Static Rope wear from a Zip line?


Original Post
johnnyrig · May 31, 2016 · Unknown Hometown · Joined Dec 2011 · Points: 65
Bought a brand spanking new Bluewater Canyonator 9mm x 200 ft (length is correct) static line, specifically to set a make-shift zip line across a creek on a camping trip.

Whether you think this is a good idea or not is immaterial at this point. The rope is rated to about 5,000 lbs, and it was tensioned in such a way as to have at least 10 degrees of sag, meaning the force generated on the rope by the rider would pretty much not exceed 3x their weight. The top end was anchored to a tree with a figure 9 and webbing. The lower end was rigged to a tree with 7mm cord and a 3-1 advantage employing a webbing klemheist to the main line and a releasable munter hitch on the pull side, in case the rig needed loosening to lower a stuck rider.

Question is, why would a Petzl Tandem pulley fuzz up the sheath? Is it just the mechanics of bending the rope at high speed? Do these static polyester lines have poor wear characteristics? Am I just pulling for a Darwin Award?

FYI, it was crossed about two dozen times. Heaviest rider probably tipped 300 lbs. The rope sheath fuzzed up far more than I would have thought for simply rolling through a pulley made for this type of thing. Anyone have any sort of valuable insight as to why?

Thanks.

20 kN · May 31, 2016 · Hawaii · Joined Feb 2009 · Points: 1,123
johnnyrig wrote:Bought a brand spanking new Bluewater Canyonator 9mm x 200 ft (length is correct) static line, specifically to set a make-shift zip line across a creek on a camping trip. Whether you think this is a good idea or not is immaterial at this point. The rope is rated to about 5,000 lbs, and it was tensioned in such a way as to have at least 10 degrees of sag, meaning the force generated on the rope by the rider would pretty much not exceed 3x their weight. The top end was anchored to a tree with a figure 9 and webbing. The lower end was rigged to a tree with 7mm cord and a 3-1 advantage employing a webbing klemheist to the main line and a releasable munter hitch on the pull side, in case the rig needed loosening to lower a stuck rider. Question is, why would a Petzl Tandem pulley fuzz up the sheath? Is it just the mechanics of bending the rope at high speed? Do these static polyester lines have poor wear characteristics? Am I just pulling for a Darwin Award? FYI, it was crossed about two dozen times. Heaviest rider probably tipped 300 lbs. The rope sheath fuzzed up far more than I would have thought for simply rolling through a pulley made for this type of thing. Anyone have any sort of valuable insight as to why? Thanks.
Is the wear occurring over the entire length of the rope, or just in one section? Is there any wear on the sideplates of the pulley from rubbing, or any fuzzed-up sheath material somewhere on the pulley? Typically a pulley dosent really cause wear on a rope unless the sideplates are rubbing on the rope along the way.

johnnyrig · May 31, 2016 · Unknown Hometown · Joined Dec 2011 · Points: 65
I'll have to look at the pulley tomorrow. I noticed a little fuzz in it, which is what prompted me to have a look at the rope. The entire length that the pulley rode fuzzed up. I did spin the pulley to ensure nothing was seized, but failed to look at the side plates. 9mm rope in a pulley made to handle 13mm, really shouldn't have been an issue, right?

johnnyrig · Jun 1, 2016 · Unknown Hometown · Joined Dec 2011 · Points: 65
After looking at the rollers, I noticed they are grooved, which I think is what caused the rope wear. Looks like the thing has been run on a steel cable, and stupid me just didn't look at it closely enough or give consideration to the possibility of it causing rope wear. Anyhow...

-ELs3yxw

Stich · Jun 1, 2016 · Colorado Springs, Colorado · Joined Jan 2001 · Points: 1,230
Yes, if you run pulleys on steel cable the groves of the cable braids will etch permanently into the pulley. I have a nylon one like that from just a few trips across to Mission Wall in Clear Creek.

JK- · Jun 5, 2016 · SLC · Joined Nov 2012 · Points: 13
I've canyoneered for years with the BW canyonator, and never had a durability problem. On the contrary I've been super impressed with the durability for a 9mm. It's lasted way longer than any other type canyon rope I've ever had regardless of thickness.

So likely either the pulley or the use... After having run challenge courses for a few years I can tell you that rope playing through a pulley at any sort of speed wears the rope out pretty quickly, I'd assume a pulley moving at high speed across rope would do the same. Grooves in the pulley would probably make it worse.

Guideline #1: Don't be a jerk.

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