Pull-through rigging

[Mark Wright]

As andrewmcleod pointed out, there shouldn't be any cyclical rub at the pitch head as the rope would generally be held in place with the knot jamming up against the anchor point.

That however wasn't the point I was trying to make with the Humber bridge example. In this case the Alpine Butterfly loop wore half way through when 100m of rope was being pulled down after use.

As I said before, using a small Maillon Rapide removes any issues of dangerously miss-loading a carabiner and protects the rope when being pulled down.

Mark

 

[MJenkinson]

We've always used a butterfly and a maillon connected back to the "down" rope.  I have used a crab but having watched one get all manner of twisted up at the top of one pitch under load (rigging error really) I don't think I'd use one again. Stick to a maillon.

 

[andrewmcleod]

As andrewmcleod pointed out, there shouldn't be any cyclical rub at the pitch head as the rope would generally be held in place with the knot jamming up against the anchor point.

That however wasn't the point I was trying to make with the Humber bridge example. In this case the Alpine Butterfly loop wore half way through when 100m of rope was being pulled down after use.

Ah, now I understand. Pretty impressive through!

 

[Bob Mehew]

Belated and embarrassing realisation that threading a rope through the eye of an anchor and subsequently pulling the rope down will cause the eye to wear.  This lead to the need to replace a couple of anchors in Giant's when the wear on them became appreciable.  (A special device was made up in that case involving a large ring to allow the wear to be dispersed across a larger surface area.)  Such use may be storing up a problem for the future when it comes to replacing worn anchors without destroying the location!

 

[andrewmcleod]

Belated and embarrassing realisation that threading a rope through the eye of an anchor and subsequently pulling the rope down will cause the eye to wear.  This lead to the need to replace a couple of anchors in Giant's when the wear on them became appreciable.  (A special device was made up in that case involving a large ring to allow the wear to be dispersed across a larger surface area.)  Such use may be storing up a problem for the future when it comes to replacing worn anchors without destroying the location!

I think it all depends on the expected usage. In sport climbing the last climber will always lower off the bolts or rings on the bolts, depending on whether they are 'smooth' bolts like P bolts or hangers with rings. For many routes just lowering off the bolts is fine (and lowering off will cause a lot more friction than just pulling a rope down). Other places where the routes are popular the bolts have been worn down enough to require replacement, and/or extra devices are used. There aren't many P-bolts in caving compared to climbing so I suspect most get a fair bit of traffic, and it might be sensible to fit any bolts that might be used for a pull through with replaceable rings or pigstails (or equivalent).

 

[MarkS]

I think the example of the anchors above the Crabwalk in Giants is not very typical. This has been discussed before on UKCaving, and I believe the wear was largely attributed to lowering people using the anchors, not from pulling the rope down.

The thread linked to below suggests that, unlike those in Giants, anchors in Swinstow Hole don't show appreciable signs of wear from the (presumably regular) pulling down of ropes. I think the Giants anchors were also discussed at some length in another thread.

http://ukcaving.com/board/index.php?topic=14296.0

[After a bit more digging, here's the other thread on the anchors in Giants: http://ukcaving.com/board/index.php?topic=4234.0]