Rigging, do'in it right
- Thread starter Joe90
- Start date
paul
Moderator
There was an incident in the Peak years ago when a caver was descending a mineshaft and felt himself being badly affected by high CO2 levels. He just managed to lock off his rack before becoming unconscious. On this occasion, the belay was a van and those on the surface were able to start the engine and quickly pull him up to the surface by driving away from the shaft. On this occasion he was lucky the rope was attached to a "mobile anchor".
cap n chris
Well-known member
It's political correctness gone mad, reckon.
andrewmcleod
Well-known member
Deathtrap 
tying a Fig 8 for the loop in a Y-hang? Surely that results in the Fig 8 being crossloaded (which Fig 8s do not like)? :chair:
tying a Fig 8 for the loop in a Y-hang? Surely that results in the Fig 8 being crossloaded (which Fig 8s do not like)? :chair:
cap n chris
Well-known member
How is it being crossloaded?
Joe90
Member
No no, I was purely wondering what people thought.droid said:
Personally if I was going to use a car I wouldn't use the wheels because of the risk off break fluid, oils, hot stuff, dust from break calipers (I guess that wouldn't be good for ropes).
For whoever (sorry I can't remember) said about driving for help, they did have another car there.
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Hey at least theg didnt do what happened in some other random country i cant recall a few years ago - rigged to the hitch of the car, wheels in line with pit, no parking break. When a bolt in cave failed the shockload pulled the car into the pit (downhill, so just took getting it rolling from that load), and all the other bolts failed too of course because holding a falling car isnt exactly within their working load limit. There were like two deaths and injuries. Now i wish i could find the article.
So yeah. Park perpendicular, put a parking brake on. If so i would do it if it was a big enough vehicle and not a tiny bug or smart car or something
So yeah. Park perpendicular, put a parking brake on. If so i would do it if it was a big enough vehicle and not a tiny bug or smart car or something
andrewmcleod
Well-known member
Cap'n Chris said:
I started trying to describe exactly what happens to the system as each bolt fails but it is not simple and I was failing to explain it well so I won't bother
Basically if 'bolt A' is the bolt with the ladder clipped into it, then the Fig 8 loop on the rope-running-down-the-ladder (for lifelining? lower belay?) is crossloaded if load falls at all onto 'bolt B' because you are opening up the two legs of a Fig 8 on the bight. Normally I would use an alpine butterfly there?PS I am much more of a climber than a caver
PeteHall
Moderator
Isn't the "ladder" a rather fancy rope protector to keep the SRT rope from rubbing on the edge?
http://www.petzl.com/en/Professional/Ropes/SET-CATERPILLAR?l=US#.VnX03FKvhVc
http://www.petzl.com/en/Professional/Ropes/SET-CATERPILLAR?l=US#.VnX03FKvhVc
Mark Wright
Active member
I was involved, a few years ago, in writing the IRATA International Code of Practice for rope access and when we were writing the section on temporary deadweight anchors we looked at some testing that had been carried out by Lyon Equipment in conjunction with the Coastguard services. On certain surfaces a Toyota Hilux Doublecab was dragged easier sideways when rigged similarly to the photograph (ropes were attached to the chassis) than if it had been rigged off the tow hook and loaded in line with the wheels.
Testing on a variety of surfaces rarely showed either configuration meeting the 15kN strength requirement for industry.
Many Coastguard services utilise a double tensioned system for hauling and lowering operations thus significantly reducing any dynamic loads should any part of the system fail. (Prior to this they regularly used a main haul/lower line and a separate safety line run through, e.g. a Petzl GriGri. The change came following testing on 300m cliffs on the west coast of Ireland demonstrated upwards of 50m stretch in some cases should the primary system fail). Because of this reduced maximum potential loading they were able to maintain the required safety factor of 2.5:1 but reduce the minimum strength requirement of the anchor system.
Which way the vehicle is positioned is very much dependent on access at the top of the cliff. Where practicable they may use two vehicles hitched together or in conjunction with other types of ground anchor systems.
As has already been mentioned making sure someone doesn't drive it away is important. The Coastguard teams have bright orange covers for the steering wheels and keys are not kept in the vehicle when it's being used as an anchor point.
As for the 'Y' hang knots, I like neat and tidy so would agree with andrewmcleod but in reality if sufficient load is going to be applied to a badly dressed, poorly set and abnormally loaded Fig. 8 to break it, it would probably break a perfectly tied Alpine Butterfly knot as well.
Maybe the 'Y' hang from the vehicle was just so you had something to clip into when getting on the main rope, which is rigged quite close to the edge, and then just clipped into the knot of the abseil rope ready for when they get back up?
Its not a ladder and lifeline system. What looks a bit like a ladder is an edge roller for the SRT rope running over it.
Mark
Testing on a variety of surfaces rarely showed either configuration meeting the 15kN strength requirement for industry.
Many Coastguard services utilise a double tensioned system for hauling and lowering operations thus significantly reducing any dynamic loads should any part of the system fail. (Prior to this they regularly used a main haul/lower line and a separate safety line run through, e.g. a Petzl GriGri. The change came following testing on 300m cliffs on the west coast of Ireland demonstrated upwards of 50m stretch in some cases should the primary system fail). Because of this reduced maximum potential loading they were able to maintain the required safety factor of 2.5:1 but reduce the minimum strength requirement of the anchor system.
Which way the vehicle is positioned is very much dependent on access at the top of the cliff. Where practicable they may use two vehicles hitched together or in conjunction with other types of ground anchor systems.
As has already been mentioned making sure someone doesn't drive it away is important. The Coastguard teams have bright orange covers for the steering wheels and keys are not kept in the vehicle when it's being used as an anchor point.
As for the 'Y' hang knots, I like neat and tidy so would agree with andrewmcleod but in reality if sufficient load is going to be applied to a badly dressed, poorly set and abnormally loaded Fig. 8 to break it, it would probably break a perfectly tied Alpine Butterfly knot as well.
Maybe the 'Y' hang from the vehicle was just so you had something to clip into when getting on the main rope, which is rigged quite close to the edge, and then just clipped into the knot of the abseil rope ready for when they get back up?
Its not a ladder and lifeline system. What looks a bit like a ladder is an edge roller for the SRT rope running over it.
Mark
andrewmcleod
Well-known member
Mark Wright said:
It's not that crossloaded Fig 8's break, it's that they roll/capsize. In this case I guess even if it does roll it will just tighten up on the crab and not fail catastrophically though. In testing for knots for tieing ropes together for double rope abseils the (offset) Fig 8 was found to roll at loads as low as bodyweight, hence the preference for joining ropes with the (offset) overhand (which also can roll but is much less prone to it and eats less tail each time it does roll). Obviously there are much better knots for joining ropes in other circumstances but in mountaineering abseiling getting the ropes stuck can be catastrophic, hence the preference for an offset knot (which tends to stay out of cracks better). Thinking about it maybe the Alpine Butterfly Bend is the answer...
