOT using those ridiculous camera phones!) and it was my hope that Jon's vast experience in the synthetic rope industry would help shed some light on what was happening.

Let's start with the incident where the winch line was being used for the 2nd time when it failed.  It was first thought that the rope simply failed due to a manufacturing defect.  Upon closer inspection, this was found not to be the case. 

 

Here is a photo of that broken line and Jon's comments concerning it:

"If this rope broke from overload the whole thing would look like the one strand on the left side that is all frayed, it looks like 11 of the 12 stands cut on the winch plate and then the last strand broke from overload since each strand has about 1000 - 1500 lbs of strength depending on size of rope."

But how did the line get cut on the winch plate?  Part of the answer lies in the above photo.  If you look, you will see that the end of the broken line that is still wrapped on the winch is routed up and over the top of the drum.  This line had been spooled onto the drum incorrectly.  Because of this, it was weakened during its first use.....and when used a second time during a vehicle recovery, the additional damage it incurred was enough to cause a complete failure.

Let's look at a couple of my famous drawings (ok, so I'll admit that I am graphically impaired....which is why I always use my camera in my write-ups) to help explain what happened to the synthetic rope.  The graphics depict a side view of the winch drum and that part of the winch mounting plate that holds either the Hawes or roller fairlead.

The above graphic shows the correct route the winch rope should take as it spools on and off the drum.  Note that it is fed under the drum, not over the top of it.  Given the relative position of the winch drum and the winch plate (which has a slot cut in it for the winch rope to feed through), the winch rope should be able to freely move back and forth through the slot in the winch plate without touching the edges of the plate.  This means no friction and no cutting and the rope is maintained in good condition.

In this graphic, the rope as been incorrectly wrapped up and over the top of the winch drum.  When the rope is fed under tension  through the slot in the winch plate, it now rubs against the upper inside edge of the plate.  This causes friction, then fraying, and sometimes quite quickly the cutting of the rope.  From the rope's perspective, it is no different than if you had tensioned it across a sharp rock while winching your vehicle.....and we all know that is NOT the proper manner in which to use synthetic rope. 

What are the lessons learned from this paticular incident?

1.  Always spool the rope onto the winch drum from the bottom.  Some winch rope suppliers/sellers attach a tag, with a reminder to do this, to the end of the line.  Unfortunately, not all of them do. 

2.  It is important to check your winch mounting plate to ensure it has adequate clearance for the synthetic rope.  It is possible that the rope may still contact one of the edges as it passes through the slot.  If it does, it will surely abrade the rope and cause it to fail.  Jon explained this to me in length before I installed my synthetic line onto my winch. 

3.  After you are done winching, ALWAYS inspect your winch line (steel or synthetic) for damage.  In this incident, it is possible that the owner may have discovered the frayed line and would have been able to take actions to prevent the subsequent failure.

For more information on installing synthetic winch rope, see my write-up.

 

When you are using your winch and there is a possibility that the rope will come in contact with a sharp rock or other object that can damage/cut the rope, you need to use a protective sleeve on the rope.  Any quality synthetic winch rope will come with a heavy duty sheath (typidcally about 6'~10' long) that can be slid up and down the length of the synthetic rope for proper positioning against a rock.
 

Jon provided me with this photo showing two spots where you would need to pay close attention to the rope while winching.  I put a red circle around both of them.  You can see the heavy duty protective sleeve (lower right corner of photo) on the winch rope and the circled area is where the rope would have been touching the rock were it not for the protector.  When your synthetic line is in this kind of a situation, you MUST use the protective sleeve to prevent damage/failure to the rope.  If you don't have a sleeve, GET ONE NOW! 

The second spot you should be aware of (in the above photo) is adjacent to the winch. It is very possible that your winch rope may rub on your bumper (and perhaps even the license plate) as depicted above.  The bumper on this vehicle has very contoured edges/corners so they do not present a problem to the winch rope.  This may not be the case for all bumper/winch mounting plate combinations. 

Be sure you know where your line is going when you are doing an off-camber or non-straight pull winching session (like shown above).  Your line may start out just fine but may end up rubbing against a sharp object before you are finished using the winch.

 

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