This is called RADS SRT. Rapid Ascent Descent SRT or some such. You can do the same thing with 2 friction hitches and some 'biners and pulleys, which will save you about $200 worth of hardware. That said the F4 device looks like a great gizmo, made for 8mm line. If/when I replace my 9mm C-IV it will probably be with 8mm Oplux or Resc-Tec, with an F4 device. As suggested above, check out
@John RB 's Youtube channel, JRB climbing. I think he has a recent video on RADS SRT with friction hitches, probably his Longhorn Agile hitch, but I can't find the video at the moment. Hopefully he'll chime in.
So first off, I consider the boys at New York Saddle to be respected friends and colleagues. I have not climbed on that system and so my commentary is about RADS SRT, not about the new Halfline system.
If you're not familiar with the concept of mechanical advantage, it basically uses a multiplication force by transferring our weight onto several strands and so we can move up by pulling less than our body weight. Long story short: RADS is a 3:1 system. That means that if we pull the rope down 18inches, we are only going to move up 6in. DRT/MRS is a 2:1 system, so we pull 18 and move 9. But a true SRT or DSRT is a 1:1 system . Personally, after having done all of em... I find it unacceptably slow to climb at anything but a 1:1. Ok, but is it hard? The answer is simply that it depends on your system. The more parts of your body which are engaged in the rising move, the easier it will be. I recently did a 1:1 climb carrying 100lbs of cast iron. The hardest part was figuring out how to wear the weight. But i was using both arms and legs for the rising move.
I once was with a guy who was 380lbs trying to execute a 1:1 climb on my gear. He had a hard time, partially because of strength and also because his body size made it difficult to get close to the rope. After that experience, I left believing that RADS might be more appealing for a bigger guy.
Ok, now even though we move at a 3:1 pace, that doesn't mean we're actually getting a 3:1 mechanical advantage... simply because there is some amount of loss as the rope bends twice and is subjected to friction. Nothing will be as lossless as a good mechanical device and pulley. I did this demonstration just to show off the properties of the hitch, not because I plan to climb that way.
Watch me climb with one hand and one foot in minute 4. Then RADS in minute 6.
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