This
happens when there is too much friction and a rappeller resorts to feeding rope
causing the bottom bar to pop off. It is possible to pop bars off of any
rack while feeding, but since a micro-rack only has four bars, the margin for
error is slight.
The
micro-rack is unique among racks in that very little variation in friction is
available. Bars cannot be added or dropped like on a regular rack. There
is only a small amount of space to spread the bars (there are long micro-racks
available which increase the spreading space, but the feeding issue is still
there). So, often the only option is to feed rope.
Imagine
a caver rigs his trusty but stiff and dirty rope to a tree about 20 feet from
the lip. The approach to the lip is sloped but not steep. The rappeller
rigs his micro-rack a safe distance from the lip, but as he begins to back down
towards the edge there is too much friction. He struggles to inch down the rope.
Even without the hyper-bar and the bars spread, it’s tough going.
Feeding some rope into the rack speeds things up. At the lip, he turns
around to look down the pit and plan his next move. Still feeding rope, he
removes his hand from the rack, maybe to adjust a pad, swat a bee or to help
balance. A loop of rope gets fed into the rack and all of a sudden, he’s on
two bars and going a lot faster.
So,
how can this be prevented? Simple, pay attention. Ok, that’s a little
obvious. The best way to prevent this is to follow a simple but often broken
rule that applies to any and all unlocked racks–ALWAYS keep a hand, finger,
thumb, or something on the last engaged bar. A bar that you are holding
will not come off.
Please
note, there is nothing wrong with these racks. While the rack pictured here is a
BMS Micro-Rack, this can happen with any four bar, U-shaped rack. They all
work just fine, as long as they are used correctly. I am definitely not
giving up my micro-rack and neither should you. Just be aware of the
hazards, be prepared, practice, simplify and think.
Scott
McCrea
Asheville, NC, USA
NSS 40839
scott@flittermouse.org
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