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Post by geneyore on Nov 11, 2013 13:32:02 GMT -8
Z-Pulley Bellingham Style I have not tried or tested this, but it seems like a really good idea. There is some art in making sure the Master Loop is redundant (doubled quick draw, or, ... What do you think?
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Post by jasonmartin on Nov 12, 2013 8:49:36 GMT -8
The backup figure eight is in the wrong position. If you want to back up the system, then the backup should be on the haul line. Currently this system would only provide a 2:1 mechanical advantage and the prussik would not mind the rope as it is hauled.
Jason
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Post by jimnelson on Nov 15, 2013 16:15:21 GMT -8
While the all in one drawing may have a place, it is also very easy to misinterpret. Is that your issue with it Jason?
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Post by jasonmartin on Nov 16, 2013 7:11:08 GMT -8
No. My issue is that the system as drawn will not work. Behind the ATC there is a figure eight. This would stop the system from operating as a 3:1.
However, as stated, I could be misinterpreting it. The figure eight behind could be a figure eight device, but that would also make it work poorly while adding undue friction.
Lastly, most guides on exams have moved away from using an ATC in the system. If you monitor the system as you haul, it's pretty easy to keep the prussik from riding up into the pulley. Additionally, many pulleys are designed to manage the prussik.
As for using a pulley in the system, most guides don't carry a pulley unless they are on a team with only one other person and may be required to complete a rescue by his or herself. This again, is to save weight.
Jason
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Post by jimnelson on Nov 16, 2013 11:40:09 GMT -8
Thanks Jason.
I can't tell what I'm looking at, at the initial change of direction of the haul rope (at the master loop). I understand the prussik, but what else is attached to the carabiner with the ATC? Gene?
The master loop as shown here is something I don't usually see. Extra carabiners being used here. Is it show this way for clarity, or intended as illustrated?
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Post by kensmall on Apr 14, 2014 13:52:17 GMT -8
Bellingham has used this successfully for at least 12 years and it does work and it is a 3:1. The drawing here is too small to make out clearly. It may be necessary to see it in action. It's exactly what Seattle has been using for years, except that instead of having 'biners clipped into each other, they are all clipped into a master loop; the clipping is easier and you can see what you're doing. It might be easier to see by following the text in our student manual, available on request.
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