Micro-Rack Vs. Full size. U-Frame Vs. J-frame

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Re: Micro-Rack Vs. Full size. U-Frame Vs. J-frame

Postby mgmills » Dec 13, 2009 1:46 pm

Dangerjudy wrote:I use a long micro-rack for shorter drops in cave and I love it. BUT for anything taller than Neversink I would use my 18" 6 bar rack. In fact for Neversink I would use it too. I get so much more control from the long rack... and I think if you are lighter you want more area to spread the bars not less...



Every one is different. I have the "long" micro-rack and I can't remember the last time I used my "standard" SMC 6-bar rack. I've done Neversink ( 164 feet?) several times on my micro. I feel I get very good control with the micro with the hyper bar.

I'm not into doing deep drops these days (I'm so out of shape - working way too much and not playing hard enough) but the last time I did Moses Tomb in AL (230 feet) I did it on my micro. I'd probaby use it up to about 350 feet. I loaned my micro to a 220+ guy at Moses Tomb who had somehow come to the pit with all his gear except for a rack and he did the pit using my micro.

I know a guy who did Fantastic Pit in Ellisons in GA on a micro. I'd probably do that on my SMC if I was in good enough physical conditon to climb back out.

Judy is correct that lighter people definitely need more space to spread the bars on a micro. Back when I weighed 140 lbs (don't ask what I weigh now :big grin: ) I tried a "short" micro rack on a bluff practice drop of about 60 feet and I had to feed the rope the whole time.

Bottom line is before making a gear purchase you should try to test out the rappel device at a practice session prior to purchase. Of course, I have not always followed my own advice and have bought gear I've sold or given away.
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Re: Micro-Rack Vs. Full size. U-Frame Vs. J-frame

Postby Dwight Livingston » Dec 14, 2009 9:37 am

NZcaver wrote:
Dwight Livingston wrote:I attach my rack via a quicklink, and you might try this to reduce friction. Mounted on a quicklink, instead of directly to the D ring, the tail of the rope can feed directly onto the bottom bar, without contacting the rack frame. To do this, you let the rope hang between your legs instead of around your hip. I find this drops a lot of friction. It also makes it easier to adjust the bars. When you need more drag, you can move the rope over to your hip. Give this a try and see what you think.

I also have a longer micro rack, and find it nicer to use than the short frame. I use an oval maillon rapide screw link to attach to my central D ring too. I found the default setup for micro racks is 'backwards' from the traditional U-frame racks I started using 20 years ago. Those rack always had bars which swing upwards (towards your face/chest) to open, not downwards. Luckily it's a simple matter to take the micro apart and reassemble it the other way. This seems to keep the rope path more linear, avoids the rope curling over the rack frame as it enters at the bottom, and allows the user to adjust friction more effectively.


Thanks for your reply, NZcaver. I also had to reverse the hyperbar, as I am right-handed and like to control the tail with my right hand. If what we first received is indeed a default set-up, then it's only good for lefties.

I've posted before about how I set up my microrack, but you're the first I've heard to say you also hit upon this method. Thanks for speaking up. I couldn't tell if the thing is too obvious to comment on or no one could tell what I was talking about. Your description seems very clear. Maybe the technique just needs a catchy name to sell. How about the "linear rig" for microrack?

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Re: Micro-Rack Vs. Full size. U-Frame Vs. J-frame

Postby NZcaver » Dec 14, 2009 2:28 pm

Dwight Livingston wrote:I've posted before about how I set up my microrack, but you're the first I've heard to say you also hit upon this method. Thanks for speaking up.

No problem. :wink: Actually you and I have previously discussed our 'linear rack rigging' on the forum here, and I've also mentioned it here. In that first link, several people are arguing about what they think a so-called 'standard' rack should be. :roll: Yep, that same ol' can o' worms. :tonguecheek:
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Re: Micro-Rack Vs. Full size. U-Frame Vs. J-frame

Postby Dwight Livingston » Dec 14, 2009 3:21 pm

NZ caver

I remember the 2007 thread, but rereading it now I see we got further along than I thought, though not to where you said actually changed your rack. I caught the November thread but read right over your "One thing I noticed . . ." part. Anyway, I concur. Since 2007 I've spent a lot of time on permenant rigs with crusty ropes, and I haven't had any problems.

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Re: Micro-Rack Vs. Full size. U-Frame Vs. J-frame

Postby ljthawk » Dec 22, 2009 12:43 pm

I have a six bar, seven bar, and long micro. Ignore the seven bar long frame for caving (more for long drops).

I play with the long micro rack, but when it comes to any drop length short (say 10’) or long (say 600’) with any rope (small / large diameter, clean / dirty, wet / dry, stiff / supple, etc), single or double line, I always feel like I have the most control and the smoothest ride on my six bar rack. Nothing like building speed to get the zing sound on a nice drop and then softly applying the brakes to come to a nice cushion stop at the bottom.

Learning how to properly operate a rack and getting it tuned is key. I thought I knew how to operate a rack, but it wasn’t until I did longer drops (say over 600’) that I started to appreciate and hone the rack operating skills. As for tuning, different bar shapes (half rounds or full rounds with greater offset), different bar material (aluminum vs stainless), different top bars (deep grooved keeper top bar, normal half or full round on top, shallow grooved hyperbar on top, etc), spacers (to space or not to space and how big of a space), and how well the bars slide are all factors in tuning the rack for you.

Example, for the longest time I used a six bar rack with 5 stainless U bars, top deep grooved aluminum keeper bar, and spacers between the top and second bar. This was perfect. I built another rack that was the same except that the top keeper bar was now a deep groove stainless version. This second rack was fast so I removed the spacers.

Other friends have racks that use the full round bars with greater bar to bar offset. This causes greater rope deviation as it goes through the rack and as a result their rack has more friction.

So in my opinion, if you are going to own one rack, get a six bar J frame with U bars and a quality top keeper bar. Keep in mind there are cavers out there that will not allow aluminum rappelling devices on their rope. I once had to use someone else’s rack at White Sides because the owner of the rope did not want my aluminum top bar on his rope.

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Re: Micro-Rack Vs. Full size. U-Frame Vs. J-frame

Postby Rick Brinkman » Dec 23, 2009 1:39 pm

I know you are asking about racks, but......

I used a micro-rack for the last few years. Before that, a Petzl Stop for several years. One of the drawbacks of the micro-rack, was the higher point of attachment of the rope. Not nearly as handy for rebelays, changeovers, or knot passing - compared to a bobbin. <-----MY opinion.

So, I am currently using a Petzl Simple. Don't have a lot of drops on it yet, but so far I REALLY like it.
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Re: Micro-Rack Vs. Full size. U-Frame Vs. J-frame

Postby Cody JW » Dec 23, 2009 7:15 pm

Rick Brinkman wrote:I know you are asking about racks, but......

I used a micro-rack for the last few years. Before that, a Petzl Stop for several years. One of the drawbacks of the micro-rack, was the higher point of attachment of the rope. Not nearly as handy for rebelays, changeovers, or knot passing - compared to a bobbin. <-----MY opinion.

So, I am currently using a Petzl Simple. Don't have a lot of drops on it yet, but so far I REALLY like it.
I tried the Petzl Stop a few years ago and both myself and someone who caves in my group( we both are over 200lbs.) found that when using this device it slowly moves you down the rope in the locked position.We wrote if off thinking it is made for skinny "euro cavers" not us corn fed midwestern types.This was a brand new one right out of the box.
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Re: Micro-Rack Vs. Full size. U-Frame Vs. J-frame

Postby Rick Brinkman » Dec 23, 2009 7:53 pm

I tried the Petzl Stop a few years ago and both myself and someone who caves in my group( we both are over 200lbs.) found that when using this device it slowly moves you down the rope in the locked position.We wrote if off thinking it is made for skinny "euro cavers" not us corn fed midwestern types.This was a brand new one right out of the box.


I had the same problem with the Stop...that's why I tried a micro-rack. But I missed the low tie in point of a bobbin...so now I'm using the Simple. (no auto lock) Trust me...the Simple does NOT have a problem feeding. If anything, the Simple feeds TOO easy.
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Re: Micro-Rack Vs. Full size. U-Frame Vs. J-frame

Postby Jeff Bartlett » Dec 29, 2009 12:13 pm

Rick Brinkman wrote:Trust me...the Simple does NOT have a problem feeding. If anything, the Simple feeds TOO easy.

I was surprised to learn this myself. It's the shape of the bollards; they're round instead of having a flat spot, and I think the flat spot creates an angle a bit too sharp for our stiff 11mm pit rope. Very smooth compared to the Stop (full disclosure: I weigh between 170-175 pounds depending on what week it is).

And now I will stop hijacking the micro-rack thread. :oops:
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Re: Micro-Rack Vs. Full size. U-Frame Vs. J-frame

Postby chh » Dec 29, 2009 7:29 pm

Three cheers for the simple. It's what I use and I love it. It's, well, simple.....
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