What is the "Minor axis" of a "D" maillon?

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What is the "Minor axis" of a "D" maillon?

Postby bill.hicks.fan » Nov 27, 2012 6:51 am

Hi,

I guess this is a rigging question but the only time I've used a maillon was when caving so here I am...

My question is, what is the minor axis of a "D" shaped maillon? The reason I'm asking is that there is quite a bit of difference between the two and i wan't to be sure if I'm loading it right.

I looked all over the Internet but could not find information. However, based on the Petl Omni booklet I would guess that any load that is not perpendicular to the straight part of the maillon is to be considered a major axis load.

Or in the terms of the image bellow, where [3] is the maillon, [4] is some load, [1] and [2] are anchor slings wrapped around lets say...two trees. So when using sling [1] it is a minor axis rating? When using sling [2] it is a major axis rating?

Image

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Does all this make sense?
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Re: What is the "Minor axis" of a "D" maillon?

Postby Scott McCrea » Nov 27, 2012 8:31 am

Welcome to Cavechat!

The little image in the Petzl booklet you linked says the strength when loaded across the opening is only 15kn compared to 20kn for other directions. Peguet's (manufacturer of Maillon Rapide's) info shows the major axis along the spine, where you would expect it.

In your drawing, I would call [2] a major axis load and [1] a minor. I would also say that if you are rigging a tree like [1], a half moon is not the best connector. But, if it was all I had, I'd use it and be total comfortable with it.

Good question. I look forward to hearing what others think.
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Re: What is the "Minor axis" of a "D" maillon?

Postby rjack » Nov 27, 2012 2:00 pm

None of your examples are a major axis load. The major axis is along the solid spine, so along the red line.
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Re: What is the "Minor axis" of a "D" maillon?

Postby NZcaver » Nov 27, 2012 2:10 pm

Interesting question.

I haven't heard anybody refer to the "minor axis" of a D shaped Maillon Rapide before, but my first thought would be outward loading against the gate and the opposing curved side. In my experience 'normal' major axis loading would either be 2-way outward loading on the right-angled corners, or 3-way with the addition of loading against the curve (as you would do suspending yourself in a harness).

While loading against the gate of a maillon is usually less than ideal, it's generally a lot stronger than loading onto the gate of a carabiner. When I hang a pack below me, I don't think twice about loading it against the gate of my harness D-link maillon (or the Petzl Omni I currently use).
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Re: What is the "Minor axis" of a "D" maillon?

Postby Jeff Bartlett » Nov 27, 2012 2:51 pm

This wins "best first post of a CaveChat career ever." Jansen & Scott, can you guys mock up an award?
"Although it pains me to say it, in this case Jeff is right. Plan accordingly." --Andy Armstrong
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Re: What is the "Minor axis" of a "D" maillon?

Postby bill.hicks.fan » Nov 28, 2012 2:36 am

rjack wrote:None of your examples are a major axis load. The major axis is along the solid spine, so along the red line.
Image

Hi, i'm not arguing or anything, but how do you reconcile the fact that the Petzl Omni has a major axis rating of 20kN and it has what in my diagram is [2] rated at 20kN?

Here is the Omni's.
Image
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Re: What is the "Minor axis" of a "D" maillon?

Postby Mike Hopley » Nov 30, 2012 4:02 am

The major axis loading is the first diagram (20 kN).

The second diagram is triaxial (three way) loading. This is also 20 kN, because the Omni has been designed for this kind of load (most carabiners are not "supposed" to be loaded like this).

The third diagram shows minor axis loading (15 kN). This is still plenty strong.
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Re: What is the "Minor axis" of a "D" maillon?

Postby Wormster » Dec 1, 2012 9:11 am

I would not be using a D maillion to rig off a tree in the first place!

D maillions are only used (in the UK) to secure your sit harness together.

When rigging an equalised load off two or more anchor points I would either use separate slings or an equalised rope anchor* connected to a oval mallion or screwgate carabeener.

* see section 2-13, figure 2-3 in the link https://rdl.train.army.mil/catalog/view/100.ATSC/B8E66480-DDDA-4B58-9791-2E3A3CAAE7C1-1274436091599/21-24/chap2.htm
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