Wild Line Ropes Featherlite Lineman's Belt

[gcr0003]

They are splitting the load across the bend. Similar principle to strength loss when something is girth hitched. Read up on how how bends and angles effect load distribution or strength loss. It’s like a knot but with less bend radius.

I’m saying high level. If the exit of the hitch reduces the force due to a bend that’s fine you can apply a factor to drop the max load down but regardless the load is 1/2 on each end.

 

[Fl Canopy Stalker]

I’m saying high level. If the exit of the hitch reduces the force due to a bend that’s fine you can apply a factor to drop the max load down but regardless the load is 1/2 on each end.

But the angle effects how that weight is applied. Look at any prusik or even Brocky’s drawing. So if the legs each cross a bend while loaded, the cord won’t be double the cord mbs, it’ll be between 1.25 and 1.75 the original strength depending on the angle of the bend. That means the cord at 5.3 kN wouldn’t meet mbs required for the 22kN that is usually sought after. Regardless life safety needs mbs to be 10x the working load limit at its weakest point: that’s not specific to lineman’s rope or tethers. It’s for all lanyards in work positioning.

 

[Brocky]

The diagrams are more representative of the bridge, the LB goes around more of a cylinder, the concerns about angles don’t apply.
I was wrong about the hitch cord only needing to be a quarter, with three sections holding the climber, the one end of the LB and the two legs of the hitch, it should be at least a third.

 

[gcr0003]

But the angle effects how that weight is applied. Look at any prusik or even Brocky’s drawing. So if the legs each cross a bend while loaded, the cord won’t be double the cord mbs, it’ll be between 1.25 and 1.75 the original strength depending on the angle of the bend. That means the cord at 5.3 kN wouldn’t meet mbs required for the 22kN that is usually sought after. Regardless life safety needs mbs to be 10x the working load limit at its weakest point: that’s not specific to lineman’s rope or tethers. It’s for all lanyards in work positioning.

mbs is a rating for the rope. If you bend the rope or add a knot you can reduce when the rope will fail but the (mbs) is a rating and won’t change. Factor of safety (what your saying is standard of 10) would be ultimate/allowable. You can’t back into your forces to determine what the max force on your rope could be to maintain you factor of safety of 10.

Also I think we’re talking past one another, because I don’t what you’re talking about. What are you referring to as crossing a bend and it being 1.25 and 1.75? Also, the “chord will be double the mbs?”

 

[Brocky]

Any bend in the rope, or strands in a rope, weakens it because of the change in direction that the load has to follow. The sharper the bend the weaker it gets.

 

[Weldabeast]

Look at the knot.... The forces/load on the top wraps/strand gotta be higher than the lower in my imagination.....if the tether rope was horizontal then the rope/knot would be seeing equal force/load on either strand/set of wraps....maybe I'm way off but it sure seems that way when using the hitch....

 

[Fl Canopy Stalker]

Any bend in the rope, or strands in a rope, weakens it because of the change in direction that the load has to follow. The sharper the bend the weaker it gets.

Yes sir! which includes where the hitch cord legs exit the friction hitch as well as loss of strength for the tied or sewn eyes. That’s why I was saying to still achieve the 2500 (half of 5000) each leg would need 1250 lbs after the loss for the eye or knot or bend. So to achieve that you’d still want something near 9 or 10 kN to account for those losses. Interestingly I can’t find anything in arborist standards that states a minimum break strength for hitch cord. Only that work positioning gear must be 10 times the working load limit or 3000 lbs whichever is higher at the weakest point in the system. And that lead line ropes including prespliced ropes must have an MBS of 5400 lbs. all metal gear including carabiners and d rings must be at least 5,000 lbs. Minimum rope size of 11mm or greater unless special training is provided for smaller ropes. All hitch chord used for friction hitches should be 2 to 3mm smaller, except for the Blake’s and taunt line which allow for the ends of the climbing line to be utilized. (I can’t find where it addresses other single leg hitches but I do know you have several that hold using rope of the same size. These are common across tree surgeon and the arbor culture industry.

 

[Fl Canopy Stalker]

mbs is a rating for the rope. If you bend the rope or add a knot you can reduce when the rope will fail but the (mbs) is a rating and won’t change. Factor of safety (what your saying is standard of 10) would be ultimate/allowable. You can’t back into your forces to determine what the max force on your rope could be to maintain you factor of safety of 10.

Also I think we’re talking past one another, because I don’t what you’re talking about. What are you referring to as crossing a bend and it being 1.25 and 1.75? Also, the “chord will be double the mbs?”

Ok if you look at hitch cord, you have 2 or 3 numbers for strength-
1- hitch cord mbs
2- a rating for the sewn cord eye to eye or loop configuration
3- if it’s an eye to eye cord you’ll also have a basket configuration mbs.

let’s say you have 2400 for hitch cord. You couldn’t use it for an OSHA approved work positioning project because it would have an eye to eye rating of around 2000 lbs which even in basket would not hit the 5000 lbs and when used as a hitch would probably only hit something around 3500 lbs. When sewn into a loop, it would achieve almost the same as the eye to eye (probably closer to 3250 lbs or so). 1.5 is the number most commonly used to rate loop configurations even though technically two legs evenly split the load. This is to account for the loss of the knot or splice. So the cord is no longer rated by its original breaking strength but rather the strength of the loop. This is one reason arborist commonly USED 12 or 13mm lead lines because to get the break strength required for their friction hitch cords, Using traditional materials it would take a 9 or 10 mm cord to get the strength needed for the work positioning. Now days you have specialty cords that use technora and high tenacity polyester blends which achieve 5000 lbs cord strength in 8mm cords. It allows them to use skinner lead lines because of stronger smaller hitch cords. When I started addressing the concern I was talking to Brocky who has a very strong knowledge base of knots, and splices. But let’s say he showed up to a job with 5.5kN cord and then had an accident, the company and himself would be in trouble because it’s his responsibility as a skills based and trained worker to know how ropes react to knots, and that his system must meet the minimum requirements at its weak point. In that scenario, his weak point would far and away be the hitch cord. Even though lineman’s ropes are used In basket configuration, the ropes still must use the lead line mbs rules and the d rings on the harnesses still must be 5,000 break strength each not 2500 on each side.
Perfect world you are right, each leg sees identical load at perfect angle (looks good on paper) but real world fall force applications don’t always apply equally and friction hitches always cross or bend so there’s loss at that point as well as at the sewn or tied end(s). Sometimes one side is higher when you fall and catch, so the angle is greater and the load is applied to one side more than the other. Like Lowg said on the other thread, prepare to fail safely. That’s real world risk mitigation and it’s also why field technicians often have to change or utilize different things in the field than the engineers put on paper. I’m not taking a dig at your profession either, I’m simply stating that it’s not as simple as your numbers add up, and we do have to account for losses.

 

[Fl Canopy Stalker]

And correction in arbor culture all lanyards including prusik style lineman’s ropes, lead ropes, and webbing must be 5400 lbs not 5000

 

[gcr0003]

Ok if you look at hitch cord, you have 2 or 3 numbers for strength-
1- hitch cord mbs
2- a rating for the sewn cord eye to eye or loop configuration
3- if it’s an eye to eye cord you’ll also have a basket configuration mbs.

let’s say you have 2400 for hitch cord. You couldn’t use it for an OSHA approved work positioning project because it would have an eye to eye rating of around 2000 lbs which even in basket would not hit the 5000 lbs and when used as a hitch would probably only hit something around 3500 lbs. When sewn into a loop, it would achieve almost the same as the eye to eye (probably closer to 3250 lbs or so). 1.5 is the number most commonly used to rate loop configurations even though technically two legs evenly split the load. This is to account for the loss of the knot or splice. So the cord is no longer rated by its original breaking strength but rather the strength of the loop. This is one reason arborist commonly USED 12 or 13mm lead lines because to get the break strength required for their friction hitch cords, Using traditional materials it would take a 9 or 10 mm cord to get the strength needed for the work positioning. Now days you have specialty cords that use technora and high tenacity polyester blends which achieve 5000 lbs cord strength in 8mm cords. It allows them to use skinner lead lines because of stronger smaller hitch cords. When I started addressing the concern I was talking to Brocky who has a very strong knowledge base of knots, and splices. But let’s say he showed up to a job with 5.5kN cord and then had an accident, the company and himself would be in trouble because it’s his responsibility as a skills based and trained worker to know how ropes react to knots, and that his system must meet the minimum requirements at its weak point. In that scenario, his weak point would far and away be the hitch cord. Even though lineman’s ropes are used In basket configuration, the ropes still must use the lead line mbs rules and the d rings on the harnesses still must be 5,000 break strength each not 2500 on each side.
Perfect world you are right, each leg sees identical load at perfect angle (looks good on paper) but real world fall force applications don’t always apply equally and friction hitches always cross or bend so there’s loss at that point as well as at the sewn or tied end(s). Sometimes one side is higher when you fall and catch, so the angle is greater and the load is applied to one side more than the other. Like Lowg said on the other thread, prepare to fail safely. That’s real world risk mitigation and it’s also why field technicians often have to change or utilize different things in the field than the engineers put on paper. I’m not taking a dig at your profession either, I’m simply stating that it’s not as simple as your numbers add up, and we do have to account for losses.

Thanks for explaining what you were talking about. None of that is news to me. I wasn’t saying real world would be the force on it, but it seemed like starting out you were saying the chords did not split the load and I was saying generally speaking they would. Obviously to what degree depends on many factors that we have already discussed and to be safe there are common factors such 1.5 as you mentioned. I haven’t done anything on paper, nor did I mention a force that would be expected to be on the cord. I know you have to account for losses, I never said you didn’t lol. Lots of talking past each other going on as well as beating dead horses. Glad ya got it figured out.

 

[Fl Canopy Stalker]

Yes sir. I was in the car coming back from Miami so I was having trouble explaining. The looks good on paper was just referring to general calculations adding up (2+2 is always 4)… I am glad we are on the same page. Rigging forces are hugely influenced by angles and bends. Thank you again for being patient with me so that I could explain what I was referring to. I know both you and Brocky and JRB for that matter are very intelligent people so sometimes I suck at explaining things to guys that are smarter than myself. Lol

 

[Brocky]

My statement was about what the minimum break strength of the LB rope and hitch cord that is needed to satisfy the 5000 lbs requirement of the total system. Ansi and osha do the same, they just give the break strength of the rope needed, but nothing about the strength needed for terminations, loss of strength due to knots, hitches, sewing, or splices. My first theory was the one side of the LB would be polite and take half the load, with the two legs of the hitch sharing the other half. In reality each of the three sections attached to the harness share the load; switching to the 5400 lbs target, each would be 1800 lbs, the minimum needed for hitch cord strength, not bringing in other regulations, or terminations.

 

[dhoff545]

I had a chance to play with this over the weekend.

Overall I was pretty impressed, good product, worked as advertised, I jumped up and down on it hung as a tether trying to get it to jam and it would break either way with 2 fingers. The hitch works very well. I've been known to use a versastrap to bypass branches, so definitely safer and easier than that as a backup linesmans. I think the system also has potential as an aftermarket bridge, very easy to adjust.

I hate the microdiameter line for a linsemans, I just don't like the diameter, it's relatively stiff and flips well for the size, but there is such a thing as too minimal.

After testing I would mostly trust it. it's definitely better than the crap alot of the treestand manufacturers are supplying. The rating of the system though is pretty poor, Brocky had it worked out at 10kN for the spliced line, I think you can be in a similar weight & volume with sewn webbing at about 18kN. Nutterbuster had a tether/bridge system that would have rated out around there using Austrialpine buckles and Aerohunter has a linesmans belt and tether using similar buckles that rates out there as well. I don't see a need to go this minimal chasing weight. 9mm canyoneering line and 6mm accessory cord pack really well, weigh slightly more, are rated much higher and I find to be easier to use. I guess to each their own, at some point the manufacturers will have to get together and argue about how low is too low I expect.

That hitch is impressive. Works well enough that it has potential in a JRB style SRT system. I haven't played around with a JRB ascender on a single line, and had never heard of the synergy X, so I might figure out how to tie those and do some SRT hitch climbing. That might be my next steps.

Thanks for all your input.

 

[Brocky]

The Beal Back Up Line has a Kevlar core, an Aramid, that are known to self abrade if run on a small diameter like a carabiner on a bridge. Some of the first arborists harness bridges were made with Technora, and began to break, having a cover makes it harder to detect any thinning that happens.

 

[raisins]

The Beal Back Up Line has a Kevlar core, an Aramid, that are known to self abrade if run on a small diameter like a carabiner on a bridge. Some of the first arborists harness bridges were made with Technora, and began to break, having a cover makes it harder to detect any thinning that happens.

yeah, folks have not (edited to include "not"....kinda changes sentence) been talking about bend radius much here lately....one reason why i use a 9 mm quick link, instead of 8 mm or smaller

 

[dhoff545]

The Beal Back Up Line has a Kevlar core, an Aramid, that are known to self abrade if run on a small diameter like a carabiner on a bridge. Some of the first arborists harness bridges were made with Technora, and began to break, having a cover makes it harder to detect any thinning that happens.

That's interesting. We will see if I find a use for it. Thanks.

 

[backvalleybrent]

Dang you guys are getting technical. I have one of the featherlite lineman ropes and love it. I am a lineman by trade and know a little about lineman lanyards. If you really do have a fall wearing nothing but a lineman rope, you will probably be at the bottom of the tree wondering what happened before the featherlite lineman rope will break or the wlr hitch fails.


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