[photo]109023[/photo]

Re this photo – that is not an ADT (sounds like a condition), it’s pull through rigging.

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Dude, its worse than an ADT, it's a self-tightening one! They amplify your load by a massive factor on the anchors, which are in this case home-made and the rock at the top of proud sump is awful as it is.

Self-tightening ADT's are suicidal.

I'm sorry I am talking like a rope-Nazi. I don't mean to preach and perhaps I have misinterpreted it from the photo. My suggested method for a pull-through would be a death-or-glory type.

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Miles, the anchors and bolts installed around Proud’s Sump are ‘home made’ and infinitely more bomb proof than commercially manufactured hangers and bolts. All stainless, M12 and 6mm thick angle. The rock is fine.

As for the pull through, see below. On the photo of me on it, it is not dressed yet.

[photo]110138[/photo]

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Just don't ab down on the wrong side of the pull through 😮

Miles, the anchors and bolts installed around Proud’s Sump are ‘home made’ and infinitely more bomb proof than commercially manufactured hangers and bolts. All stainless, M12 and 6mm thick angle. The rock is fine.

I've rigged it that way before and would happily do so again. Used a simple doubled rope with an 8 before too which was also fine. All better than relying on dubious fixed ropes.

The rock there is good. Better than much of the things rigged off in the North Pennines...

Morning!

That is an ADT because it runs free through two rather than one maillon. ADT's never 'look' bad, but when you work out the forces of you just hanging on them they take the gear close to failure levels, and their ability to stand a shock is almost zero.

The anchors do sound very meaty! Didn't realise they were that tough, sorry, they just look like a bit of Ali angle in the picks. Clearly they must be good else we'd not be having this conversation.

Would you consider leaving a nice strong chain y-hang off those anchors and doing the pull through from that? That would be a lot safer and put much less strain on the gear.

Anyway, no offence intended and I don't mean to be patronising. Just don't want another easily-avoidable death in Smallcleugh - especially an old friend!

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Doing some quick calculations on this, based on the geometry as it appears on the picture which I appreciate isn't accurate but it does give an idea...

Working on a load of 1 me which is about 100kg:
My dubious quality Y-Hang in the background, with roughly a 60 degree angle between the legs will load the bolts about 580N static and 1160N for a 2g load
Mike's megatasic quality pull though looks as it is to have a 120 degree angle between the legs which will result in a bolt load of 1930N static and 3860N for a 2g load.

None of these loads should cause a failure with even M8 bolts though the it would exceed the allowable stress levels that I use at work, the M10 bolt is fine.

Importantly this shows the stress magnification that you get the bigger the angle between the legs. Something to think about on a Tyrolean traverse! 100kg hanging on a tightly rigged traverse line giving an angle of 175 degrees would put a static load of 11470N on the anchors - nearly 11.5 times the weight applied. This still wouldn't shear off an M10 bolt but it might hurt the rock a wee bit!

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I found this website on rope work:

https://www.ropebook.com/information/angular-vector-forces/ 

If you scroll down the page to Deflection Angle of 90°, I think this suits the pull through rigging best with everything dressed and as it should be. The load on the anchor that has the stopper knot will be the ab load so 100%, the second anchor which is acting like a pully / deviation has a load of 141%, so I wieght 87kg, main load = 87kg, and the 2nd anchor gets 123kg.

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That makes sense - the not dressed setup looked like the guide crab was taking load hence my calc loading.

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I do know a bit about this stuff, and I'm just trying to help.

I know, got us all wondering and checking.

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I think it best I just leave it there :angel:

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use a rope loop knotted at the bottom, ab using a rack with both ropes passing through it. untie knot at bottom pull rope down.
Use with care.

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