Howdy,
Ken here, an associate member of the UndergroundExplorers.
Just came across this post. Knew it had to be several years old upon reading it even before seeing the date.
Thought I'd throw in mention of my current setup here. After upgrading from an ATC, I used a BMS 6-bar rack for long descents (200 to 300ft) while doing mineshaft exploration, as well as in work with trees. I like it, but it's heavy and bulky. The bulk doesn't matter so much in all the verticals I've been down with it, but the two combined lends it to being something you don't really want to lug around with you all day.
Having seen some of the "creep" issues with the stop, and the difficulty some of the crew guys had in getting it to feed smoothly; I never ended up picking one up. While at a wind turbine technician trade show I stopped by Petzl's booth and saw their new RIG descender. I'd been looking at the I'D for a while, but due to the price I never picked one up either. The RIG I was pretty instantly impressed with. Relatively light, included features I was wanted, not amazingly affordable, but getting to actually see/feel/test one made me want to try it out. So I bought one on sale for $120 USD.
The RIG weighs 380g (0.83lb) vs. the Stop at 326g (0.72lb), the I'D at 530g (1.17lb), the BMS 6bar Rack at 886g (2lbs), or an ATC at ~20g (0.04lb)
Not even gonna mention my collection of Figure 8's, cuz twisted rope just sucks.
The pictured device is the RIG, not to be confused with the I'D which looks similar.
http://www.petzl.com/us/pro/self-brakin ... ders-0/rigI *really* like it. I've used it on about a dozen 150 to 200ft descents, a 300ft descent, and dozens of shorter ones.
It is marketed as a device "for expert users only", being as how it doesn't have all the overbuilt safety features of the I'D. As with anything else, you have to learn to use it THE RIGHT WAY, or you can risk serious injury or death; pretty much like everything else in high-angle hobbies.
So far I've used it on ropes from 3/8" to my KM-III 7/16". It feeds nice and smooth, the handle is larger than on the Stop or Grigri, and is easy to feel fine manipulation of even with gloves on. When in soft-lock (not pulling on the lever) I've never had it creep on me, even on the 3/8" line (a tad smaller than what it's actually rated for), and I weigh right around 220lbs with full gear on. In the hard-lock position (handle flipped around and locked facing down) not only can nothing hit it and unlock it due to the position, but I've found that I fully trust it not to budge at all on the line.
This came in handy during the 300ft rappel down a vertical mine shaft one night. On the way between the surface and the first drift level at 295ft down, I had to stop about 10 times to clear beams and debris from the vertical haulage-way I was descending down. When approaching a plugged/blocked section, I simply flipped the handle over into the hard-lock position and then could easily work with both hands to free timbers and move them over into the (totally unusable and deteriorated) manway side of the shaft. While moving a beam weighing maybe 60lbs I was keeping a close eye on the device (and with rope still held in my brake hand just-in-case) and it stayed locked down hard; with almost 300lbs on it.
It allowed fast and simple switching back and forth to switch between rappel and lock-off for debris removal.
Couldn't have been happier with it that night. The range of descent speed is widely variable.
In the instance of being struck by debris from above, upon releasing the handle the device will soft-lock and STOP you in place. There is a bit of learning that goes along with using it, if you let up too fast while rappelling at a normal speed its return spring will stop you fast enough to bounce a little on the line, and I try to avoid that by being light-handed on it.
Not really sure how much you cavers would like it, or if it would fit with your needs. I love it though, a big two thumbs up to Petzl for this product.
Haven't got the other guys on the crew to get any yet, but spending $120 to $150 on another descender when you've already got a Stop or a Grigri isn't everyone's idea of fun I suppose
Underground ExplorersCalifornia Abandoned Mine Exploration
http://www.undergroundexplorers.com