Anchor Webbing

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11-22-2012, 11:01 AM
jdcalamia

My rigging has much more personality than any prom date! Happy Thanksgiving fellas!
11-26-2012, 03:11 PM
Ack8236

Quote:

Originally Posted by Rescue Dave

Here is a link to a great study that compares W3P2 and basket hitches using 1" webbing.
http://www.caves.org/section/vertica...tches&W3P2.pdf
Dave

Good article, thanks!

In regards to the references to 15:1 and 10:1. I was always taught that components should have a 15:1, then when you build a system and figure in knots and weak points, the system should have a 10:1 safety factor.
11-27-2012, 11:17 AM
servantleader

1 Attachment(s)

Quote:

Originally Posted by Rescue 2 Training

Research from the same guy that RescueDave provided the link for shows that a knot in one of the loaded strands is not the weak point. The failure still occurs where the webbing meets the carabiner.

I don't have the link, but it was presented at this year's ITRS.

Guess I'll have to reconsider how I teach the W3P2. :)

Michael

Attached is a webbing anchor option that I've used a few times. It's more gear intensive, but avoids the 3-way carabiner loading of the basket hitch. Might work fine padded on something like a horizontal girder. For a vertical post (like in the picture) I suppose one could do a full wrap around the post (before clipping the carabiner on the side) to help keep it from slipping down.
11-27-2012, 07:47 PM
EricUlner

Quote:

Originally Posted by servantleader

Guess I'll have to reconsider how I teach the W3P2. :)

Michael

Attached is a webbing anchor option that I've used a few times. It's more gear intensive, but avoids the 3-way carabiner loading of the basket hitch. Might work fine padded on something like a horizontal girder. For a vertical post (like in the picture) I suppose one could do a full wrap around the post (before clipping the carabiner on the side) to help keep it from slipping down.

Definitely a legit alternative... with 1-inch webbing. But wide manufactured anchor straps can abuse and weaken carabiners.
11-27-2012, 10:10 PM
FiremanLyman

Quote:

Originally Posted by servantleader

Guess I'll have to reconsider how I teach the W3P2. :)

Michael

Attached is a webbing anchor option that I've used a few times. It's more gear intensive, but avoids the 3-way carabiner loading of the basket hitch. Might work fine padded on something like a horizontal girder. For a vertical post (like in the picture) I suppose one could do a full wrap around the post (before clipping the carabiner on the side) to help keep it from slipping down.

Lost on the advantage of this over having a basket anchor? Please help, for I am only seeing an additional 2 (three total) pinch points in the webbing now, isn't this where the webbing fails; grinding on the carabiner?

Not being a smartuss as usual, really trying to think it through.

Quote:

Originally Posted by EricUlner

Definitely a legit alternative... with 1-inch webbing. But wide manufactured anchor straps can abuse and weaken carabiners.

Not to mention hard linking.
11-28-2012, 10:45 AM
servantleader

Quote:

Originally Posted by FiremanLyman

Lost on the advantage of this over having a basket anchor? Please help, for I am only seeing an additional 2 (three total) pinch points in the webbing now, isn't this where the webbing fails; grinding on the carabiner?

Not being a smartuss as usual, really trying to think it through.

Not to mention hard linking.

I was thinking about avoiding the 3-way carabiner loading that comes with the basket hitch.
11-29-2012, 03:37 AM
MichaelXYZ

3 Attachment(s)

Well, since you brought up tri-axial loading. The literature does seem to support that it is not a good thing.

Attachment 22549

I did my own setup trying to understand why? So I guess any load on the locking part is not good. Although, to me this way seems to spread the load more evenly? I was never good at physics.

Attachment 22550

I came up with another technique to avoid the tri-loading problem, but now I am violating the metal on metal rule...

I know it looks messy, I did not have an actual anchor for my quick setup.
Attachment 22551

Doesn't the anchor plate and carabiner violate the metal on metal rule as well? It seems that one of those triangle shape screw links would be a good solution for the basket.
11-29-2012, 09:02 AM
Rescue 2 Training

Quote:

Originally Posted by MichaelXYZ

\
Doesn't the anchor plate and carabiner violate the metal on metal rule as well? It seems that one of those triangle shape screw links would be a good solution for the basket.

"No metal on metal!" is not a rule. It is a sweeping generalization that is wrong more often than it is right. For instance: How do you connect your figure 8 descender to the D ring on your harness? With a carabiner? That's metal on metal on metal!

If one were to follow the "rule", you would have a soft link (webbing) between your 8 and biner, and your biner and harness.

If there is something in the system that allows for absorbing the torsional movement, like rope, webbing, etc... then the "rule" will probably not apply.
11-29-2012, 09:08 AM
EricUlner

Quote:

Originally Posted by MichaelXYZ

Well, since you brought up tri-axial loading. The literature does seem to support that it is not a good thing.

Attachment 22549

I did my own setup trying to understand why? So I guess any load on the locking part is not good. Although, to me this way seems to spread the load more evenly? I was never good at physics.

Attachment 22550

I came up with another technique to avoid the tri-loading problem, but now I am violating the metal on metal rule...

I know it looks messy, I did not have an actual anchor for my quick setup.
Attachment 22551

Doesn't the anchor plate and carabiner violate the metal on metal rule as well? It seems that one of those triangle shape screw links would be a good solution for the basket.

Yes, the delta (tri) link is always a great alternative when you're purposefully tri-loading.

A carabiner's strength is along its spine. They're designed to be pulled along the long axis, more or less parallel to the general direction of the spine. So another abuse similar to tri-loading is diagonal loading. Remove the force component from your tri-load picture that is coming into the spine on the wide end and you're left with the one coming into the gate side. The line you're left with is diagonal across the length of the carabiner. Also an abusive loading that can greatly weaken a carabiner... Not so much physics, per se. More so an issue of using a piece of equipment outside of the design intent.

As for a "no metal-on-metal rule", I hear that on occasion from fire folks. You can add that to the crazy dogma list of "rules":

"the bowline is dangerous"
"a tensionless hitch is always better because it's stronger"
"never use rope on webbing"
"never use webbing on webbing"
"everything has to be 15:1"
"directionals on belay ropes require pulleys"
and the list goes on...

Such dogma is simply born out of a lack of understanding, and then the teaching of the lack of understanding by some instructors causes the spread of the dogma. But I see that you're already seeing the flaw in the "no metal-on-metal rule". Keep on thinking critically.
12-02-2012, 02:43 PM
ProgressiveRescue

Quote:

Originally Posted by jmatthe2

Mike - I'll take a quick stab and then it's back to work! I'm working on a disaster exercise project.....

I stay away from w3p2 when my anchor is square and/or has a small diameter. I see a lot of guys force a w3p2 around rigging eyes in drill towers, small trees, or even the hooks on a fire truck. The diameter of the anchor must be large enough to provide the friction to make the w3p2 beneficial. Otherwise it looks jacked-up and is not very clean rigging. I compare my rigging to a prom date. If it looks sexy go with it. If it looks messy and cluttered, try again.

A square beam has very little surface area, so again why use a friction type anchor wrap? Larks foot...I do not use this in life safety situations except in hasty need. An untrained (or undertrained) rescuer can create a pretty good pinch point on the hitch bight if it is not loaded correctly. Climbers use this regularly to place protection, but they are dealing with very short runners, which minimizes a mistake.

Another anchor housekeeping issue is this. You rarely need more than 4 legs of webbing on a life safety anchor. I hate it when I see guys wrap something with 5 or 6 bights and then try to stuff all of that into a carabiner. Ether use a shorter piece of webbing or make your tails longer to shorten it!

Last thing. A while back I made a post about the MPD. Collin with Elevated Safety in Chicago sent me on of theirs to play with...Needless to say I mortgaged the house and bought one; great device. We used it in our last class and the students were very pleased. Let me also give a thanks to CMC, as they called to send me one as well.

Jeff

Jeff,
That MPD is a game changer. I was sent one a year ago and after playing with it I fell in love. I too it to a hands on class I did at FH Expo and let students play with it. The learning curve after explaining once was almost non existent.
12-02-2012, 05:39 PM
MichaelXYZ

I watched the CMC video of the MPD and it does look neat, but at a $650 price tag, I am not feeling it.
Now I decided to do a price comparison.
CMC boast that the MPD replaces the RPM system, so to be fair, I used CMC prices for RPM components when making my comparison.
Note: I did not include one carabiner in this comparison as both systems require it.

MPD = $650.00

RPM System components (Using CMC pricing)

Carabiner $30.0 ea x4 = $120.00
Brake Bar $130.00 ea x1 = $130.00
Pulley $52.00 ea x1 = $52.00
Anc. Plate $50.00 ea x1 = $50.00
Misc cord $10.00 50 ft. = $10.00 (For RRH and prusiks)
Total------------ $362.00

Now if I were to build my system using non- CMC parts all General use rating, I could build my system for much less, in fact; I could build two RPM's for the price of 1 MPD.

For cash strapped agencies, the MPD is a luxury, as cool as it may be.

Now if CMC were to send me one to play with, I might just change my mind. :) Oh I am bad...

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