Jump to content

ATC Guide mode in crevasse haul system?


Recommended Posts

Is there a problem with using an ATC in guide mode at the anchors instead of a pulley and prussik to build the hauling system in a z-pulley?

Is it too much friction?

Won't the ATC in guide mode also capture progress as well as a pulley/prussik?

It seems simpler but no one seems to teach it so I am interested in why.

Forgive me if this is already covered someplace else.

Link to comment
Share on other sites

  • Replies 9
  • Created
  • Last Reply

Top Posters In This Topic

It works just fine. Yes the ATC will capture the progress. When I took a 1 day crevasse course with RMI a few years ago they showed this way and we practiced both this and a carabiner with prussik. The only negative I can think of is if you needed to rappel down to get to the patient for some reason and you just used your ATC up top.

Link to comment
Share on other sites

I disagree with Marlin.


The mechanics of it will, in fact, work, but the forces are generally not considered acceptable. It will be hard to nearly impossible to haul up a victim going through an ATC (or similar) in guide mode without generating excessive forces on the anchor (by needing to add mechanical advantage).


The only way I have been taught, read, and teach is the progress capture pulley or a prussik.


Your concern of needing to rappel should also be a non-issue because you can always rappel with a munter.

Link to comment
Share on other sites

it does in fact work, but it's damned inefficient. If you're looking to save weight/complexity, bite the bullet and buy a microtraxion - a progress-capture pulley that also works as an ascender if you happen to be the one in the hole. I wouldn't normally buy/recommend a hundred-dollar pulley, but Petzl microtraxion is one that might even be worth paying retail. Mine lives on my harness, and sees more use than I ever expected before I started carrying it.


Link to comment
Share on other sites

I agree with the fact that an ATC will have a lot of friction and be inefficient in comparison to a pulley. However when compared to a single carabiner I think it would be a similar amount of inefficiency (although an experimental test with a dynamometer would be interesting to me to compare).


I have done a bunch of testing using a variety of carabiners in a 3:1 system instead of pulley and measuring their efficiency. The pulley I tested came in around 93% efficiency as compared to a true theoretically 3:1 system. The carabiners all ranged from 65% to 72% depending on how fat the carabiner was. The fatter carabiners such as a Petzl Attache were the best. My theory is that an ATC with a fat carabiner would be somewhere in the 60-70% range as similar to the carabiners. Plenty happy to abandon my theory if actual tests prove otherwise.


Anyway the best solution as Haireball stated is to just use a Petzl microtraxion. It serves the function of a pulley with a progress capture very well and it lives on my harness when I am in glaciated terrain.


Hanman I have never seen the CT Roll N Lock but it looks light and nice. Is the locking mechanism more toothed like a Microtraxion or Tblock or is it more of a general rope grab pinch mechanism. BTW your link doesn't seem to work on my computer.

Link to comment
Share on other sites

The Roll N Lock has horizontal ribs, kind of like a micro/rescuescender but perhaps a bit sharper. They say it can engage webbing as well for an adjustable PAS which I though was somewhat interesting. Really light device.


Here's another link to try... Link





Edited by hanman
Link to comment
Share on other sites

  • 2 weeks later...

I'm with you on the inefficiency due to increased friction, but a little confused on how that translates into increased force on the anchor. Is there something else about the system in not grasping? Just curious.



Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...