X-rigging rings

RescueMan said:
I'd be interested in knowing what the "pulley efficiency" is for an X-ring.

That can be easily determined by hanging a known weight from a line with a 180° turn through an X-ring (or 2 or 3), and measuring the force on the other end of the line with a strain gauge (dial or digital crane scale).
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I was talking to old fart recently about just such things. I'm trying to find the time to set up some xxperiments. Mine will not involve scales just weights so no technical measures. But I'd love to get together with someone who has some way to measure.
Edit: I didn't finish reading the posts before replying . Sounds like I may not need look to far.
 
They are nice, we bought one at work. Well actually I bought one and told them to give me money because we needed it. Use that thing a few times every month.
 
RescueMan said:
Each change of direction reduces the line load by the "pulley" efficiency ratio, but any line angle less than 120° will multiply the average (line in, line out) force at the anchor resultant vectors (big arrows).

Mark Chisholm explains this well in his article (archived on this site), Engineering a Tree Removal. One major advantage of this kind of complex rigging is that it forces the multiple stems toward each other rather than away from the primary stem (kind of like temporary cabling).

I've taken his "figure 5" and added the line loads and resultant Change-of-Direction (CD) anchor point loads - in this case assuming 90% efficient blocks and a 1¼ wrap around the GRCS. Note that two blocks (1 and 3) experience more force than the actual load, including the 3rd one which had the initial load significantly reduced by block friction (it has the smallest angle).

View attachment 30014
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With this every point with its angle sees slightly more than 1x the load but no one point sees 2x. So it does reduce the force on the tie in point. More pressure on the overall tree but less on the 1 point
 
As author of the 4 to 1 bend ratio thread I want to venture the following engineered guess. The strength of oceans splice is going to be equal to or greater than that of the standard splice w larger cordage available at this point. I would be willing to put up some dough for pulling tests. Also see a huge advantage of using a smaller sling diameter and getting more out of it. Large slings are not easy to work with especially when you have been in spikes in a removal all day. :):):)
 
And I will go with devils advocate/ simpleton and get down to the nitty,

If there is a genuine reason why I could change the way I am rigging out which will result in less ride ( having the shit pummelled out of me) by transferring the energy throughout the system by spreading the loading in a different manner to the one I and many others currently are taught to and use every day then there is ears up attention from this little duck.

It is in my mind, similar to believing the earth is flat and then someone explaining that no the earth is in fact round, all the maths and technical jargon aside how bout a dumbed down discussion for the masses?

Having caused through ignorance massive load failures resulting in total loss of the rigging point, snapping slings and lowering ropes, bending biners etc I have set out to do things better and if the X-rings achieve just that then they Will replace what I currently use because Any gain that increases the safety margin and/or increases production is a winner with me.
 
I'm sure X-rings have their place, but they seem to have a number of vulnerabilities.

From the Tree Stuff website:
  • X-Rigging Rings(XRR) are for rope rigging, NOT for climbing and life support use. The XRRs are very low friction, however, hard use and abuse could result in the ring becoming heated. Choose your sling material wisely in regards to what tasks the ring will be put through. Research your sling or rope material for degradation temperatures before choosing your cordage material.
  • Do not use a single XRR as a terminal rigging point. The bend ratio with a single XRR and most rigging rope sizes does not meet best management practices in rigging. Consider triple ring use for terminal rigging. Use arborist blocks for heavy weights, long runs and when less friction is needed.
  • XRR must be secured in a very tight professional splice. Do not splice if you are not qualified, slings can be purchased already complete with XRRs.
  • Inspect your XRR and splice before every use. If the splice is loose enough for the ring to possibly come out, do not use.
  • When an XRR is pushed to extremes, they will deform; the outside groove pinches inward and the XRR will become oval. Discontinue use if the XRR is ever deformed.
  • IF the black Hard Coat Anodize is ever worn away, discontinue ring use; as the friction will increase and heat will increase.
I'm not much of a fan of hard-coat anodizing, as when it wears away it can leave a micro-edge that can cut rope fibers. Overheating may also be a problem if ropes are allowed to run too fast.
 
Okay just read the entire thread along with the article you quoted rescue. I think all this brings up a very interesting point. I have often thought about adding friction to my blocks. Someone mentioned blocks with a clutch. My thought was simply a block where the sheave only roles in one direction. Friction when it's loaded no friction when pulling the line back up. The issue here is going to be heat generation. We don't want to melt ropes. Rescue, your complex rigging diagram is very interesting. I would like to see that tested. It is important to understand that our loads do not just run through their respective rigging points, but eventually come to a stop. They also fall into the rigging to begin with creating a shock load the force of gravity on an object. I don't know how to apply this equation
F = G * m1 * m2 / r^2
Where G is the gravitational constant, m1 and m2 are the two masses and r is the distance between them. Something about 32 feet per seconds per second. So the forces we want to work with are the maximum static force which is easily calculated and the force of gravity on our shock load. It is nice to know that when running the system, the forces are distributed and reduced by friction but we must remember to plan for the maximum which will and should include an aspect of shock load.

I like this discussion very much and am curios rescue, are you in the rescue industry ? Fireman, or special rescue? Just curious.
 
Rescue, you seem to have an passionate affinity for forces at work in roping setups. I really liked the diagram you posted. Never thought about how much force is being consumed by friction in the system. Where does your passion stem from ?
 
RescueMan said:
I'm sure X-rings have their place, but they seem to have a number of vulnerabilities.

From the Tree Stuff website:
  • X-Rigging Rings(XRR) are for rope rigging, NOT for climbing and life support use. The XRRs are very low friction, however, hard use and abuse could result in the ring becoming heated. Choose your sling material wisely in regards to what tasks the ring will be put through. Research your sling or rope material for degradation temperatures before choosing your cordage material.
  • Do not use a single XRR as a terminal rigging point. The bend ratio with a single XRR and most rigging rope sizes does not meet best management practices in rigging. Consider triple ring use for terminal rigging. Use arborist blocks for heavy weights, long runs and when less friction is needed.
  • XRR must be secured in a very tight professional splice. Do not splice if you are not qualified, slings can be purchased already complete with XRRs.
  • Inspect your XRR and splice before every use. If the splice is loose enough for the ring to possibly come out, do not use.
  • When an XRR is pushed to extremes, they will deform; the outside groove pinches inward and the XRR will become oval. Discontinue use if the XRR is ever deformed.
  • IF the black Hard Coat Anodize is ever worn away, discontinue ring use; as the friction will increase and heat will increase.
I'm not much of a fan of hard-coat anodizing, as when it wears away it can leave a micro-edge that can cut rope fibers. Overheating may also be a problem if ropes are allowed to run too fast.
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I think vulnerabilities is not the right word to place on your quote. You bring up a potential vulnerability I will address at the end. X rings have their limitation just like any other product and intelligent use is important. Rescue, you wouldn't hang a victim from a piece of hardware not designed for it. Those are instructions on proper use, care, inspection and definitions for retirement. Anything you use has these guidelines or "vulnerabilities".

That said, the potential for the coating to cut the rope is certainly a potential problem. This could be of concern. Have you had any experience with this. ? Is there record of this elsewhere?
 
baumeister said:
Anything you use has these guidelines or "vulnerabilities".

That said, the potential for the coating to cut the rope is certainly a potential problem. This could be of concern. Have you had any experience with this. ? Is there record of this elsewhere?
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Any rigging hardware also comes with a MBS and SWL, but the X-rings apparently have not been tested for load ratings.

The danger of hard anodizing is well known in the rigging community. Here is one warning in the user instructions for the Rock Exotica Figure 8 with Side Ears: "The 8’s are soft anodized. This makes it less likely to develop the sharp edges that can occur with hard anodizing."
 
baumeister said:
My thought was simply a block where the sheave only roles in one direction. Friction when it's loaded no friction when pulling the line back up.
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There is actually a combination rescue pulley/descent control/belay device with a one-way bearing, releaseable clutch and "parking brake", called the CMC MPD (multi-purpose device) that can be had for a mere $695. But it won't do the work of an arborist block.

Be wary of taking a highly effective device and making it complicated, as you increase both the cost and the number of potential failure modes. KISS (keep it simple and safe) is always the best operating principle.

The Grigri is a very popular belay device, but I know of one fatality that occurred because a single grain of sharp sand got lodged next to the cam and cut a kernmantle rope clean through.
 
baumeister said:
Never thought about how much force is being consumed by friction in the system. Where does your passion stem from ?
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Intermediate friction can reduce the load at each change of direction, but can also increase the shock load as there is less effective rope in play to absorb the dynamic loading.

I've been involved in emergency response for 30+ years, as a firefighter, EMT, wilderness EMS instructor, wilderness search & rescue specialist, and rope rescue specialist and instructor in industrial, mountain, fast-water, ice, and cave rescue environments.

And I've always loved math, physics and engineering.
 
rescueman tell the Xman David that you dont think they have been load tested, see what he has to tell you.

of all the things i use, i have the most faith in my XRR. ive dropped them from aloft onto asphalt, amongst other ways of not taking care of them. i have no signs of wear, chips, edges, whatever. wadda you call that, "bombproof"?

read waaaaay way back into this thread before saying that running ropes can over heat these rings, and that they havent been tested for weight. if you havent seen them/used them/ observed them yourself while using them (on either end of rope), i have a hard time buying into what your saying.

rescue i know you got math and physics knowledge, but im taking my tree rigging advice from personal arboriculture experience and arboriculture experience from those who have way more then me.

but if i need to rescue someone from a high angled slope and need ropes and anchors, ill come asking for you.
 
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