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TOPIC: set up for foot assisted DRT with MB 3

set up for foot assisted DRT with MB 3 2 years 7 months ago #137519

  • chiutai
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Where MB 3 denotes mechanical benefit 3
With this set up, during the climbing, the carabiner c1 will gradually descend to prussik knot, hence the climber needs to reset c1 to it's original place, this can be done by pushing loop L1 by foot several times. when it's done the climber can continue his climbing again. The process is repeated several times until the height is reached.
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Last Edit: 2 years 7 months ago by chiutai.
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set up for foot assisted DRT with MB 3 2 years 7 months ago #137520

  • moss
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Very similar to the "Super System", DRT 3:1 system. Except with the Super System nothing moves down so the climber can go to the top without moving the upper anchor piece up.

Up top


Climber end of it


-AJ
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set up for foot assisted DRT with MB 3 2 years 7 months ago #137523

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Thanks Moss, It inspired me to revise my upper anchoring ,so today I added a prussic cord shown in the photo to prevent the upper part from moving. The prussic cord is installed loosely at first to make it easy to be move up to the top, then when reached the anchoring position, the climbing rope is shacked hard to tighten the prussic cord, and it's ready to be climb.
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Last Edit: 2 years 7 months ago by chiutai.
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set up for foot assisted DRT with MB 3 2 years 7 months ago #137524

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Looks good. A few comments:

1. I'd be more comfortable with a cinching knot for the attachment at the top of the carabiner, double-overhand noose for example.

2. Where the rope is running over carabiner at the bottom, the radius of the carabiner is pretty small for a rope running under load, I'd put a micropulley there.

3. For that kind of multi-directional pull a rated delta screwlink would be superior to a carabiner.

Thanks for posting the photo, it's very helpful to see all the details of a complex or experimental system.
-AJ
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set up for foot assisted DRT with MB 3 2 years 7 months ago #137525

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Nice looking rope in the photo, what are the specs on it? For example diameter? Construction (static kernmantle or other)?

Good to see the gear, opens more avenues for discussion.
-AJ
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set up for foot assisted DRT with MB 3 2 years 7 months ago #137526

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Thanks for the suggestions Moss, this afternoon I put only a pulley with the top carabiner it helps to reduce the pulling effort in climbing though . Earlier this time,I tried a butterfly loop at the top as an anchoring point but it didn’t work as the picture shown below. The anchoring loop still silded down with the carabiners.

The climbing rope is a static kermantle with a diameter of 10 mm. During the the past several months it has been used very often that It’s sheath has stretched too much that I can feel the rope’s swollen part that is soft in touch.

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Last Edit: 2 years 7 months ago by chiutai.
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set up for foot assisted DRT with MB 3 2 years 7 months ago #137528

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I thought it was a 10mm static, cool.

So... it's not unusual for the sheath to stretch with use, what you want to do is milk the loose sheath over the core until the sheath has normal tension in relation to the core. You'll end up with anywhere from a few inches to a couple of feet or more of sheath with no core on one end of the rope. Find the point where the core ends and cut the sheath off there. I'd tape it first with vinyl electrical tape and cut it with a hot blade. Typically the sheath only stretches once when the rope is new and stays stable after that.

You can milk the rope by securing one end and pulling the sheath through your hands to milk it tight over the core. You can also use a hitch cord to milk it although I've found that cover (sheath) sometimes twists over the core when I do that. Maybe some one else will chime in with their favorite technique.
-AJ
Last Edit: 2 years 7 months ago by moss.
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set up for foot assisted DRT with MB 3 2 years 7 months ago #137536

  • StihlHusqy
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Would it be wise to secure the rope at a TIP and rap down it with a fig8 to milk the sheath or would that also twist the sheath by doing so?

Then again, i'm running 200ft of line so i'd have to rap quite a ways... just a thought
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set up for foot assisted DRT with MB 3 2 years 7 months ago #137538

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Today I milked my rope(about 100 feet) with a prussic hitch, I tried 6 times with different lengths to pull, namely 10m, 20m, 25m, 30m(three times). Each of the milking stretched the sheath with no cord inside longer.
10m with a sheath stretch of about 30cm
20m with a sheath stretch of about 70cm
25m(not measured)
30m(1st time)with a sheath stretch of about110cm
30m(2nd time)with a sheath stretch of about117cm
30m(3rd time)
with a sheath stretch of about120cm
and at the end I made a Daisy chain on the rope.

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