Moderator: Tim White
gdstorrick wrote:This thread reminded me of an exchange that I had about eight years ago, but it took me a little while to find it. Look on the ACA web site and search for the "Allp" - or try http://www.canyoneering.net/forums/showthread.php?1540-Racks-and-Trolls&highlight=Allp directly. You will find some discussions of people who preferred the Allp to the rack - "in fact, we prefer anything above a rack." Part of their problem was that they were using the Petzl rack, part seems to be technique, and part was that the Allp is also a capable long-drop device. I just reread the entire ACA "Racks and Trolls" thread and I still think it has some good comments.
LukeM wrote:gdstorrick wrote:More precisely, AOTBE (&TNA), a longer rack can provide less friction. Rack length below the bars doesn't change friction, and one can push the bars together on a long rack. If you need more friction, changing to a shorter rack won't help (unless it is so short that there isn't room for the rope ).
Thanks for clearing that up Gary. Looks like what I was taught about short micro racks being especially useful for heavier people (vs shorter) isn't necessarily correct. More like the longer version is especially helpful for lighter people and the shorter version is nice to save space/weight as long as you are heavy enough to rappel effectively without needing more bar spacing.
One device was tested by pulling over a mile of dirty rope through it under rescue sized tension, with temperature reading thermocouples being monitored at several locations during pulls. At 2kN of tension, and a lowering speed of 10M per minute, the Scarab® maintained a frame temperature at about 100 degrees C. To our knowledge, the Scarab® is the only descent control device to have been tested to this degree.
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