lefalaf wrote:chh wrote:snoboy wrote:My understanding is that the blue rope causes the system to stop feeding rope when you climb. You would weight it a little, and that would pull on the friction knot, stopping the rope from feeding into the rack. Acts like a backup prusik on rappel.
I get that, but I think that with a hitch that has been set properly, it would lock on it's own by virtue of the rope travelling through it. That's my point, it functions
exactly like a rappell backup or a self belay. All you really need is something to release the hitch by pushing it down and then stop pushing when you want to stop.
As you travel up, the PMP above the hitch pulls down on the hitch. The hitch releases. You descend, until there is no more pressure on the hitch from the PMP. The hitch would have to push the additional weight of the PMP and dangling cord up the rope as well, which is perhaps why the blue rope must be set up the way it is, I just wondered if it would work without the blue rope travelling in a "z" fashion. It's my editorial urge. I'm always trying to prune unneccessary stuff away;) But it may very well be necessary to do this, I don't know. I might try it this week if I get a chance. Perhaps lefalaf went through this permutation on the way to his current setup and can tell us why this doesn't work?
Yep - the blue cord is simply for the autostop. It really serves no other function. The rack *should* be able to take care of all other friction the system needs.
The Z arrangement is simply to translate the down pull of my body into a down pull on the knot which is at the same level as the climber.
I like your idea to try it simply tethered to a floor anchor.
That seems plausible to me and I love the simplicity, so I will definitely try that out. I don't think I'll have time for a week or two, so go to it and let us know!
Well, I tried it w/o the Z (upper tether) and instead had that tether anchored to the floor. In my limited testing, it was, well
.
What happened, as far as I could tell, was that with this variation, the friction knot was constantly pulled tightly and resulted in jerky belaying due to the other tether having more trouble releasing the friction knot. Whereas with the Z tether, the tension on the friction knot varies, allowing the other tether to release it more easily. It seems that they need to work in conjunction for it to work smoothly.
I tried different numbers of wraps on both the klem and FW to no avail, I also tried differing (tighter) lengths of the other tether to give it more force, but still no dice. That's not to say that there isn't an adjustment that might work for that variation on the system, but I couldn't find it. I like the simplicity it would add, and wanted it to work, but it just wasn't happening. Should anyone try that variation - especially if better results - do share your experience. For now I'm going back to the Z.
With the original system (w/the Z tether), the system self adjusts (in my testing at least) and I find it keeps you in a smooth equilibrium. With the variation, it was sending me up and down a foot or two at times which killed my efficiency.
The only things to know with the original system:
1) the Z/upper tether should be about the length to make a continuous loop from ceiling to floor if it were tied;
2) and the bottom tether can be any length - at 1x the distance from ceiling to floor, the system will belay you in the middle of the height; at less than 1x, then you will be belayed at less than half the height; and at greater than 1x, you will be belayed at a point above half the height of the system.
Always open to more ideas.
Happy Climbing,
Jon