Don't feed the micro-rack!

By Scott McCrea, NSS #40839

I love my micro-rack. It's great for most drops and works great with a frog system. However, there is a potential hazard with them. It is possible to accidentally drop to two bars. 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.
Micro-rack dropping two bars
  1. Micro-rack rigged with all bars including
      the hyper-bar.
  2. Hyper-bar disengaged, rope being fed
      creating a loop.
  3. The rope outside the rack will push up
      and in on the bar and pop it off.
  4. Bar swings open.
  5. Rope slips out of the rack.
  6. Rack is now rigged with only two bars.

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


Return to the Top of the Page

Return to the NH #48 Contents Page

Copyright © 2003 Vertical Section of the NSS, Inc. - All Rights Reserved.